Nanocomposite surface coatings

Abstract

The present disclosure relates to provision of surface coatings comprising a first layer on a substrate, the first layer comprising a reticulated structure and a polymer, wherein the reticulated structure is a metal-organic framework (MOF) having pores or a covalent organic framework (COF) having pores; a portion of the molecules of the polymer at least partially penetrate into the pores of the reticulated structure; and the surface of the first layer opposite the substrate is functionalised with an organosilane. Also disclosed are articles comprising such a coating, methods of coating a substrate with such a coating, and dispersions and kits useful in forming such coatings.

Description

[0001] 008864555

[0002] 1

[0003] NANOCOMPOSITE SURFACE COATINGS

[0004] The project leading to this application has received funding from the European Union’s Horizon 2020 Research and Innovation programme under grant 801229 (HARMoNIC), the European Research Council (ERC) grant 714712 (NICEDROPS), ERC PoC grant 875698 (SUNCOAT), ERC Consolidator grant (InspiringFuture) selected by the ERC, funded by UKRI Horizon Europe Guarantee (EP / X023974 / 1) and EPSRC sustainable manufacturing grant (EP / W019132 / 1).

[0005] This application claims priority from GB2418375.8 filed 13 December 2024, the contents and elements of which are herein incorporated by reference for all purposes.

[0006] Field of the Invention

[0007] The present invention relates to nanocomposite surface coatings comprising a polymer, a reticulated structure, and an organosilane (e.g. an alkyl silane), particularly although not exclusively to amphiphobic surface coatings comprising a polymer, a reticulated structure, and an alkyl silane. The present invention also relates to a method of coating a substrate, a coated substrate, and a kit.

[0008] Background

[0009] The present invention has been devised in light of the above considerations.

[0010] Impact of global warming and climate change can be widely observed in the modern world.1 2Both natural (e.g. fossil fuels, biomass, and metals etc.) and synthetic (e.g. chemicals, polymers, medicines etc.) materials have strong and complicated interlinkage to the climate change.3-6Innovation in materials and their processing such as use of safe chemicals, efficient manufacturing process, production of robust components etc. have also attracted great attention due to the direct impact on some of the United Nations sustainable development goals (SDGs): 6, 7, 9, 11 , 12, 13 and 14.7-9

[0011] Similar to any other technical advances, fabrication of liquid-repellent materials (including coatings) has attracted interest of the scientific community, targeting a wide variety of domestic and industrial applications in self-cleaning windows10, contamination prevention,11corrosion resistance,12 13antibiofouling,14 15and anti-icing16etc. However, achieving repellence, especially towards low surface tension liquids e.g. oils or, organic solvents generally require perfluorinated compounds (RFCs) which are biopersistent (non-degradable in the environment) due to very strong carbon-fluorine bonds.17In fact, there is a widespread concern regarding even a broader class of chemicals, designated as per- and polyfluoroalkyl substances (PFAS) of which PFCs are a part. Efforts have been made to produce amphiphobic surfaces / coatings using other strategies to avoid the use of hazardous PFAS in the wake of their adverse effect on the environment and human health, recently.18 19For example, re-entrant surface structures reported by Wang et al. based on monodispersed large-sized silica particles showed superamphiphobic characteristics but lack of mechanical durability and robustness is a major challenge for its practical applications.20In recent works, Lai and co-workers have demonstrated different strategies, 008864555

[0012] 2 such as the use of interpenetrating polymer networks21and dual cross-linked networks22for robust fluorine-free liquid-repellent coatings. While these approaches achieve excellent mechanical durability and liquid repellence, they primarily rely on complex polymer architectures.

[0013] In a recent study, the present inventors reported transparent and robust amphiphobic surfaces exploiting nanohierarchical (a hierarchy of all-nanoscale roughnesses) surface-grown MOF films through layer-by- layer (L / L) growth.23The characteristics of MOFs, including their large specific surface area, ultrahigh porosity, as well as their potential for chemical and structural modifications24 25make them excellent candidates for such applications. However, the L / L approach faces challenges in terms of scalability and therefore, a method that allows practical processability of bulk reticulated structures on surfaces is imperative. Additionally, achieving mechanically robust amphiphobic coatings using non-fluorinated materials, waterborne formulation, and scalable production methods is highly desirable but remains a major challenge.

[0014] The alternative nanocomposite based coatings may overcome the scalability issue; however, ensuring precise control of interfacial interaction between the polymer and nanoparticle is imperative, as it stands as a major source of (mechanochemical) weakness of the resulting nanocomposite. There are a number of natural examples from dactyl club of mantis shrimp26where a bicontinuous composite structure shows remarkable improvement in mechanical robustness and impact resistance characteristics.

[0015] In addition, the conventional liquid-repellent coatings typically utilise organic solvents, which are sources of volatile organic compounds (VOCs). The emission of VOCs during application and drying contributes to air pollution, ozone formation, and poses direct health risks. Waterborne coatings, by contrast, significantly reduce VOC emissions, aligning with global efforts to protect air quality and human health. These advancements align with the UK’s environmental policies and goals, including the push for net- zero emissions by 2050 and compliance with the European Union’s REACH (Registration, Evaluation, Authorisation, and Restriction of Chemicals) regulation.

[0016] 008864555

[0017] 3

[0018] Summary of the Invention

[0019] The invention includes the combination of the aspects and preferred features described herein except where such a combination is clearly impermissible or expressly avoided.

[0020] Surface Coating

[0021] In a first aspect, the present invention relates to a surface coating comprising, or consisting of, a first layer on a substrate, the first layer comprising a reticulated structure and a polymer, wherein: the reticulated structure is a metal-organic framework having pores or a covalent organic framework having pores; a portion of the molecules of the polymer at least partially penetrate into the pores of the reticulated structure; and the surface of the first layer opposite the substrate is functionalised with an organosilane (e.g. an alkyl silane).

[0022] The present invention also relates to a coated article comprising said surface coating.

[0023] Such coatings may be mechanically robust, optically transparent, thermally stable, and display favourable liquid interaction (e.g. amphiphobicity, hydrophobicity, and / or oleophobicity). Additionally, it is possible to make such coatings without the use of fluorinated organic groups (such as compounds having perfluoro and polyfluoro groups) which have raised concerns in recent years as being biopersistent. In some embodiments, the surface coating is fluorine-free. In some embodiments, the surface coating is substantially free of per- or poly-fluorinated compounds. In some embodiments, one or more of the polymer, the reticulated structure, and the organosilane is fluorine-free. In some embodiments, each of the polymer, the reticulated structure, and the organosilane is fluorine-free. In some embodiments, the polymer is fluorine-free. In some embodiments, the reticulated structure is fluorine-free. In some embodiments, the organosilane is fluorine-free.

[0024] The surface coatings described herein may be useful in providing one or more of the following properties to a coated substrate or article: self-cleaning, contamination prevention, corrosion resistance, antibiofouling, and anti-icing.

[0025] For the avoidance of doubt, the surface coatings of the present invention are intended to be retained on the substrate (aside from wear-and-tear). That is to say, it is not intended that the surface coating is removed from the substrate, for example, to be used a separation membrane.

[0026] Herein, “reticular”, “reticulation” and “reticulated” are given their normal meanings in the art. A reticular or reticulated structure is an extended, crystalline structure formed through the linking of smaller chemical moieties by either coordination or covalent bonds. The reticulated structures of the present invention are metal-organic frameworks (MOF) or covalent organic frameworks (COF), both of which have pores. The pores of the reticulated structure are contained within the reticulated structure itself, i.e. within the MOF or COF itself. It is understood that the pores of the reticulated structure do not refer to spaces between separate particles or layers of reticulated structure, or spaces formed by defects. 008864555

[0027] 4

[0028] Penetration of the Polymer

[0029] The surface coating includes a polymer. The term “polymer” is intended to take its usual meaning in the art. For example, a polymer is a macromolecule composed of a plurality of repeating structural units, typically derived from monomers, covalently bonded to form a chain, network, or branched structure. Polymers can be natural or synthetic. A polymer may be selected for a specific application due to its particular physical and chemical properties which depend on, inter alia, their composition, molecular weight, and structure. As used herein, the term “polymer” is a component comprising a plurality of polymer molecules, which may have the same structure or may have different structures. The polymer molecules may be of substantially the same size (e.g. molecular weight, chain length), i.e. the polymer molecules may have a monodisperse size distribution, or the polymer molecules may be different sizes (e.g., a bimodal or multimodal size distribution).

[0030] The polymer in the surface coating may be described as a polymer matrix. The term “polymer matrix” is intended to take its usual meaning in the art. For example, a polymer matrix is a continuous phase of a polymer material in which other components, such as fillers, fibres, or additives, may be embedded or dispersed to form a composite structure. The polymer matrix may provide structural support, cohesion, and physical and chemical properties to the composite.

[0031] A portion of the molecules of the polymer at least partially penetrate into the pores of the reticulated structure. In other words, for a portion of the polymer molecules (e.g., represented as a fraction, percentage or ratio of polymer molecules), at least a section of the polymer molecule is located within a pore of the reticulated structure. In other words, some polymer molecules at least partially penetrate into a pore of the reticulated structure. The section of the polymer molecule may be held within the pore, for example due to intermolecular interactions. Such a polymer may be described as being intercalated within the reticulated structure. Typically, penetration of a polymer molecule into a pore is distinct from superficial blocking of the pore aperture - that is to say, penetration of a polymer molecule requires at least part of the polymer to be located within the internal volume of the pore.

[0032] In some embodiments, a different portion of the polymer molecules do not penetrate into the pores of the reticulated structure.

[0033] Of the portion of polymer molecules which penetrate into the pores of the reticulated structure, any individual polymer molecule may independently penetrate into a single pore of the reticulated structure or may penetrate into more than one pore (i.e., two or more pores) of the reticulated structure. When a polymer molecule penetrates into two or more pores, the two or more pores may be located within the same particle of the reticulated structure, or they may be located in separate particles of the reticulated structure. 008864555

[0034] 5

[0035] The portion of the polymer molecules which at least partially penetrate into the pores of the reticulated structure may be at least 5%, at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 98%, or at least 99%.

[0036] It may be that some pores, most pores, or substantially all pores of the reticulated structure are (at least partially) occupied by a polymer molecule. For a pore to be considered as occupied by or containing a polymer molecule, it is not necessary for the entire length / volume of the pore to be occupied. For example, a length of the pore extending inwards from the pore aperture may be occupied by a polymer molecule, and said length may be less than the entire length of the pore.

[0037] It may be that some particles, most particles, or substantially all particles of the reticulated structure have at least one pore into which a polymer extends.

[0038] By utilising a layer comprising polymer molecules which penetrate into pores of the reticulated structure, it is possible to obtain a coating having improved mechanical robustness and impact resistance owing, at least in part, to the strong interfacial interactions. Such a coating also demonstrates excellent thermal stability and icing resistance. Furthermore, penetration of the polymer molecules into the reticulated structure pores may lead to increased tensile strength and Young’s modulus. It is additionally believed that the presence of reticulated structures within the polymer matrix, and into which polymer molecules penetrate, has an interlocking effect between the polymer chains and the reticulated structure, which results in a layer with improved robustness and impact resistance, thus able to resist localised stress. Additionally, this has the benefit of facilitating a uniform distribution of the reticulated structure across the layer, reducing agglomeration and improving interfacial adhesion and structural reinforcement.

[0039] In some embodiments, the reticulated structure is substantially evenly distributed within the polymer matrix. In some embodiments, the first layer is isotropic. In some embodiments, the reticulated structure is substantially homogeneously distributed within the polymer matrix.

[0040] The section of the polymer molecule which penetrates the pore of the reticulated structure may be held within the pore by one or more selected from intermolecular interactions, steric constraints, and coordination interactions. Intermolecular interactions may include hydrogen bonding, Debye forces, dipole-dipole interactions, Van der Waals forces, and London Dispersion forces, for example between groups in the polymer repeating unit and in a linker unit of the MOF or COF. Steric constraints may include the relative sizes of pore aperture and polymer chain, as discussed below. Coordination interactions include coordination bonds (i.e. dative covalent bonds) formed between a coordinating functional group (e.g. having an electron lone pair) on the polymer and a metal centre (e.g. having vacant coordination sites / incomplete valency) of a MOF.

[0041] Holding of the polymer molecules is aided by control or selection of the relative sizes of the pore apertures in the reticulated structure and the chain diameter of the polymer molecules. The polymer 008864555

[0042] 6 molecules have a section that has a chain diameter that is smaller than the pore aperture, allowing for insertion into the pores of the reticulated structure, and for strong guest-host interaction. The polymer molecules are held within the pores of the reticulated structure, but also extend therefrom, which is essential for the functioning of the surface coating - the polymer molecules must extend from the reticulated structure in order to form a polymer matrix and thus create a polymeric coating layer with good mechanical strength and robustness. Put another way, for a polymer molecule which penetrates a pore of the reticulated structure, there is a section of the polymer molecule that is held within the pore of the reticulated structure (i.e. extends inwards from the aperture of the same pore), and a section immediately adjacent to that section which extends outwards from the aperture of the same pore.

[0043] It may be that the polymer molecule fills substantially all of the pore in which it is held and inserted into, for example substantially fills the length of the pore. It may be that the polymer molecules entirely fill the pores in which they are held and inserted into, for example entirely fill the length of the pores. It may be that the polymer molecules fill > 50%, > 60%, > 70%, > 80%, > 90% or > 95% of each pore in which they are held. It may be that the polymer fills > 50%, > 60%, > 70%, > 80%, > 90% or > 95% of the total number of pores of the reticulated structure. It may be that the polymer fills > 50%, > 60%, > 70%, > 80%, > 90% or > 95% of the total pore volume of the reticulated structure. Filling of the pores of the reticulated structure can be observed, for example, using BET-surface area measurements. In such a case, it may be that the BET-surface area of the reticulated structure after infusion with polymer is reduced by > 50%, > 60%, > 70%, > 80%, > 90%, > 95%, > 96%, > 97% or > 98% relative to the BET- surface area of the reticulated structure before infusion with lubricant.

[0044] Significant, substantially complete, or complete insertion and filling of the pores of the reticulated structure is only possible due to the chain diameter of the polymer molecule being a certain amount smaller than the pore aperture diameter. It may be that the pores of the reticulated structure into which the polymer molecules are inserted are aligned pores, in that they are arranged anisotropically through the reticulated structure, for example the axis of the pores are aligned in at least one direction through the reticulated structure.

[0045] It may be that the section of polymer molecule that is held within the pores of the reticulated structure has a chain diameter that is no less than 10%, no less than 20%, no less than 30%, no less than 40%, no less than 50%, no less than 60%, no less than 70%, no less than 80% or no less than 90% of the diameter of the aperture of the pore in which it is held. It may be that the section of polymer molecule that is held within the pores of the reticulated structure has a chain diameter that is no more than 0.5 A smaller than the diameter of the aperture of the pore it is held within, in some cases, no more than 1 .0 A, no more than 1 .5 A, no more than 2 A, no more than 2.5 A, no more than 3 A, no more than 3.5 A, no more than 4 A, no more than 4.5 A, or no more than 5 A smaller than the diameter of the aperture of the pore it is held within. The matching of size and geometry between reticulated structure pore apertures and polymer molecule chain diameter maintains strong guest-host interaction, and reduces the ease in which the polymer can be removed from the reticulated structure. In turn, this creates a more robust coating, which retains low friction surface properties for longer, and even when subjected to extreme conditions (e.g. 008864555

[0046] 7 resistance to more extreme conditions compared to a material in which the pore apertures and polymer molecular chain diameter are less well matched).

[0047] It may be that the pore aperture of the reticulated structure has a diameter that is from 1 to 20 angstroms (A), from 1 to 18 A, from 2 to 15 A, from 2 to 12 A, from 3 to 10 A, or from 4 to 8 A. It may be that the pore aperture has a diameter that is about 1 , about 2, about 3, about 4, about 5, about 6, about 7, about 8, about 9, about 10, about 11 , about 12, about 13, about 14, about 15, about 16, about 17, about 18, about 19 or about 20 A, or falls within a range made from any combination of the foregoing (for example, from 13 to 17 A). In some embodiments, the pore aperture is about 6 A (e.g., as in UiO-66). It is understood that, depending on the shape of the pore aperture, diameter may be referring to the smallest distance across the centre of an aperture, or the average distance across the centre of an aperture. The pore aperture is understood to be the space or window providing access to the pore interior, that is the aperture through which the polymer molecule is inserted, to be held within the reticulated structure. Pore aperture diameters can be measured by scanning tunnelling microscopy, by high resolution transmission electron microscopy, or by DFT calculations using the confirmed crystal structure from XRD experiments.

[0048] It may be that the polymer molecule chain diameter is from 1 to 19 A, from 1 to 18 A, from 2 to 15 A, from 2 to 12 A, from 3 to 10 A, from 4 to 8 A, or from 4 to 7 A. It may be that the polymer molecule chain diameter is 15 A or less, 12 A or less, 10 A or less, 9 A or less, 8 A or less, 7 A or less, 6 A or less, 5 A or less, 4 A or less, or 3 A or less. It may be that the polymer molecule chain diameter is about 1 , about 2, about 3, about 4, about 5, about 6, about 7, about 8, about 9, about 10, about 1 1 , about 12, about 13, about 14, about 15, about 16, about 17, about 18, or about 19 A, or falls within a range made from any combination of the foregoing (for example, from 13 to 17 A). In some embodiments, the polymer molecule chain diameter is 6 A or less, for example 5 A or less. In some embodiments, the polymer molecule chain diameter is about 5 A or about 4 A. The polymer molecule chain diameter can be estimated by calculating the arithmetic sum of bond lengths of bonds branching off an atom in the chain backbone. Said bond lengths may be determined by computational methods (e.g. quantum method PM7 following structure optimisation) or crystal XRD analysis. For example, bond lengths of linear polyurethanes are reported by Saito et a!., 1982.58

[0049] The polymer molecules extend from the pore apertures of the reticulated structure pores in which they are held, and in this way are not completely contained within the pores of the reticulated structure. The extension of the polymer molecule in this way from the reticulated structure is important to ensure good performance of the surface coating. It may be that > 10%, > 20%, > 30 %, > 40%, > 50%, > 60%, > 70%, > 80%, or > 90% of the polymer molecule chain length extends from the pore aperture. It may be that the polymer molecule chain is > 2, > 3, > 4, > 5, > 6, > 7, > 8, > 9, > 10, > 20, > 50, > 100, or > 1000 times longer than the corresponding pore in which a section of the molecular chain is held.

[0050] The penetration of polymer molecules into the reticulated structure may be observed by comparing13C and / or1H NMR spectra of the pristine reticulated structure with the polymer-penetrated reticulated structure. For example, signals of intrapore bonds in the reticulated structure which interact with a 008864555

[0051] 8 penetrating polymer molecule may show increased line width when a polymer penetrates. For example, when the reticulated structure comprises aromatic groups in its pores which couple to a polymer molecule (e.g. by Van der Waals or London Dispersion forces), the corresponding13C NMR signals for aromatic C- H and / or C-C bonds may have increased line width. Additionally / alternatively as an example, when the reticulated structure comprises hydroxyl groups in its pores which couple to a polymer molecule (e.g. by hydrogen bonding, Debye forces, or dipole-dipole interactions), the corresponding1H NMR signals for the O-H bond may have increased line width.

[0052] In some embodiments, the13C NMR line width of signals from aromatic C-C and / or C-H bonds in the reticulated structure are at least 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 125%, 150%, 175%, or 200% wider in the polymer-penetrated reticulated structure as compared to the pristine reticulated structure.

[0053] In some embodiments, the1H NMR line width of signals from hydroxyl O-H bonds in the reticulated structure are at least 5%, 10%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 125%, 150%, 175%, or 200% wider in the polymer-penetrated reticulated structure as compared to the pristine reticulated structure.

[0054] The penetration of polymer molecules into the reticulated structure may be observed by comparing FTIR spectra of the pristine reticulated structure, the pristine polymer, and the polymer-penetrated reticulated structure. For example, various characteristic signals (e.g., stretching signals) may be shifted to a lower frequency due to intermolecular interactions (e.g., hydrogen bonding, Debye forces, dipole-dipole interactions, Van der Waals forces, or London Dispersion forces) between the polymer and intrapore bonds of the reticulated structure. Such characteristic signals include C-H stretching, N-H stretching, and C=O stretching.

[0055] For example, a characteristic signal may be shifted by at least 1 cm'1, at least 2 cm'1, at least 3 cm'1, at least 4 cm'1, at least 5 cm'1, at least 6 cm'1, at least 7 cm'1, at least 8 cm'1, at least 9 cm'1, at least 10 cm'1, at least 11 cm'1, at least 12 cm'1, at least 13 cm'1, at least 14 cm'1, at least 15 cm'1, or at least 16 cm'1.

[0056] Organosilane

[0057] The surface coating is functionalised with an organosilane. In other words, the surface coating is silanized. In particular, the surface of the first layer which is opposite the substrate is functionalised with an organosilane (i.e. is silanized). In some cases, the surface of the first layer which is distal to the substrate is silanized. In some cases, in situations where the first layer is in direct contact with the substrate, the surface of the first layer which is not in contact with the substrate is silanized. In some cases, when the substrate forms the bottom layer of the coated surface, the organosilane groups form an upper layer. In some cases, the outer surface of the first layer is silanized (when the inner surface is in contact with the substrate). In some cases, the order of the components of the coated surface is, a 008864555

[0058] 9 substrate (e.g. as a base), a first layer (comprising a polymer and a reticulated structure) on the substrate, and a layer of organosilane functionalisation on the first layer.

[0059] The term “organosilane” means a group comprising a silicon atom bonded to an organic group. For example, the organic group may be a substituted or unsubstituted, linear, branched, or cyclic alkyl, alkenyl, or alkynyl group, or a substituted or unsubstituted aromatic group. Hence, the term “organosilane” includes alkyl silane, alkenyl silane, alkynyl silane, and aryl silane.

[0060] The term “alkyl” refers to a monovalent saturated aliphatic hydrocarbyl group, which may be substituted or unsubstituted, and linear, branched, or cyclic. The term “alkenyl” refers to a monovalent unsaturated hydrocarbyl group comprising at least one C=C double bond, which may be substituted or unsubstituted, and linear, branched, or cyclic. The term “alkynyl” refers to a monovalent unsaturated hydrocarbyl group comprising at least one C=C triple bond, which may be substituted or unsubstituted, and linear, branched, or cyclic. The term “aryl” refers to a monovalent aromatic carbocyclic group of from 5 to 18 carbon atoms having a single ring (e.g., phenyl) or a fused ring system (e.g., naphthyl, anthryl, indanyl), and may include heteroaryl groups (e.g., pyrrole, pyridine).

[0061] The term “alkyl silane” means a group comprising a silicon atom bonded to a substituted or unsubstituted, branched or unbranched, saturated alkyl group. The alkyl group may also include cyclic aliphatic alkyl groups, such as cyclopropyl, cyclobutyl, cylcopentyl, and cyclohexyl. Alkyl silanes include: methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, propyltrimethoxysilane, propyltriethoxysilane, butyltrimethoxysilane, butyltriethoxysilane, pentyltrimethoxysilane, pentyltriethoxysilane, cyclohexyltrimethoxysilane, cyclohexyltriethoxysilane, cyclohexyltrichlorosilane, hexyltrimethoxysilane, hexyltriethoxysilane, octyltrimethoxysilane, octyltriethoxysilane, dodecyltrimethoxysilane, dodecyltriethoxysilane, hexadecyltrimethoxysilane, octadecyltrimethoxysilane, methyltrichlorosilane, ethyltrichlorosilane, propyltrichlorosilane, butyltrichlorosilane, octyltrichlorosilane, dodecyltrichlorosilane, and octadecyltrichlorosilane.

[0062] The term “alkenyl silane” means a group comprising a silicon atom bonded to a substituted or unsubstituted, branched or unbranched, alkenyl group comprising at least one C=C double bond. The alkenyl group may also include cyclic aliphatic alkenyl groups, such as cyclopropenyl, cyclobutenyl, cylcopentyl, and cyclohexyl. Alkenyl silanes include: vinyltrimethoxysilane, vinyltriethoxysilane, allyltrimethoxysilane, allyltriethoxysilane, vinyltris(methoxyethoxy)silane, and 3-butenyltrimethoxysilane.

[0063] The term “alkynyl silane” means a group comprising a silicon atom bonded to a substituted or unsubstituted, branched or unbranched, alkenyl group comprising at least one C=C triple bond. Alkynyl silanes include: ethynyltrimethylsilane, ethynyltriethoxysilane, propynyltrimethylsilane, trimethylsilylacetylene, and trimethylsilylethynylbenzene.

[0064] The term “aryl silane” means a group comprising a silicon atom bonded to a substituted or unsubstituted, monocyclic or fused, aromatic group. The aryl group may be joined to the silane via a linker, -L2-, which 008864555

[0065] 10 may be defined in the same manner as -L1- below. For example -L2- may be an alkylene group such as methylene, ethylene, propylene, butylene, pentylene or hexylene. The aryl group may also include heteroaryl groups. Aryl silanes include: phenyltrimethoxysilane, phenyltriethoxysilane, phenyltrichlorosilane, diphenyldimethoxysilane, diphenyldichlorosilane, triphenylsilane, trichloro(6- phenylhexyl)silane, and biphenyltriethoxysilane.

[0066] In some embodiments, the organosilane is or comprises an alkyl silane, an alkenyl silane, an alkynyl silane or an aryl silane. In some embodiments, the organosilane is or comprises an alkyl silane, an alkenyl silane, or an aryl silane. In some embodiments, the organosilane is or comprises an alkyl silane or an aryl silane. In some embodiments, the organosilane is or comprises an alkyl silane. In some embodiments, the organosilane is or comprises an aryl silane.

[0067] The organosilane groups (e.g. alkyl silane groups) act as surface functionalisation groups.

[0068] The terms “functionalisation with an organosilane” and “silanization” may be used interchangeably. These terms mean that an organosilane (e.g. alkyl silane) is chemically (e.g. covalently) bonded to the functionalised component. In other words, the functionalised component (i.e. the first layer) is functionalised with a group -L1-SiR3, wherein at least one R group is an organic group (e.g. a substituted or unsubstituted, branched or unbranched, alkyl group), and L1is an optional linker (for example, an alkylene group such as methylene, ethylene or propylene, an ether group such as methyl ether, ethyl ether, or propyl ether, an ester such as methylene ester, ethylene ester or propylene ester, an amide such as methylene amide, ethylene amide, or propylene amide, or an arylene such as a phenylene, naphthylene, or pyridylene). One, two, or all three R groups may be substituted or unsubstituted, branched or unbranched, alkyl groups. In some embodiments, L1is -O-. In some embodiments, the organosilane (e.g. alkyl silane) is joined to the first layer (i.e., the reticulated structure and / or the polymer) via a silyl ether bond (Si-O-C). Additionally, one or two of the R groups may act as an additional linker and form a bond with the first layer, thus improving the robustness of the organosilane functionalisation. It may be that the organic (e.g. alkyl) group is joined to the silane via a heteroatom, such as oxygen (-O-) or sulfur (-S-). For example, the silane may comprise the structure -Si-O-R.

[0069] In some embodiments, the alkyl silane comprises a C1-32 alkyl group. In some embodiments, the alkyl silane comprises an alkyl group selected from: a C2-32 alkyl group, a C2-30 alkyl group, a C6-30 alkyl group, a Ce-26 alkyl group, a Cs-26 alkyl group, a Cs-24 alkyl group, a C10-20 alkyl group, a C12-20 alkyl group, a C14-20 alkyl group, a C16-20 alkyl group, and a Cis alkyl group, any of which may be substituted or unsubstituted, branched or unbranched. In some embodiments, the alkyl silane comprises an alkyl group selected from: a C4 alkyl group, a Ce alkyl group, a Cs alkyl group, a C10 alkyl group, a C12 alkyl group, a C14 alkyl group, a C16 alkyl group, a C18 alkyl group, a C20 alkyl group, a C22 alkyl group, a C24 alkyl group, a C26 alkyl group, a C28 alkyl group, a C30 alkyl group, a C32 alkyl group, and mixtures thereof or ranges of alkyl chain lengths with a lower and upper bound selected from any of the foregoing. In some embodiments, the alkyl silane comprises a C18 alkyl group. In some embodiments, the alkyl group is C2 or longer, C4 or longer, Ce or longer, Cs or longer, C10 or longer, C12 or longer, C14 or longer, C16 or longer, Cis or longer, C20 or 008864555

[0070] 11 longer, C20 or longer, C22 or longer, C24 or longer, C26 or longer, C28 or longer, or C30 or longer. In some embodiments, the alkyl group is C32 or shorter, C30 or shorter, C28 or shorter, C26 or shorter, C24 or shorter, C22 or shorter, C20 or shorter, Cis or shorter, C16 or shorter, C14 or shorter, C12 or shorter, C10 or shorter, Cs or shorter, Ce or shorter, or C4 or shorter. In some embodiments, the alkyl group is selected from: methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl, decyl, undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, and octadecyl. The ratio of hydrophobicity to oleophobicity / lipophobicity may be adjusted by altering the length of alkyl group on the silane. In this way, the degree of amphiphobicity can be tailored for a specific use. For example, a longer alkyl chain may result in a more hydrophobic surface, but it may repel non-polar liquids (e.g. hydrocarbons) to a lesser degree, or even not at all. In the case of an alkenyl silane, the alkenyl group may be any of the carbon lengths described above with respect to the alkyl group of an alkyl silane. In the case of an alkynyl silane, the alkynyl group may be any of the carbon lengths described above with respect to the alkyl group of an alkyl silane. In the case of an aryl silane, the aryl group may be monocyclic or tricyclic, and may include heteroaryl groups. For example, the aryl group may comprise a C5-18 aryl group, such as a C5-14 aryl, a C5- 10 aryl, a C5-8 aryl, a C5-6 aryl, a C5 aryl, or a Ce aryl, such as a Ce aryl. For example, the aryl group may be selected from: phenyl, benzyl, tolyl, xylyl, naphthyl, biphenyl, phenanthryl, anthracenyl, pyridyl, pyrimidinyl, furyl, thiophenyl, imidazolyl, triazolyl, pyrazolyl, indolyl, and quinolinyl.

[0071] In some embodiments, the organic (e.g. alkyl) group on the organosilane (e.g. alkyl silane) is not functionalised or substituted. In some embodiments, the organic (e.g. alkyl) group on the organosilane (e.g. alkyl silane) does not contain an amino group. In some embodiments, the organic (e.g. alkyl) group on the organosilane (e.g. alkyl silane) is aliphatic and saturated.

[0072] In some embodiments, the alkyl group on the alkyl silane is substituted with a functional group. In some embodiments, the alkyl group on the alkyl silane is substituted with a functional group selected from: hydroxyl, thiol, carboxyl, amino, nitro, amide, halo (e.g., fluoro, chloro, iodo), alkoxy (e.g., methoxy, ethoxy, propoxy), phenyl, and oxo. In some embodiments, the alkyl group on the alkyl silane is substituted with a functional group selected from: hydroxyl, carboxyl, halo (e.g., fluoro, chloro, iodo), alkoxy (e.g., methoxy, ethoxy, propoxy), phenyl, and oxo. In some embodiments, the alkyl group on the alkyl silane is substituted with a functional group selected from: hydroxyl, thiol, carboxyl, halo (e.g., fluoro, chloro, iodo), and oxo. In such functionalised alkyl silanes, the functional group may, in some embodiments, enhance or provide hydrophobicity, and / or oleophobicity, and / or amphiphobicity. In some embodiments, one or more carbon atoms (i.e. in the form of a methylene group) in the alkyl group is replaced with a heteroatom, such as O or S. For example, one carbon atom may be replaced with O, two carbon atoms may be replaced with O, or one carbon atom may be replaced with S.

[0073] In some embodiments, the organosilane (e.g. alkyl silane) is functionalised with a group to improve hydrophobicity of the surface coating. In some embodiments, the organosilane (e.g. alkyl silane) is functionalised with a hydrophobic functional group. In some embodiments, the organosilane (e.g. alkyl silane) is functionalised with a non-polar functional group. 008864555

[0074] 12

[0075] In some embodiments, the organosilane (e.g. alkyl silane) is fluorine-free. In some embodiments, the organosilane (e.g. alkyl silane) is not functionalised with a fluorine group.

[0076] In some embodiments, the reticulated structure is silanized. In some embodiments, only the reticulated structure is silanized. In some embodiments, the polymer is not silanized. In some embodiments, the reticulated structure acts as nucleation point for silanization.

[0077] In some embodiments, the polymer is silanized. In some embodiments, only the polymer is silanized. In some embodiments, the reticulated structure is not silanized.

[0078] When the reticulated structure is silanized, an organosilane group is covalently bonded to an organic group in the reticulated structure, such as an organic linker or ligation group in a MOF or COF. When the polymer is silanized, an organosilane is covalently bonded to a main chain of the polymer or to a side / pendant group of the polymer.

[0079] In some embodiments, a portion of the reticulated structure is not fully embedded within the polymer matrix, i.e. a portion of the reticulated structure is at least partially exposed with respect to the polymer. In some embodiments, said portion of the reticulated structure is silanized. In some embodiments, said portion of the reticulated structure is silanized, and the remaining portion not exposed with respect to the polymer is not silanized.

[0080] In some embodiments, the functionalisation with an organosilane results in an organosilane layer (e.g. an alkyl silane layer) of the surface coating. In some embodiments, the organosilane layer (e.g. alkyl silane layer) is substantially a monolayer of organosilane groups (e.g. alkyl silane groups) bonded to the first layer. In some embodiments, the organosilane layer is hydrophobic.

[0081] By functionalising the first layer of the surface coating with an organosilane, such as an alkyl silane, it is possible to obtain a surface coating having low surface roughness and improved flexibility. In turn, this allows for improved transparency and liquid repellence. Without wishing to be bound by theory, it is believed that the organic silane groups form a liquid-like upper layer of the surface coating. This reduces the effective contact area (e.g. the solid-liquid contact area), thus minimising contact points, reducing interfacial friction, and improving slipperiness of the coating. This helps the coating to be one or more of hydrophobic, oleophobic, amphiphobic, and icephobic.

[0082] Functionalisation I silanization may be achieved using a halosilane or an alkoxy silane, for example in which a halo group or alkoxy group on the silane is replaced with a group on surface being functionalised. In some embodiments, the halosilane is a chlorosilane. In some embodiments, the halosilane is a dichlorosilane or a trichlorosilane. In some embodiments, the halosilane is a trichlorosilane. In some embodiments, the halosilane is trichloro octadecyl silane (OTS). In some embodiments, the alkoxy silane is a methoxysilane. In some embodiments, the alkoxy silane is a dimethoxysilane or a trimethoxysilane. In some embodiments, the trimethoxysilane. For example, a chlorosilane or methoxysilane may react with a 008864555

[0083] 13 hydroxyl group on the reticulated structure or polymer to form a silyl ether linkage. When a dichlorosilane, a trichlorosilane, a dimethoxysilane, or a trimethoxysilane is used, the silane may form two or three covalent bonds with the surface being functionalised, which provides a strong connection between the organosilane layer and the first layer of the surface coating, thus improving robustness of the coating.

[0084] Amphiphobicity

[0085] The surface coatings of the present invention are capable of exhibiting amphiphobicity, hydrophobicity or lipophobicity, depending on how they are formulated. “Amphiphobicity” is the ability to display both hydrophobic and oleophobic properties. It may be that amphiphobic surface coatings of the present invention repel both aqueous liquids and low surface tension solvents. Low surface tension solvents include, for example butanone, ethanol, methanol, acetone, 1 -butanol, 1 -decanol, glycol, cyclohexanol and 1 ,2-butanediol, and vegetable oil. For example, in addition to being hydrophobic, the surface coatings of the present invention may be repellent to liquids having a surface tension of 100 mN / m or less, 75 mN / m or less, 60 mN / m or less, 50 mN / m or less, 45 mN / m or less, 40 mN / m or less, 35 mN / m or less, 30 mN / m or less, or 25 mN / m or less.

[0086] In some embodiments, the surface coating is amphiphobic.

[0087] Hydrophobicity and hydrophilicity may be assessed by measuring water drop contact angle. For example, it may be that a hydrophobic surface has a water drop contact angle of > 90°, > 95°, > 100°, > 105°, or > 1 10°. For example, it may be that a hydrophilic surface has a water drop contact angle of < 90°, < 85°, < 80°, < 75°, or < 70°. The water drop contact angle hysteresis is a measure of slipperiness of the surface coating, and is calculated from the advancing (0Adv) and receding (0Rec) contact angles of a water drop, for example using computer software and video recordings in ways which are well known to the skilled reader. It may be that the contact angle hysteresis of the present coatings is < 15°, < 12.5°, < 10°, < 7.5°, or < 5°. The slipperiness of the surface coatings may also be characterized by inclination angle that causes slippage. It may be that the inclination angle to cause water droplet slippage for the present coatings is < 20°, < 15°, < 10°, or < 5°.

[0088] In some embodiments, the surface coating has a contact angle (0Adv) with water of > 90°, > 95°, > 100°, > 105°, or > 1 10°. In some embodiments, the surface coating has a contact angle (0Adv) with ethylene glycol of > 60°, > 65°, > 75°, > 80°, > 85°, or > 90°. In some embodiments, the surface coating has a contact angle (0Adv) with diiodomethane of > 40°, > 45°, > 50°, > 55°, > 60°, or > 65°. In some embodiments, the surface coating has a contact angle (0Adv) with cyclohexanol of > 30°, > 35°, > 40°, > 45°, > 50°, or > 55°. In some embodiments, the surface coating has a contact angle (0Adv) with decanol of > 25°, > 30°, > 35°, > 40°, > 45°, or > 50°. In some embodiments, the surface coating has a contact angle (0Adv) with butanol of > 30°, > 35°, > 40°, > 45°, > 50°, or > 55°.

[0089] In some embodiments, a droplet of water on the surface coating has a contact angle hysteresis (A0) of < 40°, < 30°, < 25°, < 20°, < 18°, < 15°, < 12°, < 10°, or < 8°. In some embodiments, a droplet of ethylene 008864555

[0090] 14 glycol on the surface coating has a contact angle hysteresis (A0) of < 40°, < 30°, < 25°, < 20°, < 18°, < 15°, or < 12°. In some embodiments, a droplet of diiodomethane on the surface coating has a contact angle hysteresis (A0) of < 40°, < 30°, < 25°, < 20°, < 18°, or < 15°. In some embodiments, a droplet of cyclohexanol on the surface coating has a contact angle hysteresis (A0) of < 40°, < 30°, < 25°, < 20°, < 18°, < 15°, or < 12°. In some embodiments, a droplet of decanol on the surface coating has a contact angle hysteresis (A0) of < 40°, < 30°, < 25°, < 20°, < 18°, or < 15°. In some embodiments, a droplet of butanol on the surface coating has a contact angle hysteresis (A0) of < 40°, < 30°, < 25°, < 20°, < 18°, or

[0091] < 15°.

[0092] In some embodiments, the sliding angle for a droplet of water on the surface coating is < 40°, < 30°, < 25°, < 20°, < 18°, < 15°, < 12°, < 10°, < 8°, or < 5°. In some embodiments, the sliding angle for a droplet of ethylene glycol on the surface coating is < 40°, < 30°, < 25°, < 20°, < 18°, < 15°, < 12°, < 10°, or < 8°. In some embodiments, the sliding angle for a droplet of glycerol on the surface coating is < 40°, < 30°, < 25°,

[0093] < 20°, < 18°, < 15°, < 12°, < 10°, or < 8°. In some embodiments, the sliding angle for a droplet of butanol on the surface coating is < 40°, < 30°, < 25°, < 20°, < 18°, < 15°, < 12°, < 10°, or < 8°. The sliding angle is the angle at which the droplet begins to slide when the surface is tilted (relative to being completely flat).

[0094] The amphiphobicity of the surface coating may be a result of the surface roughness awarded by the incorporation of a reticulated structure into the polymer, resulting in a nano-hierarchical structure. The amphiphobicity of the surface coating may also be a result of functionalising the surface coating with organosilanes which reduce the effective contact area of a liquid on the surface.

[0095] The amphiphobicity of the surface coating may provide self-cleaning properties of the surface coating. In some embodiments, the surface coating has self-cleaning properties. In some embodiments, the surface coating is a self-cleaning coating.

[0096] Polymer

[0097] The polymer is selected such that a portion of the polymer molecules are able to at least partially penetrate into the pores of reticulated structure. That is to say, the polymer has a portion of polymer molecules which have at least a section which is capable of at least partially fitting within a pore of the reticulated structure. Preferably, the polymer is selected such that said section of said portion comprises one or more functional groups capable of forming intermolecular interactions with the interior of a pore of the reticulated structure.

[0098] For the avoidance of doubt, the portion of polymer molecules may be all of the polymer molecules.

[0099] The exact combination of features of the polymer which make it suitable for penetrating the pores of the reticulated structure will depend on the nature of the reticulated structure (e.g., pore size, functional groups present). Therefore, it is envisaged that a range of polymer types will be suitable for a range of reticulated structures. For example, if the reticulated structure comprises polar functional groups (e.g. 008864555

[0100] 15 hydroxyl, carboxyl, amide, carbonyl, nitro, amino) within its pores, the polymer may be selected to contain polar functional groups (e.g. hydroxyl, carboxyl, amide, carbonyl, nitro, amino) which may form hydrogen bonds or dipole-dipole interactions within the pores. Additionally or alternatively, if the reticulated structure comprises non-polar functional groups (e.g. alkyl groups) and / or aromatic groups (e.g. phenyl groups) within its pores, the polymer may be selected to contain non-polar functional groups (e.g. alkyl groups) and / or aromatic groups (e.g. phenyl groups) which may form Van der Waals or London Dispersion forces within the pores.

[0101] In some embodiments, the polymer comprises a repeating polar group. In some embodiments, the polymer comprises a repeating non-polar group. In some embodiments, the polymer comprises a repeating aromatic group. In some embodiments, the polymer comprises a repeating polar group and a repeating non-polar group. In some embodiments, the polymer comprises a repeating polar group and a repeating aromatic group. In some embodiments, the repeating polar group is or comprises an amino, a hydroxyl, a carbonyl, an amide, a carboxyl, a nitro, or a phosphate group. In some embodiments, the repeating aromatic group is or comprises a substituted or unsubstituted pyrrole, furan, thiophene, imidazole, pyrazole, oxazole, thiazole, benzene, pyridine, pyrazine, pyrimidine, pyridazine, (1 ,2,3)- triazine, (1 ,2,4)-triazine, (1 ,3,5)-triazine, indole, benzofuran, isobenzofuran, benzothiophene, purine, benzimidazole, indazole, benzoxazole, benzisoxazole, benzothiazole, naphthalene, anthracene, quinoline, isoquinoline, quinoxaline, quinazoline, acridine, phenazine, cinnoline, or phthalazine. In some embodiments, the repeating aromatic group is or comprises a substituted or unsubstituted pyrrole, furan, thiophene, imidazole, pyrazole, oxazole, thiazole, benzene, pyridine, pyrazine, pyrimidine, pyridazine, (1 ,2,3)-triazine, (1 ,2,4)-triazine, or (1 ,3,5)-triazine. When a polymer is said to include a repeating group, it may be that said group is included in one or more repeating units of the polymer.

[0102] In some embodiments, the polymer comprises a repeating polar group which is a hydroxyl group. In some embodiments, the polymer comprises a repeating polar group which is a carbonyl group. In some embodiments, the polymer comprises a hydrogen bond donor (e.g. hydroxyl). In some embodiments, the polymer comprises a hydrogen bond acceptor (e.g. carbonyl). In this way, the polymer is able to form strong hydrogen bonds with the reticulated structure.

[0103] In some embodiments, the polymer comprises a repeating group which is capable of coordinating a transition metal ion. In some embodiments, the polymer comprises a coordination group / ligand for coordinating a metal ion. Such groups may have a lone pair of electrons for forming a coordination bond. Examples of such groups include: amines (-NH2, -NR2), carboxylates (-COO-), phosphines (-PR3), pyridines and other nitrogen heterocycles, thiols (-SH), olefins (C=C), carbonyls (-C=O), and enolates (- C-O“). In this way, when the reticulate structure is a MOF, the polymer may be able to coordinate metal centres of the MOF to enhance the interfacial interaction between the polymer and the MOF.

[0104] In some embodiments, the polymer comprises one or more groups which reacts with a silane. In some embodiments, the one or more groups which react with a silane are selected from: hydroxyl, amine, amide, carbonyl, carboxyl, thiol, isocyanate, alkene (-C=C-), alkyne (-0=0-), epoxide, and phenol. In 008864555

[0105] 16 some embodiments, the one or more groups which react with a silane includes a hydroxyl group. Such groups may form part of the backbone of the polymer (e.g. part of the repeating unit), and / orthey may form pendant groups. The polymer may be synthesised / provided with such groups, or the groups may be added via post-synthetic functionalisation. When it is said that the polymer comprises a group which reacts with a silane, it is to be interpreted that said group is present in the polymer prior to functionalisation with the organosilane. Following functionalisation with the organosilane, some or none of said group may remain in the polymer within the surface coating.

[0106] In some embodiments, the polymer is fluorine-free. In some embodiments, the polymer is not functionalised with a fluorine. In some embodiments, the repeating unit of the polymer does not comprise a fluorine group. In some embodiments, the polymer does not comprise a per- or poly-fluorinated group.

[0107] The polymer may be a homopolymer or a copolymer. The polymer may comprise a mixture of two or more types of polymer. When the polymer is a copolymer, it may be a random copolymer, an alternating copolymer, a block copolymer, or a graft copolymer, for example an alternating copolymer.

[0108] The polymer molecules of the polymer may be of substantially the same size (e.g. molecular weight, chain length), i.e. the polymer molecules may have a monodisperse size distribution, or the polymer molecules may be different sizes (e.g., a bimodal or multimodal size distribution).

[0109] Molecular weight of the polymer may be measured using gel permeation chromatography (GPC), such as using a polystyrene standard having a dispersity of less 1 .2. For example, the molecular weight may be measured using size-exclusion chromatography, such as outlined in ISO 16014-2:2019.

[0110] The polymer may have a number-average molecular weight of 500 g / mol or more, 1000 g / mol or more, 2500 g / mol or more, 5000 g / mol or more, 7500 g / mol or more, 10,000 g / mol or more, 15,000 g / mol or more, 20,000 g / mol or more, 25,000 g / mol or more, 30,000 g / mol or more, 40,000 g / mol or more, 50,000 g / mol or more, 60,000 g / mol or more, 70,000 g / mol or more, 75,000 g / mol or more, 80,000 g / mol or more, 90,000 g / mol or more, 100,000 g / mol or more, 125,000 g / mol or more, 150,000 g / mol or more, 175,000 g / mol or more, or 200,000 g / mol or more. The polymer may have a number-average molecular weight of 200,000 g / mol or less, 175,000 g / mol or less, 150,000 g / mol or less, 125,000 g / mol or less, 100,000 g / mol or less, 90,000 g / mol or less, 80,000 g / mol or less, 75,000 g / mol or less, 70,000 g / mol or less, 60,000 g / mol or less, 50,000 g / mol or less, 40,000 g / mol or less, 30,000 g / mol or less, 25,000 g / mol or less, 20,000 g / mol or less, 15,000 g / mol or less, 10,000 g / mol or less, 7500 g / mol or less, 5000 g / mol or less, 2500 g / mol or less, or 1000 g / mol or less.

[0111] The polymer may have a weight-average molecular weight of 500 g / mol or more, 1000 g / mol or more, 2500 g / mol or more, 5000 g / mol or more, 7500 g / mol or more, 10,000 g / mol or more, 15,000 g / mol or more, 20,000 g / mol or more, 25,000 g / mol or more, 30,000 g / mol or more, 40,000 g / mol or more, 50,000 g / mol or more, 60,000 g / mol or more, 70,000 g / mol or more, 75,000 g / mol or more, 80,000 g / mol or more, 90,000 g / mol or more, 100,000 g / mol or more, 125,000 g / mol or more, 150,000 g / mol or more, 175,000 008864555

[0112] 17 g / mol or more, 200,000 g / mol or more, 300,000 g / mol or more, or 400,000 g / mol or more. The polymer may have a weight-average molecular weight of 400,000 g / mol or less, 300,000 g / mol or less, 200,000 g / mol or less, 175,000 g / mol or less, 150,000 g / mol or less, 125,000 g / mol or less, 100,000 g / mol or less, 90,000 g / mol or less, 80,000 g / mol or less, 75,000 g / mol or less, 70,000 g / mol or less, 60,000 g / mol or less, 50,000 g / mol or less, 40,000 g / mol or less, 30,000 g / mol or less, 25,000 g / mol or less, 20,000 g / mol or less, 15,000 g / mol or less, 10,000 g / mol or less, 7500 g / mol or less, 5000 g / mol or less, 2500 g / mol or less, or 1000 g / mol or less.

[0113] The polymer may have a number-average chain length (i.e., number of repeating units) of 10 or more, 20 or more, 25 or more, 30 or more, 40 or more, 50 or more, 75 or more, 100 or more, 150 or more, 200 or more, 250 or more, 300 or more, 400 or more, 500 or more, 600 or more, 700 or more, 800 or more, 900 or more, 1000 or more, 1250 or more, 1500 or more, 1750 or more, 2000 or more, 2500 or more, 3000 or more, 4000 or more, 5000 or more, 7500 or more, 10,000 or more, 12,500 or more, 15,000 or more, or 17,500 or more. The polymer may have a number-average chain length (i.e., number of repeating units) of 20,000 or less, 17,500 or less, 15,000 or less, 12,500 or less, 10,000 or less, 7500 or less, 5000 or less, 4000 or less, 3000 or less, 2500 or less, 2000 or less, 1750 or less, 1500 or less, 1250 or less, 1000 or less, 900 or less, 800 or less, 700 or less, 600 or less, 500 or less, 400 or less, 300 or less, 250 or less, 200 or less, 150 or less, 100 or less, 75 or less, 50 or less, 40 or less, 30 or less, or 25 or less.

[0114] The polymer may have a weight-average chain length (i.e., number of repeating units) of 10 or more, 20 or more, 25 or more, 30 or more, 40 or more, 50 or more, 75 or more, 100 or more, 150 or more, 200 or more, 250 or more, 300 or more, 400 or more, 500 or more, 600 or more, 700 or more, 800 or more, 900 or more, 1000 or more, 1250 or more, 1500 or more, 1750 or more, 2000 or more, 2500 or more, 3000 or more, 4000 or more, 5000 or more, 7500 or more, 10,000 or more, 12,500 or more, 15,000 or more, or 17,500 or more. The polymer may have a weight-average chain length (i.e., number of repeating units) of 20,000 or less, 17,500 or less, 15,000 or less, 12,500 or less, 10,000 or less, 7500 or less, 5000 or less, 4000 or less, 3000 or less, 2500 or less, 2000 or less, 1750 or less, 1500 or less, 1250 or less, 1000 or less, 900 or less, 800 or less, 700 or less, 600 or less, 500 or less, 400 or less, 300 or less, 250 or less, 200 or less, 150 or less, 100 or less, 75 or less, 50 or less, 40 or less, 30 or less, or 25 or less.

[0115] In some embodiments, the polymer is selected from the group consisting of: polyurethane, polyester, polyether, polyacrylate, alkyd, vinyl polymer, polyimide, polysulfone, polyaniline, polycarbonate, polysulfide, polyphenylene, and polyamide, mixtures thereof and copolymers thereof. In some embodiments, the polymer is selected from the group consisting of polyurethane, polyester, polyether, polyacrylate, nylon, copolymers thereof and mixtures thereof.

[0116] In some embodiments, the polymer is selected from the group consisting of: polyester polyurethane, polyethylene oxide (PEO), polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polypropylene glycol (PPG), polyethylene glycol (PEG), polymethyl methacrylate (PMMA), polyethyl acrylate (PEA), Nylon 6, Nylon 6,6, polyvinyl alcohol (PVA), polystyrene (PS), Kapton, polysulfone (PSU), polyether sulfone (PESU), polyphenylene sulfone (PPSU), polyaniline (PANI), polylactic acid (PLA), 008864555

[0117] 18 polycarbonate (PC), polyphenylene sulfide (PPS), and polyphenylene oxide (PPO), copolymers thereof and mixtures thereof.

[0118] In some embodiments, the polymer is a polyether selected from the group consisting of: epoxy resin, polyethylene glycol (PEG), polypropylene glycol (PPG), polytetramethylene ether glycol (PTMEG), polyether ether ketone (PEEK), polyvinyl ether (PVE), and polyethylene oxide) (PEG).

[0119] In some embodiments, the polymer is a polyacrylate selected from the group consisting of: polymethyl methacrylate (PMMA), polyethyl acrylate (PEA), polybutyl acrylate (PBA), polyhydroxyethyl methacrylate (PHEMA), polyacrylic acid (PAA), sodium polyacrylate, poly(2-ethylhexyl acrylate), poly(isobutyl methacrylate), copolymers thereof and mixtures thereof.

[0120] In some embodiments, the polymer is a polyester selected from the group consisting of: polyethylene terephthalate (PET), polybutylene terephthalate (PBT), polytrimethylene terephthalate (PTT), polylactic acid (PLA), polycarbonate (PC), glyptal, unsaturated polyester resins (UPR), polycaprolactone (PCL), polyethylene naphthalate (PEN), liquid crystal polymers (LCP), copolymers thereof and mixtures thereof.

[0121] In some embodiments, the polymer is an aromatic polyamide (e.g. an aramid).

[0122] In some embodiments, the polymer is a polyurethane (PU). PU refers to a class of polymers composed of organic units joined by carbamate (urethane) links. A polyurethane is typically produced by reacting a polymeric isocyanate with a polyol. Since a polyurethane contains two types of monomers, which polymerize one after the other, they may be classed as alternating copolymers. Both the isocyanates and polyols used to make a polyurethane contain two or more functional groups per molecule. In some embodiments, the isocyanate used to form the PU may be a methylene diphenyl diisocyanate (MDI) or a toluene diisocyanate (TDI).

[0123] In some embodiments, the polymer is a polyester polyurethane. In other words, in some embodiments, the polymer is a polyester-based polyurethane. A polyester polyurethane is a polymer having polyester groups and polyurethane groups in its backbone. In other words, it is a copolymer of polyester and polyurethane. In some embodiments, the polyester polyurethane is an alternating copolymer. In some embodiments, the polyester polyurethane is a random copolymer.

[0124] In some embodiments, the polymer is commercial product Bayhydrol® UH 240, supplied by Covestro AG, which is a polyester polyurethane.

[0125] By using PU as the polymer, strong interactions between the polymer and substrate can be achieved, such as intermolecular interactions (e.g., H-bonding between the amide groups and polar groups on the substrate (e.g. hydroxyl groups), and Van der Waals forces from the benzene rings in PU). Additionally, the use of PU allows for weather-resistant or weather-proof surface coatings due to its exceptional durability, abrasion resistance, and chemical resistance. Additionally, PU displays UV resistant properties, 008864555

[0126] 19 which makes it suitable for coatings which are exposed to sunlight - such a coating is resistant to degradation in the sunlight, and may also act as a UV-protective barrier to the substrate.

[0127] In some embodiments, the polymer used to form the first layer is a waterborne polymer. By waterborne polymer, it is intended to mean a polymer which is dispersed or solvated in water, for example in the absence of an organic solvent.

[0128] In some embodiments, the PU used to form the first layer is a waterborne PU (WPU). In other words, in some embodiments, the PU used to form the first layer, prior to curing / drying, is solvated or dispersed in water or an aqueous solution. However, once the WPU layer has been cured / dried, the resulting polymer is water-resistant (i.e., it does not readily dissolve or degrade in water). Water-borne polyurethanes are binary colloid water-soluble polymers that are obtained by introducing hydrophilic groups (carboxylate, sulfonate, quaternary ammonium salt, or hydrophilic segments) into polyurethane molecular chains in order to provide it with a hydrophilic property. In this way, a more environmentally friendly manufacturing process can be used as compared to a scenario requiring organic solvents.

[0129] Reticulated Structure

[0130] In some embodiments, the reticulated structure comprises a group which reacts with a silane, such as a hydroxyl (-OH), an amine (-NH2), a carboxyl (-COOH), a thiol (-SH), an isocyanate (-N=C=O), an unsaturated carbon-carbon bond (e.g. C=C or CEC), or a halide (-CI, -Br, -I). In some embodiments, the group which reacts with a silane is a hydroxyl. For example, the group may be present in an organic linker of a MOF or COF. When it is said that the reticulated structure comprises a group which reacts with a silane, it is to be interpreted that said group is present in the reticulated structure prior to functionalisation with the organosilane. Following functionalisation with the organosilane, some or none of said group may remain in the reticulated structure within the surface coating.

[0131] In some embodiments, the pore apertures of the reticulated structure have a diameter within the range of 1 to 20 A.

[0132] It may be that the reticulated structure is microporous. As is commonly understood in the field, a microporous material has pores with dimensions below 2nm. The microporosity of the reticulated structure (i.e. having pores with apertures within the range of 1 to 20 A) creates high capillary forces, which contribute to penetration of the polymer molecules within the pores of the reticulated structure.

[0133] The capillary pressure of the pores of the reticulated structure can be calculated using the following equation:

[0134] Pc= 4YLGcosdAdv / D where D is the average capillary diameter, yLGis the surface energy at liquid-gas interface, and 0Advis the advancing contact angle of water on a smooth reticulated structure surface. 008864555

[0135] 20

[0136] In some embodiments, the pores of the reticulated structure have an average (e.g. mean) capillary pressure of at least 5 MPa, at least 10 MPa, at least 20 MPa, at least 25 MPa, at least 30 MPa, at least 40 MPa, at least 50 MPa, at least 60 MPa, at least 70 MPa, at least 75 MPa, at least 80 MPa, at least 90 MPa, at least 100 MPa, at least 110 MPa, at least 125 MPa, at least 150 MPa, at least 175 MPa, at least 180 MPa, or at least 200 MPa.

[0137] When the pores of the reticulated structure have a capillary pressure greater than the hammer pressure of an impacting liquid (e.g. water, such as in the form of raindrops), the impacting liquid is not able to, or is only slightly able to, displace the polymer molecules held within the pores. Hammer pressure of an impacting stream of water may be calculated using the following equation:

[0138] Ph= k pCv where C is the sound velocity in water (i.e., C = 1497 m / s), p is the density of water, v is the velocity of the impacting water, and k is experimental constant, often approximated as 0.2. The skilled person is aware of how to calculate the hammer velocity of other impacting liquids.

[0139] The high capillary forces created by the microporosity of the reticulated structure act together with the matching of the polymer molecules chain diameter and the pore aperture diameter to insert the polymer molecules within the pores of the reticulated structure synergistically to improve penetration of the polymer molecules within the pores and to increase the robustness of the surface coating.

[0140] The high capillary forces created by the microporosity of the reticulated structure acts together with the functional group of the reticulated structure and / or the functional group of the polymer molecules synergistically to improve penetration of the polymer molecules within the pores of the reticulated structure and to increase the robustness of the surface coating.

[0141] In some embodiments, the reticulated structure comprises a functional group that is complementary to the polymer molecules.

[0142] In some embodiments, the reticulated structure does not comprise a functional group, i.e. is not functionalised. In some embodiments, the reticulated structure is not functionalised post-synthesis.

[0143] In some embodiments, the functional group of the reticulated structure is aprotic.

[0144] In some embodiments, the polymer molecules comprise a functional group that is complementary to the reticulated structure.

[0145] In some embodiments, the functional group of the polymer molecules is aprotic.

[0146] It may be that the reticulated structure comprises a functional group that is complementary to, and interacts with, a functional group on the polymer molecules. 008864555

[0147] 21

[0148] In some embodiments, the reticulated structure is a metal-organic framework having pores.

[0149] The reticulated structure may comprise a functional group that is complementary to the polymer molecules. It may be that this functional group is a post-synthetic functionalisation or modification, that is added to the reticulated structure after it has been formed. For example, in the case of the reticulated structure being a MOF, it may be that the MOF is prepared, and the functional group is added to a reactive group of a linker therein. Alternatively, it may be that the functional group of the reticulated structure is an intrinsic part of the reticulated structure, for example it forms part of the organic linker used to link nodes during synthesis in the case of the reticulated structure being a MOF or COF.

[0150] It may be that the functional group of the reticulated structure stabilises the polymer molecules in the pores of the reticulated structure, holding and retaining the polymer molecules in the pores. It may be that the functional group of the reticulated structure and the polymer molecules form chemical or physiochemical bonds with one another. It may be that such bonds are stronger than the bonds created between polymer molecules and reticulated structure in the absence of the functional group of the reticulated structure. For example, the complementary nature of the functional group of the reticulated structure and the polymer molecules may result in one or more of dipole-dipole interactions, the Debye force and Van der Waals interactions which act to hold the polymer molecules within the pores of the reticulated structure.

[0151] The polymer molecules may comprise a functional group. It may be that the functional group of the polymer molecules is a post-synthetic functionalisation or modification, that is added to the polymer molecular structure after it has been formed or acquired. For example, the functional group of the polymer molecules may be directly bonded to the main chain or backbone of the polymer molecule, or may be indirectly bonded to the main chain or backbone. Alternatively, it may be that the functional group of the polymer molecules is an intrinsic part of the polymer chain, for example it forms part of the monomer from which the polymer is formed.

[0152] It may be that the functional group of the polymer molecules stabilises the polymer molecules in the pores of the reticulated structure, holding and retaining the polymer molecules in the pores. It may be that the functional group of the polymer molecules and the reticulated structure form chemical or physiochemical bonds with one another. It may be that such bonds are stronger than the bonds created between polymer molecules and reticulated structure in the absence of the functional group of the polymer molecules. For example, the complementary nature of the functional group of the polymer molecules and the reticulated structure may result in one or more of dipole-dipole interactions, the Debye force and Van der Waals interactions which act to hold the polymer molecules within the pores of the reticulated structure

[0153] It may be that both a functional group on the reticulated structure and a functional group on the polymer molecules are present in the surface coating of the present invention. The functional group of the reticulated structure and the functional group of the polymer molecules in such a case are complementary and stabilise, possibly to a greater extent than when only including one of the functional groups on either 008864555

[0154] 22 the reticulated structure or polymer molecules, the polymer molecules in the pores of the reticulated structure, holding and retaining the polymer molecules in the pores. It may be that the functional groups on the reticulated structure and the polymer molecules form chemical or physiochemical bonds with one another. For example, the complementary nature of the functional groups on the reticulated structure and the polymer molecules may result in one or more of dipole-dipole interactions, the Debye force and Van der Waals interactions which act to hold the polymer molecules within the pores of the reticulated structure. The functional group on the reticulated structure and the functional group on the polymer molecules may be the same or different.

[0155] It may be that the functional group of the reticulated structure is an aprotic group. Independently, it may be that the functional group of the polymer molecules is an aprotic group. If both present, it may be that both the functional group of the reticulated structure and the functional group of the polymer molecules are aprotic groups.

[0156] Examples of aprotic groups include halogen atoms, halogen containing groups (e.g. haloalkyl), alkyl groups, alkenyl groups, alkynyl groups, alkoxy, aminoalkyl, aryl, aralkyl and heteroaryl groups. It may be that the functional group of the reticulated structure is or comprises alkyl, ethyl, propyl or butyl. It may be that the functional group of the reticulated structure is or comprises a fluorine, chlorine or bromine. It may be that the functional group of the polymer molecules is or comprises alkyl, ethyl, propyl or butyl. It may be that the functional group of the polymer molecules is or comprises a fluorine, chlorine or bromine. If both present, it may be that both of the functional groups of the reticulated structure and polymer molecules independently are or comprise fluorine, chlorine or bromine. If both present, it may be that both of the functional groups of the reticulated structure and polymer molecules independently are or comprise methyl, ethyl, propyl or butyl.

[0157] It may be that the functional group of the reticulated structure is a substantially non-polar or weakly polar group. Independently, it may be that the functional group of the polymer molecules is a substantially nonpolar, or weakly polar group. If both present, it may be that both of the functional groups of the reticulated structure and the polymer molecules are non-polar or weakly polar groups.

[0158] It may be that the functional group of the reticulated structure is a polar group. Independently, it may be that the functional group of the polymer molecules is a polar group. If both present, it may be that both of the functional groups of the reticulated structure or the polymer molecules are polar groups.

[0159] It may be that the functional group of the reticulated structure is a protic group. Independently, it may be that the functional group of the polymer molecules is a protic group. If both present, it may be that both of the functional groups of the reticulated structure and the polymer molecules are protic groups. Examples of protic groups include hydroxyl, alkyl hydroxyl, amine, and alkyl amine.

[0160] If both present, the functional group of the reticulated structure and the functional group of the polymer molecules may be complementary and may be formed from any complementary combination of the 008864555

[0161] 23 aprotic, weakly polar, polar, or protic groups described above. For example, the functional group of the reticulated structure may be alkyl, and the functional group of the polymer molecules may be fluorine. It may be that reticulated structure comprises no protic groups. It may be that the polymer molecules comprise no protic groups.

[0162] In some embodiments, the reticulated comprises a polar group. In some embodiments, the repeating polar group is or comprises an amino, a hydroxyl, a carbonyl, an amide, a carboxyl, a nitro, or a phosphate group. In some embodiments, the polar group is a hydroxyl group. In some embodiments, the polymer comprises a repeating polar group which is a carbonyl group. In some embodiments, the polymer comprises a hydrogen bond donor (e.g. hydroxyl). In some embodiments, the polymer comprises a hydrogen bond acceptor (e.g. carbonyl).

[0163] When both present, the complementary nature of the functional group of the reticulated structure and the functional group of the polymer molecules, act together to hold the polymer molecules within the pores of the reticulated structure more strongly to increase the robustness of the surface coating, and the longevity of the low-friction properties it exhibits.

[0164] In some embodiments, the reticulated structure is fluorine-free. In some embodiments, the reticulated structure is not functionalised with a fluorine. In some embodiments, the linking / ligating unit of the reticulated structure does not comprise a fluorine group. In some embodiments, the reticulated structure does not comprise a per- or poly-fluorinated group.

[0165] In some embodiments, the reticulated structure is particulate, for example micro- or nano-particulate. In some embodiments, the reticulated structure is crystalline. In some embodiments, the reticulated structure is crystalline and comprises defects within the pores. In this way, it is thought that defects within the pores may provide additional locations where a penetrating polymer molecule can form an intermolecular interaction. For example, defects within UiO-66 pores may result in an increased number of exposed Zr-OH groups which are able to form hydrogen bonds with a penetrating polymer.

[0166] The size of the particles of the reticulated structure may be selected to tailor desired properties of the first layer, such as surface roughness, uniformity of distribution, degree of polymer penetration, degree of interfacial interaction between the polymer and the reticulated structure, or influence of the properties of the reticulated structure on the properties of the resulting layer.

[0167] In some embodiments, the reticulated structure comprises or consists of particles having a numberaverage mean particle size of at least 1 nm, at least 5 nm, at least 10 nm, at least 20 nm, at least 25 nm, at least 30 nm, at least 40 nm, at least 50 nm, at least 60 nm, at least 70 nm, at least 75 nm, at least 80 nm, at least 90 nm, at least 100 nm, at least 125 nm, at least 150 nm, at least 175 nm, at least 200 nm, at least 225 nm, at least 250 nm, at least 275 nm, at least 300 nm, at least 325 nm, at least 350 nm, at least 375 nm, at least 400 nm, at least 450 nm, at least 500 nm, at least 550 nm, at least 650 nm, at least 700 nm, at least 750 nm, at least 800 nm, at least 900 nm, or at least 1000 nm. In some embodiments, the 008864555

[0168] 24 number-average mean particle size is at least 75 nm. In some embodiments, the number-average mean particle size is at least 100 nm. In some embodiments, the number-average mean particle size is at least 125 nm. In some embodiments, the number-average mean particle size is at least 150 nm. In some embodiments, the number-average mean particle size is at least 175 nm. In some embodiments, the number-average mean particle size is at least 200 nm.

[0169] In some embodiments, the reticulated structure comprises or consists of particles having a numberaverage mean particle size of at most 1000 nm, at most 900 nm, at most 800 nm, at most 750 nm, at most 700 nm, at most 650 nm, at most 550 nm, at most 500 nm, at most 450 nm, at most 400 nm, at most 375 nm, at most 350 nm, at most 325 nm, at most 300 nm, at most 275 nm, at most 250 nm, at most 225 nm, at most 200 nm, at most 175 nm, at most 150 nm, at most 125 nm, at most 100 nm, at most 90 nm, at most 80 nm, at most 75 nm, at most 70 nm, at most 60 nm, at most 50 nm, at most 40 nm, at most 30 nm, at most 25 nm, at most 20 nm, or at most 10 nm. In some embodiments, the numberaverage mean particle size is at most 300 nm. In some embodiments, the number-average mean particle size is at most 250 nm. In some embodiments, the number-average mean particle size is at most 200 nm. In some embodiments, the number-average mean particle size is at most 175 nm. In some embodiments, the number-average mean particle size is at most 150 nm.

[0170] In some embodiments, the reticulated structure comprises or consists of particles having a numberaverage mean particle size of between 50 nm and 250 nm, between 75 nm and 225 nm, or between 100 nm and 200 nm.

[0171] In some embodiments, the reticulated structure comprises or consists of particles having a weightaverage mean particle size of at least 1 nm, at least 5 nm, at least 10 nm, at least 20 nm, at least 25 nm, at least 30 nm, at least 40 nm, at least 50 nm, at least 60 nm, at least 70 nm, at least 75 nm, at least 80 nm, at least 90 nm, at least 100 nm, at least 125 nm, at least 150 nm, at least 175 nm, at least 200 nm, at least 225 nm, at least 250 nm, at least 275 nm, at least 300 nm, at least 325 nm, at least 350 nm, at least 375 nm, at least 400 nm, at least 450 nm, at least 500 nm, at least 550 nm, at least 650 nm, at least 700 nm, at least 750 nm, at least 800 nm, at least 900 nm, or at least 1000 nm. In some embodiments, the weight-average mean particle size is at least 75 nm. In some embodiments, the weight-average mean particle size is at least 100 nm. In some embodiments, the weight-average mean particle size is at least 125 nm. In some embodiments, the weight-average mean particle size is at least 150 nm. In some embodiments, the weight-average mean particle size is at least 175 nm. In some embodiments, the weight-average mean particle size is at least 200 nm.

[0172] In some embodiments, the reticulated structure comprises or consists of particles having a weightaverage mean particle size of at most 1000 nm, at most 900 nm, at most 800 nm, at most 750 nm, at most 700 nm, at most 650 nm, at most 550 nm, at most 500 nm, at most 450 nm, at most 400 nm, at most 375 nm, at most 350 nm, at most 325 nm, at most 300 nm, at most 275 nm, at most 250 nm, at most 225 nm, at most 200 nm, at most 175 nm, at most 150 nm, at most 125 nm, at most 100 nm, at most 90 nm, at most 80 nm, at most 75 nm, at most 70 nm, at most 60 nm, at most 50 nm, at most 40 008864555

[0173] 25 nm, at most 30 nm, at most 25 nm, at most 20 nm, or at most 10 nm. In some embodiments, the weightaverage mean particle size is at most 300 nm. In some embodiments, the weight-average mean particle size is at most 250 nm. In some embodiments, the weight-average mean particle size is at most 200 nm. In some embodiments, the weight-average mean particle size is at most 175 nm. In some embodiments, the weight-average mean particle size is at most 150 nm.

[0174] In some embodiments, the reticulated structure comprises or consists of particles having a weightaverage mean particle size of between 50 nm and 250 nm, between 75 nm and 225 nm, or between 100 nm and 200 nm.

[0175] In some embodiments, the reticulated structure comprises or consists of particles having a median particle size (i.e., d50, i.e., the particle size which 50% of the particles are smaller than) of at least 1 nm, at least 5 nm, at least 10 nm, at least 20 nm, at least 25 nm, at least 30 nm, at least 40 nm, at least 50 nm, at least 60 nm, at least 70 nm, at least 75 nm, at least 80 nm, at least 90 nm, at least 100 nm, at least 125 nm, at least 150 nm, at least 175 nm, at least 200 nm, at least 225 nm, at least 250 nm, at least 275 nm, at least 300 nm, at least 325 nm, at least 350 nm, at least 375 nm, at least 400 nm, at least 450 nm, at least 500 nm, at least 550 nm, at least 650 nm, at least 700 nm, at least 750 nm, at least 800 nm, at least 900 nm, or at least 1000 nm. In some embodiments, the median particle size is at least 75 nm. In some embodiments, the median particle size is at least 100 nm. In some embodiments, the median particle size is at least 125 nm. In some embodiments, the median particle size is at least 150 nm. In some embodiments, the median particle size is at least 175 nm. In some embodiments, the median particle size is at least 200 nm.

[0176] In some embodiments, the reticulated structure comprises or consists of particles having a median particle size (i.e., d50, i.e., the particle size which 50% of the particles are smallerthan) of at most 1000 nm, at most 900 nm, at most 800 nm, at most 750 nm, at most 700 nm, at most 650 nm, at most 550 nm, at most 500 nm, at most 450 nm, at most 400 nm, at most 375 nm, at most 350 nm, at most 325 nm, at most 300 nm, at most 275 nm, at most 250 nm, at most 225 nm, at most 200 nm, at most 175 nm, at most 150 nm, at most 125 nm, at most 100 nm, at most 90 nm, at most 80 nm, at most 75 nm, at most 70 nm, at most 60 nm, at most 50 nm, at most 40 nm, at most 30 nm, at most 25 nm, at most 20 nm, or at most 10 nm. In some embodiments, the median particle size is at most 300 nm. In some embodiments, the median particle size is at most 250 nm. In some embodiments, the median particle size is at most 200 nm. In some embodiments, the median particle size is at most 175 nm. In some embodiments, the median particle size is at most 150 nm.

[0177] In some embodiments, the reticulated structure comprises or consists of particles having a median particle size of between 50 nm and 250 nm, between 75 nm and 225 nm, or between 100 nm and 200 nm.

[0178] In some embodiments, the reticulated structure comprises or consists of particles having a d10 particle size (i.e., the particle size which 10% of the particles are smaller than) of at least 1 nm, at least 5 nm, at 008864555

[0179] 26 least 10 nm, at least 20 nm, at least 25 nm, at least 30 nm, at least 40 nm, at least 50 nm, at least 60 nm, at least 70 nm, at least 75 nm, at least 80 nm, at least 90 nm, or at least 100 nm. In some embodiments, the d10 particle size is at least 5 nm. In some embodiments, the d10 particle size is at least 10 nm. In some embodiments, the d10 particle size is at least 25 nm. In some embodiments, the d10 particle size is at least 50 nm. In some embodiments, the d10 particle size is at least 75 nm. In some embodiments, the d10 particle size is at least 100 nm.

[0180] In some embodiments, the reticulated structure comprises or consists of particles having a d10 particle size (i.e., the particle size which 10% of the particles are smaller than) of at most 300 nm, at most 275 nm, at most 250 nm, at most 225 nm, at most 200 nm, at most 175 nm, at most 150 nm, at most 125 nm, at most 100 nm, at most 90 nm, at most 80 nm, at most 75 nm, at most 70 nm, at most 60 nm, at most 50 nm, at most 40 nm, at most 30 nm, at most 25 nm, at most 20 nm, or at most 10 nm. In some embodiments, the d10 particle size is at most 150 nm. In some embodiments, the d10 particle size is at most 100 nm. In some embodiments, the d10 particle size is at most 75 nm. In some embodiments, the d10 particle size is at most 50 nm. In some embodiments, the d10 particle size is at most 25 nm. In some embodiments, the d10 particle size is at most 10 nm.

[0181] In some embodiments, the reticulated structure comprises or consists of particles having a d10 particle size of between 1 nm and 150 nm, between 5 nm and 100 nm, or between 10 nm and 50 nm.

[0182] In some embodiments, the reticulated structure comprises or consists of particles having a d90 particle size (i.e., the particle size which 90% of the particles are smaller than) of at least 100 nm, at least 125 nm, at least 150 nm, at least 175 nm, at least 200 nm, at least 225 nm, at least 250 nm, at least 275 nm, at least 300 nm, at least 325 nm, at least 350 nm, at least 375 nm, at least 400 nm, at least 450 nm, at least 500 nm, at least 550 nm, at least 650 nm, at least 700 nm, at least 750 nm, at least 800 nm, at least 900 nm, or at least 1000 nm. In some embodiments, the d90 particle size is at least 75 nm. In some embodiments, the d90 particle size is at least 100 nm. In some embodiments, the d90 particle size is at least 150 nm. In some embodiments, the d90 particle size is at least 200 nm. In some embodiments, the d90 particle size is at least 250 nm. In some embodiments, the d90 particle size is at least 300 nm.

[0183] In some embodiments, the reticulated structure comprises or consists of particles having a d90 particle size (i.e., the particle size which 90% of the particles are smaller than) of at most 1000 nm, at most 900 nm, at most 800 nm, at most 750 nm, at most 700 nm, at most 650 nm, at most 550 nm, at most 500 nm, at most 450 nm, at most 400 nm, at most 375 nm, at most 350 nm, at most 325 nm, at most 300 nm, at most 275 nm, at most 250 nm, at most 225 nm, at most 200 nm, at most 175 nm, at most 150 nm, at most 125 nm, at most 100 nm. In some embodiments, the d90 particle size is at most 1000 nm. In some embodiments, the d90 particle size is at most 750 nm. In some embodiments, the d90 particle size is at most 500 nm. In some embodiments, the d90 particle size is at most 300 nm. In some embodiments, the d90 particle size is at most 200 nm. 008864555

[0184] 27

[0185] In some embodiments, the reticulated structure comprises or consists of particles having a d90 particle size of between 150 nm and 1000 nm, between 200 nm and 750 nm, or between 250 nm and 500 nm.

[0186] Unless specified otherwise, particle size is intended to mean the longest dimension of a projection of a particle, for example imaged using optical microscopy or scanning electron microscopy. Particle size is measured for a sample which is considered to be representative of the population. An imaging software, such as Imaged, may be used to measure particle size from images.

[0187] It may be that the metal-organic framework (MOF) comprises: metal ions selected from Zr, Zn, Al, Fe, Cr, Cu and Ti; and linker groups having the structure according to formula (I) wherein A is one or more groups selected from: an aryl group, a heteroaryl group, an alkyl group, an alkenyl group, an alkynyl group, a cycloalkyl group and a heterocyclic group, each of which may be substituted with one or more groups selected from alkyl, alkenyl, alkynyl, amino, halo or hydroxyl;

[0188] L is a ligation group, each independently selected from carboxyl, hydroxyl and 5- or 6-membered heteroaryl having from 1 to 3 nitrogen heteroatoms; and n is an integer in the range from 0 to 6.

[0189] It may be that the metal ions are selected from the group consisting of Zr3+, Zr4*, Zn2+, Al3+, Fe2+, Fe3+, Cr2+, Cr3+, Cr®+, Cu+, Cu2+, Ti3+and Ti4+. It may be that the MOF comprises only a single type of metal ion. The skilled person is aware of appropriate metal salts which may be used to obtain the required metal ions. For example, the respective halide may be used. The metal ion may be derived from a metal salt selected from a chloride of any of the above-recited metal ions.

[0190] It may be that A is selected from a C5-C30 aryl group, a C3-C29 heteroaryl group, a C1-C30 alkyl group, a C2-C30 alkenyl group, a C2-C30 alkynyl group, a C3-C30 cycloalkyl group, and a C2-C29 heterocyclic group. It may be that A is Ce-18 aryl. It may be that A is selected from phenyl, naphthalene, biphenyl, fluorene, anthracene, phenanthrene, phenalene, terphenyl, tetracene, chrysene, triphenylene, pyrene, pentacene, perylene, benzo[a]pyrene, corannulene, and coronene. It may be that A is selected from a Ce aryl group, and a C3 heteroaryl. It maybe that A is benzene or imidazole. It may be that A comprises two or more Ce phenyl rings linked together by single bonds; preferably the two or more phenyl rings are bonded together in a linear manner. In some cases, A is selected from phenyl, biphenyl, and terphenyl (preferably paraterphenyl).

[0191] The group L is a ligation group each of which is independently selected from carboxyl, hydroxyl and 5- or 6-membered heteroaryl having from 1 to 3 nitrogen heteroatoms. The 5- or 6-membered heteroaryl having from 1 to 3 nitrogen heteroatoms may be, for example, pyrrole, imidazole, pyrazole, triazole, 008864555

[0192] 28 pyridine, diazine, and triazine. It may be that the ligation groups are each selected from carboxyl and hydroxyl; preferably carboxyl. It may be that all of the ligation groups in the linker group are the same. The integer n defines the number of ligation groups attached to each A group and is in the range 0-6. It may be that n is 2-3, it may be that n is 2. In the case where n is 0, the group A is capable of ligating to the metal ion to form the MOF, in place of a separate ligation group, L.

[0193] It may be that the linker group is selected from benzodicarboxylic acid, biphenyldicarboxylic acid, or terphenyldicarboxylic acid; optionally substituted with one or more groups selected from amino, halo, hydroxyl, nitro, azido, and C2-4 alkynyl and cyclooctynyl; it may be that the optional substituents are selected from amino and hydroxyl.

[0194] It may be that the linker is selected from one of the following molecules: 1 ,4-benzodicarboxylic acid, 4,4" biphenyldicarboxylic acid and p-terphenyl-4,4"-dicarboxylic acid, optionally the linker is substituted with one or more groups selected from OH and NH2.

[0195] For example, the linker may be selected from: 2,5 dihydroxy-1 ,4-benzenedicarboxylic acid, 2,5 diamino- 1 ,4-benzenedicarboxylic acid, 2,2’-dihydroxy-4,4' biphenyldicarboxylic acid, 3,3’-dihydroxy-4,4' biphenyldicarboxylic acid, 2,2’-diamino-4,4' biphenyldicarboxylic acid, 3,3’-amino-4,4' biphenyldicarboxylic acid, 2,2”-dihydroxy-p-terphenyl-4,4"-dicarboxylic acid, 2,2”-diamino-p-terphenyl- 4,4"-dicarboxylic acid, 3,3”-dihydroxy-p-terphenyl-4,4"-dicarboxylic acid, 3,3”-diamino-p-terphenyl-4,4"- dicarboxylic acid, and 2’,5’-dihydroxy-[1 ,1 ’:4’,1 ”]-terphenyl-4,4"-dicarboxylic acid.

[0196] It may be that the linker is 2,5 dihydroxy-1 ,4-benzenedicarboxylic acid.

[0197] It may be that the combination of metal ion and linker is chosen to generate one of the following MOFs: Zr(UiO-66-OH) [that is, Zr4* with 2,5 dihydroxy-1 ,4-benzenedicarboxylic acid linker], Zr(UiO-66-NH2) [that is, Zr4* with 2,5 diamino-1 ,4-benzenedicarboxylic acid linker or with 2-aminoterepthalic acid], Zr(UiO-67- OH) [that is, Zr4* with 3,3’-dihydroxy-4,4' biphenyldicarboxylic acid linker], Zr(UiO-67- NH2) [that is, Zr4* with 3,3’-amino-4,4' biphenyldicarboxylic acid linker], Zr(UiO-68-OH) [that is, Zr4* with 3,3”-dihydroxy-p- terphenyl-4,4"-dicarboxylic acid linker], and Zr(UiO-68- NH2) [that is, Zr4* with 3,3”-diamino-p-terphenyl- 4,4"-dicarboxylic acid linker].

[0198] It may be that, the metal ion and linker is chosen to generate the MOF Zr(UiO-66-OH), that is Zr4* with 2,5 dihydroxy-1 ,4-benzenedicarboxylic acid linker.

[0199] UiO-66 may be synthesised solvothermally, which is beneficial as it is more environmentally friendly than alternative methods. Its synthetic method is known in the art. In some embodiments, UiO-66 is synthesised by dissolving ZrOCl2.8H2O and TPA in DMF and reacting solvothermally, with crystallisation occurring under static conditions. 008864555

[0200] 29

[0201] If the reticulated structure is a MOF, and a functional group (below: FG) is added to the reticulated structure, it may be that, for example, the hydroxy or amino groups in such a MOF are used to add the functional group. The functional groups are as described elsewhere herein. For example, the MOFs used in the surface coating may be one of the following: Zr(UiO-66-O-FG) [that is, Zr4* with 2,5 dihydroxy-1 ,4- benzenedicarboxylic acid linker, where one or more hydroxy groups are substituted with a functional group (FG) as described above], Zr(UiO-66-NHFG) [that is, Zr4* with 2,5 diamino-1 ,4-benzenedicarboxylic acid linker or with 2-aminoterepthalic acid, with one or more amino groups substituted with a functional group (FG) as described above], Zr(UiO-67-OFG) [that is, Zr4* with 3,3’-dihydroxy-4,4' biphenyldicarboxylic acid linker, where one or more hydroxy groups are substituted with a functional group (FG) as described above], Zr(UiO-67- NHFG) [that is, Zr4* with 3,3’-amino-4,4' biphenyldicarboxylic acid linker, with one or more amino groups substituted with a functional group (FG) as described above], Zr(UiO-68-OFG) [that is, Zr4* with 3,3”-dihydroxy-p-terphenyl-4,4"-dicarboxylic acid linker, where one or more hydroxy groups are substituted with a functional group (FG) as described above], and Zr(UiO-68- NHFG) [that is, Zr4* with 3,3”-diamino-p-terphenyl-4,4"-dicarboxylic acid linker, with one or more amino groups substituted with a functional group (FG) as described above].

[0202] In some embodiments, the reticulated structure is a covalent organic framework having pores.

[0203] It may be that the covalent organic framework (COF) is an imine-based COF, a triazine-based COF, a p-ketoenamine-based COF, or a boron-based COF. The benefits described herein in relation to MOFs as the reticulated structure apply also to the use of COFs as the reticulated structure.

[0204] Imine-based COFs:

[0205] Amine monomer. p-Phenylenediamine (PDA) or, benzidine

[0206] Aldehyde monomer. 2,4,6-Trihydroxybenzene-1 ,3,5-Triformylbenzene or, terephthaldehyde (TPA) Properties'. Surface area = 500-2000 m2 / g, Pore size = 1 .5-4.5 nm

[0207] Triazine-based COFs:

[0208] Triazine monomer. 2,4,6-Tris(4-aminophenyl)-1 ,3,5-triazine (TAPT)

[0209] Aldehyde monomer. 1 ,3,5-Triformylbenzene (TFB) or, terephthaldehyde (TPA).

[0210] Properties'. Surface area = 700-1500 m2 / g, Pore size = 1-2 nm

[0211] B-ketoenamine-based COFs:

[0212] Aromatic diamine', p-phenylenediamine (PDA), benzidine Aldehyde monomer: 1 ,3,5-Triformylphloroglucinol (TFP) Properties: Surface area = 900-2000 m2 / g, Pore size = 2-3 nm

[0213] First Layer Composition

[0214] In some embodiments, relative to the combined weight of the polymer and the reticulated structure in the first layer, the reticulated structure is contained in an amount of at least 1 wt%, at least 2 wt%, at least 3 008864555

[0215] 30 wt%, at least 4 wt%, at least 5 wt%, at least 7.5 wt%, at least 10 wt%, at least 12.5 wt%, at least 15 wt%, at least 17.5 wt%, at least 20 wt%, at least 25 wt%, at least 30 wt%, at least 35 wt%, at least 40 wt%, at least 45 wt%, or at least 50 wt%. In some embodiments, the amount of the reticulated structure is at least 5 wt%. In some embodiments, the amount of the reticulated structure is at least 10 wt%. In some embodiments, the amount of the reticulated structure is at least 15 wt%. In some embodiments, the amount of the reticulated structure is at least 20 wt%.

[0216] In some embodiments, relative to the combined weight of the polymer and the reticulated structure in the first layer, the reticulated structure is contained in an amount of at most 80 wt%, at most 75 wt%, at most 70 wt%, at most 65 wt%, at most 60 wt%, at most 55 wt%, at most 50 wt%, at most 45 wt%, at most 40 wt%, at most 35 wt%, at most 30 wt%, at most 27.5 wt%, at most 25 wt%, at most 22.5 wt%, at most 20 wt%, at most 17.5 wt%, at most 15 wt%, at most 12.5 wt%, at most 10 wt%, at most 7.5 wt%, or at most 5 wt%. In some embodiments, the amount of the reticulated structure is at most 40 wt%. In some embodiments, the amount of the reticulated structure is at most 30 wt%. In some embodiments, the amount of the reticulated structure is at most 25 wt%. In some embodiments, the amount of the reticulated structure is at most 20 wt%.

[0217] In some embodiments, relative to the combined weight of the polymer and the reticulated structure in the first layer, the reticulated structure is contained in an amount of about 1 wt%, about 5 wt%, about 7.5 wt%, about 10 wt%, about 12.5 wt%, about 15 wt%, about 17.5 wt%, about 20 wt%, about 22.5 wt%, about 25 wt%, about 27.5 wt%, about 30 wt%, about 35 wt%, or about 40 wt%.

[0218] In some embodiments, relative to the combined weight of the polymer and the reticulated structure in the first layer, the reticulated structure is contained in an amount of between 1 and 40 wt%. In some embodiments, relative to the combined weight of the polymer and the reticulated structure in the first layer, the reticulated structure is contained in an amount of between 5 and 40 wt%. In some embodiments, relative to the combined weight of the polymer and the reticulated structure in the first layer, the reticulated structure is contained in an amount of between 1 and 30 wt%. In some embodiments, relative to the combined weight of the polymer and the reticulated structure in the first layer, the reticulated structure is contained in an amount of between 1 and 25 wt%. In some embodiments, relative to the combined weight of the polymer and the reticulated structure in the first layer, the reticulated structure is contained in an amount of between 5 and 25 wt%. In some embodiments, relative to the combined weight of the polymer and the reticulated structure in the first layer, the reticulated structure is contained in an amount of between 5 and 20 wt%. In some embodiments, relative to the combined weight of the polymer and the reticulated structure in the first layer, the reticulated structure is contained in an amount of between 10 and 20 wt%. In some embodiments, relative to the combined weight of the polymer and the reticulated structure in the first layer, the reticulated structure is contained in an amount of between 15 and 20 wt%.

[0219] The surface coatings described herein show desirable liquid-repellent properties, mechanical robustness, and optical transparency with even a relatively low content of the reticulated structure (such as 40 wt% or 008864555

[0220] 31 less, or even 30 wt% or less, or even 20 wt% or less). In this way, the surface coatings may be cost- effective and viable for large-scale applications.

[0221] The interfacial layer (IL) is defined as the fraction of polymer chains in direct contact with a particle of the reticulated structure. In some embodiments, the IL is at least 5%, at least 10%, at least 15%, at least 20%, at least 25%, at least 30%, at least 35%, at least 40%, at least 45%, at least 50%, at least 55%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 90%, at least 95%, at least 98%, or at least 99%.

[0222] The polymer and the reticulated structure form physical interactions with one another. Such interactions are present between the polymer and the interior of the pores of the reticulated structure. Physical interactions may additionally be present between the polymer and the exterior (e.g. outer surface) of the reticulated structure. Such interactions may include hydrogen bonding, Van der Waals forces, London dispersion forces, Debye forces, and / or dipole-dipole interactions.

[0223] Transparency

[0224] The surface coating according to the present invention may be substantially optically transparent. For the avoidance of doubt, when transparency is discussed regarding the surface coating, it is intended to mean the transparency of the first layer and the layer of organosilanes. That is to say, the substrate may be non-transparent, but the surface coating may still be transparent (as such, the substrate would be visible through the surface coating).

[0225] In some embodiments, the surface coating (e.g., not including the substrate) is optically transparent. In some embodiments, the surface coating (e.g., not including the substrate) has a light transmittance (i.e. transmits light) in the 400-800 nm range of at least 40%, at least 50%, at least 60%, at least 65%, at least 70%, at least 75%, at least 80%, at least 85%, at least 87%, at least 90%, or at least 91%. In some embodiments, the surface coating (e.g., not including the substrate) has a light transmittance (i.e. transmits light) in the 400-800 nm range of at least 75%. In some embodiments, the surface coating (e.g., not including the substrate) has a light transmittance (i.e. transmits light) in the 400-800 nm range of at least 80%. In some embodiments, the surface coating (e.g., not including the substrate) has a light transmittance (i.e. transmits light) in the 400-800 nm range of at least 85%. In some embodiments, the surface coating (e.g., not including the substrate) has a light transmittance (i.e. transmits light) in the 400- 800 nm range of at least 87%. In some embodiments, the surface coating (e.g., not including the substrate) has a light transmittance (i.e. transmits light) in the 400-800 nm range of at least 90%.

[0226] In some embodiments, the substrate is transparent. In some embodiments, the substrate is not transparent. In some embodiments, the substrate is translucent. In some embodiments, the substrate is opaque. In some embodiments, the substrate comprises surface decoration, for example which is visible through the first layer of the surface coating (and through the organosilane layer). In this way, the surface coating can be applied to transparent substrates and the coated article may retain its transparency, or the 008864555

[0227] 32 surface coating can be applied to an opaque / translucent as its colour / decoration may remain visible in the coated article.

[0228] It may be that the substrate permits high optical transmission. For example, the optical transmission of the substrate may be greater than 70%, greater than 80% or greater than 90% to light having a wavelength in the range 400-700 nm. It may be that the substrate is a transparent material, such as glass or a transparent polymer (e.g. low density polyethylene (LDPE), high density polyethylene (HDPE), polyurethane (PU), polyethylene terephthalate (PET), polycarbonate (PC), polymethylmethacrylate (PM MA)). This optical transmissivity provides particular benefits, for example the ability to use the coatings to provide optically transmissive hydrophobic, oleophobic, or amphiphobic coatings. This may be beneficial, for example if applied to a substrate in a scenario where it is desired to be able to see the surface decoration of the substrate through the coating. This is also particularly beneficial when combined with optically transmissive, or transparent, substrates such as windows, windshields etc. where the beneficial coating properties can be achieved with minimal or no impairment to the optical transmissivity.

[0229] It may be that the reticulated structures are partially optically transparent. In some embodiments, infusing the reticulated structure with lubricant, to hold the lubricant molecules within the pores of the reticulated structure, increases the transparency of the surface coating, relative to the reticulated structure in isolation.

[0230] Surface Coating Thickness

[0231] In some embodiments, the surface coating has a thickness of between 100 nm and 100 pm. The thickness of the surface coating is to be interpreted as the thickness of the first layer and the layer of organosilane functionalisation, but not including the thickness of the substrate.

[0232] In some embodiments, the surface coating has a thickness of at least 100 nm, at least 200 nm, at least 250 nm, at least 300 nm, at least 400 nm, at least 500 nm, at least 600 nm, at least 700 nm, at least 750 nm, at least 800 nm, at least 900 nm, at least 1 pm, at least 2 pm, at least 3 pm, at least 4 pm, at least 5 pm, at least 7.5 pm, at least 10 pm, at least 12.5 pm, at least 15 pm, at least 17.5 pm, at least 20 pm, at least 25 pm, at least 30 pm, at least 40 pm, at least 50 pm, at least 60 pm, at least 70 pm, at least 75 pm, at least 80 pm, or pm, at least 90 pm. In some embodiments, the surface coating has a thickness of at most 100 pm, at most 90 pm, at most 80 pm, at most 75 pm, at most 70 pm, at most 60 pm, at most 50 pm, at most 40 pm, at most 30 pm, at most 25 pm, at most 20 pm, at most 17.5 pm, at most 15 pm, at most 12.5 pm, at most 10 pm, at most 7.5 pm, at most 6 pm, at most 5 pm, at most 4 pm, at most 3 pm, at most 2 pm, at most 1 pm, at most 900 nm, at most 800 nm, at most 750 nm, at most 700 nm, at most 600 nm, at most 500 nm, at most 400 nm, at most 300 nm, at most 250 nm, at most 200 nm, or at most 100 nm. 008864555

[0233] 33

[0234] In some embodiments, the surface coating has a thickness of between 100 nm and 50 pm, between 250 nm and 25 pm, between 500 nm and 15 pm, between 750 nm and 10 pm, between 1 pm and 10 pm, between 1 pm and 7.5 pm, between 2 pm and 6 pm, between 1 pm and 5 pm, between 3 pm and 6 pm, or between 4 pm and 6 pm.

[0235] In some embodiments, the surface coating has a thickness of between 4 pm and 6 pm.

[0236] In some embodiments, the surface coating has a thickness of about 100 nm, about 200 nm, about 250 nm, about 300 nm, about 400 nm, about 500 nm, about 600 nm, about 700 nm, about 750 nm, about 800 nm, about 900 nm, about 1 pm, about 2 pm, about 3 pm, about 4 pm, about 5 pm, about 7.5 pm, about 10 pm, about 12.5 pm, about 15 pm, about 17.5 pm, about 20 pm, about 25 pm, about 30 pm, about 40 pm, about 50 pm, about 60 pm, about 70 pm, about 75 pm, about 80 pm, about 90 pm, or about 100 pm. In some embodiments, the surface coating has a thickness of about 5 pm.

[0237] In some embodiments, the first layer has a thickness of between 100 nm and 100 pm. The thickness of the first layer is to be interpreted as the thickness of the first layer, including the polymer and the reticulated structure, only. In other words, it does not include the thickness of the layer of organosilane functionalisation or the substrate.

[0238] In some embodiments, the first layer has a thickness of at least 100 nm, at least 200 nm, at least 250 nm, at least 300 nm, at least 400 nm, at least 500 nm, at least 600 nm, at least 700 nm, at least 750 nm, at least 800 nm, at least 900 nm, at least 1 pm, at least 2 pm, at least 3 pm, at least 4 pm, at least 5 pm, at least 7.5 pm, at least 10 pm, at least 12.5 pm, at least 15 pm, at least 17.5 pm, at least 20 pm, at least 25 pm, at least 30 pm, at least 40 pm, at least 50 pm, at least 60 pm, at least 70 pm, at least 75 pm, at least 80 pm, or pm, at least 90 pm. In some embodiments, the first layer has a thickness of at most 100 pm, at most 90 pm, at most 80 pm, at most 75 pm, at most 70 pm, at most 60 pm, at most 50 pm, at most 40 pm, at most 30 pm, at most 25 pm, at most 20 pm, at most 17.5 pm, at most 15 pm, at most 12.5 pm, at most 10 pm, at most 7.5 pm, at most 6 pm, at most 5 pm, at most 4 pm, at most 3 pm, at most 2 pm, at most 1 pm, at most 900 nm, at most 800 nm, at most 750 nm, at most 700 nm, at most 600 nm, at most 500 nm, at most 400 nm, at most 300 nm, at most 250 nm, at most 200 nm, or at most 100 nm.

[0239] In some embodiments, the first layer has a thickness of between 100 nm and 50 pm, between 250 nm and 25 pm, between 500 nm and 15 pm, between 750 nm and 10 pm, between 1 pm and 10 pm, between 1 pm and 7.5 pm, between 2 pm and 6 pm, between 1 pm and 5 pm, between 3 pm and 6 pm, or between 4 pm and 6 pm.

[0240] In some embodiments, the first layer has a thickness of between 4 pm and 6 pm.

[0241] In some embodiments, the first layer has a thickness of about 100 nm, about 200 nm, about 250 nm, about 300 nm, about 400 nm, about 500 nm, about 600 nm, about 700 nm, about 750 nm, about 800 nm, about 900 nm, about 1 pm, about 2 pm, about 3 pm, about 4 pm, about 5 pm, about 7.5 pm, about 10 008864555

[0242] 34 pm, about 12.5 pm, about 15 pm, about 17.5 pm, about 20 pm, about 25 pm, about 30 pm, about 40 pm, about 50 pm, about 60 pm, about 70 pm, about 75 pm, about 80 pm, about 90 pm, or about 100 pm. In some embodiments, the first layer has a thickness of about 5 pm.

[0243] The thickness of the first layer can be adjusted during preparation of the surface coating. For example, a thicker first layer can be obtained by applying a larger quantity of the dispersion of the polymer and reticulated structure, providing continuous application for a longer period of time, and / or repeating the application more times. The thickness may be selected to provide an optimum balance between robustness of the layer and transparency, flexibility and / or cost.

[0244] The thickness of the first layer and of the surface coating may be measured by imaging a cross-section of the surface coating or first layer using optical microscopy or scanning electron microscopy. An imaging software, such as Imaged, may be used to measure coating thickness from images.

[0245] Surface Roughness

[0246] Surface coatings according to the present invention have a nano-hierarchical structure due to the reticulated structure. Such a nano-hierarchical structure results in the surface coatings having a certain surface roughness. Such a (e.g. nano-hierarchical) surface roughness may help contribute to hydrophobic and / or oleophobic properties of the surface. Functionalisation with an organosilane may also affect the surface roughness, for example the alkyl groups may reduce the surface roughness.

[0247] In some embodiments, the surface has a root mean square roughness 0"RMS) of at least 0.1 nm, at least 0.25 nm, at least 0.5 nm, at least 0.75 nm, at least 1 nm, at least 1 .25 nm, at least 1 .5 nm, at least 1 .75 nm, at least 2 nm, at least 2.1 nm, at least 2.2 nm, at least 2.25 nm, at least 2.3 nm, at least 2.5 nm, at least 2.75 nm, at least 3 nm, at least 3.25 nm, at least 3.5 nm, at least 4 nm, at least 4.5 nm, or at least 5 nm. In some embodiments, the surface has a root mean square roughness 0"RMS) of at least 1 nm. In some embodiments, the surface has a root mean square roughness 0"RMS) of at least 1.5 nm. In some embodiments, the surface has a root mean square roughness 0"RMS) of at least 2 nm. In some embodiments, the surface has a root mean square roughness 0"RMS) of at least 2.1 nm. In some embodiments, the surface has a root mean square roughness 0"RMS) of at least 2.2 nm.

[0248] In some embodiments, the surface has a root mean square roughness 0"RMS) of at most 10 nm, at most 9 nm, at most 8 nm, at most 7.5 nm, at most 7 nm, at most 6 nm, at most 5 nm, at most 4.5 nm, at most 4 nm, at most 3.5 nm, at most 3.25 nm, at most 3 nm, at most 2.75 nm, at most 2.5 nm, at most 2.3 nm, at most 2.25 nm, at most 2.2 nm, at most 2.1 nm, at most 2 nm, at most 1 .75 nm, at most 1 .5 nm, at most 1 .25 nm, at most 1 nm, at most 0.75 nm, or at most 0.5 nm. In some embodiments, the surface has a root mean square roughness 0"RMS) of at most 10 nm. In some embodiments, the surface has a root mean square roughness 0"RMS) of at most 7.5 nm. In some embodiments, the surface has a root mean square roughness 0"RMS) of at most 5 nm. In some embodiments, the surface has a root mean square roughness 008864555

[0249] 35

[0250] (PRMS) of at 3 nm. In some embodiments, the surface has a root mean square roughness 0"RMS) of at most 2.5 nm. In some embodiments, the surface has a root mean square roughness 0"RMS) of at most 2.2 nm.

[0251] In some embodiments, the surface has a root mean square roughness 0"RMS) of about 1 nm, about 1.5 nm, about 1 .75 nm, about 2 nm, about 2.1 nm, about 2.2 nm, about 2.3 nm, about 2.5 nm, about 2.75 nm, or about 3 nm. In some embodiments, the surface has a root mean square roughness 0"RMS) of about 2 nm. In some embodiments, the surface has a root mean square roughness 0"RMS) of about 2.1 nm. In some embodiments, the surface has a root mean square roughness 0"RMS) of about 2.2 nm. In some embodiments, the surface has a root mean square roughness 0"RMS) of about 2.3 nm. In some embodiments, the surface has a root mean square roughness 0"RMS) of about 2.5 nm.

[0252] Root mean square roughness 0"RMS) may be measured by atomic force microscopy (AFM). The data obtained by AFM may be processed using an appropriate software, such as NanoScope Analysis 1 .7, in order to calculate TRMS.

[0253] Surface Robustness

[0254] Surface coatings according to the present invention may be mechanically robust.

[0255] In some embodiments, the surface coatings have an (ultimate) tensile strength of at least 1 MPa, at least 2 MPa, at least 2.5 MPa, at least 5 MPa, at least 7.5 MPa, at least 8 MPa, at least 9 MPa, at least 10 MPa, at least 11 MPa, at least 12 MPa, at least 13 MPa, at least 14 MPa, or at least 15 MPa. In some embodiments, the surface coatings have a tensile strength of at least 10 MPa. In some embodiments, the surface coatings have an (ultimate) tensile strength of at least 11 MPa. In some embodiments, the surface coatings have an (ultimate) tensile strength of at least 12 MPa. In some embodiments, the surface coatings have an (ultimate) tensile strength of at least 13 MPa. In some embodiments, the surface coatings have an (ultimate) tensile strength of about 12 MPa, about 13 MPa, about 13.2 MPa, about 13.5 MPa, or about 14 MPa.

[0256] In some embodiments, the surface coatings have a Young’s modulus of at least 0.5 MPa, at least 1 MPa, at least 2 MPa, at least 2.5 MPa, at least 3MPa, at least 4 MPa, at least 5 MPa, at least 6 MPa, at least 7 MPa, at least 7.5 MPa, at least 7.8 MPa, at least 8 MPa, at least 9 MPa, or at least 10 MPa. In some embodiments, the surface coatings have a Young’s modulus of at least 5 MPa. In some embodiments, the surface coatings have a Young’s modulus of at least 6 MPa. In some embodiments, the surface coatings have a Young’s modulus of at least 7 MPa. In some embodiments, the surface coatings have a Young’s modulus of at least 7.5 MPa. In some embodiments, the surface coatings have a Young’s modulus of at least 7.8 MPa. In some embodiments, the surface coatings have a Young’s modulus of about 5 MPa, about 6 MPa, about 7 MPa, about 7.5 MPa, about 7.8 MPa, or about 8 MPa.

[0257] In some embodiments, the surface coatings have an elongation at break of at least 200 %, at least 250 %, at least 300 %, at least 400 %, at least 500 %, at least 600 %, at least 700 %, at least 750 %, at least 008864555

[0258] 36

[0259] 800 %, at least 900 %, at least 1000 %, at least 1100 %, at least 1200 %, at least 1250 %, or at least 1500 %. In some embodiments, the surface coatings have an elongation at break of at least 500 %. In some embodiments, the surface coatings have an elongation at break of at least 600 %. In some embodiments, the surface coatings have an elongation at break of at least 700 %. In some embodiments, the surface coatings have an elongation at break of at least 750 %.

[0260] In some embodiments, the surface coatings have a toughness of at least 10 MJ / m3, at least 20 MJ / m3, at least 25 MJ / m3, at least 30 MJ / m3, at least 40 MJ / m3, at least 50 MJ / m3, at least 60 MJ / m3, at least 70 MJ / m3, at least 75 MJ / m3, at least 80 MJ / m3, at least 85 MJ / m3, at least 90 MJ / m3, at least 95 MJ / m3, at least 100 MJ / m3, at least 110 MJ / m3, at least 120 MJ / m3, at least 125 MJ / m3, at least 130 MJ / m3, at least 140 MJ / m3, or at least 150 MJ / m3. In some embodiments, the surface coatings have a toughness of at least 50 MJ / m3. In some embodiments, the surface coatings have a toughness of at least 75 MJ / m3. In some embodiments, the surface coatings have a toughness of at least 85 MJ / m3. In some embodiments, the surface coatings have a toughness of at least 90 MJ / m3.

[0261] (Ultimate) tensile strength, Young’s modulus, elongation at break, and toughness may be measured from the stress-strain curve obtained from a tensile strength testing machine, such as an Instron 5659 testing machine with a 500 N load cell. To calculate these parameters, first normalise the force by the cross- sectional area to obtain tensile strength, and then: (ultimate) tensile strength is the maximum tensile strength before sample break; Young’s modulus is the linear slope of the tensile strength-strain curve; elongation at break is the maximum strain at break; and toughness is the integration of the area under the tensile strength-strain curve.

[0262] A surface may be considered thermally stable up to a certain temperature if after exposure at said temperature for a period of time (e.g. 2 hours), the contact angle hysteresis of a water droplet on the surface increases by less than 100%. In some embodiments, the surface coatings are thermally stable up to 50 °C, up to 60 °C, up to 70 °C, up to 75 °C, up to 80 °C, up to 90 °C, up to 100 °C, up to 125 °C, up to 150 °C, up to 175 °C, up to 200 °C, up to 225 °C, up to 250 °C, up to 275 °C, up to 300 °C, up to 350 °C, up to 400 °C, up to 500 °C, up to 600 °C, or up to 700 °C. In some embodiments, the surface coatings are thermally stable up to 150 °C. In some embodiments, the surface coatings are thermally stable up to 175 °C. In some embodiments, the surface coatings are thermally stable up to 200 °C. In some embodiments, the surface coatings are thermally stable up to 250 °C. The thermal stability of the surface coatings may be dictated by organic components, such as the polymer and / or the organosilane.

[0263] In some embodiments, the contact angle hysteresis of a water droplet on the surface increases by 500 % or less following exposure to a temperature of 200 °C for 2 hours. In some embodiments, the contact angle hysteresis increases by 400 % or less, by 300 % or less, by 250 % or less, by 200 % or less, by 175 % or less, by 150 % or less, by 125 % or less, by 100 % or less, by 90 % or less, by 80 % or less, by 75 % or less, 70 % or less, 67 % or less, 65 % or less, 60 % or less, 50 % or less, 40 % or less, 30 % or less, or 25 % or less. In some embodiments, the contact angle hysteresis increases by 150 % or less. In some embodiments, the contact angle hysteresis increases by 100 % or less. In some embodiments, the 008864555

[0264] 37 contact angle hysteresis increases by 90 % or less. In some embodiments, the contact angle hysteresis increases by 75 % or less. In some embodiments, the contact angle hysteresis increases by 67 % or less.

[0265] In some embodiments, the surface coatings have an interfacial strength (i.e. adhesion strength) between the first layer and the substrate of at least 0.1 MPa, at least 0.2 MPa, at least 0.25 MPa, at least 0.3 MPa, at least 0.4 MPa, at least 0.5 MPa, at least 0.6 MPa, at least 0.7 MPa, at least 0.75 MPa, at least 0.8 MPa, at least 0.9 MPa, at least 1 .0 MPa, at least 1 .1 MPa, at least 1 .2 MPa, at least 1 .25 MPa, at least 1 .3 MPa, at least 1 .4 MPa, at least 1 .5 MPa, at least 1 .6 MPa, at least 1 .7 MPa, at least 1 .8 MPa, at least 1 .9 MPa, at least 2.0 MPa, at least 2.25 MPa, at least 2.5 MPa, at least 2.75 MPa, or at least 3.0 MPa. In some embodiments, the surface coatings have an interfacial of at least 0.4 MPa. In some embodiments, the surface coatings have an interfacial strength of at least 0.5 MPa. In some embodiments, the surface coatings have an interfacial strength of at least 0.75 MPa. In some embodiments, the surface coatings have an interfacial strength of at least 1.0 MPa. In some embodiments, the surface coatings have an interfacial strength of at least 1.5 MPa. In some embodiments, the surface coatings have an interfacial strength of at least 1.6 MPa. In some embodiments, the surface coatings have an interfacial strength of at least 1 .75 MPa.

[0266] The interfacial strength depends on the interactions between the substrate and the polymer and / or the reticulated structure. Therefore, a desirable interfacial strength may be achieved by selecting an appropriate substrate for the selected polymer / reticulated structure. Interfacial strength may be measured using a lap shear test (e.g., see inset of Figure 20), such as described in ISO 4587:2003.

[0267] In some embodiments, the surface coatings may be icephobic. Icephobicity is the ability of a solid surface to repel ice or prevent ice formation due to the structure or properties of the surface. A surface is considered to be icephobic if it has an ice adhesion strength (Tice) of < 100 kPa. Ice adhesion strength may be measured by measuring the peak shear force required to remove a layer of ice from the surface. For example, the ice adhesion strength may be measured according to the method as described in, and using an icing chamber and measurement apparatus as described in, Zheng et al. 2022.21

[0268] In some embodiments, the surface coatings have an ice adhesion strength of 150 kPa or less, 125 kPa or less, 100 kPa or less, 90 kPa or less, 80 kPa or less, 75 kPa or less, 70 kPa or less, 60 kPa or less, 50 kPa or less, 40 kPa or less, 35 kPa or less, 30 kPa or less, 25 kPa or less, 20 kPa or less, or 10 kPa or less. In some embodiments, the surface coatings have an ice adhesion strength of 100 kPa or less. In some embodiments, the surface coatings have an ice adhesion strength of 75 kPa or less. In some embodiments, the surface coatings have an ice adhesion strength of 50 kPa or less. In some embodiments, the surface coatings have an ice adhesion strength of 40 kPa or less. In some embodiments, the surface coatings have an ice adhesion strength of 30 kPa or less. 008864555

[0269] 38

[0270] Substrate

[0271] Surface coatings of the present invention may be used in combination with a wide range of substrates. For example, the substrate may be smooth or textures, rigid or flexible, transparent, translucent or opaque. In other words, the surface coatings are substantially substrate-independent. That is to say, the surface coatings are effective for a wide range of substrates. In some embodiments, the substrate is selected from the group consisting of: glass, metal, plastic, ceramic, fabric (i.e. made of fibres), paper, wood, concrete, rubber, and composites. In some embodiments, the substrate is glass, metal, plastic, and ceramic. In some embodiments, the substrate is a plastic selected from: polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polystyrene (PS), polyethylene terephthalate (PET), polycarbonate (PC), polymethyl methacrylate (PMMA), acrylonitrile butadiene styrene (ABS), nylon (polyamide), and polytetrafluoroethylene (PTFE). In some embodiments, the substrate is a metal selected from: iron, steel, aluminium, copper, brass, stainless steel, titanium, tin, lead, zinc, nickel, chromium, and magnesium. In some embodiments, the substrate is a glass selected from: soda-lime glass, borosilicate glass, tempered glass, laminated glass, glass used in displays (e.g., LCD, OLED), automotive glass, architectural glass, container glass. In some embodiments, the substrate is a ceramic selected from: alumina (AI2O3), silicon carbide (SiC), zirconia (ZrO2), titanium dioxide (TiO2), magnesia (MgO), porcelain, steatite (soapstone), beryllium oxide (BeO), and clay-based ceramic. In some embodiments, the substrate is made of fibres selected from: glass fiber, carbon fiber, aramid fiber, basalt fiber, ceramic fiber, and natural fibers (e.g., cotton, flax, hemp).

[0272] The surface coating is on the substrate. In other words, the surface coating coats a surface of the substrate. The surface coating may coat an entire surface of the substrate or part of a surface of the substrate. In some cases, the first layer is in direct contact with the substrate. In some cases, the first layer is in direct contact with an intermediate layer which is in direct contact with the substrate. For the avoidance of doubt, in situations where the first layer is in direct contact with the substrate, the first layer of the surface coating is in contact with the substrate, and the organosilane (e.g. alkyl silane) layer / groups is not in contact with the substrate (i.e. the organosilanes and the substrate contact opposing surfaces of the first layer, respectively). That is to say, in use, the organosilanes are exposed whereas the coated surface of the substrate is covered by the surface coating. In this way, a droplet of liquid on the coated surface comes into contact with the organosilanes upon which the droplet may slide or be repelled, without coming into contact with or adhering to the substrate. In some embodiments, a droplet of liquid on the coated surface comes into contact with the organosilanes does not come into contact with or adhere to the first layer.

[0273] The first layer of the surface coating may be physically adhered to the substrate, i.e. via intermolecular interactions such as hydrogen bonding, Van der Waals forces, London dispersion forces, Debye forces, and / or dipole-dipole interactions. Such forces may be present between the reticulated structure and the substrate, between the polymer and the substrate, or between the reticulated structure and the substrate as well as between the polymer and the substrate. 008864555

[0274] 39

[0275] An additional intermediate layer may be present between the first layer and the substrate to enhance contact of first layer with the substrate, for example having functional groups which react with one or more of the substrate, the polymer and the reticulated structure, thus improving robustness of the coating and / or interfacial strength. For example, the intermediate layer may be an adhesive layer. Examples of suitable adhesives include Epoxy, polyurethane, acrylic, silicone, cyanoacrylate, polyvinyl acetate (PVA), phenolic, rubber-based adhesives, anaerobic adhesives, and melamine-based adhesives.

[0276] The first layer of the surface coating may be chemically bonded to the substrate. For example, the polymer and / or the reticulated structure may be covalently bonded to the substrate surface.

[0277] In some embodiments, the substrates used herein for coating with a surface coating are reactive to a MOF layer or are functionalizable to be made reactive to the reticulated structure.

[0278] For example, the substrate may contain functional groups on its surface that are capable of bonding to the metal ions or linker molecules of the reticulated structure, and / or to groups in the polymer chain. Alternatively, the substrate surface can be reacted with a priming reagent to obtain functional groups that are capable of bonding to the metal ions or linker molecules of the reticulated structure, and / or to groups in the polymer chain.

[0279] Functional groups which are capable of bonding to the metal ions, linker molecules, and / or to the polymer may be, for example amino groups, alcohol groups, thiol groups or carboxyl groups.

[0280] When the substrate is glass, a priming reagent may be used to provide functional groups which are reactive to the reticulated structure on the surface of the glass. For example, a glass surface may be primed with 3-aminopropyltriethoxy silane (APTES) to provide amino groups on the surface of the glass.

[0281] Providing a layer of functional groups which are reactive to the reticulated structure (e.g., metal ion or linker) on the surface of the substrate is advantageous to obtain a firmly attached and uniform first layer. Alternatively, this surface attachment may be achieved by using an intermediate layer between the surface and the first layer, such as an adhesive layer that has good adhesion to the substrate surface and has surface groups that are reactive to the reticulated structure (e.g., metal ion of linker). Without wishing to be bound by theory, a firmly attached and uniform first layer is an important feature for obtaining a robust surface coating which is resistant to surface impalement.

[0282] Method of Coating a Substrate

[0283] In a second aspect, the present invention relates to a method of coating a substrate comprising: (a) applying a dispersion comprising, or consisting of, a polymer and a reticulated structure that is a metalorganic framework having pores or a covalent organic framework having pores to a substrate surface to form a first coating layer; and then (b) functionalising the first coating layer with an organosilane. 008864555

[0284] 40

[0285] For the avoidance of doubt, step (b) occurs after step (a). That is to say, the component(s) of the first layer are functionalised with an organosilane after being applied to the substrate surface.

[0286] Any of the preceding features mentioned with respect to the surface coating are relevant to the method of coating a substrate, the components used in the method, and the resulting coated substrate, as applicable.

[0287] Dispersion

[0288] In step (a), above, a dispersion comprising a polymer and a reticulated structure that is a metal-organic framework having pores or a covalent organic framework having pores is used.

[0289] Such a dispersion may be formed prior to step (a) by mixing a polymer, a reticulated structure that is a metal-organic framework having pores or a covalent organic framework having pores, and a solvent. The solvent may be an organic solvent or water, or a mixture of two or more solvents. In some embodiments, the solvent is or comprises water. In some embodiments, the solvent is or comprises an organic solvent. In some embodiments, the solvent is or comprises water and an organic solvent. In some embodiments, the organic solvent is selected from: methanol, ethanol, n-propanol, isopropanol, dimethylformamide (DMF), dimethyl sulfoxide (DMSO), acetone, hexane, tetrahydrofuran (THF), toluene, xylene, and cyclohexane. In some embodiments, the organic solvent is selected from: methanol ethanol, isopropanol, acetone, hexane, and toluene. The dispersion may be formed by simultaneously mixing the polymer, the reticulated structure, and the solvent. Alternatively, the dispersion may be formed by first mixing the polymer and the solvent, and then adding the reticulated structure, or the dispersion may be formed by first mixing the reticulated structure and the solvent, and then adding the polymer, or the dispersion may be formed by first mixing the reticulated structure and the polymer, and then adding the solvent. Alternatively, the dispersion may be formed by separately mixing the polymer with a solvent and the reticulated structure with a solvent, and then combining the two dispersions.

[0290] In some embodiments, in the dispersion, the polymer is a waterborne polymer (e.g., it is dispersed in water). For example, in the dispersion, the polymer is dissolved or dispersed in water. For example, in the dispersion, the polymer is not dissolved or dispersed in an organic solvent.

[0291] In some embodiments, prior to mixing with the reticulated structure, the polymer is a waterborne polymer (e.g., it is dispersed in water). For example, prior to mixing with the reticulated structure, the polymer is dissolved or dispersed in water. For example, prior to mixing with the reticulated structure, the polymer is not dissolved or dispersed in an organic solvent.

[0292] Therefore, the dispersion may be formed by:

[0293] Concomitantly mixing a polymer, a reticulated structure, and a solvent;

[0294] Mixing a reticulated structure with a dispersion comprising a polymer and solvent;

[0295] Mixing a polymer with a dispersion comprising a reticulated structure and a solvent; or 008864555

[0296] 41

[0297] Mixing a dispersion comprising a polymer and a solvent with a dispersion comprising a reticulated structure and a solvent.

[0298] The dispersion may be formed by mixing the reticulated structure and the polymer in a solvent and mixing until a homogeneous dispersion is obtained.

[0299] When the polymer is mixed with the reticulated structure in a dispersion, a portion of the polymer may at least partially penetrate into the pores of the reticulated structure, as described above with respect to the surface coating.

[0300] Therefore, also disclosed is a dispersion comprising a reticulated structure that is a metal-organic framework having pores or a covalent organic framework having pores and a polymer, wherein a portion of the molecules of the polymer at least partially penetrate into the pores of the reticulated structure. The dispersion may comprise or consist of the reticulated structure, the polymer, and a solvent.

[0301] In some embodiments of the dispersion, the polymer is a polyurethane. In some embodiments of the dispersion, the polymer is a polyester polyurethane copolymer. In some embodiments of the dispersion, the polymer is waterborne. In other words, in some embodiments of the dispersion, the solvent comprises water. In some embodiments of the dispersion, the polymer is waterborne polyurethane (WPU).

[0302] In some embodiments of the dispersion, the reticulated structure is a MOF having pores. In some embodiments of the dispersion, the MOF is UiO-66.

[0303] In some embodiments of the dispersion, the dispersion is homogeneous.

[0304] In some embodiments of the dispersion, the dispersion has a shear rate dependent viscosity, at a shear rate of 100 s-1, of 1000 mPa.s or less, 900 mPa.s or less, 800 mPa.s or less, 750 mPa.s or less, 700 mPa.s or less, 600 mPa.s or less, 500 mPa.s or less, 300 mPa.s or less, 250 mPa.s or less, 200 mPa.s or less, 150 mPa.s or less, or 100 mPa.s or less. In some embodiments, the dispersion has a shear rate dependent viscosity, at a shear rate of 100 s-1, of 500 mPa.s or less. In some embodiments, the dispersion has a shear rate dependent viscosity, at a shear rate of 100 s-1, of 400 mPa.s or less. In some embodiments, the dispersion has a shear rate dependent viscosity, at a shear rate of 100 s-1, of 300 mPa.s or less. In some embodiments, the dispersion has a shear rate dependent viscosity, at a shear rate of 100 s-1, of 250 mPa.s or less. In some embodiments, the shear rate dependent viscosity decreases with higher loading of the reticulated structure.

[0305] The shear rate dependent viscosity may be measured using a rheometer at 25 °C, such as a Discovery Hybrid rotational rheometer (DHR3, TA instrument), measured at shear rates between 0.1 and 1000 s-1.

[0306] In some embodiments of the dispersion, the dispersion is shear-thickening. 008864555

[0307] 42

[0308] The dispersion may be stable. In some embodiments, the dispersion is stable at room temperature. In some embodiments, the dispersion is stable when stored for an amount of time. In some embodiments, the dispersion is stable when stored for at least 12 hours, at least 1 day, at least 2 days, at least 3 days, at least 5 days, at least 1 week, at least 2 weeks, at least 3 weeks, at least 4 weeks, at least 1 month, at least 2 months, at least 3 months, at least 6 months, at least 9 months, at least 12 months, at least 18 months, or at least 24 months. The stability may be indicated by only a small change in shear viscosity over the time period, such as an increase of 200% or less, 150% or less, 125% or less, 100% or less, 75% or less, 50% or less, 25% or less, or 10% or less.

[0309] The dispersion may comprise other components. For example, the dispersion may comprise a crosslinking agent, a buffering agent, a softening agent, a fluidity agent, a pigment, a stabiliser, a UV stabilising agent, a surfactant (e.g. sodium dodecyl sulphate (SD) or a polysorbate), and / or a preservative.

[0310] Hence, also disclosed is a dispersion comprising a metal-organic framework having pores and a polyurethane, wherein a portion of the molecules of the polyurethane at least partially penetrate into the pores of the MOF.

[0311] Application of the Dispersion

[0312] The dispersion may be applied to a surface of the substrate by any method known in the art. For example, suitable methods include spraying, dipping (e.g. immersing), brushing, roll coating, spin coating, powder coating, and screen printing.

[0313] In some embodiments, the dispersion is applied to the substrate surface by spraying. In some embodiments, the dispersion is sprayed onto the substrate surface from a distance of between 1 cm and 1 m, such as between 5 cm and 50 cm, such as between 5 cm and 30 cm, such as between 10 cm and 25 cm, such as between 10 cm and 20 cm, such as about 15 cm. In some embodiments, the dispersion is sprayed using an air gun. In some embodiments, the dispersion is sprayed at a pressure of between 0.5 bar and 5 bar, such as between 1 bar and 4 bar, such as between 2 bar and 3 bar, such as about 2.5 bar.

[0314] In some embodiments, a single application of the dispersion may be performed (e.g., a single pass with a spray). In some embodiments, multiple applications of the dispersion may be performed (e.g., multiple passes with a spray). In some embodiments, at least 2, at least 3, at least 4, at least 5, at least 7, at least 10, at least 15, at least 20, at least 25, at least 30, at least 40 or at least 50 applications of the dispersion may be performed (e.g., at least that many passes with a spray). In some embodiments, about 20 applications of the dispersion may be performed (e.g., about passes with a spray). In some embodiments, the dispersion on the substrate surface is fully or partially dried between applications, for example there may be a period of time between applications. For example, the period of time between applications may be at least 1 min, at least 2 min, at least 5 min, at least 10 min, at least 15 min, at least 20 min, at least 30 min, at least 45 min, at least 60 min, at least 90 min, or at least 120 min. 008864555

[0315] 43

[0316] In some embodiments, the method further comprises a step, before (a), or treating the substrate. For example, the substrate may be primed (e.g. with a primer to enhance contact with the first layer) or may be washed. For example, the substrate may be cleaned using water and / or an organic solvent (e.g. isopropanol). Following cleaning / treating, the substrate may be dried, for example under an N2 flow.

[0317] Additionally, in some embodiments, prior to or during step (a) the substrate is heated, which may speed up or enable evaporation of the solvent when a dispersion is applied to the surface. For example, the substrate may be heated to at least 40 °C, at least 50 °C, at least 60 °C, at least 70 °C, at least 80 °C, at least 90 °C, at least 100 °C, at least 110 °C, at least 120 °C, at least 130 °C, at least 140 °C, at least 150 °C, at least 160 °C, at least 180 °C, or at least 200 °C. In some embodiments, the substrate is heated to at least 80 °C. In some embodiments, the substrate is heated to at least 100 °C. In some embodiments, the substrate is heated to at least 110 °C. In some embodiments, the substrate is heated to at least 120 °C. In some embodiments, the substrate is heated to about 80 °C. In some embodiments, the substrate is heated to about 90 °C. In some embodiments, the substrate is heated to about 100 °C. In some embodiments, the substrate is heated to about 110 °C.

[0318] Once applied to the substrate surface, the dispersion may be allowed to fully or partially dry before step (b). In other words, the water / solvent in the dispersion is fully or partially evaporated. This may also be referred to as curing the first layer. In some embodiments, the solvent is evaporated by leaving at room temperature for a period of time. In some embodiments, the solvent is evaporated by heating the dispersion for a period of time. For example, the applied dispersion may be heated to at least 40 °C, at least 50 °C, at least 60 °C, at least 70 °C, at least 80 °C, at least 90 °C, at least 100 °C, at least 110 °C, at least 120 °C, at least 130 °C, at least 140 °C, at least 150 °C, at least 160 °C, at least 180 °C, or at least 200 °C. In some embodiments, the applied dispersion is heated to at least 80 °C. In some embodiments, the applied dispersion is heated to at least 100 °C. In some embodiments, the applied dispersion is heated to at least 110 °C. In some embodiments, the applied dispersion is heated to at least 120 °C. In some embodiments, the applied dispersion is heated to about 80 °C. In some embodiments, the applied dispersion is heated to about 100 °C. In some embodiments, the applied dispersion is heated to about 110 °C. In some embodiments, the applied dispersion is heated to about 120 °C.

[0319] Alternatively, once applied to the surface, step (b) may be performed before the dispersion is dried.

[0320] In some embodiments, once applied to the surface, a crosslinking step may take place in which additional crosslinking of the polymer is induced, for example due to the inclusion of a crosslinking agent. Such a step may take place after step (a) but before step (b), or after step (b).

[0321] In some embodiments, the method may comprise a further step, after step (a), of removing excess polymer and / or reticulated structure from the substrate. In some embodiments, the method may comprise a further step, after step (a), of removing polymer molecules which do not penetrate into a reticulated 008864555

[0322] 44 structure. In some embodiments, the method may comprise a further step, after step (a), of washing the first layer before step (b). Such steps may occur before or after a drying step.

[0323] Silanization

[0324] In step (b), the first layer of the surface coating is functionalised with an organosilane. In other words, in step (b), the first layer of the surface coating is silanized.

[0325] The organosilane used in step (b) may be as described above with respect to the surface coating.

[0326] As with the surface coating, the organosilane may be an alkyl silane, an alkenyl silane, an alkynyl silane, or an aryl silane, for example an alkyl silane.

[0327] The organosilane (e.g. alkyl silane) used in step (b) (prior to reacting with the first layer) has general structure QSiRs, wherein Q is a group capable of a reacting with a group present in the first layer (e.g., a hydroxyl on the reticulated structure and / or the polymer), and at least one R group is an organic group, such as those described above with respect to the surface coating (e.g., a substituted or unsubstituted, branched or unbranched alkyl group). For example, Q may be selected from: halo (e.g., fluoro, chloro, iodo), alkoxy (e.g. methoxy, ethoxy, propoxy), acetoxy, and isocyanate. In some embodiments, Q is a chloro group or a methoxy group. In some embodiments, Q is a chloro group. In some embodiments, Q is a methoxy group. One, two, or three of the R groups may be an alkyl group as described above, and they may be the same or different. One or two of the R groups may also act as a Q group. In other words, the alkyl silane may have a formula selected from: QSiRs, Q2SiR2, and QsSiR, where Q and R are as defined above.

[0328] In some embodiments, the organosilane has at two or three Q groups. In some embodiments, the organosilane has three Q groups. In some embodiments, the organosilane has two or three chloro groups. In some embodiments, the organosilane has three chloro groups. In some embodiments, the organosilane has two or three methoxy groups. In some embodiments, the organosilane has three methoxy groups.

[0329] In some embodiments, the organosilane is an alkyl silane. In some embodiments, the alkyl silane is a trichloro alkyl silane. In some embodiments, the alkyl silane is trichloro octadecyl silane.

[0330] In some embodiments, the organosilane is selected from the group consisting of: trimethoxyoctadecylsilane, methyltrimethoxysilane, octyltriethoxysilane, aminopropyltriethoxysilane, vinyltrimethoxysilane, chloropropyltrimethoxysilane, glycidoxypropyltrimethoxysilane, phenyltrimethoxysilane, mercaptopropyltrimethoxysilane, isocyanatopropyltriethoxysilane, trichlorooctadecylsilane, methyltrichlorosilane, octyltrichlorosilane, aminopropyltrichlorosilane, vinyltrichlorosilane, chloropropyltrichlorosilane, glycidoxypropyltrichlorosilane, phenyltrichlorosilane, mercaptopropyltrichlorosilane, cyclohexyltrichlorosilane, trichloro(6-phenylhexyl)silane, 008864555

[0331] 45 trichlorotriacontylsilane, triethoxy(triacontyl)silane, (dotriacontyloxy)trimethylsilane, and isocyanatopropyltrichlorosilane. In some embodiments, the organosilane is selected from the group consisting of: trimethoxyoctadecylsilane, methyltrimethoxysilane, octyltriethoxysilane, vinyltrimethoxysilane, chloropropyltrimethoxysilane, glycidoxypropyltrimethoxysilane, phenyltrimethoxysilane, mercaptopropyltrimethoxysilane, isocyanatopropyltriethoxysilane, trichlorooctadecylsilane, methyltrichlorosilane, octyltrichlorosilane, vinyltrichlorosilane, chloropropyltrichlorosilane, glycidoxypropyltrichlorosilane, phenyltrichlorosilane, mercaptopropyltrichlorosilane, cyclohexyltrichlorosilane, trichloro(6-phenylhexyl)silane, trichlorotriacontylsilane, triethoxy(triacontyl)silane, (dotriacontyloxy)trimethylsilane, and isocyanatopropyltrichlorosilane.

[0332] The organosilane (e.g. alkyl silane) used in step (b) may be present as a solution or a dispersion. In some embodiments, the organosilane is in solution. In some embodiments, the organosilane is dissolved in water and / or an organic solvent. In some embodiments, the organosilane is dissolved in water. In some embodiments, the organosilane is dissolved in an organic solvent, such as methanol, ethanol, n-propanol, i-propanol, acetone, toluene, hexane, chloroform, dichloromethane, ethyl acetate, benzene, tetrahydrofuran (THF), diethyl ether, chloroform, acetonitrile, dimethyl sulfoxide (DMSO), or a mixture thereof. In some embodiments, the organosilane is dissolved in a mixture of water and an organic solvents (such as one of those listed above). In some embodiments, the organosilane is dissolved in a mixture of water and isopropanol. In some embodiments, the organosilane is dissolved in a solvent mixture with an isopropanol:water ratio between 1 :9 and 9:1 , such as between 2:8 and 9:1 , between 3:7 and 9:1 , between 4:6 and 9:1 , between 5:5 and 9:1 , between 5:5 and 8:2, between 6:4 and 8:2, between 6:4 and 7:3, or between 7:3 and 8:2. In some embodiments, the organosilane is dissolved in a solvent mixture with an isopropanol :water ratio of 7:3.

[0333] The organosilane may be applied to the first layer (which has been applied to the substrate surface) by any suitable method. Suitable methods include spraying, dipping (e.g. immersing), brushing, roll coating, and spin coating. In some embodiments, the organosilane is applied by spraying (e.g., spraying alkyl silane solution) or immersion (i.e., immersing first layer in alkyl silane solution).

[0334] In some embodiments, the organosilane is applied by spraying. In some embodiments, a single application of the organosilane may be performed (e.g., a single pass with a spray). In some embodiments, multiple applications of the organosilane may be performed (e.g., multiple passes with a spray). In some embodiments, at least 2, at least 3, at least 4, at least 5, at least 7, at least 10, at least 15, at least 20, at least 25, at least 30, at least 40 or at least 50 applications of the organosilane may be performed (e.g., at least that many passes with a spray). In some embodiments, the organosilane on the substrate surface is fully or partially dried between applications, for example there may be a period of time between applications. For example, the period of time between applications may be at least 1 min, at least 2 min, at least 5 min, at least 10 min, at least 15 min, at least 20 min, at least 30 min, at least 45 min, at least 60 min, at least 90 min, or at least 120 min. In some embodiments, the first layer is 008864555

[0335] 46 functionalised between applications, i.e. the first layer reacts with the applied organosilane before further organosilane is applied. In other words, in some embodiments, step (b) is repeated a number of times.

[0336] It may be necessary to apply certain conditions to initiate silanization once the organosilane is applied to the first layer. For example, step (b) may involve the application of heat (e.g. to a temperature of at least 100°C, such as 120°C) and / or the application of radiation (e.g. UV light). In some embodiments, the organosilane, prior to application to the surface, may be present in a solution / dispersion and may comprise one or more additional components, such as an initiator.

[0337] In some embodiments, once the organosilane has been applied to the first layer, step (b) comprises heating the organosilane on the first layer to initiate / accelerate silanization and / or to evaporate excess solvent. This step may be referred to as curing. For example, it may be heated to a temperature of at least 40 °C, at least 50 °C, at least 60 °C, at least 70 °C, at least 80 °C, at least 90 °C, at least 100 °C, at least 110 °C, at least 120 °C, at least 130 °C, at least 140 °C, at least 150 °C, at least 160 °C, at least 180 °C, or at least 200 °C. In some embodiments, the organosilane is heated to at least 80 °C. In some embodiments, the organosilane is heated to at least 100 °C. In some embodiments, the organosilane is heated to at least 110 °C. In some embodiments, the organosilane is heated to at least 120 °C. In some embodiments, the organosilane is heated to about 80 °C. In some embodiments, the organosilane is heated to about 100 °C. In some embodiments, the organosilane is heated to about 110 °C. In some embodiments, the organosilane is heated to about 120 °C.

[0338] In some embodiments, in step (b), the reticulated structure (e.g. the organic linker / ligating units in a MOF / COF) is silanized. In some embodiments, in step (b), the polymer is silanized. In some embodiments, in step (b), the reticulated structure (e.g. the organic linker / ligating units in a MOF / COF) and the polymer are silanized.

[0339] After step (b), there may be a further step of drying the coating to remove excess solvent (from the first layer dispersion, the organosilane solution / dispersion, or both). After step (b), there may be a further step of curing the coating.

[0340] After step (b), there may be a further step of treating and / or cleaning the surface coating. For example, the surface may be washed with water and / or an organic solvent (such as isopropanol). In some embodiments, a flow of nitrogen gas is applied to the surface (e.g., for drying).

[0341] Product-by-Process

[0342] In a third aspect, the present invention relates to a coated substrate or a coated article obtained by the method according to the second aspect. That is to say, the invention also relates to a coated substrate or a coated article obtained by: (a) applying a dispersion comprising a polymer and a reticulated structure to a substrate surface to form a first coating layer, wherein the reticulated structure is a metal-organic framework having pores or a covalent organic framework having pores, and a portion of the molecules of 008864555

[0343] 47 the polymer at least partially penetrate into the pores of the reticulated structure; and then (b) functionalising the first coating layer with an organosilane.

[0344] Each of the polymer, the reticulated structure, and the organosilane may be as described herein.

[0345] Such a coated substrate may be useful for a range of applications. For example, the coated substrate may be a liquid-repellent window or mirror (including, e.g., a camera lens), a liquid-repellent body of a vehicle, aerospace component (e.g., external aeroplane components), item of engineering or infrastructure (e.g., for energy generation, such as wind turbines), a liquid-repellent electronic component, liquid or gas pipelines (e.g., for transporting oil, natural gas, hydrogen, water, etc.), or a liquid-repellent item of construction. The coated substrate may be suitable for use as or with self-cleaning transparent surfaces (e.g., solar panels and screens), anti-icing aerospace components, durable automotive parts, components for energy generation, transmission and transportation, and components for chemical and physical processing.

[0346] A coated substrate obtained by the above method is protected by the surface coating from physical damage (owing to the mechanical robustness and weather-resistance of the surface coating) and from photodegradation, for example in the case where a photo-resistant polymer is used (such as a PU).

[0347] Ki

[0348] In a fourth aspect, the present invention relates to a kit comprising, or consisting of, a polymer, a reticulated structure that is a metal-organic framework having pores or a covalent organic framework having pores, and an organosilane.

[0349] Such a kit may be useful in a method coating a substrate according to the second aspect, or to provide a surface coating according to the first aspect.

[0350] The polymer, the reticulated structure, and the organosilane of the kit are as described previously herein.

[0351] The polymer in the kit is capable of at least partially penetrating into the pores of the reticulated structure, for example in a manner as described above with respect to the surface coating. That is, the polymer in the kit is selected to be capable of at least partially penetrating into the pores of the reticulated structure.

[0352] In some embodiments, the reticulated structure in the kit is provided as a dispersion. In some embodiments, the polymer in the kit is provided as a dispersion. In some embodiments, the polymer and the reticulated structure are provided together in a dispersion. In some embodiments, the polymer and the reticulated structure are provided together in a dispersion in which a portion of the polymer at least partially penetrates into the pores of the reticulated structure. In some embodiments, the organosilane of the kit is provided as a dispersion or a solution. In some embodiments, the organosilane of the kit is an alkyl silane. 008864555

[0353] 48

[0354] In some embodiments, the kit comprises a dispersion and an organosilane (e.g. an alkyl silane), the dispersion comprising a polymer and a reticulated structure that is a metal-organic framework having pores or a covalent organic framework having pores. The dispersion may be defined as described above.

[0355] For example, in the dispersion, a portion of the polymer may at least partially penetrate into the pores of the reticulated structure, as described above with respect to the surface coating.

[0356] In some embodiments, the kit further comprises a substrate to be coated.

[0357] The kit may comprise one or more further components, which will be apparent to the person skilled in the art. For example, the kit may further comprise a curing agent, a crosslinking agent, a cleaning agent, a pre-coating surface treatment, or a post-coating surface treatment.

[0358] In some embodiments, the kit comprises an applicator for the polymer / reticulated structure dispersion and / or an applicator for the organosilane. In some embodiments, the applicators) comprise a spray device or an atomiser.

[0359] 008864555

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[0361] Summary of the Figures

[0362] Embodiments and experiments illustrating the principles of the invention will now be discussed with reference to the accompanying figures in which:

[0363] Figure 1. Design principle: schematic illustration of sequential spray deposition of waterborne amphiphobic coatings.

[0364] Figure 2. PXRD pattern of MOF (UiO-66)

[0365] Figure 3. Raman spectra of MOF (UiO-66)

[0366] Figure 4. Effect of filler concentration on advancing contact angle (left bars) and contact angle hysteresis (right bars) of the WPU-MOF coating. Error bars represent standard deviation from at least four different measurements at different locations of the coating. WPU-MOF nanocomposites with varying filler concentrations were prepared to determine optimal nanoparticle concentration with best possible liquid repellence.

[0367] Figure 5. Shear viscosity of WPU-MOF coating immediately after preparation and following one month of storage.

[0368] Figure 6. Schematic illustration of WPU-MOF coating via spraying.

[0369] Figure 7. WPU / MOF / water suspension as prepared (left vial) and stored at room temperature for 1 month (right vial).

[0370] Figure 8. Optical image of WPU-MOF coating on different substrates: copper (50 mm x 50 mm), aluminium (50 mm x 50 mm), and plastic (50 mm x 50 mm). Liquid droplets of different surface tensions are placed on coated surfaces; 1) Water, 2) Glycerol, and 3) Ethylene glycol.

[0371] Figure 9. SEM images of MOF nanoparticles (UiO-66).

[0372] Figure 10. SEM images of WPU-MOF coating on glass.

[0373] Figure 11. Samples showing effect of spray passes on the transparency.

[0374] Figure 12. Cross-sectional SEM image of WPU-MOF coating on glass.

[0375] Figure 13. 2D topographical feature of the coating recorded using AFM.

[0376] Figure 14. Height profile recorded along the two white lines in Figure 13.

[0377] Figure 15. 3D AFM topography confirming the nanoscale roughness.

[0378] Figure 16. The UV-vis transmission spectra of different samples: glass as a control (Bare), trichlorooctadecyl silane coated glass (OTS), and WPU-MOF coating on glass.

[0379] Figure 17. Optical image showing droplets of water and other low surface tension liquids on transparent WPU-MOF coating. 008864555

[0380] 50

[0381] Figure 18. FTIR spectra of WPU (bottom trace), MOF (middle trace), and the intercalated WPU-MOF nanocomposite (top trace).

[0382] Figure 19. Stress-strain curves of WPU and the intercalated WPU-MOF nanocomposite (standard dumbbell shape specimen, ASTM D412, obtained at a constant deformation speed of 1 mm / min).

[0383] Figure 20. Adhesion force-displacement curves for glass and metal (copper) lap joints. Inset is the schematic of sandwich specimen for the lap shear test.

[0384] Figure 21. Force-displacement curves for adhesion testing of copper lap joints coated with WPU and WPU-MOF nanocomposite.

[0385] Figure 22. Shear viscosity of WPU and the intercalated WPU-MOF nanocomposite dispersion as a function of nanoparticle concentrations.

[0386] Figure 23. Advancing (0Adv) and receding (0Rec) contact angles of a water droplet on the intercalated WPU-MOF coating.

[0387] Figure 24. Bar diagram of 0Adv and contact angle hysteresis (A0) of water and different organic solvents with a wide range of surface tensions on the WPU-MOF coating; water (72.8 mN / m), ethylene glycol (47.3 mN / m), diiodomethane (50.8 mN / m), cyclohexanol (32.9 mN / m), decanol (28.5 mN / m), and butanol (25.0 mN / m).

[0388] Figure 25. Image sequence showing the amphiphobicity of WPU-MOF coating through sliding of low surface tension liquid droplets (10 pL) at 30° tilt angles. The low surface tension liquids are arranged with increasing viscosity (from top to bottom), which affect their sliding speed. The scale bar is 1 mm

[0389] Figure 26. SEM image of nanohierarchical MOF embedded into WPU matrix.

[0390] Figure 27. Schematic of water jet impact setup.

[0391] Figure 28. Snapshots of a 2.5 mm waterjet impacting on WPU-MOF coating at (A) ~6 m / s, (B) ~18 m / s, and (C) ~35 m / s. The jets are indicated as laminar, transitional, and turbulent depending on standard jet atomisation thresholds. (D) A turbulent water jet (~35 m / s) impacting on the WPU-MOF coating inclined at 45°.

[0392] Figure 29. 3D-microscope image of WPU-MOF on glass after repeated jet impacts (3 times) at 35 m / s.

[0393] Figure 30. Images indicating that the coating showed no signs of impalement as tested with rolling droplets immediate after several jet impacts.

[0394] Figure 31. Snapshots of 2.5 mm waterjet impacting on WPU-SiO2 coating vertically with a speed of 35 m / s.

[0395] Figure 32. 3D-microscope image of WPU-SiO2 coatings on glass after repeated jet impacts (3 times) at 35 m / s.

[0396] Figure 33. FTIR spectra of WPU, MOF (as synthesised), and WPU intercalated MOF. Inset: schematic representation of intercalation of WPU in MOF. 008864555

[0397] 51

[0398] Figure 34.13C NMR spectra of WPU, MOF, and WPU-MOF nanocomposite. Spinning frequency: 14 kHz.

[0399] Figure 35.1H NMR spectra of WPU, MOF, and WPU-MOF nanocomposite. Spinning frequency: 14 kHz. Inset: Zoomed view of aromatic protons in MOF and WPU-MOF coating.

[0400] Figure 36. The effect of tape peel cycles. Dynamic wetting behaviour remains unaffected even after 50 repeated cycles. Inset: SEM image of the coating after repeated tape peeling cycles.

[0401] Figure 37. Chemical stability of WPU-MOF coating. Variation of 0Adv and A0 in (A) acid (pH~1-2), and (B) alkali (pH~12-13) solution over a period of 24 hours.

[0402] Figure 38. Thermal stability of the WPU-MOF coated surface up to 200 °C (0Adv on the left scale and top trace; A0 on the right scale and bottom trace).

[0403] Figure 39. Ice adhesion strength of different surface treatments including bare glass as control, trichlorooctadodecyl silane coated glass (OTS), trichlorooctadodecyl silane coated PU on glass (WPU) and a WPU-MOF coating (as described herein) on glass (WPU-MOF).

[0404] Figure 40. Variation of ice adhesion strength of WPU-MOF coating up to 20 icing / deicing cycles.

[0405] Figure 41. SEM image of the coating showing some cracks after 20 icing / deicing cycles.

[0406] Detailed Description of the Invention

[0407] Aspects and embodiments of the present invention will now be discussed with reference to the accompanying figures. Further aspects and embodiments will be apparent to those skilled in the art. All documents mentioned in this text are incorporated herein by reference.

[0408] In light of the prior art discussed in the Background, and drawing from natural examples of biocomposites having remarkable mechanical robustness and impact resistance characteristics (such as the dactyl club of mantis shrimp), the present inventors have developed a strategy to produce a mechanically robust and impact resistant nanocomposite where polymer chains intercalate (i.e. penetrate) into pores of a reticulated structure (e.g. a MOF), and where the resulting coating layer is post-silanized with flexible alkyl chains.

[0409] In a specific embodiment of the present invention, off-the-shelf waterborne polyurethane (WPU) and MOF nanoparticles are dispersed together followed by spraying to create nanocomposite coatings. This is followed by exploiting functional groups on the MOF and polymer (e.g., the hydroxyl groups of the MOF) for post silanization with flexible alkyl chains. Beyond simplicity and scalability of application, the resulting coating shows a number of desirable and surprising properties. The nanohierarchical roughness contributes to optical transparency as well as amphiphobicity, with excellent slipperiness to low surface tension liquids. The combination of these unique features makes this coating suitable for self-cleaning transparent surfaces (e.g., solar panels and screens), anti-icing aerospace components, and durable automotive parts. Although MOF materials have higher preparation costs than traditional nanofillers, advancements in scalable synthesis methods, such as mechanochemical and continuous flow processes,27 28along with the low MOF content (~20 wt%) in the coating, enhance its cost-effectiveness 008864555

[0410] 52 and viability for large-scale applications. The coatings are transparent at thicknesses up to tens of micrometres, can be applied readily onto a diverse range of substrates (such as smooth / textured, rigid / flexible, and transparent / opaque etc.) and are able to sustain extensive surface damage. The polymer intercalation and robustness allow the coatings to retain their amphiphobic characteristics even after they are subject to high-speed waterjet impacts (v ~ 35 m / s) and repetitive icing / deicing cycles. The polymer intercalation is indicated through spectroscopic analyses. The present surface coatings demonstrate superior performance having the MOF nanocomposite when compared to silica nanoparticle-based composites. In this embodiment, the coatings show thermal stability up to 200 °C (which is dictated by organic components), and stability to chemical exposure and repeated tape peel tests.

[0411] Hence, the present inventors have developed a simple and scalable, optionally water-based, formulation for a surface coating, which may additionally be non-fluorinated and amphiphobic, that exhibit comprehensive robustness and optical transparency. For embodiments utilising a water-based polyurethane (WPU), the WPU provides excellent adhesion to the substrates, while the intercalation of WPU into the nanohierarchical MOF pores significantly enhances the mechanical durability of the coating. This intercalation, combined with the intrinsic properties of the MOF, endows the coating with superior amphiphobic characteristics. Such desirable properties can additionally be achieved in coatings using other types of the polymer and reticulated structure as described herein.

[0412] Application of the coatings described herein, including the silanization step, may be spray based, thus facilitating scalability. Previously, except surface-grown MOF which involves a tedious L / L approach,23amphiphobicity (to surface tension as low as 25 mN / m) using fluorine-free chemistry remained unachievable.56’57

[0413] By including the additional step of silanization, the coating possesses yet improved liquid repellence with low A0 and roll-off angles for a wide range of low surface tension liquids from alcohols to ketones. Coatings according to the present invention (such as WPU-MOF coatings) simultaneously demonstrate very good thermal stability, mechanical durability, liquid impalement resistance (e.g., at ~35 m / s jet impact), and anti-icing properties (e.g., having a low ice adhesion strength of~30 kPa).

[0414] The specific embodiment of a water-based spray formulation, with multifunctionality and robustness, offers ample opportunities for different industrial applications.

[0415] Overall, in some embodiments, the present invention provides a new approach to synthesise water-based fluorine-free coatings that are not only environmentally friendly, but also features the robustness that is necessary for industrial use.

[0416] The features disclosed in the foregoing description, or in the following claims, or in the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, 008864555

[0417] 53 or a method or process for obtaining the disclosed results, as appropriate, may, separately, or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

[0418] While the invention has been described in conjunction with the exemplary embodiments described above, many equivalent modifications and variations will be apparent to those skilled in the art when given this disclosure. Accordingly, the exemplary embodiments of the invention set forth above are considered to be illustrative and not limiting. Various changes to the described embodiments may be made without departing from the spirit and scope of the invention.

[0419] For the avoidance of any doubt, any theoretical explanations provided herein are provided for the purposes of improving the understanding of a reader. The inventors do not wish to be bound by any of these theoretical explanations.

[0420] Any section headings used herein are for organizational purposes only and are not to be construed as limiting the subject matter described.

[0421] Throughout this specification, including the claims which follow, unless the context requires otherwise, the word “comprise” and “include”, and variations such as “comprises”, “comprising”, and “including” will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

[0422] It must be noted that, as used in the specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. Ranges may be expressed herein as from “about” one particular value, and / or to “about” another particular value. When such a range is expressed, another embodiment includes from the one particular value and / or to the other particular value. Similarly, when values are expressed as approximations, by the use of the antecedent “about,” it will be understood that the particular value forms another embodiment. The term “about” in relation to a numerical value is optional and means for example + / - 10%.

[0423] 008864555

[0424] 54

[0425] Examples

[0426] Design principles, characteristics and properties of certain embodiments of the surface coatings and methods described herein will now be demonstrated in the following examples.

[0427] Methods and Materials

[0428] The following methods and materials were utilised in the Examples.

[0429] Materials

[0430] The water-based polyurethane (BAYHYDROL® UH 240) was obtained from Covestro AG (Germany). Microscopic glass slides (75 mm x 25 mm) were purchased from Thorlabs. All the chemicals including, zirconium chloride octahydrate (ZrOCI2.8H2O), terepthalic acid (TPA), dimethylformamide (DMF), acetone, ethanol, isopropanol, 1-butanol, glycol, glycerol, 1 ,2-butanediol, cyclohexanol, n-hexane, diiodomethane, and trichlorooctadecyl silane (OTS) were purchased from Sigma Aldrich. All the chemicals were used as received without further purification.

[0431] Instrumentation

[0432] The morphology of all the samples (MOF powder and coated samples) were characterised using scanning electron microscope (SEM, Carl Zeiss EVO25) and atomic force microscope (AFM, Bruker ICON SPM). For SEM, the samples were coated with a thin gold film to avoid charging and observed at an accelerating voltage of 20 kV. To confirm the chemical composition, FTIR spectra were recorded on a PerkinElmer Spectrum TwoTM spectrophotometer equipped with an iD5-ATR accessory, in a range of 4000 to 500 cm'1at a resolution of 4 cm'1. The PXRD (Stoe STADI-P) of MOF was collected with CuKa radiation (A=1 .542 A) in the range of 5-40° with a step size of 5° / min. Raman spectrometer (Renishaw), equipped with a 532 nm argon-ion laser source with a power of 2.5 mW was used to confirm the chemical structure of MOF. The rheological properties of WPU and the composite coating dispersion were measured using a Discovery Hybrid rotational rheometer (DHR3, TA instrument). The viscosities were measured at different shear rates (from 0.1 to 1000 s-1) under ambient conditions (25 °C). Mechanical properties of WPU and intercalated WPU-MOF nanocomposite films were studied by tensile test using an Instron 5659 testing machine provided with a 500 N load cell. Tensile strength, Young’s modulus, elongation at break, and toughness were calculated from stress-strain curves, as described previously herein. The UV-vis transmission spectra was recorded on an Orion™ AquaMate UV-vis spectrophotometer in the wavelength range of 300-800 nm.

[0433] Solid-State NMR

[0434] Solid-state NMR experiments were conducted on a Bruker Avance III HD spectrometer using a Bruker double-resonance 4 mm magic-angle spinning (MAS) probe. Quantitative13C NMR spectra were acquired using multiCP at a spinning rate of 14 kHz, with a Hahn spin echo sequence generated by a 180° pulse and EXORCYCLE phase cycling. To ensure quantitative results, all multiCP samples were packed in 008864555

[0435] 55

[0436] HRMAS rotors. The Ti p spectra were obtained using cross-polarisation total sideband suppression (CPTOSS). The recycle delay and contact time were optimised for each sample, determined to be 4 s and 4 ms, respectively. All Ti p measurements were performed at a sample spin rate of 7 kHz, with a 40 kHz spin lock, and at a calibrated sample temperature of 21 °C.

[0437] 1H direct excitation spectra were acquired with a 4 s recycle delay, calibrated for each sample, at a spinning rate of 10 kHz. Spectral referencing for13C and1H was done with respect to an external sample of tetramethylsilane, using the line from adamantane set to 38.5 ppm and 1 .9 ppm, respectively.

[0438] MOF Synthesis

[0439] MOF (UiO-66) were synthesised using an environment friendly solvothermal process.29In brief, 322.25 mg (25 mM) ZrOCI2.8H2O and 166.13 mg (25 mM) TPA were mixed in 40 mL DMF at room temperature and stirred for 5 minutes to achieve a clear solution. Then the solution was sealed and placed in a preheated oven at 120 °C for 12 hrs. The crystallisation was carried out at static conditions. After cooling down to room temperature, the resulted mixture was centrifuged at 6500 rpm for 10 min and washed with DMF and acetone thrice. Then the powder was dried in vacuum oven at 80 °C for overnight.

[0440] Spray coating and Silanization

[0441] A measured amount of MOF nanoparticles (50-500 mg) were added to 1 .0 g WPU and magnetically stirred for 20 min at 500 rpm to get a homogeneous dispersion. 20 mL water was added to the mixture and stirred for another 10 min to dilute the suspension. This diluted homogeneous mixture was stored in sealed glass bottles at room temperature for further use.

[0442] Prior to spraying, glass slides were cleaned ultrasonically using isopropanol and DI water for 15 minutes each, followed by drying with N2 flow. The diluted homogeneous mixture was sprayed on glass slides at 2.5 bar pressure from a working distance of 15 cm using an air gun (Iwata Eclipse, ECL2000, nozzle diameter = 0.5 mm). During spray, the glass slides were fixed vertically on a hot plate at 90 °C to accelerate the water evaporation and then the coating was cured at 90 °C for another one hour. Further, the surface chemistry was modified by spraying 1 % of OTS solution (isopropanol:water = 7:3) followed by curing at 120 °C for 2 hrs. The same process was followed to coat other substrates such as metals and plastics.

[0443] Contact angles measurement

[0444] The dynamic contact angles were measured using a custom made goniometer setup.30The setup consisted of adjustable stage, syringe pump (World Precision Instruments, Aladdin single-syringe infusion pump), retort stand, a light source (Thorlabs, OSL2), and a zoom lens (Thorlabs, MVL7000) fitted to a CMOS camera. The videos of the droplets were analysed using Imaged software to calculate advancing 008864555

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[0446] (0Adv) and receding (0Rec) contact angles. The reported values are the average of at least five measurements at different locations on a surface.

[0447] High-speed jet impact and tape peel test

[0448] High-speed jet impact experiments were performed to access impalement resistance of the coating using a setup described by Peng et al..30A high-pressure nitrogen gas cylinder connected to an electronic pressure valve was used to force water through a nozzle (a needle / syringe assembly). Different nozzles with nominal diameters 2.5 mm and 0.5 mm were used and the jet speed was controlled by tuning gas pressure. For 2.5 mm nozzle, maximum jet speed achieved in our experiment was 35 m / s with the corresponding Weber number, WeI= 42,534. The coating showed no signs of liquid impalement even after repeated jet impact on same spot. The lack of liquid impalement was confirmed by droplet mobility test.

[0449] To evaluate the mechanical durability of the coatings, a pressure-sensitive and strong adhesive tape (3M VHBTM tape 5952 with adhesive peel strength of 3,900 N / m) was applied to the coatings and pressed evenly using a 2 kg roller to ensure adhesion to the coatings and peeled off after 60 sec. This is considered as one cycle and the contact angle measurements were performed after each cycle to check the durability of the coating.

[0450] Thermal stability and ice adhesion measurement

[0451] Thermal stability of WPU-MOF coatings was evaluated by heating the samples from 40 °C - 200 °C for 1 hr on a temperature-controlled hotplate and the droplet mobility (sliding angle) was tested after cooling down to ambient temperature. Change in contact angle hysteresis (A0) was measured to quantify the droplet mobility after thermal treatment.

[0452] The ice adhesion strength of the coating was measured using a custom designed bench-top icing chamber whose details are described in our previous report.23The samples were fixed to the base plate, and plastic cuvettes of base area 1 cm x 1 cm were placed on them. The entire chamber was cooled down to -15 °C using a refrigeration unit (FP50-HL Refrigerated / Heating Circulator, Julabo). Then water was poured into the cuvettes and temperature was maintained for 2 hrs to ensure complete freezing of water. An extension rod connected to a force gauge (M4-50, MARK-10) was used to apply a shear force to the cuvettes and the peak force required to remove the ice was recorded. The ice adhesion strength was calculated by normalising the maximum force (Fm) required to remove the ice with the area of cuvettes (rice= Fm / A, where A is the contact area between cuvettes and the coating surface). At least three parallel samples were measured to obtain an average adhesion value. 008864555

[0453] 57

[0454] Example 1 - Design Principle and Morphology

[0455] The formulation and application strategy of the coating is shown in Figure 1 . Owing to their excellent thermal and mechanical stability, zirconium based MOF (UiO-66) were utilised as nanoparticle loading in the WPU matrix.31The crystallinity and chemical composition of as synthesised MOF nanoparticles were confirmed by PXRD and Raman spectra (Figure 2 and Figure 3, respectively). The PXRD spectra of MOF presents three characteristic diffraction peaks (20) at 7.3°, 11 .96°, and 25.5°, which are in agreement with literature.29Commercially available WPU (Bayhdrol® UH 240, Covestro) was selected as polymer matrix over alternatives like polyolefins due to its superior flexibility, impact resistance, inherent transparency, and compatibility with MOF for effective intercalation.32The nanoparticle concentration was adjusted to 20% by weight to achieve the best of transparency, liquid-repellence, and mechanical robustness through the intercalation strategy conceived. Relatively higher concentration of nanoparticles, to -40%, resulted in an increase in A0 from -9° to -24° (Figure 4). The optimal dispersion is stable (stored over a month at room temperature) as confirmed by rheological measurements. The viscosity measurements indicate that the solution exhibited minimal variation over the storage period (Figure 5), with only a minor increase at higher shear rates. This observed increase is attributed to shear-thickening behaviour, a phenomenon typically seen in concentrated polymer particle suspensions where the alignment of particles under shear leads to transient network formation, resulting in elevated resistance to flow.33These results indicate that the precursor solution maintained its stability without significant changes in its rheological characteristics. The dispersion can be sprayed on different substrates, such as glass, metals, and polymers (Figures 6-8) which demonstrate the substrate-independence of the coatings.

[0456] The surface morphology of MOF and the coating was characterised using scanning electron microscopy (SEM). As synthesised MOF exhibited octahedral crystal structures with an average size of -100-200 nm (Figure 9). Figure 10 confirms the uniformity of spraying process and revealed the presence of well- dispersed MOF nanoparticles within the coating. The thickness of the sprayed composite was adjusted through number of spray passes (-20) to achieve a trade-off between the transparency, mechanical robustness, and liquid repellence (Figure 11). Cross-section of the optimised coating on glass was imaged under SEM and thickness of the coating was measured to be -5 pm (Figure 12).The coating appeared homogeneous and smooth with very low local surface roughness scanned under atomic force microscope (AFM). Figures 13-15 show the 2D morphology, corresponding height profile, and 3D topography of the coating obtained from AFM. The root-mean square roughness 0"RMS) was measured -2.2 nm (scan area = 5x5 pm2). The low roughness and flexibility from grafted silanes is thought to help in promoting the liquid-repellence and transparency of the coating.

[0457] Example 2 - Transparency, Chemical Composition and Mechanical Properties

[0458] Optical transparency of the coating was measured using UV-vis spectroscopy in transmittance mode and the obtained spectra is shown in Figure 16. The WPU-MOF coating exhibited >87% transmittance in 400- 800 nm spectral range with maximum 91 % transmission. The transparency was also reflected by the 008864555

[0459] 58 easy visibility / readability of the characters underneath the coated surface and the amphiphobicity is demonstrated by placing droplets of different low surface tension liquids such as water, ethylene glycol, glycerol, and butanol (Figure 17). The submicron chemically homogeneous and highly porous nanoparticles (MOF) avoided the light scattering - resulting into enhanced transparency. The WPU, MOF, and intercalated WPU-MOF nanocomposite (cured) were examined using FTIR spectroscopy to confirm their chemical structure and identify the possible non-covalent interactions between the two components in the nanocomposite (Figure 18). The characteristics peaks at 3360 cm-1(N-H stretching), 2938 cm-1(C-H stretching), 1730 cm-1(C=O stretching), and 1174 cm-1(O-C-O) confirmed the chemical structure of WPU.34The spectral band at 1656 cm4was attributed to stretching vibrations of C=O in the carboxylic acid of MOF linker.35 36In case of the intercalated WPU-MOF nanocomposite, the C-H stretching of WPU centred at 2938 cm4and C=O vibrations centred at 1730 cm4were slightly shifted to 2916 cm4and 1726 cm4, respectively with significant increment in the peak intensity. These changes might have occurred due to the physical interactions of WPU and MOF caused by van der Waals, London dispersive, and electrostatic forces.36

[0460] The mechanical properties of the intercalated WPU-MOF nanocomposite, including stiffness and substrate adhesion was measured to confirm the robustness of the coating. The (ultimate) tensile strength, Young’s modulus, elongation at break, and toughness obtained for WPU and the intercalated WPU-MOF nanocomposite (Figure 19) are summarised in Table 1 , below. Addition of MOF into WPU matrix resulted in slight increase in the tensile strength and Young’s modulus of the film. However, the incorporation of MOF led to smaller elongation at break, reduced from 1028% to 758% and toughness was also reduced by 22.5%. This was expected as MOF can act as reinforcement to polymer matrix which makes the nanocomposite film more rigid than that obtained from only WPU. The high adhesion of WPU was tested on two different substrates (glass and copper), shown in Figure 20. The coating shows an interfacial bonding strength of 1 .9 MPa and 0.5 MPa with copper and glass substrate, respectively. The obtained excellent adhesion could be due to the hydrogen bonding from N-H and C=O functional groups and strong non-covalent interaction (e.g. van der Waals forces) from the benzene ring of WPU to the hydroxyl groups on the substrates.37In presence of MOF in WPU, the interfacial strength of the coating decreased to 1 .6 MPa with copper (Figure 21). The slight reduction in adhesion strength is likely due to the disruption of the uniform interaction between WPU and the substrate by the MOF nanoparticles. However, this does not significantly affect the coating’s overall performance, as the nanocomposite retains sufficient adhesion for practical applications.

[0461] Table 1. Tensile properties of WPU and the intercalated WPU-MOF nanocomposite film

[0462] The rheological properties of nanocomposites are known to be influenced by shape, size, orientation, and dispersion of the nanoparticles.38Figure 22 shows the shear rate dependent viscosity of the intercalated 008864555

[0463] 59

[0464] WPU-MOF nanocomposite as a function of nanoparticle concentration. At a shear rate of 100 s-1, the viscosity of WPU was 556 mPa.s which gradually reduced to 210 mPa.s with increase in the nanoparticle concentration from 5 to 20 wt%, respectively. The addition of MOF nanoparticles led to shear thinning and no significant change in the viscosity was observed beyond 20 wt% nanoparticle concentration i.e. optimised nanoparticle concentration. At high shear rate of 1000 s-1, the viscosities remain similar for each case irrespective to the nanoparticle concentrations. The interfacial layer (IL) of WPU plays a major role in determining the rheological behaviour of the nanocomposite.39 40The IL, defined as the fraction of polymer chains in direct contact with the particle surface,41can impact the mobility and entanglement of these chains with the bulk polymer matrix. Upon intercalation, a part of the polymer chain is likely to remain outside to maintain mobility, ensuring that the viscosity remain unaffected.

[0465] Example 3 - Surface Wettability

[0466] Irrespective of the substrate, the WPU-MOF coating appeared to be smooth with excellent repellence to a wide range of probing liquids. Dynamic wettability of the coated surfaces was assessed by measuring the advancing (0Adv) and receding (0Rec) contact angles, and contact angle hysteresis (A0) of water droplets. As shown in Figure 23, the coating is hydrophobic with 0Adv and A0 measured ~112 ± 3° and ~9 ± 2°, respectively. Droplets of water and other low surface tension liquids such as, ethylene glycol, glycerol, and butanol were observed to slide off at <30° tilt angle, demonstrating excellent amphiphobicity of the WPU-MOF coatings. The 0Adv of the polar and non-polar liquids decreased with reduction of surface tension (Figure 24). A0 of low surface tension liquids were recorded slightly higher (~15 ± 2°) when compared to water (~9 ± 2°). The viscosity and surface energy of these liquids may explain this increase. Higher viscosity can slow down the movement of the contact line whereas lower surface energy of liquid enhances adhesion to the solid surface which results in higher A0. The sliding behaviour of these liquids are shown in Figure 25.

[0467] To understand the nanohierarchical effect of MOF, only WPU coating (without MOF) after silanisation was also tested. Interestingly, WPU coating can only repel water but not the low surface tension liquids. In addition to nanohierarchical roughness, the controlled functionalisation of silane on the repeated crystalline units of embedded MOF contributes to amphiphobicity. This underscores the importance of nanohierarchical MOF (Figure 26) and the flexibility of the long silane chains which reduced the solidliquid contact area and facilitated the easy sliding of liquid droplets.23

[0468] Example 4 - Surface Wettability

[0469] Mechanical robustness is one of the major challenges in commercial applications. Substrate adhesion and inherent mechanical stability (cohesion) of coating components play a significant role in overall robustness.42Therefore, in addition to nanohierarchical characteristics, a zirconium based MOF, with high shear modulus of 13.7 GPa was chosen.43Two different types of tests, high-speed jet impact and standard tape-peel were performed to assess the mechanical durability of the WPU-MOF coating. Highspeed waterjets were generated by pneumatic forcing of water through a nozzle to overcome the 008864555

[0470] 60 limitation of terminal velocity of gravity-accelerated drops (Figure 27).30 44The coating was impacted with continuous waterjets of different velocities and the events were captured by high-speed camera shown in Figure 28. The liquid Weber number (WeL= pv2d / yLC) was calculated to quantify the severity of the impact. With 2.5-mm nozzle, the maximum speed achieved in this setup is ~35 m / s with the corresponding WeL= ~ 42,534. The jet forms a stagnation point at the point of impact and follows an axisymmetric stagnation flow trajectory. The ability of the WPU-MOF coating to withstand the repeated jet impacts at an average speed of 21 m / s was also tested. After subjecting to repeated jet impacts, the coatings showed no damage or, impalement by the liquid (Figure 29). Post-impact measurements did not show significant changes in the wettability either. The liquid impalement resistance was confirmed by placing a water droplet at impacted area followed by normal sliding (Figure 30). The impact resistance of the coating can be explained by comparing capillary pressure (Pe) of the MOF pores with the water hammer pressure (Ph) generated in the jet impact. The capillary pressure from pores needs to resist the compressive water hammer pressure in order to avoid the liquid impalement.45The capillary pressure can be calculated using following equation (1):

[0471] Pc = ^YLG<:osdAdv / D (1)

[0472] Here, D is the average capillary diameter, yLGis the surface energy at liquid-gas interface, and 0Adv is the advancing contact angle of water on a smooth MOF surface. Taking the average pore diameter of MOF as 0.6 nm,46 Pcwas estimated to be ~181 MPa. On the other hand, to a first approximation, the water hammer pressure can be estimated using the following equation (2):

[0473] Ph= k pCv (2) where C = 1497 m / s is the sound velocity in water, p density of water, v is the impact velocity, and k is an experimental constant, often approximated as 0.2.47Taking v = 35 m / s, the Phcomes out as ~10.5 MPa which is much less than the estimated capillary pressure. In other words, these amphiphobic coatings can withstand the waterjet impact without any impalement damage. The water hammer pressure is also lower than the mechanical strength of the coating (see Table 1). To demonstrate the superior mechanical robustness of the WPU-MOF coatings, waterjet tests were also performed on WPU-SiO2 coatings (Figure 31). Commercially available fumed silica nanoparticles (nonporous), incorporated into WPU matrix (WPU- SiO2), was used as a control for comparison. The WPU-SiO2 coatings failed in jet impact and clearly showed damage at the impact location (Figure 32), confirming the benefits of MOF in mechanical integrity. Unlike WPU-SiO2, in case of WPU-MOF coatings, intercalation of polyurethane chains into MOF pores facilitates a more uniform distribution and interlocking at the molecular level which will be expected to help in resisting localised stress concentrations.48 49To verify the intercalation of WPU molecular chains into MOF pores, dispersion of WPU and MOF nanoparticles was washed several times to remove unbound / loosely adhered WPU, dried (80°C for 6 hrs), and subjected to FTIR together with controls i.e. MOF and WPU. As evident from the spectra (Figure 33), in addition to characteristics peaks of MOF and WPU, a clear shift of symmetric and asymmetric stretching of -CH2 from 2863 cm4to 2853 cm4and 2938 cm4to 2922 cm4was observed in the spectra of WPU-MOF washed sample. Further, the broad 008864555

[0474] 61 band centred at 3342 cm-1arises due to stretching of aliphatic amine groups, N-H of polyurethane. This shows the possible van der Waals interaction of WPU phenyl ring to the MOF structure.

[0475] Furthermore, solid-state NMR was employed to investigate the interaction between MOF and WPU.13C and1H MAS NMR spectra of WPU, MOF, and WPU-MOF coating are shown in Figure 34 and 35, respectively.13C MAS NMR spectrum of MOF contains three characteristics peaks located at isotropic chemical shifts of 129.8, 137.7, and 170.5 ppm. The peak at high chemical shift is characteristic of C atoms from the carboxylic group. The aromatic C-H and C-C groups in the MOF exhibit negligible chemical shift (< 1 ppm) but significantly increased line width in the presence of WPU, indicating a strong interaction between WPU and MOF. Further, the1H NMR spectrum of MOF contains two main regions (Figure 35) characteristic of the aromatic protons (~8 ppm) and of the Zr-OH groups (0-3 ppm). In presence of WPU, the line width of aromatic proton peak increases, which is attributed to1H-1H dipolar coupling of these protons to those of WPU within sub-nm distances. This indicates the presence of WPU within the MOF pores.50 51These initial signatures of intercalated WPU-MOF nanocomposite indicate improved interfacial adhesion, reduced particle agglomeration, and enhanced structural reinforcement, leading to increased strength, durability, and impact resistance.

[0476] A standard tape peel test (using a 3M VHBTM tape 5952) was also performed to assess the mechanical durability of the coating.52As shown in Figure 36, with increasing tape peel cycles, 0Adv remains almost same with a slight increase in A0, from 9 ± 2° to 14 ± 2°. No delamination was observed (Inset: Figure 36), and the coating maintained its repellence even after 50 repetitive tape peeling cycles - again confirming mechanical robustness of the WPU-MOF coating. However, when subjected to Taber abrasion tests, these coatings exhibited limited wear resistance. This is possibly due to the inherent flexibility of the waterborne polyurethane matrix, which, while beneficial for impact resistance and tensile properties, may reduce the coating’s ability to withstand continuous abrasive forces. Additionally, these coatings can retain its structural integrity in acidic environments (pH ~1-2) for 24 hours and in moderately alkaline conditions (pH ~11-12) for up to 12 hours (Figure 37).

[0477] Example 5 - Thermal stability and ice adhesion measurement

[0478] The thermal stability of amphiphobic coatings is essential to ensure the adequate performance in outdoor applications such as energy generation and storage (wind turbine blades), chemical and thermochemical processing operations, aviation and power transmission.53Thermal stability of WPU-MOF coatings was tested in the temperature range of 40 °C to 200 °C; a 2 hrs exposure was used at each temperature and the change in A0 was recorded to assess the damage following cool off of the coating down to room temperature. At the highest tested temperature of 200 °C, A0 increased slightly from 9 ± 2° to 15 ± 2° and no significant change was observed in the 0Adv (Figure 38). Therefore, the choice of porous MOF with very good thermochemical and mechanical robustness contributes favourably.

[0479] Owing to the smoothness and excellent liquid repellence of the WPU-MOF coating, its anti-icing properties were assessed next by measuring the ice adhesion strength. The WPU-MOF coating was 008864555

[0480] 62 compared with different control surfaces including bare glass, silane coated glass, and silane coated WPU on glass for its ice adhesion strength. As shown in Figure 39, the ice adhesion strength of Tice=30 ± 6 kPa was recorded on WPU-MOF coatings which is ~92% lower compared to bare glass and well below the threshold to designate it as an ‘icephobic’ surface (Tice<100 kPa).54For these amphiphobic coatings, the mobility of flexible alkyl silanes might have facilitated the easy removal of ice via interfacial slippage.

[0481] Newby et al.55first verified the phenomenon of interfacial slippage and proved that adhesion strengths of a viscoelastic adhesive on a liquid-like silane monolayer is not controlled by thermodynamic work of adhesion, rather depends on the mobility of the grafting silanes. The dynamic, liquid-like behaviour of the silanes reduces interfacial friction, minimises contact points, and weakens adhesion through reduced effective contact area and dynamic interactions. This results in lower adhesion strength, allowing ice to be removed with minimal force.

[0482] Furthermore, the robustness of the coating was tested by repeating icing / deicing cycles; followed by measuring ice adhesion strengths after each cycle (Figure 40). No significant change in the ice adhesion strength was observed up to 15 cycles. After 20 cycles, the ice adhesion strength increased gradually to 52 ± 8 kPa and some cracks were observed in the coating (Figure 41). The 0Adv decreased to 104 ± 2° while A0 increased to 16 ± 3° (see inset in Figure 41) after 20 icing / deicing cycles. No significant deterioration of liquid repellence was observed.

[0483] 008864555

[0484] 63

[0485] References

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Claims

00886455569Claims1 . A surface coating comprising a first layer on a substrate, the first layer comprising a reticulated structure and a polymer, wherein: the reticulated structure is a metal-organic framework (MOF) having pores or a covalent organic framework (COF) having pores; a portion of the molecules of the polymer at least partially penetrate into the pores of the reticulated structure; and the surface of the first layer opposite the substrate is functionalised with an organosilane.

2. The surface coating of claim 1 , wherein the surface coating is amphiphobic.

3. The surface coating of claim 1 or 2, wherein the surface coating, not including the substrate, has a light transmittance in the 400-800 nm range of at least 75%.

4. The surface coating of any preceding claim, wherein the polymer comprises a repeating polar group and a repeating non-polar group.

5. The surface coating of claim 4, wherein the polymer is a polyurethane.

6. The surface coating of any preceding claim, wherein the reticulated structure comprises a group which reacts with an organosilane, optionally wherein said group is a hydroxyl group.

7. The surface coating of any preceding claim, wherein the organosilane is an alkyl silane, optionally wherein the alkyl silane is bonded to the first layer via a silyl ether bond (-C-O-Si-).

8. The surface coating of any preceding claim, wherein the reticulated structure is a MOF having pores.

9. The surface coating of any one of claims 1 to 7, wherein the reticulated structure is a COF having pores.

10. The surface coating of any preceding claim, wherein the reticulated structure is contained in the first layer in an amount of between 5 and 40 wt%, relative to the combined weight of the reticulated structure and the polymer.

11. A coated article comprising a surface coating according to any preceding claim.

12. A method of coating a substrate comprising:(a) applying a dispersion comprising a polymer and a reticulated structure to a substrate surface to form a first coating layer, wherein the reticulated structure is a metal-organic framework having pores or a covalent organic framework having pores, and a portion of the molecules of the polymer at00886455570 least partially penetrate into the pores of the reticulated structure; and then(b) functionalising the first coating layer with an organosilane.

13. A coated substrate or coated article obtained by: (a) applying a dispersion comprising a polymer and a reticulated structure to a substrate surface to form a first coating layer, wherein the reticulated structure is a metal-organic framework having pores or a covalent organic framework having pores, and a portion of the molecules of the polymer at least partially penetrate into the pores of the reticulated structure; and(b) functionalising the first coating layer with an organosilane.

14. A kit comprising a polymer, a reticulated structure that is a metal-organic framework having pores or a covalent organic framework having pores, and an organosilane, wherein the polymer is selected to be capable of at least partially penetrating into the pores of the reticulated structure, and optionally wherein the polymer and the reticulated structure are present together in a dispersion.

15. A dispersion comprising a polyurethane and a reticulated structure, wherein the reticulated structure is a metal-organic framework having pores or a covalent organic framework having pores, and a portion of the molecules of the polyurethane at least partially penetrate into the pores of the reticulated structure.

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