Photo-thermal synergistic self-repairing super-hydrophobic transparent coating and preparation method thereof

Abstract

The invention discloses a photo-thermal synergistic self-repairing super-hydrophobic transparent coating and a preparation method thereof. The photo-thermal synergistic self-repairing super-hydrophobic transparent coating comprises a bottom layer, a middle layer and a surface layer which are connected in sequence, and specifically, the bottom layer is an organic-inorganic hybrid binding phase containing a silane coupling group; the middle layer comprises a graded coarse structure and metal-organic framework (MOF) nano-particles, and the MOF nano-particles are loaded with photocrosslinkable monomers and / or low surface energy molecules; and the surface layer comprises a photo-initiation system sensitive to ultraviolet light, a photo-crosslinkable unsaturated group and a low-surface-energy component. According to the coating provided by the invention, the optical transparency, super-hydrophobic self-repairing, antifouling and anti-adhesion, wear resistance, weather resistance and the like are synergistically improved, and stable mass production can be realized under a spraying / pre-curing process at the temperature of less than or equal to 90 DEG C.

Description

Technical Field

[0001] This invention relates to the field of functional coatings and surface engineering technology, and in particular to a photothermal synergistic self-healing superhydrophobic transparent coating and its preparation method. Background Technology

[0002] Transparent superhydrophobic coatings can impart properties such as antifouling, self-cleaning, and anti-icing / anti-condensation to substrates. However, existing technologies generally suffer from the following drawbacks: (1) the surface micro-nano rough structure is easily damaged by wiping, sand, or raindrops, resulting in rapid performance degradation; (2) it is difficult to balance high transmittance with a rough structure, leading to increased haze; (3) insufficient adhesion between the coating and the substrate; and (4) a lack of self-repair capability without external energy under in-service conditions, resulting in high maintenance costs. There is an urgent need to prepare a transparent superhydrophobic coating that can continuously repair itself under natural UVA and ≤90°C conditions, while also achieving both high transmittance and low haze. Summary of the Invention

[0003] This invention solves the problems existing in the prior art and provides a photothermal synergistic self-healing superhydrophobic transparent coating and its preparation method. This invention relies on the synergistic triggering of UVA (365 nm) and medium-low temperature (60°C-80°C) to achieve multi-channel self-healing transparent superhydrophobic coating through photocrosslinking / thermal migration / MOF slow release. Without sacrificing optical performance, it achieves an average transmittance of ≥90% for visible light (400–800 nm) and a haze of ≤1.5%, while maintaining a static water contact angle of ≥160° and a roll-off angle of ≤5°. It can also maintain hydrophobicity and high transmittance for a long time after wear resistance and accelerated aging conditions, and can be prepared on a large scale by spraying at a pre-curing temperature of ≤90°C.

[0004] The first objective of this invention is to provide a photothermal synergistic self-healing superhydrophobic transparent coating with an average visible light transmittance ≥90%, haze ≤1.5%, static water contact angle ≥160°, roll-off angle ≤5°, and a coating thickness of 1-10 μm. The coating comprises a bottom layer, an intermediate layer, and a top layer connected sequentially. Specifically, the bottom layer is an organic-inorganic hybrid binder phase containing silane coupling groups; the intermediate layer contains a hierarchical rough structure and metal-organic framework (MOF) nanoparticles, wherein the MOF nanoparticles are loaded with photocrosslinkable monomers and / or low surface energy molecules; and the top layer contains a photoinitiating system sensitive to ultraviolet light, photocrosslinkable unsaturated groups, and low surface energy components.

[0005] Organic-inorganic hybrid binder phase (tetraethoxysilane (TEOS) / 3-aminopropyltriethoxysilane (APTES) / γ-glycidoxypropyltrimethoxysilane (GPTMS) sol-gel system): TEOS, APTES and GPTMS are the silane precursor components for the bottom film formation. Solvent, water and catalyst are used to promote hydrolysis and condensation and to regulate the viscosity and solid content of the system. The amount of solvent and water can be adjusted under the premise of meeting the requirements of hydrolysis and condensation reaction and film formation.

[0006] The preferred preparation conditions are as follows: the molar ratio of TEOS to water is 1:(2–6), preferably 1:(2.0–3.0); the amount of glacial acetic acid is 0.02–0.05 wt% (based on solvent) as an acid catalyst; the viscosity parameters of the underlayer sol are as follows: the underlayer sol can be in the form of a high-solids content mother liquor or a diluent for application. When used as a high-solids content mother liquor, its apparent viscosity at 25°C can be 200–2000 mPa·s (e.g., about 1530 mPa·s), which is used to improve the film density and adhesion continuity; when used as an application coating, the high-solids content mother liquor can be diluted with ethanol / isopropanol, so that its application viscosity at 25°C is preferably 10–100 mPa·s, to meet the requirements of spray atomization and uniform spreading. The viscosity values ​​given in the examples can be the measured viscosity or converted value of the high-solids content mother liquor, all of which fall within the above range.

[0007] Preferably, the thickness of the coating is 2-6 μm.

[0008] Preferably, the MOF is a zeolite imidazole skeleton-8 or an amino-modified UiO-66 with a particle size of 10-100 nm.

[0009] Preferably, the low surface energy molecule is selected from perfluorohexyltriethoxysilane and / or perfluorohexyl acrylate, polydimethylsiloxane terminal silane, long-chain alkyl silane and / or cage-like silsesquioxane.

[0010] The photocrosslinkable unsaturated groups (or photocrosslinkable monomers) are selected from unsaturated compounds containing carbon-carbon double bonds and are used to undergo free radical polymerization or graft crosslinking reactions under the action of photoinitiators; specifically, they can be one or more of allyl monomers, (meth)acrylate monomers, styrene monomers, and polymerizable silane monomers with unsaturated end groups.

[0011] Preferably, the polymerizable silane monomer is selected from 3-(meth)acryloyloxypropyltrialkoxysilane (such as 3-(meth)acryloyloxypropyltrimethoxysilane or 3-(meth)acryloyloxypropyltriethoxysilane), allyltrialkoxysilane (such as allyltrimethoxysilane or allyltriethoxysilane), etc.; the above are exemplary examples, and the specific selection can be adjusted according to the crosslinking efficiency, film density and wear resistance requirements.

[0012] The low surface energy component in the surface layer can be selected from one or more of fluorinated silanes, fluorinated acrylates, and / or non-fluorinated low surface energy silanes; preferably, perfluorohexyltriethoxysilane (C6 fluorosilane) and / or perfluorohexyl acrylate, the total amount of which can be 0.5-3.0 wt% of the surface layer; in fluorine-free alternatives, terminal silanized PDMS, hexadecyltrimethoxysilane (HDTMS) and / or cage-like silsesquioxane (POSS) can be selected, the total amount of which can be 1.0-4.0 wt% of the surface layer. The above components and content ranges are exemplary conditions, and can be adjusted according to the target light transmittance and hydrophobicity requirements.

[0013] Photoinitiation system (365 nm): selected from TPO / TPO-L / benzophenone, total amount of which accounts for 0.1-1.5 wt% of the surface layer.

[0014] The second objective of this invention is to provide a method for preparing the aforementioned photothermal synergistic self-healing superhydrophobic transparent coating, comprising the following steps:

[0015] S1. Pre-treat the substrate and deposit an underlayer of an organic-inorganic hybrid binder phase containing silane coupling groups;

[0016] S2. Spray an intermediate layer containing a graded rough structure and MOF nanoparticles onto the bottom surface;

[0017] S3. A surface layer is formed by spraying a coating onto the surface of the intermediate layer. The surface layer contains at least a photoinitiating system and a low surface energy component, and contains photocrosslinkable unsaturated groups. The photocrosslinkable unsaturated groups are allyl or (meth)acrylate unsaturated groups. The photocrosslinkable unsaturated groups are directly introduced by the surface coating liquid or provided by MOF nanoparticles preloaded with the photocrosslinkable unsaturated groups in the intermediate layer. Under subsequent ultraviolet light irradiation, polymerization and crosslinking occur to form a continuous and dense low surface energy crosslinked layer, resulting in a photothermal synergistic self-healing superhydrophobic transparent coating. The coating liquids used in steps S1–S3 are independently prepared and sprayed sequentially. Each layer is formed on the basis of the previous layer being cured or semi-cured, thereby constructing a layered structure of bottom layer-intermediate layer-surface layer.

[0018] The photocrosslinkable unsaturated groups can be provided in any of the following ways: First, photocrosslinkable monomers or oligomers containing unsaturated bonds are directly added to the surface coating liquid; Second, the MOF nanoparticles in the intermediate layer are preloaded with the photocrosslinkable monomers. During the surface spraying and pre-curing process, the monomers are slowly released from the MOF channels and migrate to the intermediate-surface interface, so that a crosslinkable phase containing unsaturated groups is formed in the surface region. Under subsequent ultraviolet light irradiation, it undergoes free radical polymerization / crosslinking in synergy with the photoinitiating system, thereby forming a continuous and dense photocrosslinking network on the surface and achieving a stable construction of a low surface energy layer.

[0019] Preferably, the deposition of an organic-inorganic hybrid binder phase substrate containing silane coupling groups in step S1 specifically includes the following sub-steps:

[0020] S11. Preparation of hydrolysis solvent: Anhydrous ethanol, deionized water and glacial acetic acid are mixed to obtain the hydrolysis solvent, wherein the deionized water accounts for 3%–8% of the total volume of the hydrolysis solvent and the amount of glacial acetic acid accounts for 0.05–0.10 wt% of the total mass of the mixed solvent; after mixing, the temperature is cooled and controlled at 20°C–25°C.

[0021] S12. Adding silane precursors and hydrolyzing: Tetraethoxysilane (TEOS), 3-aminopropyltriethoxysilane (APTES), and γ-glycidoxypropyltrimethoxysilane (GPTMS) are added to the hydrolysis solvent. The molar ratio of TEOS to deionized water is 1:(2-6). The mixture is stirred for 10-120 min to complete the initial hydrolysis and condensation, obtaining the bottom sol. APTES and GPTMS together introduce organic functional groups to enhance interfacial coupling and reactivity. Tetraethoxysilane (TEOS), 3-aminopropyltriethoxysilane (APTES), and GPTMS are added to the hydrolysis solvent, and the mixture is stirred for 10–120 min to complete the initial hydrolysis and condensation, obtaining the bottom sol. Preferably, the molar ratio of TEOS:APTES:GPTMS is (6.0–10.0):(4.0–7.0):1.0; and / or the mass ratio of TEOS:(APTES+GPTMS) is (3–8):1, and the mass ratio of APTES:GPTMS is (0.5–2.0):1. The above ratio range can be used to balance inorganic network formation, interfacial coupling, and film density, and can cover the proportions obtained from the raw material amounts in specific embodiments.

[0022] S13. Curing and Deposition: The underlying sol is further cured for 2-24 hours and then deposited on the substrate surface by spraying, coating or spin coating.

[0023] S14. Pre-curing: After deposition, pre-curing is carried out at 80°C-90°C for 10-30 min to form a continuous and dense organic-inorganic hybrid bonding substrate.

[0024] Preferably, in step S1, the substrate is deposited by spraying or coating and pre-cured at 80°C-90°C for 10-30 min.

[0025] Preferably, the intermediate layer in step S2 is used to provide a hierarchical rough structure and introduce a reservoir of MOF nanoparticles, and its preparation may include the following steps:

[0026] S21. MOF-loaded photocrosslinkable monomer: Disperse MOF in ethanol, impregnate under vacuum of 0.06-0.08 MPa for 20-40 min, then add dropwise an ethanol solution containing 1-3 wt% allyl / (meth)acrylate silane monomer, and continue impregnation for 50-70 min; wash and dry to obtain powder B; based on the mass of MOF, the loading of allyl / (meth)acrylate silane monomer in powder B is 13 wt%;

[0027] S22. Constructing a graded coarse filler: Disperse nano-SiO2 and micro-SiO2 in a mixed solvent of ethanol and isopropanol in a mass ratio of (3-5):1, add 1 wt% APTES for reflux treatment, centrifuge, wash and dry to obtain powder C;

[0028] S23. Preparation of intermediate layer coating solution: Prepare a mixed solvent of ethanol, isopropanol and PGMEA, and add powder C and powder B to the mixed solvent in sequence and stir to disperse; wherein, the mass ratio of powder C to powder B is preferably (2-6):1. After the addition of powder C and powder B, thermally responsive elastic phase PDMS, photoinitiator TPO-L and low surface energy component F-C6 can be further added and dispersed to obtain an intermediate layer coating solution with solid content and viscosity that meet the requirements of spray coating film formation.

[0029] S24. Intermediate layer spraying: The intermediate layer coating liquid is sprayed onto the bottom layer obtained in step S1 to form an intermediate layer containing a graded rough structure and MOF reservoir; the spraying conditions can be: spraying solid content 4-10 wt%, nozzle diameter 0.8-1.0 mm, atomization pressure 0.8-1.5 bar, spraying distance 10-20 cm, single or double spraying.

[0030] The metal-organic framework (MOF) can be loaded with photocrosslinkable monomers and / or low surface energy molecules, with the loading amount being 0.5–15 wt% by MOF mass, preferably 1–13 wt%, to provide a sufficient reservoir of repairable components while ensuring the release capability of the pores. The loaded components are preferably allyl or (meth)acrylate silane monomers and / or low surface energy silane molecules, which can be slowly released from the MOF pores under UV and thermal stimulation and participate in surface crosslinking and surface energy reconstruction.

[0031] The preferred particle size D of nano-silica (SiO2, the main roughness phase) 50 =20-50 nm, specific surface area (BET) 150-300 m² / g, surface hydroxyl density 2-6 OH / nm²; optional surface treatment is methyl / amino / epoxysilane to improve dispersion and interfacial compatibility. Micron-sized silica (SiO2, secondary roughness phase) with preferred particle size D. 50 =0.8-1.5 μm, spherical, low refractive index (n≈1.44–1.46), light transmittance.

[0032] Preferably, the surface layer in step S3 serves to provide a photoinitiated crosslinking network and a low surface energy interface, and its preparation may include the following steps:

[0033] S31. Preparation of the surface coating solution: A photoinitiator (preferably TPO-L), a low surface energy component (preferably C6 fluorosilane), and a thermoresponsive elastic phase (preferably PDMS) are added to an organic solvent system and stirred to obtain the surface coating solution. Based on the total mass of the surface coating solution, the total amount of the photoinitiator is preferably 0.1-1.5 wt%, the total amount of the low surface energy component is preferably 0.5-3.0 wt%, and the mass of PDMS is preferably 5-15 wt%.

[0034] S32. Surface coating and pre-curing: The surface coating liquid is sprayed onto the intermediate layer and pre-cured at 80-90°C for 10-30 min to form the outermost layer of the coating.

[0035] Preferably, in step S3, the surface coating liquid has a spray solids content of 4-10 wt% and is pre-cured at 80°C-90°C.

[0036] Thermoresponsive elastic phase (PDMS): The thermoresponsive elastic phase is polydimethylsiloxane (PDMS), preferably with a number-average molecular weight M. n The viscosity ranges from 5,000 to 20,000 mPa·s at 25°C, and the structure consists of terminal hydroxyl or alkoxy groups. Under conditions of 60°C to 80°C, PDMS undergoes chain segment migration and interfacial rearrangement, which is beneficial for structural reconstruction and self-repair in damaged areas.

[0037] Low surface energy components: preferably perfluorohexyltriethoxysilane (C6 fluorosilane) and / or perfluorohexyl acrylate, total amount 0.5-3.0 wt%; fluorine-free alternatives may be PDMS terminal silane / hexadecyltrimethoxysilane (HDTMS) / cage silsesquioxane (POSS), total amount 1.0-4.0 wt%.

[0038] Photoinitiator (365 nm): Selected from TPO / TPO-L / benzophenone, total amount 0.1-1.5 wt%.

[0039] Substrate and Solvent System: The substrate can be a glass substrate or a polymer substrate. For glass substrates, the solvent system of the surface coating liquid can be ethanol:isopropanol:PGMEA = 70:20:10 (volume ratio), and may contain 1-3% deionized water and 0.02-0.05 wt% glacial acetic acid (based on total solvent). For polymer substrates (such as PC or PMMA), the solvent system of the surface coating liquid can be composed of isopropanol, dipropylene glycol methyl ether (DPM), and deionized water in a volume ratio of 80:15:5. Avoid using strong ketone solvents to prevent swelling or cracking of the polymer substrate.

[0040] Spraying and pre-curing process window: coating liquid solid content 4-10 wt%, viscosity at 25°C 8-20 mPa·s; nozzle 0.8-1.0 mm, atomization pressure 0.8-1.5 bar, spray distance 10-20 cm; pre-curing at 80-90°C for 10-30 min, followed by 365 nm UV irradiation at 5-20 mW·cm⁻² for 2-10 min.

[0041] Preferably, the ultraviolet irradiation conditions in step S3 are: irradiation at an ultraviolet irradiation intensity of 5-20 mW·cm⁻² at 365 nm for 2-10 min, with an irradiation distance of 8-12 cm, so that the surface layer undergoes a photocrosslinking reaction.

[0042] The third objective of this invention is to provide a method for self-repairing the aforementioned photothermal synergistic self-healing superhydrophobic transparent coating, comprising the following steps: after microscopic damage occurs on the coating surface, the coating is subjected to 365 nm ultraviolet irradiation of 5-15 mW·cm⁻² for 2-10 min, and treated at 60°C-80°C for 10-60 min to restore hydrophobic and optical properties.

[0043] Compared with the prior art, the present invention has the following advantages:

[0044] 1. This invention achieves online self-healing and long-term durability of a transparent superhydrophobic coating through a triple synergistic mechanism of ultraviolet A (365 nm) light triggering, medium-low temperature (60°C–80°C) thermal assistance, and MOF slow release. Under the synergistic effect of 365 nm ultraviolet light and medium-low temperature thermal field, the photocrosslinkable unsaturated groups in the surface layer undergo free radical polymerization, while the silane component further condenses to form a dense silicon-oxygen network, thereby achieving rapid sealing of microcracks and reconstruction of low surface energy interfaces. The aforementioned chemical structural evolution can be characterized by infrared spectroscopy. For example, the characteristic peaks related to unsaturated double bonds (C=C) are typically located at approximately 1630–1650 cm⁻¹, and their intensity tends to decrease after photocrosslinking; the characteristic peaks of carbonyl groups (C=O) are typically located at approximately 1720 cm⁻¹; while the characteristic peaks related to silicon-oxygen bonds (Si–O–Si) are generally distributed in the 1020–1120 cm⁻¹ range, and their enhancement can be used to indicate the further formation of the silicon-oxygen network structure and the improvement of the degree of crosslinking. Simultaneously, the thermal field induced by 60°C–80°C leads to the migration and dynamic reversible rearrangement of the thermoresponsive elastic phase PDMS and low glass transition temperature segments, promoting the exposure and reconstruction of the hierarchical SiO₂ rough structure, enabling the damaged region to rapidly recover a low-adhesion superhydrophobic interface characterized by the Cassie–Baxter state. Furthermore, the MOF porous framework provides a continuous supply of low surface energy molecules and photosensitive monomers through adsorption-slow release-recrosslinking, maintaining repair flux during light / thermal cycling and thus avoiding performance degradation caused by one-time depletion. Based on the above synergistic mechanism, after simulated abrasion such as #1000 sandpaper (0.5 kPa, 10 times) or Taber CS-10 (1 kg, 500 cycles), the coating, after irradiation with 365 nm 10-15 mW·cm⁻² for 6-9 min and supplemented with treatment at 70 °C for 30 min, can rapidly recover the static water contact angle from ≤140° after damage to ≥150° while maintaining a roll-off angle ≤5°. The average visible light transmittance (T_avg, 400-800 nm) is ≥90% and the haze is ≤1.5%, which remains basically unchanged. The underlying silane coupling and sol-gel hybrid framework ensure that the cross-cut adhesion reaches 5B. In terms of weather resistance and corrosion resistance, the superhydrophobicity and transmittance decrease by ≤3% after QUV (UVA-340, 60°C, 1000 h) and salt spray (ASTM B117, 240 h). Therefore, the coating proposed in this invention achieves synergistic improvements in optical transparency, superhydrophobic self-healing, antifouling and anti-adhesion, wear resistance and weather resistance, and can be stably mass-produced under a spraying / pre-curing process at ≤90 °C. Detailed Implementation

[0045] The following embodiments are further illustrations of the present invention, but not limitations thereof.

[0046] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention. Unless otherwise specified, the experimental materials and reagents used herein are commercially available products conventionally available in this technical field.

[0047] A method for preparing a photothermal synergistic self-healing superhydrophobic transparent coating includes the following steps:

[0048] S1. Pre-treat the substrate and deposit an underlayer of an organic-inorganic hybrid binder phase containing silane coupling groups;

[0049] S2. Spray an intermediate layer containing a graded rough structure and MOF nanoparticles onto the bottom surface;

[0050] S3. A surface layer is formed by spraying on the surface of the intermediate layer. The surface layer contains at least a photoinitiating system and a low surface energy component, and contains photocrosslinkable unsaturated groups. The photocrosslinkable unsaturated groups are allyl or (meth)acrylate unsaturated groups. The photocrosslinkable unsaturated groups are directly introduced by the surface coating liquid or provided by MOF nanoparticles preloaded with photocrosslinkable unsaturated groups in the intermediate layer. Under subsequent ultraviolet light irradiation, polymerization and crosslinking occur to form a continuous and dense low surface energy crosslinked layer, resulting in a photothermal synergistic self-healing superhydrophobic transparent coating. The coating liquids used in each layer in steps S1–S3 are independently prepared and sprayed sequentially. Each layer is formed on the basis of the previous layer being cured or semi-cured, thereby constructing a layered structure of bottom layer-intermediate layer-surface layer.

[0051] Step S1 involves depositing an organic-inorganic hybrid binder phase substrate containing silane coupling groups, specifically including the following sub-steps:

[0052] S11. Preparation of hydrolysis solvent: Anhydrous ethanol, deionized water, and glacial acetic acid are mixed to obtain the hydrolysis solvent, wherein deionized water accounts for 3%–8% of the total volume of the hydrolysis solvent, and glacial acetic acid accounts for 0.05–0.10 wt% of the total mass of the mixed solvent; after mixing, the temperature is lowered and controlled at 20°C–25°C. The above ratio range is an exemplary condition and can be selected according to the amount of raw materials used in specific embodiments; for example, in a specific embodiment, 60 mL of anhydrous ethanol, 4 mL of deionized water, and 0.04 mL of glacial acetic acid are used to prepare the hydrolysis solvent.

[0053] S12. Add silane precursor and hydrolyze: Add tetraethoxysilane (TEOS), 3-aminopropyltriethoxysilane (APTES), and γ-glycidoxypropyltrimethoxysilane (GPTMS) to the hydrolysis solvent. The molar ratio of TEOS, APTES, and GPTMS is (5–12):(1–6):(0.2–3), preferably (6–10):(2–5):(0.5–2). Simultaneously, control the molar ratio of TEOS to water to be 1:(2–6). Stir for 10–120 min to complete the initial hydrolysis and condensation, obtaining the bottom sol. The above ratio range is used to define the composition window of the bottom sol-gel reaction and can cover the ratios calculated based on the specific amounts used in the examples.

[0054] S13. Curing and Deposition: The underlying sol is further cured for 2-24 hours and then deposited on the substrate surface by spraying, coating or spin coating.

[0055] S14. Pre-curing: After deposition, pre-curing is carried out at 80°C-90°C for 10-30 min to form a continuous and dense organic-inorganic hybrid bonding substrate. The substrate thickness is 0.3–0.8 μm, preferably 0.5 μm.

[0056] The above steps are used to provide the underlying general preparation conditions; in the examples, representative parameters can be selected according to the equipment conditions, but they should fall within the above range.

[0057] In the preferred embodiment described below, the substrate in step S1 is deposited by spraying or coating and pre-cured at 80°C-90°C for 10-30 min.

[0058] In the preferred embodiment described below, the intermediate layer in step S2 is used to provide a hierarchical rough structure and introduce a reservoir of MOF nanoparticles, and its preparation may include the following steps:

[0059] S21. MOF-loaded photocrosslinkable monomer: Disperse MOF in ethanol, impregnate under vacuum of 0.06-0.08 MPa for 20-40 min, then add dropwise an ethanol solution containing 1-3 wt% allyl / (meth)acrylate silane monomer, and continue impregnation for 50-70 min; wash and dry to obtain powder B; based on the mass of MOF, the loading of allyl / (meth)acrylate silane monomer in powder B is 13 wt%;

[0060] S22. Constructing a graded coarse filler: Disperse nano-SiO2 and micro-SiO2 in a mixed solvent of ethanol and isopropanol in a mass ratio of (3-5):1, add 1 wt% APTES for reflux treatment, centrifuge, wash and dry to obtain powder C;

[0061] S23. Preparation of the intermediate layer coating solution: Prepare a mixed solvent of ethanol, isopropanol, and PGMEA (volume ratio 70:20:10). Add powder C and powder B sequentially to the mixed solvent and stir to disperse. The preferred mass ratio of powder C to powder B is (2–6):1, more preferably (3–4):1. For example, when the total mass fraction of nano-SiO2 and micro-SiO2 in the intermediate layer is approximately 10 wt% and the MOF mass fraction is approximately 3 wt%, the mass ratio of powder C to powder B can be approximately 10:3 (approximately 3.3:1). After adding powder C and powder B, the thermally responsive elastic phase PDMS, the photoinitiator TPO-L, and the low surface energy component F-C6 can be further added and dispersed to obtain an intermediate layer coating solution with solid content and viscosity that meets the requirements for spray coating film formation.

[0062] S24. Intermediate Layer Spraying and Film Formation: The intermediate layer coating liquid is sprayed onto the substrate obtained in step S1 to form an intermediate layer containing a graded rough structure and MOF reservoirs. The spraying conditions can be: spray solids content 4-10 wt%, nozzle diameter 0.8-1.0 mm, atomization pressure 0.8-1.5 bar, spray distance 10-20 cm, single or double spraying. The intermediate layer thickness is 1.0–2.5 μm, preferably 1.8 μm.

[0063] The metal-organic framework (MOF) can be loaded with photocrosslinkable monomers and / or low surface energy molecules, with the loading amount being 0.5–15 wt% by MOF mass, preferably 1–13 wt%, to provide a sufficient reservoir of repairable components while ensuring the release capability of the pores. The loaded components are preferably allyl or (meth)acrylate silane monomers and / or low surface energy silane molecules, which can be slowly released from the MOF pores under UV and thermal stimulation and participate in surface crosslinking and surface energy reconstruction.

[0064] The preferred particle size D of nano-silica (SiO2, the main roughness phase) 50 =20-50 nm, specific surface area (BET) 150-300 m² / g, surface hydroxyl density 2-6 OH / nm²; optional surface treatment is methyl / amino / epoxysilane to improve dispersion and interfacial compatibility. Micron-sized silica (SiO2, secondary roughness phase) with preferred particle size D. 50 =0.8-1.5 μm, spherical, low refractive index (n≈1.44–1.46), light transmittance.

[0065] In the preferred embodiment described below, the surface layer in step S3 is used to provide a photoinitiated crosslinking network and a low surface energy interface, and its preparation may include the following steps:

[0066] S31. Preparation of the surface coating solution: A photoinitiator (preferably TPO-L), a low surface energy component (preferably C6 fluorosilane), and a thermoresponsive elastic phase (preferably PDMS) are added to an organic solvent system and stirred to obtain the surface coating solution. Based on the total mass of the surface coating solution, the total amount of photoinitiator is preferably 0.1-1.5 wt%, the total amount of low surface energy component is preferably 0.5-3.0 wt%, and the mass of PDMS is preferably 5-15 wt%.

[0067] S32. Surface coating and pre-curing: The surface coating liquid is sprayed onto the intermediate layer and pre-cured at 80-90°C for 10-30 min to form the outermost layer of the coating. The surface layer thickness is 0.1–0.6 μm, preferably 0.3 μm.

[0068] In the preferred embodiment described below, the surface coating liquid in step S3 has a spray solids content of 4-10 wt% and is pre-cured at 80°C-90°C.

[0069] Thermoresponsive elastic phase (PDMS): The thermoresponsive elastic phase is polydimethylsiloxane (PDMS), preferably with a number-average molecular weight M. n The viscosity ranges from 5,000 to 20,000 mPa·s at 25°C, and the structure consists of terminal hydroxyl or alkoxy groups. Under conditions of 60°C to 80°C, PDMS undergoes chain segment migration and interfacial rearrangement, which is beneficial for structural reconstruction and self-repair in damaged areas.

[0070] Low surface energy components: preferably perfluorohexyltriethoxysilane (C6 fluorosilane) and / or perfluorohexyl acrylate, total amount 0.5-3.0 wt%; fluorine-free alternatives may be PDMS terminal silane / hexadecyltrimethoxysilane (HDTMS) / cage silsesquioxane (POSS), total amount 1.0-4.0 wt%.

[0071] Photoinitiator (365 nm): Selected from TPO / TPO-L / benzophenone, total amount 0.1-1.5 wt%.

[0072] Substrate and Solvent System: The substrate can be a glass substrate or a polymer substrate. For glass substrates, the solvent system of the surface coating liquid can be ethanol:isopropanol:PGMEA = 70:20:10 (volume ratio), and may contain 1-3% deionized water and 0.02-0.05 wt% glacial acetic acid (based on total solvent). For polymer substrates (such as PC or PMMA), the solvent system of the surface coating liquid can be composed of isopropanol, dipropylene glycol methyl ether (DPM), and deionized water in a volume ratio of 80:15:5. Avoid using strong ketone solvents to prevent swelling or cracking of the polymer substrate.

[0073] Spraying and pre-curing process window: coating liquid solid content 4-10 wt%, viscosity at 25°C 8-20 mPa·s; nozzle 0.8-1.0 mm, atomization pressure 0.8-1.5 bar, spray distance 10-20 cm; pre-curing at 80-90°C for 10-30 min, followed by 365 nm UV irradiation at 5-20 mW·cm⁻² for 2-10 min.

[0074] Preferably, the conditions for ultraviolet irradiation in step S3 are: irradiation at an ultraviolet light intensity of 5-20 mW·cm⁻² at 365 nm for 2-10 min, with an irradiation distance of 8-12 cm, so that the surface layer undergoes a photocrosslinking reaction.

[0075] The testing methods for the coatings in the following embodiments or comparative examples are as follows:

[0076] Initial performance: average visible light transmittance (T_avg, 400-800 nm), haze, static water contact angle (WCA), roll-off angle (SA), and cross-cut adhesion.

[0077] Abrasion resistance test: #1000 sandpaper, load 0.5 kPa, 10 cycles.

[0078] Self-healing conditions: 365 nm UV irradiation (10-15 mW·cm⁻², 6-10 min) and heat treatment (70 °C, 30 min).

[0079] Recovery rate calculation: The ratio of WCA and T_550 after repair to the initial values.

[0080] Example 1

[0081] The preparation method of C6 fluorosilane coating A is as follows:

[0082] Step S1: The substrate (glass / transparent polymer) is ultrasonically treated with deionized water and isopropanol for 10 min each, and then dried at 80°C for 10 min.

[0083] Step S2: Mix 60 mL of anhydrous ethanol, 4.0 mL of deionized water, and 0.04 mL of glacial acetic acid to obtain a hydrolysis solvent, and cool to 20°C-25°C. Add 20.0 g of TEOS, 2.0 g of APTES, and 3.0 g of GPTMS, and hydrolyze and condense at 500 rpm for 2 h to obtain sol A (viscosity at 25°C 1530 mPa·s, solid content 30 wt%). Further mature sol A for 12 h. The spray deposition conditions are as follows: sol A is directly sprayed onto the substrate surface using a nozzle diameter of 0.8 mm, atomization pressure of 1.0 bar, and a spray distance of 15 cm, in a single pass. After spraying, pre-cur at 80°C for 30 min to form a continuous and dense organic-inorganic hybrid adhesive underlayer with a thickness of 0.5 μm.

[0084] Step S3: Disperse 2.0 g of ZIF-8 (D50=30-60 nm) (3 wt% based on coating solids) in 100 mL of ethanol; after impregnation under -0.07 MPa vacuum for 30 min, add 20 mL of ethanol solution containing 2 wt% allyl / (meth)acrylate silane monomer, and continue impregnation for 60 min; centrifuge at 6000 rpm for 10 min, wash twice with ethanol, and dry under vacuum at 50 °C for 3 h to obtain supported ZIF-8 powder B (monomer loading 13 wt%, based on MOF).

[0085] Step S4: Disperse 8.0 g of nano-SiO2 (D50=20-50 nm) and 2.0 g of micron-sized SiO2 (D50=0.815 μm) in 80 mL of a mixed solvent of ethanol:isopropanol=80:20 (volume ratio), add 1 wt% APTES (based on particles), reflux at 60 °C for 1 h, centrifuge and wash twice, and dry at 50 °C for 2 h to obtain treated powder C (used to improve dispersion and interfacial bonding).

[0086] Step S5: Preparation and Spraying of Intermediate Layer Coating: Prepare 100 mL of mixed solvent according to the ratio of ethanol:isopropanol:PGMEA = 70:20:10 (volume ratio). Add powder C obtained in step S4 and powder B obtained in step S3 sequentially, and add PDMS (12 wt% based on the solid content of the intermediate layer coating). Stir until homogeneous to obtain the intermediate layer coating. The viscosity of the intermediate layer coating at 25°C is 8–15 mPa·s. Spray the intermediate layer coating onto the substrate formed in step S2 to form an intermediate layer containing a graded rough structure and MOF reservoirs. The spraying conditions are: nozzle diameter 0.8 mm, atomization pressure 1.0 bar, spray distance 15 cm, single-pass spraying; the solid content of the sprayed coating is 7 wt%.

[0087] Step S6: Prepare a mixed solvent with ethanol:isopropanol:PGMEA = 70:20:10 (volume ratio), add TPO-L (0.5 wt%) and perfluorohexyltriethoxysilane F-C6 (3.5 wt%), disperse at high speed for 5000 rpm × 5 min, then sonicate (200-300 W, 20 kHz) for 12 min (ice bath temperature control ≤25 °C), adjust the solid content to 8 wt%, and the viscosity at 25 °C is 10 mPa·s to obtain the surface solution.

[0088] Step S7: Pass the sample through 0.45 μm and 0.22 μm PTFE filters sequentially to remove impurities, and allow it to mature at room temperature for 12 h. If long-term storage is required, store at 4°C-8°C in the dark (≤7 d).

[0089] Step S8: Spray the surface coating liquid onto the intermediate layer. The spraying conditions are as follows: spray gun nozzle diameter 0.8 mm, atomization pressure 1.0 bar, spray distance 15 cm, blade feed rate 300 mm / s; single wet film thickness 8 μm, spray 2 times with an interval of 2-3 min; ambient temperature 20°C -30°C, RH 40%-60%.

[0090] Step S9: Pre-curing at 90°C for 15 min; target dry film thickness 5 μm, haze ≤1.5%, to obtain the surface layer.

[0091] Step 10: Then irradiate the surface with ultraviolet light, 365 nm ultraviolet light, illuminance of 10-15 mW / cm², irradiation distance of 8-12 cm, for 6-9 min continuously; maintain the substrate surface temperature at 50°C-65°C (a hot table or infrared assistance can be used), and the resulting coating will have an intermediate layer thickness of 1.8 μm and a surface layer thickness of 0.3 μm.

[0092] Step S11: Place at room temperature for 12-24 h; measure T_avg (400–800 nm), haze, static water contact angle (WCA) / roll-off angle (SA), and cross-cut adhesion; T_avg ≥ 90%, haze ≤ 1.5%, WCA ≥ 160°, and SA ≤ 5° are considered qualified.

[0093] Step S12: Apply #1000 sandpaper and load 0.5 kPa back and forth 10 times to induce slight wear, then apply 365 nm 12 mW / cm² × 6 min + 70 °C × 30 min; record WCA / SA and T_550 recovery rate (≥85%).

[0094] Example 2

[0095] The coating B of the fluorine-free branch used in this embodiment is processed as follows:

[0096] Similar to coating A in Example 1, except that in step S5 the low surface energy component is replaced with: 2.5 wt% PDMS terminal silane + 1.0 wt% hexadecyltrimethoxysilane (HDTMS), and the solvent system is adjusted to "isopropanol:DPM:deionized water = 80:15:5 (volume ratio)", and PGMEA is not used; all other parameters remain unchanged. Film formation acceptance criteria: T_avg≥90%, haze≤1.5%, WCA≥155°, SA≤8°.

[0097] Key points of the UiO-66-NH2 substitution route: If UiO-66-NH2 is used as the reservoir, replace ZIF-8 with UiO-66-NH2 powder in step S2; to improve the dispersion of the ethanol system, 0.1–0.3 wt% polyvinylpyrrolidone (PVP, K30) can be added as a dispersant; the rest remain unchanged.

[0098] When the viscosity is too high, the solid content can be appropriately reduced or the ethanol ratio can be increased. If the spray atomization is insufficient, the pressure can be adjusted to 1.4-1.5 bar. When the haze exceeds the standard, the content of micron-sized SiO2 should be reduced to ≤2 wt% and the pre-curing time should be appropriately extended to improve the network density. At the same time, check whether the particles are agglomerated and extend the ultrasonic time to 15-20 min if necessary. If the adhesion is insufficient, it is mostly caused by insufficient hydrolysis time of the primer or incomplete cleaning of the substrate. Plasma / UV ozone activation can be added for 5-10 min after the primer to enhance the interfacial bonding. When the self-healing effect is insufficient, the light dose can be increased to 912 J / cm² (e.g., 12 mW / cm²×12 min) or the heat assistance can be increased to 70°C-80°C×30-45 min. The MOF loading can be checked to ≥1 wt% (based on MOF).

[0099] Example 3

[0100] The following examples demonstrate the preparation of a photothermal synergistic self-healing superhydrophobic transparent coating by layer-by-layer spraying and step-by-step curing / cross-linking. The coating liquids used for each functional layer are prepared independently and deposited sequentially on the basis of the previous layer being cured or semi-cured, thereby forming a layered structure of bottom layer – middle layer – top layer.

[0101] A method for preparing a coating containing ZIF-8 and C6 fluorosilane includes the following steps:

[0102] S1: Substrate (glass) pretreatment: Ultrasonic cleaning with deionized water and isopropanol for 10 min each, followed by drying at 80°C for 10 min. A hydrolysis solvent was prepared by mixing 60 mL of anhydrous ethanol, 4.0 mL of deionized water, and 0.04 mL of glacial acetic acid, and then cooled to 20–25°C. 20.0 g of TEOS, 3.0 g of APTES, and 3.0 g of GPTMS were added, and the mixture was magnetically stirred at 500 rpm for 2 h to obtain sol A (viscosity approximately 1530 mPa·s at 25°C, solid content approximately 30 wt%). After sol A was cured for 12 h, it was deposited onto the substrate surface by spraying with a nozzle diameter of 0.8 mm, atomization pressure of 1.2 bar, and a spray distance of 15 cm in a single pass. After spraying, it was pre-cured at 90°C for 10 min to form a continuous and dense organic-inorganic hybrid adhesive underlayer. The underlayer thickness was 0.5 μm.

[0103] S2: Using ethanol:isopropanol:PGMEA = 70:20:10 (volume ratio) as the dispersion solvent, glacial acetic acid (0.03 wt% of the total solvent mass) was added to adjust the acidity of the system and improve the dispersion stability. Powder C (or untreated SiO2) obtained in step S4 of Example 1 and powder B obtained in step S3 were added sequentially to 100 mL of the dispersion solvent. The amount of powder B and powder C added was the same as in Example 1. The mixture was mixed under high-speed dispersion conditions (5000 rpm × 5 min) and ultrasonically treated for 10 min (ice bath temperature control ≤25°C). The solid content was adjusted to 7 wt%. After filtration, the mixture was aged for 12 h to obtain the intermediate layer coating liquid, which was used to form an intermediate layer with a hierarchical rough structure and functional filler distribution on the bottom surface.

[0104] S3: Intermediate layer spraying: The intermediate layer coating liquid obtained in step S2 is sprayed onto the bottom layer surface formed in step S1. The spray gun nozzle diameter is 0.8 mm, the atomization pressure is 1.0 bar, and the spray distance is 15 cm. After a single coat, it is pre-cured at 80°C for 10 min to form an intermediate layer with a graded rough structure. The thickness of the intermediate layer is 1.8 μm.

[0105] S4: Surface Solution Preparation and Spraying: A mixed solvent was prepared according to the volume ratio of ethanol:isopropanol:PGMEA = 70:20:10. Photoinitiator TPO-L, the low surface energy component perfluorohexyltriethoxysilane F-C6, and PDMS terminal silane were added to the mixed solvent. The amounts of each component added were based on the total mass of the surface solution: TPO-L 0.8 wt%, F-C6 2.0 wt%, and PDMS terminal silane 1.6 wt%. After high-speed dispersion (5000 rpm × 5 min), ultrasonic treatment (250 W, 20 kHz) was performed for 12 min (ice bath temperature control ≤25°C). Subsequently, the solid content of the surface solution was adjusted to 7.0 wt% by adding the mixed solvent, and the viscosity at 25°C was adjusted to 10.0 mPa·s to obtain the surface coating. The surface coating solution was sprayed onto the surface of the intermediate layer twice, with a 2-minute interval between coats, and then pre-cured at 80°C for 20 minutes to form the outermost surface layer of the coating. To promote silane hydrolysis, 1.0 wt% deionized water (based on the total mass of the surface solution) was added during the solid content adjustment process without affecting the system compatibility and film uniformity.

[0106] S5: Ultraviolet crosslinking: Under 365 nm ultraviolet light (13 mW·cm⁻²), at a distance of 10 cm, continuous irradiation for 8 min causes a photocrosslinking reaction to occur on the surface.

[0107] S6: Let it stand for 24 hours at room temperature.

[0108] The coating consists of: a bottom layer of organic-inorganic hybrid binder containing silane coupling groups (TEOS / APTES / GPTMS sol-gel system); an intermediate layer of hierarchical coarse structure (8 wt% nano-SiO2, 2 wt% micron-SiO2) and ZIF-8 nanoparticles (3 wt%, particle size 30-60 nm), loaded with photocrosslinkable monomers (acryloyloxypropyltriethoxysilane, 2 wt%); and a top layer of photoinitiator TPO-L (0.5 wt%), photocrosslinkable unsaturated groups (preferably allyl / (meth)acrylate silane monomers, such as acryloyloxypropyltriethoxysilane (AcPTES) and / or (meth)acryloyloxypropyltrimethoxysilane (MAPTMS); the monomers can be loaded by the intermediate MOF layer and released under UV conditions to participate in crosslinking), a low surface energy component (perfluorohexyltriethoxysilane, 3.5 wt%), and a thermoresponsive elastic phase PDMS (12 wt%).

[0109] Test methods: Visible light average transmittance (T_avg) was measured using a UV-Vis spectrophotometer, with the average value taken within the 400-800 nm wavelength range; haze was measured using a haze meter. Static water contact angle (WCA) and roll-off angle (SA) were measured using a contact angle meter with a water droplet volume of 5 μL. Abrasion resistance was tested using #1000 sandpaper, subjected to 10 cycles of reciprocating rubbing under a 0.5 kPa load. In the self-healing test, the abrasion-treated coating was irradiated with 365 nm UV light (10-15 mW·cm⁻², 6-10 min) and heat-treated at 70°C for 30 min, followed by testing of the coating's hydrophobic and optical properties.

[0110] Following the above testing method, the test results are as follows: Initial performance: average visible light transmittance (T_avg) 92%, haze 1.2%, static water contact angle (WCA) 162°, roll-off angle (SA) 4°. Self-healing test: After abrasion with #1000 sandpaper (0.5kPa, 10 times), WCA decreased to 142°; after 365 nm ultraviolet irradiation (13 mW·cm⁻², 8 min) and heat treatment at 70 °C for 30 min, WCA recovered to 158°, T_avg recovered to 91%, and haze 1.3%. The resulting coating exhibits a layered structure along the thickness direction: bottom layer – intermediate layer – top layer. Each layer is distinct in composition and function and works synergistically.

[0111] Example 4

[0112] A method for preparing a coating containing UiO-66-NH2 and C6 fluorosilane includes the following steps:

[0113] Same as Example 3, but the intermediate layer uses UiO-66-NH2 instead of ZIF-8, and 0.2 wt% PVP K30 is added as a dispersant.

[0114] The coating consists of: an intermediate layer composed of a hierarchical rough structure (8 wt% nano-SiO2 and 2 wt% micron-sized SiO2) and UiO-66-NH2 nanoparticles (4 wt%, particle size 60-100 nm), loaded with a photocrosslinkable monomer (acryloyloxypropyltriethoxysilane, 2 wt% loading). Other components are the same as in Example 3.

[0115] Test results showed the following: Initial performance: T_avg 91%, haze 1.4%, WCA 160°, SA 5°. After self-healing: WCA recovered to 156°, T_avg recovered to 90%, and haze 1.5%.

[0116] Example 5

[0117] The method for preparing a fluorine-free coating includes the following steps:

[0118] Same as Example 3, but using a fluorine-free low surface energy component and a modified solvent system.

[0119] The coating composition is as follows: low surface energy components: PDMS terminal silane (2.5 wt%) and hexadecyltrimethoxysilane (HDTMS, 1.0 wt%). Other components are the same as in Example 3, but the solvent is adjusted to isopropanol:DPM:deionized water = 80:15:5 (volume ratio).

[0120] Test results showed the following: Initial performance: T_avg 90%, haze 1.5%, WCA 156°, SA 7°. After self-healing: WCA recovered to 152°, T_avg recovered to 89%, and haze 1.6%.

[0121] Example 6

[0122] The preparation method of a high-micron SiO2 content coating includes the following steps:

[0123] Same as Example 3, but the micron-sized SiO2 content is increased to 4 wt%, and the pre-curing time is extended to 30 min.

[0124] The coating composition is as follows: intermediate layer: hierarchical rough structure (nano SiO2 8 wt%, micron SiO2 4 wt%). Other components are the same as in Example 3.

[0125] Test results showed the following: Initial performance: T_avg 90%, haze 1.5%, WCA 161°, SA 5°. After self-healing: WCA recovered to 157°, T_avg recovered to 90%, and haze 1.6%.

[0126] Example 7

[0127] A method for preparing a low MOF content coating includes the following steps:

[0128] Same as Example 3.

[0129] The coating composition is as follows: Intermediate layer: ZIF-8 content reduced to 1 wt%. Other components are the same as in Example 3.

[0130] Test results showed the following: Initial performance: T_avg 91%, haze 1.3%, WCA 159°, SA 5°. After self-healing: WCA recovered to 153°, T_avg recovered to 90%, and haze 1.4%.

[0131] Comparative Example 1

[0132] The method for preparing a MOF-free coating includes the following steps:

[0133] For ease of comparison, in Comparative Example 1 without the introduction of ZIF-8, the amount of TPO-L added can be increased accordingly so that the total amount of photoinitiator added is on the same order of magnitude as the combined mass of ZIF-8 and TPO-L in Example 1; the above settings are only for comparative illustration and do not constitute a limitation of the present invention.

[0134] The coating composition is the same as in Example 3, but ZIF-8 is removed.

[0135] Test results showed the following: Initial performance: T_avg 92%, haze 1.2%, WCA 161°, SA 4°. After self-healing: WCA only recovered to 145° after wear, T_avg recovered to 88%, and haze 1.8%.

[0136] Comparative Example 2

[0137] A method for preparing a photoinitiator-free coating includes the following steps:

[0138] Similar to Example 3, TPO-L is not added in step S2, and the amount of ZIF-8 added is the sum of the masses of ZIF-8 and TPO-L in Example 1.

[0139] The coating consists of:

[0140] Same as Example 3, but TPO-L is removed.

[0141] Test results showed the following: Initial performance: T_avg 91%, haze 1.4%, WCA 160°, SA 5°. After self-healing: WCA only recovered to 142° after wear, T_avg recovered to 87%, and haze 2.0%.

[0142] In Comparative Example 2, the absence of the photoinitiator TPO-L resulted in the presence of an MOF reservoir in the system, but the photocrosslinking reaction could not be effectively triggered, making it difficult to achieve the same self-healing effect as in the example.

[0143] In Comparative Example 1, ZIF-8 was not added, only the photoinitiator TPO-L was retained; in Comparative Example 2, no photoinitiator was added, only ZIF-8 was retained. Test results show that when either ZIF-8 or the photoinitiator was introduced alone, the self-healing effect of the coating after wear was significantly insufficient. However, in Example 1, after simultaneously introducing ZIF-8 and the photoinitiator TPO-L, the coating was able to significantly recover its hydrophobic and optical properties under ultraviolet light and heat-assisted conditions. These results indicate that ZIF-8 and the photoinitiator TPO-L in the system of this invention are not simply additive, but rather form a synergistic effect through an "adsorption-slow release-photocrosslinking" mechanism. This synergistic effect has been fully demonstrated by the comparison results between Example 1 and Comparative Examples 1-2.

[0144] Comparative Example 3

[0145] A method for preparing a coating without low surface energy components includes the following steps:

[0146] Same as Example 3, except that: the low surface energy component C6 fluorosilane is not added in step S2; the composition of the coating is the same as in Example 3, but the low surface energy component C6 fluorosilane is removed.

[0147] According to the above test method, the test results show that the average visible light transmittance (T_avg) of the coating is 92% and the haze is 1.2%. Due to the lack of low surface energy components, the coating surface cannot form a stable low surface energy interface. Its static water contact angle (WCA) is only about 105° and the roll-off angle (SA) is greater than 90°, and it does not have superhydrophobic properties.

[0148] After wear and UV-heat treatment, the water contact angle of the coating did not show significant recovery, indicating that even with the presence of a photoinitiating system and MOF structure, it is difficult to achieve effective hydrophobic property reconstruction in the absence of low surface energy components.

[0149] The test results of Example 3 and Comparative Examples 1-3 show that the photothermal synergistic self-healing superhydrophobic coating proposed in this invention relies on the synergistic effect of multiple functional units. When MOF nanoparticles are lacking in the system, although the coating can undergo photocrosslinking, the self-healing effect is limited due to the lack of adsorption and slow release of active components. When photoinitiators are lacking, even with the presence of MOF structures, it is difficult to trigger an effective crosslinking reaction under ultraviolet light. When low surface energy components are lacking, a stable superhydrophobic interface cannot be constructed on the coating surface, and it does not possess the core performance of this invention from the outset. In contrast, after simultaneously introducing MOF nanoparticles, a photoinitiating system, and low surface energy components in the examples, the coating can achieve rapid and effective recovery of hydrophobic and optical properties under ultraviolet light and thermal assistance conditions, demonstrating a comprehensive effect that is significantly better than any single or partial combination of functional components. This fully demonstrates that the photothermal synergistic self-healing mechanism proposed in this invention has significant synergistic enhancement characteristics.

[0150] Example 8

[0151] Same as Example 1, except that:

[0152] In step S2, the hydrolysis solvent is prepared by mixing anhydrous ethanol, deionized water, and glacial acetic acid. The deionized water accounts for 3% of the total volume of the hydrolysis solvent, and the amount of glacial acetic acid accounts for 0.05 wt% of the total mass of the hydrolysis solvent. The molar ratio of TEOS, APTES, and GPTMS is 6:5:2. At the same time, the molar ratio of TEOS to water is controlled at 1:26. The mixture is stirred for 10 min to complete the initial hydrolysis and condensation to obtain the bottom layer sol. The bottom layer sol is cured for 2 h and pre-cured at 80°C for 30 min to obtain a bottom layer thickness of 0.3 μm.

[0153] In step S4, nano-SiO2 and micro-SiO2 are dispersed in a mixed solvent of ethanol and isopropanol in a mass ratio of 3:1.

[0154] In step S5, the mass ratio of powder C to powder B is 3:1, and the spraying conditions are: 4 wt% solid content, nozzle diameter 0.8 mm, atomization pressure 0.8 bar, spraying distance 10 cm, and intermediate layer thickness 1.0 μm.

[0155] In step S6, based on the total mass of the surface coating liquid, the total amount of photoinitiator is 0.1 wt%, the total amount of low surface energy components is 0.5 wt%, and the mass of PDMS is 5 wt%.

[0156] In step S9, pre-curing is performed at 80°C for 30 min, resulting in a surface layer thickness of 0.1 μm.

[0157] Example 9

[0158] Same as Example 1, except that:

[0159] In step S2, the hydrolysis solvent is prepared by mixing anhydrous ethanol, deionized water, and glacial acetic acid. The deionized water accounts for 8% of the total volume of the hydrolysis solvent, and the amount of glacial acetic acid accounts for 0.10 wt% of the total mass of the hydrolysis solvent. The molar ratio of TEOS, APTES, and GPTMS is 10:5:2. At the same time, the molar ratio of TEOS to water is controlled to be 1:6. The mixture is stirred for 120 min to complete the initial hydrolysis and condensation, resulting in the bottom layer sol. The bottom layer sol is cured for 24 h and pre-cured at 90°C for 10 min, resulting in a bottom layer thickness of 0.8 μm.

[0160] In step S4, nano-SiO2 and micro-SiO2 are dispersed in a mixed solvent of ethanol and isopropanol in a mass ratio of 5:1.

[0161] In step S5, the mass ratio of powder C to powder B is 4:1, and the spraying conditions are: 10 wt% solid content, 1.0 mm nozzle diameter, 1.5 bar atomization pressure, 20 cm spray distance, and 2.5 μm intermediate layer thickness.

[0162] In step S6, based on the total mass of the surface coating liquid, the total amount of photoinitiator is 1.5 wt%, the total amount of low surface energy components is 3.0 wt%, and the mass of PDMS is 15 wt%.

[0163] In step S9, pre-curing at 90°C for 10 min forms a coating surface with a thickness of 0.6 μm.

[0164] The above description of the embodiments is only for the purpose of helping to understand the technical solution and core idea of ​​the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made to the present invention without departing from the principle of the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

Claims

1. A photothermal synergistic self-healing superhydrophobic transparent coating, characterized in that: The coating has an average visible light transmittance ≥90%, haze ≤1.5%, static water contact angle ≥160°, roll-off angle ≤5%, and a coating thickness of 1-10 μm. The coating comprises a bottom layer, an intermediate layer, and a top layer connected in sequence. Specifically, the bottom layer is an organic-inorganic hybrid binder phase containing silane coupling groups; the intermediate layer contains a hierarchical rough structure and metal-organic framework MOF nanoparticles, wherein the MOF nanoparticles are loaded with photocrosslinkable monomers and / or low surface energy molecules; and the top layer contains a photoinitiating system sensitive to ultraviolet light, photocrosslinkable unsaturated groups, and low surface energy components.

2. The photothermal synergistic self-healing superhydrophobic transparent coating according to claim 1, characterized in that, The coating thickness is 2-6 μm.

3. The photothermal synergistic self-healing superhydrophobic transparent coating according to claim 1 or 2, characterized in that, The MOF is a zeolite imidazole skeleton-8 or an amino-modified UiO-66 with a particle size of 10–100 nm.

4. The photothermal synergistic self-healing superhydrophobic transparent coating according to claim 1 or 2, characterized in that, The low surface energy molecules are selected from perfluorohexyltriethoxysilane, perfluorohexyl acrylate, polydimethylsiloxane-terminated silane, long-chain alkyl silane and / or cage-like silsesquioxane.

5. The method for preparing the coating according to any one of claims 1–4, characterized in that, Includes the following steps: S1. The substrate is pretreated and deposited to form an organic-inorganic hybrid binder phase bottom layer containing silane coupling groups; S2. Spraying an intermediate layer containing a graded rough structure and MOF nanoparticles onto the bottom surface; S3. A surface layer is formed by spraying a coating onto the surface of the intermediate layer. The surface layer contains a photoinitiating system, a low surface energy component, and photocrosslinkable unsaturated groups. The photocrosslinkable unsaturated groups are allyl or (meth)acrylate unsaturated groups. The photocrosslinkable unsaturated groups are directly introduced by the surface coating liquid or provided by MOF nanoparticles preloaded with the photocrosslinkable unsaturated groups in the intermediate layer. Under subsequent ultraviolet light irradiation, polymerization and crosslinking occur to form a continuous and dense low surface energy crosslinked layer, resulting in a photothermal synergistic self-healing superhydrophobic transparent coating. The coating liquids used in steps S1–S3 are independently prepared and sprayed sequentially. Each layer is formed on the basis of the previous layer being cured or semi-cured, thereby constructing a layered structure of bottom layer-intermediate layer-surface layer.

6. The preparation method according to claim 5, characterized in that, In step S1, the substrate is deposited by spraying or coating and pre-cured at 80°C-90°C for 10-30 min.

7. The preparation method according to claim 5, characterized in that, The intermediate coating liquid in step S2 contains polydimethylsiloxane (PDMS) as a thermo-responsive elastic phase.

8. The preparation method according to claim 5, characterized in that, In step S3, the surface coating liquid has a spray solids content of 4-10 wt% and is pre-cured at 80°C-90°C.

9. The preparation method according to claim 5, characterized in that, The ultraviolet irradiation conditions in step S3 are: wavelength 365 nm, irradiation intensity 5-20 mW·cm⁻², irradiation time 2-10 min.

10. The coating self-healing method according to any one of claims 1–4, characterized in that: After microscopic damage occurs on the coating surface, the coating is subjected to 365 nm ultraviolet irradiation of 5-15 mW·cm⁻² for 2-10 min, and then treated at 60°C-80°C for 10-60 min to restore hydrophobic and optical properties.