Porous polymer materials

Abstract

The present invention relates to porous polymer materials capable of absorbing and releasing water for surface cooling purposes. Described is a copolymer composition comprising repeat units derived from three or more monomers selected from acrylamide (AAm); an ionic monomer selected from styrene sulfonic acid or a salt thereof (SS), a zwitterionic monomer (ZI), and mixtures thereof; an adhesion-promoting monomer selected from acrylonitrile (AN), vinyltrimethoxysilane (VTMS), and mixtures thereof; and acrylic acid (AA). Also described are related composite materials, porous materials, methods of producing a porous material and methods of applying the material to surfaces, for example by aerosol deposition or in a paint-like form. In addition, the design of the materials and the method of synthesis are described, as well as the formation of the porous structure and the mechanism by which surface cooling occurs. Furthermore, the invention concerns the application to photovoltaic cells and reducing the drop in efficiency caused by temperature increases of the cell itself.

Description

[0001] Porous polymer materials

[0002] Field of the Invention

[0003] The present invention relates to porous polymer materials capable of passively cooling surfaces, including photovoltaic devices.

[0004] Background

[0005] Photovoltaic cells (PV cells) are commonly used to generate power by converting solar energy into electricity. However, there is a problem associated with PV cells in that their temperature increases during peak sunlight hours, which can result in a decrease in efficiency of the PV cell.

[0006] Active cooling systems such as fans and water pumping systems may be used to counter such temperature increases, but these systems are expensive to set up, run, and maintain.

[0007] Passive cooling systems have also been investigated. Li et al. (Nature Sustainability, vol. 3, 2020, 636-643) describes a hydrogel material comprising polyacrylamide and carbon nanotubes.

[0008] However, drawbacks associated with the use of this material as a passive cooling system for solar cells include low efficiency increase, requiring a large amount of the expensive hydrogel material.

[0009] There is therefore a need for further cooling systems that are capable of increasing PV cell efficiency.

[0010] Summary of the Invention

[0011] The present invention provides a low-cost polymer hydrogel that is capable of acting as a passive cooling system which is easy to apply, and requires minimum maintenance.

[0012] Accordingly, in a first aspect, the present invention provides a copolymer composition comprising a polymer having first and second repeat units, wherein the first repeat unit is derived from acrylamide and / or acrylic acid and / or N-isopropylacrylamide and / or vinyl alcohol, and the second repeat unit is derived from a crosslinking monomer. In a second aspect, the present invention provides a copolymer composition comprising repeat units derived from three or more monomers selected from: acrylamide (AAm); and an ionic monomer selected from styrene sulfonic acid or a salt thereof (SS), a zwitterionic monomer (ZI), and mixtures thereof; and an adhesion-promoting monomer selected from acrylonitrile (AN), vinyltrimethoxysilane (VTMS), and mixtures thereof; and acrylic acid (AA).

[0013] In a third aspect, the present invention provides a composite material comprising a copolymer composition of the first aspect and a plurality of template regions.

[0014] In a fourth aspect, the present invention provides a composite material comprising: acrylamide (AAm); and an ionic monomer selected from styrene sulfonic acid or a salt thereof (SS), a zwitterionic monomer (ZI), and mixtures thereof; and an adhesion-promoting monomer selected from acrylonitrile (AN), vinyltrimethoxysilane (VTMS), and mixtures thereof; and a plurality of template regions.

[0015] In a fifth aspect, the present invention provides a porous material comprising a copolymer composition of the first aspect and a plurality of pores, wherein the copolymer composition comprises crosslinking.

[0016] In a sixth aspect, the present invention provides a method for producing a porous material, comprising:

[0017] (i) providing a composite material of the third aspect; and

[0018] (ii) removing the plurality of template regions from the composite material to provide a plurality of pores; to produce a porous material.

[0019] The method of the sixth aspect for producing a porous material typically comprises: (a) providing a composite material comprising a copolymer composition and a plurality of template regions, the copolymer composition comprising first repeat units derived from acrylamide (AAm) and / or acrylic acid (AA), and second repeat units derived from a crosslinking monomer, wherein the crosslinking monomer is preferably N,N’- methylenebisacrylamide (MBAA); and

[0020] (b) removing the plurality of template regions from the composite material to provide a plurality of pores; to produce a porous material.

[0021] In a seventh aspect, the present invention provides a method for producing a porous material, comprising:

[0022] (i) providing a composite material as defined in any one of claims 5 to 16;

[0023] (ii) polymerising the composite material; and

[0024] (iii) removing at least some of the plurality of template regions from the composite material to provide a plurality of pores; to produce a porous material.

[0025] In an eighth aspect, the present invention provides a porous material comprising a copolymer composition according to the second aspect of the invention, and a plurality of pores.

[0026] In a ninth aspect, the present invention provides a porous material obtainable by a method of the sixth or seventh aspects.

[0027] In a 10thaspect, the present invention provides a photovoltaic cell, wherein a porous material of the fifth, eighth or ninth aspects is disposed on a surface thereof.

[0028] In an 11thaspect, the present invention provides a method of modifying a photovoltaic cell, comprising applying a porous material of the fifth, eighth or ninth aspects to a surface of the photovoltaic cell.

[0029] In a 12thaspect, the present invention provides use of a porous material of the fifth, eighth or ninth aspects to regulate the temperature of a photovoltaic cell. The porous material of the invention is capable of acting as a passive cooling system. Accordingly, the porous material of the invention is capable of providing a cooling effect, for example when applied to a PV cell, counteracting the temperature increase that may occur during peak sunlight hours. The porous material can be applied to a surface of a PV cell (e.g. the backside), and the porous material can absorb as much as 250 times its weight in atmospheric water during low / no light hours. When the temperature of the cell reaches a critical temperature (e.g. during peak sunlight hours), water in the pores of the porous material is evaporated off. This evaporation of water requires energy input, which is supplied by heat energy from the PV cell, thereby reducing the temperature of the cell. The tendency of the PV cell to increase in temperature during peak sunlight hours is reduced, thereby increasing the efficiency of the cell throughout the day. This is a low-maintenance cooling system, as once the hydrogel has been applied, e.g. in the form of a paint or an aerosol, no input to the system is required.

[0030] The co-polymer composition of the first aspect can be loaded with template regions and crosslinked to form the composite material of the third aspect. The template regions of the composite material of the third aspect can then be removed to form the porous material of the fifth and ninth aspects.

[0031] The composite material of the fourth aspect can be polymerised and the template regions in the composite material can be removed to form the porous material of the eighth and ninth aspects.

[0032] Brief Description of the Figures

[0033] Figure 1 is a schematic diagram showing the relationship between the copolymer composition, composite material, and porous material of the invention

[0034] Figure 2 shows the rehydration performance of the porous material of the invention.

[0035] Figure 3 shows Fourier Transform Infra Red (FTIR) spectra of materials according to the invention. Figure 4 shows the thermocouple data of a metal plate to which a layer of the material of the invention had been applied. Data sets are, in order from highest temperature to lowest temperature at t=60 minutes: Front face no gel; Back face no gel; Front face gel; Back face gel.

[0036] Figure 5 shows the thermocouple data of a small cell to which a layer of the material of the invention had been applied. Data sets are, in order from highest temperature to lowest temperature at t=60 minutes: Front no gel; Back no gel; Front gel; Back gel.

[0037] Figure 6 shows the relative efficiency under solar simulation of cells to which a layer of the material of the invention had been applied. Data sets are, in order from highest efficiency to lowest efficiency at t=5 hours: Sample; Control.

[0038] Figure 7 shows the atmospheric water absorption performance of the porous material of the invention.

[0039] Figure 8 shows SEM images of the porous material of the invention.

[0040] Figure 9 shows outdoor PV panel temperatures between 7am and 5pm for a summer day in the United Kingdom, in Oxfordshire. The panel treated with a porous material of the present invention is shown in green (bottom trace) and the untreated control panel shown in blue (top trace). The average difference in temperature between the two was 7.9°C.

[0041] Figure 10 shows a solar simulator setup of a treated and an untreated panel.

[0042] Figure 11 shows solar simulator set up with a 20W RS panel in a vertical (left) and horizontal (right) supported position. The enclosed blackout environment ensures accuracy.

[0043] Figure 12 shows IV curves of a control (untreated cell) top and sample (panel treated with a porous material of the present invention) bottom, the x axis cross point represents Pmax. The greater shift left of the x axis cross point over time with the untreated panel shows decreasing efficiency.

[0044] Figure 13 shows setup and state of 200W 90 day solar panels on a roof. All panels are south facing and reclined at an angle of 30°C. Figure 14 shows an example of a hydrogel coated 200W panel placed on a roof (top), and the weight in kg of a treated panel measured over a 90 day period (below).

[0045] Figure 15 shows a 110W bifacial panel before coating (left) and after treatment with a clear glass bound porous material of the present invention.

[0046] Figure 16 shows microscope images at 20x magnification of some samples of the hydrated hydrogel porous material of the present invention, exhibiting, macro, micro and Nano porosity.

[0047] Figure 17 shows FT-IR analysis of a completely dehydrated sample of the porous material of the present invention.

[0048] Detailed Description of the Invention

[0049] Copolymer composition

[0050] The present invention provides a copolymer composition comprising a polymer having first and second repeat units, wherein the first repeat unit is derived from acrylamide and / or acrylic acid and / or N-isopropylacrylamide and / or vinyl alcohol, and the second repeat unit is derived from a crosslinking monomer.

[0051] The present invention also provides a copolymer composition comprising repeat units derived from three or more monomers selected from: acrylamide (AAm); and an ionic monomer selected from styrene sulfonic acid or a salt thereof (SS), a zwitterionic monomer (ZI), and mixtures thereof; and an adhesion-promoting monomer selected from acrylonitrile (AN), vinyltrimethoxysilane (VTMS), and mixtures thereof; and acrylic acid (AA). The copolymer composition of the present invention may comprise an alternating copolymer, a block copolymer and / or a random copolymer. Thus, the first and second repeat units may be present as alternating repeat units, blocks of repeat units and / or random repeat units.

[0052] As used herein, the term “crosslinking” refers to the presence of crosslinks in a polymer. As used herein the term “crosslink” refers to a bond or a short sequence of bonds that links one polymer chain to another.

[0053] As used herein, the term “crosslinking monomer” refers to a monomer which is capable of forming crosslinking to form a crosslinked copolymer.

[0054] As used herein, the term “monomer” refers to a compound from which a repeating unit in the polymer is derived.

[0055] Preferably, the crosslinking monomer is selected from the group consisting of an alcohol-bearing monomer, allyl thiol, acrylic acid, N,N’-methylenebisacrylamide (MBAA), an amine-bearing monomer, an aldehyde-bearing monomer, vinyl alcohol, or a mixture thereof.

[0056] As used herein, the term “alcohol-bearing monomer” refers to a monomer comprising an alcohol (OH) functional group. Preferably, the amine-bearing monomer is vinyl alcohol.

[0057] As used herein, the term “amine-bearing monomer” refers to a monomer comprising an amine (NH2) functional group. Preferably, the amine-bearing monomer is selected from allyl amine, and vinyl amine. Most preferably, the amine-bearing monomer is allyl amine.

[0058] As used herein, the term “aldehyde-bearing monomer” refers to a monomer comprising an aldehyde (C=O) functional group. Preferably, the aldehyde -bearing monomer is selected from glyoxal, glutaraldehyde, propanedial, butanedial, pentanedial, and hexanedial. Most preferably, the aldehyde-bearing monomer is glyoxal.

[0059] Preferably, when the crosslinking monomer is an alcohol-bearing monomer, the composition comprises a repeat unit derived from acrylic acid. Preferably, when the crosslinking monomer is an amine bearing monomer, the composition comprises a further polymer having a repeat unit derived from a monomer selected from acrylamide and / or acrylic acid and / or N-isopropylacrylamide and / or vinyl alcohol, and a repeat unit derived from an aldehyde-bearing monomer.

[0060] Preferably, when the crosslinking monomer is an aldehyde bearing monomer, the composition comprises a further polymer having a repeat unit derived from a monomer selected from acrylamide and / or acrylic acid and / or N-isopropylacrylamide and / or vinyl alcohol, and a repeat unit derived from an amine-bearing monomer.

[0061] The first repeat unit in the copolymer composition is derived from acrylamide and / or acrylic acid and / or N-isopropylacrylamide and / or vinyl alcohol. A repeat unit derived from acrylamide and / or acrylic acid and / or N-isopropylacrylamide will typically have the following structure: wherein X is NH2, OH or NHCH(CH3)2.

[0062] A repeat unit derived from AAm will typically have the structure above in which X is NH2. A repeat unit derived from AA will typically have the structure above in which X is OH.

[0063] A repeat unit derived from SS will typically have the structure: A repeat unit derived from AN will typically have the structure:

[0064] A repeat unit derived from VTMS will typically have the structure:

[0065] First repeat units derived from acrylic acid and acrylamide may be preferred due to the high versatility of the acrylic acid and acrylamide monomers. Further, when the first repeat unit is derived from acrylic acid or acrylamide, the resulting polymer possesses high hydrophilicity and biocompatibility. First repeat units derived from acrylic acid are particularly preferred as the acrylic acid monomer has good environmental and safety profiles.

[0066] When the first repeat unit is derived from N-isopropylacrylamide, hydrophilicity of the composition is good, and thermoresponsivity of a hydrogel produced from the composition can be achieved at high concentrations.

[0067] When the first repeat unit is derived from vinyl alcohol, the alcohol group may contribute to further crosslinking in the crosslinked copolymer compositions described herein (e.g. in addition to the crosslinking described elsewhere herein). The alcohol group in a first repeat unit derived from vinyl alcohol may contribute to further crosslinking for example by forming crosslinking with aldehyde or acid groups as described elsewhere herein.

[0068] The second repeat unit in the copolymer composition is derived from a crosslinking monomer. When the crosslinking monomer is allyl thiol the second repeat unit will typically have the following structure:

[0069] When the crosslinking monomer is acrylic acid the second repeat unit will typically have the following structure:

[0070] When the crosslinking monomer is N,N’ -methylenebisacrylamide (MBAA) the second repeat unit will typically have the following structure:

[0071] That is, a repeat unit derived from MBAA will typically have the structure above.

[0072] When the crosslinking monomer is an alcohol-bearing monomer the second repeat unit will typically have the following structure: wherein the wavy line is the backbone of the second repeat unit. When the crosslinking monomer is an amine-bearing monomer the second repeat unit will typically have the following structure: wherein the wavy line is the backbone of the second repeat unit.

[0073] When the crosslinking monomer is aldehyde-bearing monomer the second repeat unit will typically have the following structure: wherein the wavy line is the backbone of the second repeat unit.

[0074] When the crosslinking monomer is vinyl alcohol the second repeat unit will typically have the following structure:

[0075] The copolymer composition may not be a crosslinked polymer. Alternatively, the copolymer composition may comprise crosslinking. Copolymer compositions which are not crosslinked polymers may be converted into copolymer compositions comprising crosslinking by forming crosslinking in the copolymer composition.

[0076] Typically, crosslinking in the copolymer composition comprises crosslinks derived from:

[0077] (i) an alcohol-bearing monomer as a crosslinking monomer, and a repeat unit of the copolymer composition derived from acrylic acid;

[0078] (ii) acrylic acid as a crosslinking monomer, and ethylene glycol;

[0079] (iii) allyl thiol as a crosslinking monomer; (iv) N,N’ -methylenebisacrylamide (MBAA) as a crosslinking monomer;

[0080] (v) vinyl alcohol as a crosslinking monomer, and (a) a di -acid (e.g. oxalic acid), or (b) a further polymer comprised in the composition, the further polymer having a repeat unit derived from acrylamide and / or acrylic acid and / or N-isopropylacrylamide and / or vinyl alcohol and a repeat unit derived from an acid-bearing monomer, the crosslinks being derived from the vinyl alcohol and the acid-bearing monomer;

[0081] (vi) an amine-bearing monomer, and a further polymer comprised in the composition, the further polymer having a repeat unit derived from acrylamide and / or acrylic acid and / or N- isopropylacrylamide and / or vinyl alcohol and a repeat unit derived from an aldehyde- bearing monomer, the crosslinks being derived from the amine-bearing monomer and the aldehyde-bearing monomer;

[0082] (vii) an aldehyde-bearing monomer, and a further polymer comprised in the composition, the further polymer having a repeat unit derived from acrylamide and / or acrylic acid and / or N- isopropylacrylamide and / or vinyl alcohol and a repeat unit derived from an amine-bearing monomer, the crosslinks being derived from the aldehyde-bearing monomer and the amine-bearing monomer; or a mixture thereof.

[0083] Preferably, crosslinking in the copolymer composition comprises crosslinks derived from:

[0084] (i) an alcohol-bearing monomer as a crosslinking monomer, and a repeat unit of the copolymer composition derived from acrylic acid;

[0085] (ii) acrylic acid as a crosslinking monomer, and ethylene glycol;

[0086] (iii) allyl thiol as a crosslinking monomer;

[0087] (v) vinyl alcohol as a crosslinking monomer, and (a) a di -acid (e.g. oxalic acid), or (b) a further polymer comprised in the composition, the further polymer having a repeat unit derived from acrylamide and / or acrylic acid and / or N-isopropylacrylamide and / or vinyl alcohol and a repeat unit derived from an acid-bearing monomer, the crosslinks being derived from the vinyl alcohol and the acid-bearing monomer;

[0088] (vi) an amine-bearing monomer, and a further polymer comprised in the composition, the further polymer having a repeat unit derived from acrylamide and / or acrylic acid and / or N- isopropylacrylamide and / or vinyl alcohol and a repeat unit derived from an aldehyde- bearing monomer, the crosslinks being derived from the amine-bearing monomer and the aldehyde-bearing monomer; (vii) an aldehyde-bearing monomer, and a further polymer comprised in the composition, the further polymer having a repeat unit derived from acrylamide and / or acrylic acid and / or N- isopropylacrylamide and / or vinyl alcohol and a repeat unit derived from an amine-bearing monomer, the crosslinks being derived from the aldehyde-bearing monomer and the amine-bearing monomer; or a mixture thereof.

[0089] More preferably, crosslinking in the copolymer composition comprises crosslinks derived from:

[0090] (i) an alcohol-bearing monomer as a crosslinking monomer, and a repeat unit of the copolymer composition derived from acrylic acid;

[0091] (ii) acrylic acid as a crosslinking monomer, and ethylene glycol;

[0092] (v) vinyl alcohol as a crosslinking monomer, and (a) a di -acid (e.g. oxalic acid), or (b) a further polymer comprised in the composition, the further polymer having a repeat unit derived from acrylamide and / or acrylic acid and / or N-isopropylacrylamide and / or vinyl alcohol and a repeat unit derived from an acid-bearing monomer, the crosslinks being derived from the vinyl alcohol and the acid-bearing monomer;

[0093] (vi) an amine-bearing monomer, and a further polymer comprised in the composition, the further polymer having a repeat unit derived from acrylamide and / or acrylic acid and / or N- isopropylacrylamide and / or vinyl alcohol and a repeat unit derived from an aldehyde- bearing monomer, the crosslinks being derived from the amine-bearing monomer and the aldehyde-bearing monomer;

[0094] (vii) an aldehyde-bearing monomer, and a further polymer comprised in the composition, the further polymer having a repeat unit derived from acrylamide and / or acrylic acid and / or N- isopropylacrylamide and / or vinyl alcohol and a repeat unit derived from an amine-bearing monomer, the crosslinks being derived from the aldehyde-bearing monomer and the amine-bearing monomer; or a mixture thereof.

[0095] Still more preferably, crosslinking in the copolymer composition comprises crosslinks derived from:

[0096] (i) an alcohol-bearing monomer as a crosslinking monomer, and a repeat unit of the copolymer composition derived from acrylic acid;

[0097] (ii) acrylic acid as a crosslinking monomer, and ethylene glycol; (v) vinyl alcohol as a crosslinking monomer, and (a) a di -acid (e.g. oxalic acid), or (b) a further polymer comprised in the composition, the further polymer having a repeat unit derived from acrylamide and / or acrylic acid and / or N-isopropylacrylamide and / or vinyl alcohol and a repeat unit derived from an acid-bearing monomer, the crosslinks being derived from the vinyl alcohol and the acid-bearing monomer; or a mixture thereof.

[0098] Even further preferably, crosslinking in the copolymer composition comprises crosslinks derived from:

[0099] (i) an alcohol-bearing monomer as a crosslinking monomer, and a repeat unit of the copolymer composition derived from acrylic acid;

[0100] (ii) acrylic acid as a crosslinking monomer, and ethylene glycol; or a mixture thereof.

[0101] Most preferably, crosslinking in the copolymer composition comprises crosslinks derived from an alcohol-bearing monomer as a crosslinking monomer, and a repeat unit of the copolymer composition derived from acrylic acid.

[0102] A crosslink derived from acrylic acid as a crosslinking monomer, and ethylene glycol will typically have the following structure:

[0103] Wherein the asterisks represent the points of attachment of the crosslink to the crosslinked polymer chains.

[0104] A crosslink derived from allyl thiol as a crosslinking monomer will typically have the following structure: A crosslink derived from N,N’-methylenebisacrylamide (MBAA) as a crosslinking monomer will typically have the following structure:

[0105] A crosslink derived from vinyl alcohol as a crosslinking monomer, and a di -acid (e.g. oxalic acid) or an acid-bearing monomer will typically have the following structure:

[0106] A crosslink derived from an alcohol-bearing monomer and repeat unit of the copolymer composition derived from acrylic acid will typically have the following structure:

[0107] A crosslink derived from an amine-bearing monomer and an aldehyde-bearing monomer will typically have the following structure:

[0108] A crosslink derived from an aldehyde-bearing monomer and an amine-bearing monomer will typically have the following structure:

[0109] In (i) to (iv), the asterisks typically represent a point of direct attachment of the crosslink to the crosslinked polymer chains.

[0110] In (v) and (vi) the asterisks may represent a point of direct or indirect attachment of the crosslink to the crosslinked polymer chains.

[0111] The present invention also provides a copolymer composition comprising repeat units derived from three or more monomers selected from: acrylamide (AAm); and an ionic monomer selected from styrene sulfonic acid or a salt thereof (SS), a zwitterionic monomer (ZI), and mixtures thereof; and an adhesion-promoting monomer selected from acrylonitrile (AN), vinyltrimethoxysilane (VTMS), and mixtures thereof; and acrylic acid (AA).

[0112] The SS is typically in the form of a group 1 styrene sulfonate, preferably sodium styrene sulfonate.

[0113] The ZI is typically selected from [2-(methacryloyloxy)ethyl]dimethyl-(3-sulfopropyl)ammonium hydroxide, 2-methacryloyloxyethyl phosphorylcholine, 2-oleoyl-l-palmitoyl-sn-glycero-3- phosphocholine, and mixtures thereof.

[0114] Preferably, the ionic monomer is SS.

[0115] Preferably, the adhesion-promoting monomer is acrylonitrile (AN).

[0116] The copolymer composition of the present invention typically comprises repeat units derived from: acrylamide (AAm); and an ionic monomer selected from styrene sulfonic acid or a salt thereof (SS), a zwitterionic monomer (ZI), and mixtures thereof; and an adhesion-promoting monomer selected from acrylonitrile (AN), vinyltrimethoxysilane (VTMS), and mixtures thereof; and acrylic acid (AA).

[0117] The copolymer composition typically further comprises crosslinking. Crosslinking may comprise crosslinks derived from a crosslinking monomer as described above, and / or may comprise crosslinks in the form of ionic bonds. Typically, when crosslinking comprises crosslinks derived from a crosslinking monomer, the crosslinking monomer is N,N’ -methylenebisacrylamide (MBAA). Typically, when crosslinks are in the form of ionic bonds, the ionic bonds are formed between negatively charged or polar groups in the repeat units derived from AAm, SS, ZI, AN and / or AA, and cations of a group 1 or 2 element (e.g. in the form of a salt of a group 1 or 2 element), preferably cations of a group 2 element (e.g. in the form of a salt of a group 2 element), more preferably Ca2+ions (e.g. in the form of a Ca salt such as CaCT). The negatively charged groups may be a carboxylate group in a repeat unit derived from AA or a sulfonate group in a repeat unit derived from SS, or a negatively charged group in repeat unit derived from ZI. The polar group may be a nitrile group in a repeat unit derived from AN, or an amide group in a repeat unit derived from AAm.

[0118] Accordingly, when the copolymer composition comprises crosslinking, the copolymer composition may further comprise repeat units derived from N,N’ -methylenebisacrylamide (MBAA) and / or may further comprise Ca2+ions (e.g. in the form of a Ca salt such as CaCT).

[0119] Preferably, the copolymer composition comprises repeat units derived from: acrylamide (AAm); and an ionic monomer selected from styrene sulfonic acid or a salt thereof (SS), a zwitterionic monomer (ZI), and mixtures thereof; and an adhesion-promoting monomer selected from acrylonitrile (AN), vinyltrimethoxysilane (VTMS), and mixtures thereof; and acrylic acid (AA); and N,N’ -methylenebisacrylamide (MBAA); and further comprises Ca2+ions; and comprises crosslinks derived from MBAA and crosslinks derived from the Ca2+ions.

[0120] The presence of repeat units derived from styrene sulfonate may facilitate water absorption in the copolymer composition.

[0121] The presence of repeat units derived from acrylonitrile may facilitate water absorption in the copolymer composition and may facilitate adhesion of the copolymer composition to organic materials such as PET (e.g. to the surface of a photovoltaic cell) by donation of the lone pair on the nitrile group to electron deficient groups within PET or other organic materials.

[0122] The presence of repeat units derived from vinyltrimethoxysilane (VTMS) may facilitate adhesion of the copolymer composition to inorganic materials such as glass (e.g. to the surface of a photovoltaic cell).

[0123] Ca2+cross linking between SS groups may facilitate self-healing of the copolymer composition.

[0124] In the copolymer composition, the amount by weight of the repeat unit derived from the ionic monomer, relative to the amount by weight of AAm, is typically in the range of 0.5 / (10x) to 1.5 / (10x), preferably 0.8 / (10x) to 1.2 / (10x), more preferably about l / (10x), wherein x is the amount by weight of AAm.

[0125] In the copolymer composition, the amount by weight of the repeat unit derived from the adhesionpromoting monomer , relative to the amount by weight of AAm, is typically in the range of 0.5x / 20 to 1.5x / 20, preferably 0.8x / 20 to 1.2x / 20, more preferably about x / 20, wherein x is the amount by weight of AAm.

[0126] In the copolymer composition, the amount by weight of the repeat unit derived from AA, relative to the amount by weight of AAm, is typically in the range of 0.5 / (20x) to 1.5 / (20x), preferably 0.8 / (20x) to 1.2 / (20x), more preferably about l / (20x)„ wherein x is the amount by weight of AAm.

[0127] In the copolymer composition, the amount by weight of the repeat unit derived from MBAA, relative to the amount by weight of AAm, is typically in the range of 2 / (1 OOx) to 6 / (1 OOx), preferably 3.2 / (100x) to 4.8 / (100x), more preferably about 4 / (100x), wherein x is the amount by weight of AAm. In the copolymer composition, the amount of Ca2+ions, based on the equivalent weight of CaCb relative to the amount by weight of AAm, is typically in the range of 4x to 12x, preferably 6.4x to 9.6x, more preferably about 8x, wherein x is the amount by weight of AAm.

[0128] Composite material

[0129] The present invention further provides a composite material. The composite material may be a polymer composite material comprising a copolymer composition as described in the previous section and a plurality of template regions, as in the third aspect of the invention. The composite may be a monomer composite material comprising unpolymerised monomers and a plurality of templated, as in the fourth aspect of the invention. The terms “polymer composite material” and “monomer composite material” are used herein to distinguished between types of composite material as and when necessary.

[0130] As used herein, the term “template regions” refers to regions in the composite material capable of being removed (for example, by dissolution in a solvent, by photoresist lithography, or by degradation by light and / or heat, or by chemical decomposition) to form of a plurality of pores in the material. The pores typically occupy the spaces formerly occupied by the template regions prior to their removal.

[0131] The plurality of template regions may comprise template particles. As used herein, the term “templates particles” refers to particles capable of being removed (for example, by dissolution in a solvent or by photoresist lithography) to form of a plurality of pores in the material. The pores typically occupy the spaces formerly occupied by the template particles prior to their removal.

[0132] The polymer composite material may be a block copolymer composition comprising:

[0133] (i) a first block comprising the copolymer composition of the invention; and

[0134] (ii) a second block comprising a third repeat unit derived from a photoresist monomer; wherein the template regions comprise the second block. In such embodiments the template regions comprise a repeat unit derived from a photoresist monomer. As used herein, the term “photoresist monomer” relates to a radiation-sensitive monomer (e.g. a light-sensitive monomer, such as UV light-sensitive monomer) that is capable of being decomposed when subjected to photoresist lithography. The repeat unit derived from the photoresist monomer will typically be capable of being decomposed in the same way. Preferably, the photoresist monomer is methyl methacrylate.

[0135] As used herein, the term “photoresist lithography” refers to the decomposition of a repeat unit derived from a photoresist monomer upon exposure to radiation (e.g. light, such as UV light). When the template regions comprise a polymer comprising a repeat unit derived from a photoresist monomer, photoresist lithography typically creates pores within the composite material, thereby forming a porous material.

[0136] Typically, the template regions comprise a polymer comprising a repeat unit derived from a photoresist monomer (e.g. poly(methyl methacrylate) and / or poly (lactic-co -glycolic acid)), a salt of a Group 1 element, a salt of a Group 2 element, a silicon-based material or a carbon-based material. Preferably, the template regions comprise a polymer comprising a repeat unit derived from a salt of a Group 1 element, a salt of a Group 2 element, a silicon-based material or a carbonbased material

[0137] A repeat unit derived from poly(methyl methacrylate) typically has the following structure:

[0138] A repeat unit derived from poly(lactic-co -glycolic acid) typically has either of the following structures:

[0139] Preferably, the salt of a Group 1 element is a lithium salt, a sodium salt, or a potassium salt. Most preferably, the salt of a Group 1 element is a lithium salt. The salt may be a chloride salt, a nitrate salt, or a sulfate salt. Preferably, the salt is a chloride salt.

[0140] Preferably, the salt of a Group 2 element is a calcium salt or a magnesium salt. Most preferably, the salt of a Group 2 element is a calcium salt. The salt may be a chloride salt, a nitrate salt, or a sulfate salt. Preferably, the salt is a chloride salt.

[0141] Preferably, the silicon-based material is sodium silicate or calcium silicate. Preferably, the carbonbased material is sodium carbonate or calcium carbonate. More preferably the carbon based material is hydrogencarbonate or carbonate salt, such as sodium hydrogencarbonate, sodium carbonate, calcium hydrogencarbonate, or sodium carbonate. Still more preferably, the carbon based material is sodium hydrogencarbonate or sodium carbonate. Most preferably the carbon based material is sodium hydrogencarbonate.

[0142] When the template particles comprises a carbon-based material (e.g. sodium hydrogencarbonate), the carbon-based material may be present in the composite material (e.g. the monomer composite material) in combination with a surfactant. Suitable surfactants include sodium dodecyl sulfate (SDS) or poloxamer 407. When the carbon-based material (e.g. sodium hydrogencarbonate) is present in the composite material (e.g. the monomer composite material) in combination with a surfactant, the particles of carbon-based material (e.g. sodium hydrogencarbonate) may be present in the composite material (e.g. the monomer composite material) in the form of a surfactant micelle. The presence of the carbon-based material in the form of a surfactant micelle may aid pore formation and may, in the case of monomer composite material, enable emulsification polymerisation when the monomer composite material is subsequently polymerised. The use of a carbon-based material such as a hydrogencarbonate or carbonate as the template particle facilitates pore formation because pores can be generated by the formation of CO2 microbubbles by chemical decomposition of the hydrogencarbonate or carbonate on exposure to an acidic moiety in the composite material, such as AA or repeat units derived from AA. The particles can themselves also act as a physical template for pore formation as polymerisation and / or crosslinking takes place around them.

[0143] Typically, the template regions have a size in the range of from 10 nm to 500 pm. Preferably, the template regions have a size in a range of from 10 nm to 10 pm or 50 nm to 500 pm, more preferably from 50 nm to 7 pm, further preferably from 1 pm to 6 pm, most preferably from 3 pm to 4 pm.

[0144] The size of the template regions is typically as measured by dynamic light scattering, e.g. in accordance with the following method:

[0145] The size of nanoparticles is measured using a Malvern Instruments Zetasizer Nano (Microtrac UK, Verder Scientific UK Utd., Hope Valley, UK). Samples are prepared in 0.1-1 mg / ml solutions in distilled water and run in disposable capillary cells. Samples are run 100 times for a measurement and each sample is measured three times to produce an average. 50nm gold particles are used as a reference standard for the size.

[0146] Preferably, in the polymer composite material of the invention, the copolymer composition is as defined in the previous section. Preferably in the monomer composite material of the invention, the monomer composition is as described in the previous section with reference to the repeat units derived from the monomers.

[0147] The composite material (e.g. the monomer composite material) may comprise: acrylamide (AAm); and an ionic monomer selected from sodium styrene sulfonate styrene sulfonic acid or a salt thereof (SS), a zwitterionic monomer (ZI), and mixtures thereof; and an adhesion-promoting monomer selected from acrylonitrile (AN), vinyltrimethoxysilane (VTMS), and mixtures thereof; and a plurality of template regions.

[0148] The composite material (e.g. the monomer composite material) may further comprise N,N’- methylenebisacrylamide (MBAA).

[0149] The composite material (e.g. the monomer composite material) may further comprise Ca2+ ions.

[0150] In the composite material (e.g. the monomer composite material), the template particles may comprise a poly(lactic-co-glycolic acid), or a carbon-based material, wherein the carbon-based material is as described above.

[0151] The composite material (e.g. the monomer composite material) may further comprise a surfactant, typically selected from sodium dodecyl sulfate (SDS), poloxamer 407, or a mixture thereof.

[0152] The composite material (e.g. the monomer composite material) may further comprise an initiator such as a photoinitiator (e.g. for UV / VIS initiation) or a thermal initiator. The photoinitiator is typically 2-Hydroxy-4'-(2-hydroxyethoxy)-2 -methylpropiophenone (2H) or benzophenone, or a combination thereof.

[0153] The composite material (e.g. the monomer composite material) may further comprise acrylic acid (AA).

[0154] Porous material

[0155] The present invention further provides a porous material comprising a copolymer composition as defined in the previous section and a plurality of pores.

[0156] The porous material can be obtained by providing a composite material as defined in the previous section, and removing the plurality of template regions to provide the plurality of pores. Thus, the structure of the porous material typically corresponds to that of the composite material, but wherein the template regions are replaced by pores. In the case where the composite material is a monomer composite material, formation of the porous material may also comprise polymerising and optionally crosslinking the monomer composite material. As used herein, a pore is typically a space within the copolymer compositon into which a liquid (e.g. water) can be absorbed, (e.g. from the atmosphere surrounding the copolymer composition) and / or from which a liquid (e.g. water) can be evaporated (e.g. into the atmosphere surrounding the copolymer composition).

[0157] One or more pore(s) in the plurality of pores may contact one or more adjacent pore(s). Contact between adjacent pores may allow liquid (e.g. water) to move between pores.

[0158] The plurality of pores may be present in the form of an interconnected network of pores in which one or more pore(s) contacts one or more adjacent pore(s). The interconnected network of pores may allow liquid (e.g. water) to move between pores, and may further allow liquid (e.g. water) to move between the atmosphere surrounding the copolymer composition and the plurality of pores.

[0159] Preferably, the porous material has a pore size in a range of from 10 nm to 10 pm, more preferably from 50 nm to 7 pm, further preferably from 1 pm to 6 pm, most preferably from 3 pm to 4 pm.

[0160] The size of the pores is typically as measured by scanning electron microscope or surface area measurements, e.g. in accordance the following methods:

[0161] Surface area: porous material is lyophilized with a laboratory freeze dryer (Lyolab, LSI, USA). The Brunauer-Emmett-Teller (BET) surface area and pore size of the lyophilized composite hydrogels are measured using a surface area analyzer (Autosorb IQC, Quan- tachrome, USA) through N2adsorption at 77 K and then applied to determine the pore-size distribution using the Barret-Joyner-Halenda(BJH) method

[0162] SEM: Scanning electron microscopy (SEM) is used to characterize the porous material using a Carl Zeiss LSI 5 VP machine at 15 kV. SEM specimens, together with 200 nm diameter polystyrene particles used as a reference standard for the size, are sputter coated with a 5 nm layer of Au-Pd and are in powder form.

[0163] Typically, the porous material has a porosity in a range of 5% to 50%. The porous material may have a porosity in a range of 10% or more, e.g. 10% to 50%, 10% to 40%, 10% to 30%, or 10% to 20%. The porous material may have a porosity in a range of 20% or more, e.g. 20% to 50%, 20% to 40%, or 20% to 30%. The porous material may have a porosity in a range of 30% or more, e.g. 30% to 50%, or 30% to 40%. The porous material may have a porosity in a range of 40% or more, e.g. 40% to 50%. The porous material may have a porosity in a range of 45% or less, e.g. 5% to 45%, 5% to 35%, 5% to 25%, or 5% to 15%. The porous material may have a porosity in a range of 35% or less, e.g. 5% to 35%, 5% to 25%, or 5% to 15%. The porous material may have a porosity in a range of 25% or less, e.g. 5% to 25%, or 5% to 15%. The porous material may have a porosity in a range of 15% or less, e.g. 5% to 15%.

[0164] Porosities of the porous material referred to herein are typically as measured by determining the pore volume of the porous material (e.g. in accordance with the BET method as described above) and expressing the pore volume as a percentage of the total volume of the porous material.

[0165] Preferably, in the porous material according to the present embodiment, the pores are impregnated with an ion. Preferably, the ion is Ca2+, Mg2+, Li+, Na+or K+. Further preferably, the ion is Ca2+or Mg2+. Most preferably, the ion is Ca2+.

[0166] In the present embodiment, the presence of an ion as described above within the pores allows for increased absorption of water.

[0167] Method for producing a porous material

[0168] The present invention further provides a method for producing a porous material, comprising providing a composite material as defined previously and removing the plurality of template regions from the composite material to provide a plurality of pores, to produce a porous material.

[0169] The method typically comprises:

[0170] (a) providing a composite material comprising a copolymer composition and a plurality of template regions, the copolymer composition comprising first repeat units derived from acrylamide (AAm) and / or acrylic acid (AA), and second repeat units derived from a crosslinking monomer, wherein the crosslinking monomer is preferably N,N’ -methylenebisacrylamide (MBAA); and

[0171] (b) removing the plurality of template regions from the composite material to provide a plurality of pores; to produce a porous material.

[0172] Step (a) may comprise:

[0173] (i) providing a monomer composite material comprising: acrylamide (AAm); and an ionic monomer selected from styrene sulfonic acid or a salt thereof (SS), a zwitterionic monomer (ZI), and mixtures thereof; and an adhesion-promoting monomer selected from acrylonitrile (AN), vinyltrimethoxysilane (VTMS), and mixtures thereof; and a plurality of template regions; and

[0174] (ii) polymerising the monomer composite material.

[0175] In such aspects part (ii) of step (a) may be carried out simultaneously with step (b).

[0176] As used herein, removing the plurality of template regions from the composite material to provide a plurality of pores incudes removing at least some of the plurality of template regions.

[0177] The plurality of template regions is typically as described above with reference to the composite material of the present invention.

[0178] When the plurality of template regions comprise a salt of a Group 1 element, a salt of a Group 2 element, a silicon-based material or a carbon-based material, removing the plurality of template regions typically comprises the application of a solvent. In the case of carbon-based materials such as hydrogencarbonates and carbonates, removing the plurality of template regions may comprise contacting the carbon-based material with an acidic moiety. The solvent can be any solvent which is capable of dissolving the salt of a Group 1 element, salt of a Group 2 element, silicon-based material or carbon-based material which is present in the template region. A skilled person will understand the solubility of the material present in the template region, and accordingly will be able to select an appropriate solvent. The salt of a Group 1 element, salt of a Group 2 element, silicon-based material or carbon-based material which is present in the template region is typically water soluble. When the salt of a Group 1 element, salt of a Group 2 element, silicon-based material or carbon-based material which is present in the template region is water soluble, the solvent is typically water.

[0179] When the plurality of template regions comprise a repeat unit derived from a photoresist monomer (e.g. poly(methyl methacrylate) and / or poly(lactic-co-glycolic acid)), removing the plurality of template regions typically comprises decomposition of said repeat unit derived from a photoresist monomer (e.g. poly(methyl methacrylate) and / or poly(lactic-co-glycolic acid), preferably by photoresist lithography, followed by removal of decomposition product(s) with a solvent. In the case of poly(lactic-co -glycolic acid), removing the plurality of template regions may comprise contacting the poly(lactic-co-glycolic acid) with an acidic moiety.

[0180] The solvent can be any solvent which is capable of dissolving the decomposition product(s). A skilled person will understand the solubility of the decomposition product(s), and accordingly will be able to select an appropriate solvent. The decomposition product(s) are typically water soluble. When the decomposition product(s) are water soluble, the solvent is typically water.

[0181] In the method for producing a porous material, providing the polymer composite material may comprise providing a copolymer composition as defined previously, and providing a plurality of template regions as previously defined.

[0182] In the method for producing a porous material, providing the polymer composite material may comprise providing a copolymer composition as defined previously, providing a plurality of template regions as defined previously, and forming crosslinking in the copolymer composition.

[0183] Preferably, when the method for producing a porous material includes the step of forming crosslinking in the copolymer composition, the terms “copolymer composition” and “forming crosslinking in the copolymer composition” are defined according to any of (i) to (vi) below. (i) the copolymer composition comprises an alcohol-bearing monomer as a crosslinking monomer, and a repeat unit derived from acrylic acid, and forming crosslinking in the copolymer composition comprises application of a catalyst;

[0184] (ii) the copolymer composition comprises acrylic acid as a crosslinking monomer, and forming crosslinking in the copolymer composition comprises application of ethylene glycol and a catalyst;

[0185] (iii) the copolymer composition comprises allyl thiol as a crosslinking monomer, and forming crosslinking in the copolymer composition comprises exposing the copolymer composition to oxygen;

[0186] (iv) the copolymer composition comprises N,N’-methylenebisacrylamide (MBAA) as a crosslinking monomer, and forming crosslinking in the copolymer composition comprises radical addition of MBAA monomers in different polymer chains (e.g. during polymerisation of the copolymer composition);

[0187] (v) the copolymer composition comprises an amine-bearing monomer (that is preferably allyl amine) as a crosslinking monomer and forming crosslinking in the copolymer composition comprises application of a further polymer and a catalyst, wherein the further polymer has a repeat unit derived from acrylamide and / or acrylic acid and / or N-isopropylacrylamide and / or vinyl alcohol and a repeat unit derived from an aldehyde -bearing monomer; or

[0188] (vi) the copolymer composition comprises an aldehyde-bearing monomer (that is preferably glyoxal) as a crosslinking monomer and forming crosslinking in the copolymer composition comprises application of a further polymer and a catalyst, wherein the further polymer has a repeat unit derived from acrylamide and / or acrylic acid and / or N- isopropylacrylamide and / or vinyl alcohol and a repeat unit derived from an amine-bearing monomer.

[0189] In (i) above, the catalyst is typically an acid or base catalyst.

[0190] In (ii) above, the catalyst is typically an acid or base catalyst.

[0191] In (iii) above, exposing the copolymer composition to oxygen typically comprises exposing the copolymer composition to atmospheric air.

[0192] In (iv) above, forming crosslinking typically comprises use of TEMED during polymerisation of the copolymer composition.

[0193] In (v) above, the catalyst is typically an acid or base catalyst.

[0194] In (vi) above, the catalyst is typically an acid or base catalyst. Acid and base catalysts referred to in connection with the steps of forming crosslinking in the copolymer composition are not particularly limited. Suitable acids include sulfonic acids. Suitable bases include sodium hydroxide.

[0195] The method for producing a porous material may further comprise washing the porous material with a solvent. For example, the method for producing a porous material may comprise washing the porous material with a solvent following removal of the template regions.

[0196] Preferably, the method for producing a porous material further comprises immersing the porous material in a salt solution. Preferably, the salt solution comprises Ca2+, Mg2+, Li+, Na+or K+ions. Further preferably, the salt solution comprises Ca2+or Mg2+ions. Most preferably, the salt solution comprises Ca2+ions. Immersion of the porous material in the salt solution may result the pores being impregnated with an ion from the salt solution (e.g. being impregnated with a Ca2+ion).

[0197] The method for producing a porous material may comprise

[0198] (i) providing a composite material as described above (e.g. a monomer composite material);

[0199] (ii) polymerising the composite material; and

[0200] (iii) removing at least some of the plurality of template regions from the composite material to provide a plurality of pores; to produce a porous material.

[0201] In such methods for producing a porous material, steps (i) and (ii) are typically carried out simultaneously.

[0202] When the template regions are template particles comprising a solid hydrogencarbonate or carbonate salt, removing at least some of the plurality of template regions typically comprises:

[0203] (a) contacting the solid hydrogencarbonate or carbonate salt with an acidic moiety to decompose the solid hydrogencarbonate or carbonate salt and form carbon dioxide; and / or

[0204] (b) removal of at least some of the template regions with a solvent. In such methods, when the composite material comprises AA, the acidic moiety is typically the AA.

[0205] The method for producing a porous material may further comprise irradiation with UV light, visible light (e.g. high intensity visible light), or a combination thereof.

[0206] When the porous material is formed from a monomer composite material, and the composite monomer material comprises a crosslinking monomer (e.g. MBAA) and cations of a group 1 or 2 element (e.g. Ca2+ ions), the method for producing a porous material typically comprises polymerisation, crosslinking, pore formation and salt impregnation. One or more or all of the polymerisation, crosslinking, pore formation and salt impregnation acts may be carried out simultaneously. These processes can be carried out at the same time as applying the porous material to a surface of a photovoltaic cell (i.e., in situ formation of the porous material).

[0207] The components of the monomer composite material may be kept as two separate solutions (e.g. aqueous solutions), and mixed in situ at the point of applying to the photovoltaic cell.

[0208] For example, a first aqueous solution may comprise all components of the composite material (e.g. the monomer composite material) except AA and the initiator, and a second aqueous solution may comprise the AA and the initiator. The first and second aqueous solutions may be mixed, e.g. in situ at the point of application to the photovoltaic cell.

[0209] In another example, a first aqueous solution may comprise all components of the composite material (e.g. a polymer composite material) except a catalyst suitable for forming crosslinking in the composite material, as described above, and a second aqueous solution may comprise the catalyst suitable for forming crosslinking in the composite material, as described above.

[0210] Method of modifying a photovoltaic cell

[0211] The present invention further provides a method of modifying a photovoltaic cell, comprising applying a porous material as defined previously to a surface of the photovoltaic cell.

[0212] Applying the porous material to the surface of the photovoltaic cell may comprise producing the porous material in situ by carrying out a method for producing a porous material as defined previously. Thus, the porous material may be applied to the surface of the photovoltaic cell by providing a composite material of the invention to the surface of the photovoltaic cell (e.g. by providing a copolymer composition of the invention and providing a plurality of template regions as described above; or by providing a copolymer composition of the invention, providing a plurality of template regions as described above, and forming crosslinking in the copolymer composition), and removing the plurality of template regions from the composite material to provide a plurality of pores. These features of providing a composite material of the invention to the surface of the photovoltaic cell are typically as described above with reference to the method for producing a porous material of the invention.

[0213] Preferably, “applying the porous material to the surface of the photovoltaic cell” comprises a technique selected from painting, spin coating, drop casting, aerosol deposition, and combinations thereof. Further preferably, the technique is selected from painting and aerosol deposition. Most preferably, the technique is painting.

[0214] The method of modifying a photovoltaic cell may further comprise preparing the surface of the photovoltaic cell by contacting the surface of the photovoltaic cell with benzophenone and / or vinyltrimethoxy silane. Preparing the surface of the photovoltaic cell may be carried out before applying the porous material to the surface of the photovoltaic cell. Preparation with benzophenone is preferred for organic surfaces. Preparation with vinyltrimethoxysilane is preferred for inorganic surfaces (e.g. glass or ceramic).

[0215] Use of the porous material

[0216] The porous material of the present invention may be used to regulate the temperature of a photovoltaic cell. For example, the porous material of the present invention may be used to decrease the temperature of an operating photovoltaic cell during peak sunlight hours as compared to the temperature that would be observed for a reference cell not having a porous material of the present invention disposed on a surface thereof, but being otherwise identical to the operating photovoltaic cell, and operated under the same conditions as the operating photovoltaic cell. Peak sunlight hours will vary geographically but is typically used herein to refer to a time period of solar noon ± 2 hours, such as for example solar noon ± 1 hour, solar noon ± 0.5 hours, about solar noon, or solar noon.

[0217] The porous material of the present invention may be used as a passive coolant for packaging, and so has applications in the transportation of sensitive medical supplies and temperature -sensitive food.

[0218] The porous material of the present invention may also be used for the cooling of architecture and in temperature-dependent transparency for windows.

[0219] The porous material of the present invention may also be used for the cooling of electronics, such as photovoltaics, electric vehicle batteries, servers, super computers and high performance graphics cards.

[0220] The porous material of the present invention may also be used as a smart molecule absorbance and release gel, which has has applications in the cosmetics industry, for example in hydrating gels, as well as in pharmaceuticals, for example in smart active release systems for drugs into tissue, and scaffolding and drug release for tissue repair.

[0221] The following are examples that illustrate the present invention. However, these examples are in no way intended to limit the scope of the invention.

[0222] Examples

[0223] Preparatory Example 1

[0224] Acrylic acid was dissolved in distilled water at a concentration of 5-10% (w / v) and nitogen gas was bubbled through the solution for 30 minutes to remove oxygen. Following this, a radical initiator (such as potassium persulphate) was added at a concentration of 0.05-0.1% (w / v) and the reaction heated to 90°C for 30 minutes. The reaction was allowed to occur for 8 hours with constant stirring. The poly acrylic acid was subsequently dried and redissolved in ethanol. Poly lactic - glycolic acid nanoparticles were then added to a concentration of 0. 1-2.5%. Another solution of poly vinyl alcohol was made up at 10% (w / v) with 0.001% (v / v) sulphuric acid in distilled water. Immediately prior to application on a surface the two solutions were combined and then spread onto the desired surface.

[0225] Example 1 : Rehydration performance

[0226] 5g of the hydrogel according to Preparatory Example 1 was subjected to repeated cycles of dehydration and re-hydration steps over a three-week period in order to evaluate the rehydration performance of the composition. In the dehydration step, the gel was heated at 100°C for 12 hours. In the re-hydration step, the hydrogel was placed in water for 8 hours. This process was repeated over many cycles. 5g of the hydrogel was found to be capable of absorbing over 70g of water in this period, and showed no significant drop in absorption capability. The results are shown in Figure 2.

[0227] Example 2: Characterisation using Fourier Transform Infra Red Spectroscopy (FTIR)

[0228] A sample of the hydrogel of Preparatory Example 1 was applied to one section of a metallic plate and the rear of the plate was imaged using a thermal imaging camera. The plate was subjected to successive heating cycles. Throughout these cycles, the gel-covered section of the plate remained 1.5-9°C cooler than the sections that were not covered by the gel. The FT-IR spectra are shown in Figure 3.

[0229] Example 3 : Thermocouple data (metal plate)

[0230] Thermocouples were applied in various positions on the surface of a metal plate in order to obtain data on the surface temperature at these positions. Two thermocouples were applied to a first side (the “front side”), and two thermocouples were applied to a second side (the “back side”). The porous material of the present invention, in its dehydrated form, was applied to an area of the “back side” of the metal plate to create a surface with a thickness of 1mm. The metal plate was then subjected to high intensity light of increasing intensity from the “front” side. The results are shown in Figure 4. As can be seen from Figure 4, the surface temperature of the back side and the front side was lower at the area corresponding to where the porous material had been applied to the back side.

[0231] Example 4: Thermocouple data (Small panel)

[0232] Thermocouples were applied in various positions on the surface of a small panel in order to obtain data on the surface temperature at these positions. Two thermocouples were applied to a first side (the “front side”), and two thermocouples were applied to a second side (the “back side”). The porous material of the present invention, in its dehydrated form, was applied to an area of the “back side” of the small panel to create a layer with a thickness of 1mm. The small panel was then subjected to high intensity light of increasing intensity from the “front” side. The results are shown in Figure 5. As can be seen from Figure 5, the surface temperature of the back side and the front side was lower at the area corresponding to where the porous material had been applied to the back side.

[0233] Example 5 : Efficiency under solar simulation

[0234] Solar cells were placed in a sealed environment and subjected to known solar irradiation of varying intensities over a 5-hour period, in order to simulate an accelerated day in the UK. Solar irradiation started at 120 Wm'2, and was then increased to 250 Wm'2at 60 minutes, then 350 Wm'2at 2 hours, and was then reduced back to 250 Wm'2at 4 hours.

[0235] The solar cells included a set of control cells and a set of cells to which a 5mm layer of the porous material of the present invention (in its hydrated form) had been applied (“sample cells”). The relative efficiency rates of the cells are shown in Figure 6. As used herein, “relative efficiency rate” refers to the % efficiency of a given cell relative to the maximum power provided by the cell at t=0.

[0236] As can be seen from Figure 6, sample cells demonstrated increased efficiency compared to the control cells. This is due to the reduction in operating temperature of the sample cells provided by the material of the present invention. An average 13% increase in efficiency over the course of the simulated day was observed in the sample cells. Example 6: Atmospheric water absorption

[0237] Samples of the porous material of the invention were completely dehydrated. The samples were then left in a sealed container at 60% humidity (typical UK night humidity) for 14 hours and the weight of the gel was measured.

[0238] The samples were then heated at 50°C for 10 hours to simulate the heat from a solar cell. Once again the samples were left in a sealed container at 60% humidity and the process repeated.

[0239] The results are shown in Figure 7. The results shown in Figure 7 demonstrate that the porous material of the invention is capable of absorbing atmospheric water at high rates at a relatively low humidity environment. Performance was maintained over a large number of cycles. The samples did not reach complete dehydration at any point in the experiment.

[0240] Preparatory Example 2

[0241] Materials (ratios listed in brackets give the amounts relative to acrylamide; w / w unless otherwise specified)

[0242] - Distilled water (16x V / w)

[0243] - PF 127 (Pluronic Fl 27) (4 / 1000x)

[0244] - Monomers:

[0245] - Acrylamide (AAm) (x)

[0246] - Sodium styrene sulfonate (SS) or Zwitterionic monomers (ZI) (l / 10x)

[0247] - Acrylonitrile (AN) (x / 20)

[0248] - Acrylic acid (AA) (l / 20x)

[0249] - Crosslinker: N,N'-Methylenebisacrylamide (MBAA) (4 / 100x)

[0250] - Calcium chloride (CaC12) (8x)

[0251] - Photo initiator: 2-Hydroxy-4'-(2-hydroxyethoxy)-2 -methylpropiophenone (2H) (l / 50x)

[0252] - Foaming agent: Sodium bicarbonate (NaHCO3) (l / 10x)

[0253] - Surfactant: Sodium dodecyl sulfate (SDS) (4 / 1000x)

[0254] - Clean solar panel

[0255] - UV light source: 250-400nm Visible light, high intensity.

[0256] Equipment:

[0257] - Reactor

[0258] - Syringe

[0259] - Degassing equipment (N2)

[0260] - Thermocouples

[0261] - Datalogger

[0262] Procedure:

[0263] 1. Preparation of Hydrogel Solution:

[0264] 1. 1. An appropriate amount of distilled water is added into a container.

[0265] 1.2. PF 127 is added to the container and mixed until dissolved.

[0266] 1.3. The monomers AAm, SS (or ZI), and AN are added sequentially to the mixture.

[0267] 1.4. The crosslinker MBAA is added to the mixture.

[0268] 1.5. The mixture is degassed using appropriate degassing equipment.

[0269] 1.6. Degassing is continued until the solution becomes transparent (approximately 10 minutes).

[0270] 2. Calcium Chloride Addition:

[0271] 2. 1. CaCh is added as a powder directly into the reactor containing the degassed solution.

[0272] 2.2. The mixture is degassed for 30 minutes. The reaction may become exothermic and heat up significantly.

[0273] 3. Photo Initiator and Foaming Agent Addition:

[0274] 3.1. Using a syringe, the photo initiator (2H) is added to the mixture.

[0275] 3.2. The mixture is degassed for an additional 10 minutes.

[0276] 3.3. Glycerol is added

[0277] 3.4. The foaming agent NaHCCh and the surfactant SDS are added to the mixture.

[0278] 3.5. The becomes foamy upon addition.

[0279] 4. Activation and Polymerization: 4. 1. The monomer AA is added to the foamy mixture to activate the foaming agent and participate in the copolymerization.

[0280] 4.2. Degassing of the mixture is stopped.

[0281] 5. Application to Solar Panel:

[0282] 5.1. The surface of the clean solar panel is activated by exposing it to UV light for 5 minutes.

[0283] 5.2. The prepared hydrogel solution is poured onto the activated back surface of the solar panel.

[0284] 5.3. The non-polar sites in the hydrogel are allowed to align with the panel surface by waiting for 2 minutes.

[0285] 5.4. 4 UV lights are used to cure the hydrogel for 30 minutes.

[0286] Solar panels treated with porous material of the invention in accordance with Example 6 are illustrated in Figures 9 to 17

[0287] Example 7: Testing Panels on the Roof

[0288] Equipment:

[0289] - Thermocouples

[0290] - Batteries

[0291] - Datalogger

[0292] Procedure

[0293] 1. Thermocouple Installation:

[0294] 1.1. The hydrogel is cut to create slots for the thermocouples.

[0295] 1.2. Two thermocouples are inserted on the back side (top and bottom) of the panel.

[0296] 1.3. Two thermocouples are inserted on the front face (top and bottom) of the panel.

[0297] 1.4. Thermocouples are tested and verified to be functioning using the datalogger.

[0298] 2. Setting Up the Datalogger:

[0299] 2. 1. The thermocouples are connected to the slots of the datalogger.

[0300] 2.2. The solar panel is placed with the thermocouples installed on the roof at an inclined angle for optimal testing. 3. Data Collection:

[0301] 3.1. Recording of data is started by pressing the "REC" button on the datalogger.

[0302] 3.2. The data is extracted daily to prevent memory overflow in the datalogger.

[0303] Solar panels tested in accordance with Example 7 are illustrated in Figures 9 to 17

[0304] The following numbered embodiments form part of the present disclosure. However the disclosure is not limited thereto.

[0305] [Embodiment 1]

[0306] A copolymer composition comprising a polymer having first and second repeat units, wherein the first repeat unit is derived from acrylamide and / or acrylic acid and / or N-isopropylacrylamide and / or vinyl alcohol, and the second repeat unit is derived from a crosslinking monomer.

[0307] [Embodiment 2]

[0308] The copolymer composition of embodiment 1, wherein the crosslinking monomer is:

[0309] (i) an alcohol-bearing monomer;

[0310] (ii) allyl thiol;

[0311] (iii) acrylic acid;

[0312] (iv) N,N’-methylenebisacrylamide (MBAA);

[0313] (v) an amine-bearing monomer;

[0314] (vi) an aldehyde-bearing monomer

[0315] (vii) vinyl alcohol; or a mixture thereof.

[0316] [Embodiment 3]

[0317] The copolymer composition of embodiment 1 or 2, wherein, (a) the crosslinking monomer is an alcohol-bearing monomer, and the composition comprises a repeat unit derived from acrylic acid; (b) the crosslinking monomer is an amine bearing monomer and the composition comprises a further polymer having a repeat unit derived from acrylamide and / or acrylic acid and / or N- isopropylacrylamide and / or vinyl alcohol and a repeat unit derived from an aldehyde-bearing monomer; or (c) the crosslinking monomer is an aldehyde bearing monomer, and the composition comprises a further polymer having a repeat unit derived from acrylamide and / or acrylic acid and / or N-isopropylacrylamide and / or vinyl alcohol and a repeat unit derived from an amine- bearing monomer. [Embodiment 4]

[0318] The copolymer composition of any one of embodiments 1 to 3, comprising crosslinking.

[0319] [Embodiment 5]

[0320] The copolymer composition of embodiment 4, wherein the crosslinking comprises crosslinks derived from:

[0321] (i) an alcohol-bearing monomer as a crosslinking monomer, and a repeat unit of the copolymer composition derived from acrylic acid;

[0322] (ii) acrylic acid as a crosslinking monomer, and ethylene glycol;

[0323] (iii) allyl thiol as a crosslinking monomer;

[0324] (iv) N,N’-methylenebisacrylamide (MBAA) as a crosslinking monomer;

[0325] (v) vinyl alcohol as a crosslinking monomer, and (a) a di-acid (e.g. oxalic acid), or (b) a further polymer comprised in the composition, the further polymer having a repeat unit derived from acrylamide and / or acrylic acid and / or N- isopropylacrylamide and / or vinyl alcohol and a repeat unit derived from an acidbearing monomer, the crosslinks being derived from the vinyl alcohol and the acid-bearing monomer;

[0326] (vi) an amine-bearing monomer and a further polymer comprised in the composition, the further polymer having a repeat unit derived from acrylamide and / or acrylic acid and / or N-isopropylacrylamide and / or vinyl alcohol and a repeat unit derived from an aldehyde-bearing monomer, the crosslinks being derived from the amine- bearing monomer and the aldehyde-bearing monomer;

[0327] (vii) an aldehyde-bearing monomer and a further polymer comprised in the composition, the further polymer having a repeat unit derived from acrylamide and / or acrylic acid and / or N-isopropylacrylamide and / or vinyl alcohol and a repeat unit derived from an amine-bearing monomer, the crosslinks being derived from the aldehyde-bearing monomer and the amine-bearing monomer; or a mixture thereof. [Embodiment 6]

[0328] A composite material comprising a copolymer composition as defined in any one of embodiments 1 to 5 and a plurality of template regions.

[0329] [Embodiment 7]

[0330] The composite material of embodiment 6 wherein the plurality of template regions comprise template particles.

[0331] [Embodiment 8]

[0332] The composite material of embodiment 7, wherein the template particles comprise poly(methyl methacrylate), poly(lactic-co-glycolic acid), a salt of a Group 1 element, a salt of a Group 2 element, a silicon-based material or a carbon-based material.

[0333] [Embodiment 9]

[0334] A composite material according to any one of embodiments 6 to 8, which is a block copolymer composition comprising:

[0335] (i) a first block comprising the copolymer composition of any one of embodiments 1 to 5; and

[0336] (ii) a second block comprising a third repeat unit derived from a photoresist monomer; wherein the template regions comprise the second block.

[0337] [Embodiment 10]

[0338] The composite material of embodiment 9, wherein the photoresist monomer is methyl methacrylate.

[0339] [Embodiment 11]

[0340] The composite material of any one of embodiments 6 to 10, wherein the template regions have a size in a range of from 10 pm to 10 nm.

[0341] [Embodiment 12]

[0342] The composite material of any one of embodiments 6 to 11, wherein the copolymer composition is as defined in embodiment 4 or embodiment 5. [Embodiment 13]

[0343] A porous material comprising a copolymer composition as defined in embodiment 4 or 5 and a plurality of pores.

[0344] [Embodiment 14]

[0345] The porous material of embodiment 13, which is obtainable by providing a composite material as defined in embodiment 12, and removing the plurality of template regions to provide the plurality of pores.

[0346] [Embodiment 15]

[0347] The porous material of embodiment 14, wherein removing the plurality of template regions comprises removal of template regions comprising a salt of a Group 1 element, a salt of a Group 2 element, a silicon-based material or a carbon-based material, with a solvent.

[0348] [Embodiment 16]

[0349] The porous material of embodiment 14, wherein removing the plurality of template regions comprises decomposition of template regions comprising poly(methyl methacrylate) and / or poly (lactic-co -glycolic acid), preferably by photoresist lithography, followed by removal of decomposition product(s) with a solvent.

[0350] [Embodiment 17]

[0351] The porous material of any one of embodiments 13 to 16, wherein the pore size is in a range of 10 pm to 10 nm.

[0352] [Embodiment 18]

[0353] The porous material of any one of embodiments 13 to 17, wherein the porosity of the material is in a range of X to Y.

[0354] [Embodiment 19]

[0355] The porous material of any one of embodiments 13 to 18, wherein the pores are impregnated with an ion. [Embodiment 20]

[0356] The porous material of embodiment 19, wherein the ion is Ca2+.

[0357] [Embodiment 21]

[0358] A method for producing a porous material, comprising:

[0359] (i) providing a composite material as defined in any one of embodiments 6 to 12; and

[0360] (ii) removing the plurality of template regions from the composite material to provide a plurality of pores; to produce a porous material.

[0361] [Embodiment 22]

[0362] The method of embodiment 21, wherein the plurality of template regions comprise a salt of a Group 1 element, a salt of a Group 2 element, a silicon-based material or a carbon-based material, and removing the plurality of template regions comprises the application of a solvent.

[0363] [Embodiment 23]

[0364] The method of embodiment 21, wherein the plurality of template regions comprise poly(methyl methacrylate) and / or poly(lactic-co -glycolic acid), and removing the plurality of template regions comprises decomposition of said poly(methyl methacrylate) and / or poly(lactic-co-glycolic acid), preferably by photoresist lithography, followed by removal of decomposition product(s) with a solvent.

[0365] [Embodiment 24]

[0366] The method of any one of embodiments 21 to 23, wherein the porous material is as defined in any one of embodiments 17 to 20.

[0367] [Embodiment 25]

[0368] The method of any one of embodiments 21 to 23, wherein providing the composite material comprises providing a copolymer composition as defined in any one of embodiments 1 to 5, and providing a plurality of template regions as defined in any one of embodiments 6 to 11.

[0369] [Embodiment 26] The method of any one of embodiments 21 to 23, wherein providing the composite material comprises providing a copolymer composition as defined in any one of embodiments 1 to 3, providing a plurality of template regions as defined in any one of embodiments 6 to 11, and forming crosslinking in the copolymer composition.

[0370] [Embodiment 27]

[0371] The method of embodiment 26, wherein:

[0372] (i) the copolymer composition comprises an alcohol-bearing monomer as a crosslinking monomer, and a repeat unit derived from acrylic acid, and forming crosslinking in the copolymer composition comprises application of a catalyst;

[0373] (ii) the copolymer composition comprises acrylic acid as a crosslinking monomer, and forming crosslinking in the copolymer composition comprises application of ethylene glycol and a catalyst;

[0374] (iii) the copolymer composition comprises allyl thiol as a crosslinking monomer, and forming crosslinking in the copolymer composition comprises exposing the copolymer composition to oxygen;

[0375] (iv) the copolymer composition comprises N,N’-methylenebisacrylamide (MBAA) as a crosslinking monomer, and forming crosslinking in the copolymer composition comprises radical addition of MBAA monomers in different polymer chains ;

[0376] (v) the copolymer composition comprises an amine-bearing monomer as a crosslinking monomer and forming crosslinking in the copolymer composition comprises application of a further polymer and a catalyst, wherein the further polymer has a repeat unit derived from acrylamide and / or acrylic acid and / or N-isopropylacrylamide and / or vinyl alcohol and a repeat unit derived from an aldehyde-bearing monomer; or

[0377] (vi) the copolymer composition comprises an aldehyde-bearing monomer as a crosslinking monomer and forming crosslinking in the copolymer composition comprises application of a further polymer and a catalyst, wherein the further polymer has a repeat unit derived from acrylamide and / or acrylic acid and / or N-isopropylacrylamide and / or vinyl alcohol and a repeat unit derived from an amine-bearing monomer. [Embodiment 28]

[0378] The method of any one of embodiments 21 to 27, further comprising washing the porous material with a solvent.

[0379] [Embodiment 29]

[0380] The method of any one of embodiments 21 to 28, further comprising immersing the porous material in a salt solution.

[0381] [Embodiment 30]

[0382] The method of embodiment 29, wherein the salt solution comprises Ca2+ions.

[0383] [Embodiment 31]

[0384] A porous material obtainable by a method as defined in any one of embodiments 21 to 30.

[0385] [Embodiment 32]

[0386] A photovoltaic cell, wherein a porous material as defined in any one of embodiments 13 to 20 and 31 is disposed on a surface thereof.

[0387] [Embodiment 33]

[0388] A method of modifying a photovoltaic cell, comprising applying a porous material as defined in any one of embodiments 13 to 20 and 31 to a surface of the photovoltaic cell.

[0389] [Embodiment 34]

[0390] The method of modifying a photovoltaic cell of embodiment 33, wherein applying the porous material to the surface of the photovoltaic cell comprises producing the porous material in situ by carrying out a method as defined in any one of embodiments 21 to 30.

[0391] [Embodiment 35]

[0392] The method of embodiment 33 or 34, wherein applying the porous material to the surface of the photovoltaic cell comprises a technique selected from painting, spin coating, drop casting, aerosol deposition, and combinations thereof. [Embodiment 36]

[0393] Use of a porous material as defined in any one of embodiments 13 to 20 and 31 to regulate the temperature of a photovoltaic cell.

Claims

CLAIMS1. A copolymer composition comprising repeat units derived from three or more monomers selected from: acrylamide (AAm); an ionic monomer selected from styrene sulfonic acid or a salt thereof (SS), a zwitterionic monomer (ZI), and mixtures thereof; an adhesion-promoting monomer selected from acrylonitrile (AN), vinyltrimethoxysilane (VTMS), and mixtures thereof; and acrylic acid (AA).

2. The copolymer composition according to claim 1, further comprising repeat units derived from N,N’ -methylenebisacrylamide (MBAA).

3. The copolymer composition of claim 2, comprising crosslinking.

4. The copolymer composition of claim 3, wherein the crosslinking comprises crosslinks derived from MBAA, and / or wherein the copolymer composition further comprises Ca2+ions and the crosslinking comprises crosslinks derived from the Ca2+ions.

5. A composite material comprising: acrylamide (AAm); and an ionic monomer selected from styrene sulfonic acid or a salt thereof (SS), a zwitterionic monomer (ZI), and mixtures thereof; and an adhesion-promoting monomer selected from acrylonitrile (AN), vinyltrimethoxysilane (VTMS), and mixtures thereof; and a plurality of template regions.

6. A composite material according to claim 5 further comprising N,N’- methylenebisacrylamide (MBAA).

7. A composite material according to claim 5 or 6 further comprising Ca2+ions.

8. The composite material of claim 7 wherein the plurality of template regions comprise template particles.

9. The composite material of claim 8, wherein the template particles comprise poly(lactic-co- glycolic acid), or a carbon-based material, wherein the carbon-based material is preferably a hydrogencarbonate or carbonate salt.

10. The composite material of claim 9, wherein the template particles comprise sodium hydrogencarbonate .

11. The composite material of any one of claims 5 to 10 which further comprises a surfactant.

12. The composite material of claim 11 wherein the surfactant is sodium dodecyl sulfate (SDS) or poloxamer 407.

13. The composite material of any one of claims 5 to 12 which further comprises a photoinitiator or a thermal initiator.14 The composite material of claim 13 wherein the photoinitiator is 2-Hydroxy-4'-(2- hydroxyethoxy)-2 -methylpropiophenone (2H) or benzophenone.

15. The composite material of any one of claims 5 to 14, wherein the template regions have a size in a range of from 10 nm to 500 pm.

16. The composite material of any one of claims 5 to 12, further comprising acrylic acid (AA).

17. A method for producing a porous material, comprising:(i) providing a composite material as defined in any one of claims 5 to 16;(ii) polymerising the composite material; and(iii) removing at least some of the plurality of template regions from the composite material to provide a plurality of pores; to produce a porous material.

18. The method of claim 17, wherein (i) and (ii) are carried out simultaneously.

19. The method of claim 17 or 18, wherein the template regions are template particles comprising a hydrogencarbonate or carbonate salt, and removing at least some of the plurality of template regions comprises:(a) contacting the hydrogencarbonate or carbonate salt with an acidic moiety to decompose the hydrogencarbonate or carbonate salt and form carbon dioxide; and / or(b) removal of at least some of the template regions with a solvent.

20. The method of claim 19, wherein the composite material is as defined in claim 16, and wherein the acidic moiety is the acrylic acid (AA).

21. The method of any one of claims 17 to 20, further comprising irradiation with UV light, visible light (preferably high intensity visible light), or a combination thereof.

22. A porous material comprising a copolymer composition as defined in any one of claims 1 to 4 and a plurality of pores.

23. The porous material of claim 22, which is obtainable by a method according to any one of claims 17 to 21.

24. A photovoltaic cell, wherein a porous material as defined in claim 22 or 23 is disposed on a surface thereof.

25. A method of modifying a photovoltaic cell, comprising applying a porous material as defined in claim 22 or 23 to a surface of the photovoltaic cell.

26. The method of modifying a photovoltaic cell of claim 25, wherein applying the porous material to the surface of the photovoltaic cell comprises producing the porous material in situ by carrying out a method as defined in any one of claims 17 to 21.

27. The method of claim 25 or 26, wherein applying the porous material to the surface of the photovoltaic cell comprises a technique selected from painting, spin coating, drop casting, aerosol deposition, and combinations thereof.

28. The method of any one of claims 25 to 27, further comprising preparing the surface of the photovoltaic cell by contacting the surface of the photovoltaic cell with benzophenone and / or vinyltrimethoxysilane .

29. Use of a porous material as defined in claim 22 or 23 to regulate the temperature of a photovoltaic cell.

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