Membrane having a crosslinked block copolymer and method for producing the same

Abstract

The present disclosure provides certain block copolymer membranes useful as components of filters for liquid purification and / or filtration. The block copolymers of the present disclosure are subjected to a crosslinking reaction that raises the overall molecular weight and thus imparts improved solvent resistance properties to the membranes, whereby such membranes are considered suitable for use with solvents such as photolithography solvents. Further, this crosslinking treatment is thought to improve the integrity of the pore structure of the membranes during the drying process.

Description

Technical Field

[0001] The present disclosure relates to a filtration membrane comprising a specific block copolymer.

Background Art

[0002] Filter products are essential tools in modern industry and are used to remove unwanted substances from the flow of useful fluids. Useful fluids processed using filters include water, liquid industrial solvents and process fluids, industrial gases used in manufacturing or processing (e.g., in semiconductor fabrication), and liquids for medical or pharmaceutical applications. Unwanted substances removed from the fluid include impurities and contaminants such as particles, microorganisms, and dissolved species. Specific examples of filter applications include use with liquid materials for semiconductor and microelectronics device manufacturing.

[0003] To perform a filtering function, a filter can include a filtration membrane that is responsible for removing unwanted substances from the fluid passing through the filtration membrane. The filtration membrane can be in the form of a flat sheet that can be wound (e.g., spirally), flat, pleated, or disk-shaped as needed. Alternatively, the filtration membrane can be in the form of hollow fibers. The filtration membrane is housed within a housing or otherwise supported such that the fluid being filtered is required to enter through a filter inlet, pass through the filtration membrane, and then pass through a filter outlet.

[0004] The filtration membrane can be constructed from a porous structure having an average pore size that can be selected based on the application of the filter, i.e., the type of filtration performed by the filter. Typical pore sizes are in the micron or submicron range, such as from about 0.001 micron to about 10 microns. Membranes having an average pore size from about 0.001 to about 0.05 microns are sometimes classified as ultrafiltration membranes. Membranes having a pore size between about 0.05 and 10 microns are sometimes referred to as microporous membranes.

[0005] Filtration membranes having pore diameters in the micron or sub-micron range can be effective in removing unwanted substances from fluid flow, either by a sieving mechanism, a non-sieving mechanism, or both. The sieving mechanism is a filtration method in which particles are removed from the liquid flow by mechanical retention of the particles on the surface of the filtration membrane that mechanically interferes with the movement of the particles and acts to retain the particles within the filter, mechanically preventing the flow of particles through the filter. Typically, the particles may be larger than the pores of the filter. The "non-sieving" filtration mechanism is a non-mechanical method that includes, for example, an electrostatic mechanism in which particulate matter or dissolved impurities are electrostatically attracted to and retained on the filter surface and removed from the fluid flow, and in which the filtration membrane retains suspended particles or dissolved substances contained in the flow of fluid through the filtration membrane, and the particles can be dissolved or can be solids having a particle size smaller than the pores of the filter medium.

[0006] The self-assembly of block copolymers is a unique membrane-forming technique that precisely controls the pore size and pore size distribution. Polymer design is important, and careful consideration is given to designing macromolecules that microphase-separate into a periodic ordered structure. One such polymer is poly(isoprene-b-styrene-b-4-vinylpyridine), which is currently used to fabricate filtration membranes for the life science and ultrapure water markets. However, such polymers are not entirely suitable for use with many common solvents, such as photolithography solvents, because the pore structure tends to collapse upon drying and / or the polymer can dissolve in the photolithography solvent. Therefore, a filtration membrane comprising a block copolymer and having such a highly ordered pore structure that is compatible with such common solvents is highly desirable. SUMMARY OF THE INVENTION

[0007] In summary, the present disclosure provides certain block copolymer membranes useful as components of filters for liquid purification and / or filtration. The block copolymers of the present disclosure are subjected to a crosslinking reaction to increase the overall molecular weight, and thus impart improved solvent resistance properties to the membrane, whereby such membranes are considered suitable for use with solvents such as photolithography solvents. Further, this crosslinking treatment is considered to improve the integrity of the pore structure of the membrane during the drying process.

Brief Description of the Drawings

[0008]

Figure 1

Modes for Carrying Out the Invention

[0009] As used in this specification and the appended claims, the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise. As used in this specification and the appended claims, the term "or" is generally used in the sense of including "and / or" unless the context clearly dictates otherwise.

[0010] The term "about" generally refers to a range of numerical values that are considered equivalent to the recited value (e.g., having the same function or result). In many cases, the term "about" may include numerical values that are rounded to the nearest significant digit.

[0011] Numerical ranges expressed using endpoints include all numerical values included in that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5).

[0012] In a first aspect, the present disclosure provides a membrane comprising a crosslinked block copolymer that exhibits less than about 20 percent change in bubble point when exposed to one or more photolithography solvents over a 24-hour period. As described more fully below, crosslinked block copolymer membranes can be prepared starting from block copolymers having carbon-carbon double bonds available for crosslinking reactions or anthracene moieties capable of dimerization reactions. Accordingly, the crosslinked block copolymer membranes of the present disclosure are useful as filtration membranes for various fluids and are believed to have higher stability to organic solvents and higher drying stability compared to non-crosslinked membranes.

[0013] The membranes of the present disclosure are believed to have drying stability that substantially alleviates the need for the use of wetting agents, such as glycerin, which are often used in conventional membranes to preserve pore structure during manufacture and drying. Thus, in another embodiment, the present disclosure provides a membrane of the present disclosure wherein the crosslinked block copolymer contains less than about 10 weight percent, less than about 5 weight percent, or less than about 1 weight percent wetting agent. In this regard, the presence of such a humectant in a given membrane can be detected by extracting the humectant from the membrane and analyzing it by NMR and / or IR spectroscopy to determine the amount of the humectant, if present.

[0014] In addition to higher stability in the presence of organic solvents, such as photolithography solvents, the membranes of the present disclosure are believed to exhibit improved performance when subjected to tensile testing as contemplated by ASTM method D638-14. As a further quality of the crosslinked block copolymer membranes, the inventors believe that the membranes exhibit a tensile strain at break of greater than about 5 percent as determined by ASTM method D638-14.

[0015] When the crosslinked block copolymer membrane has sufficient mechanical stability, it can be used directly as a component within a filtration device. Alternatively, in another aspect of the present disclosure, the block copolymer membrane may be cast onto a porous substrate or base layer to form a composite membrane, and then subjected to a crosslinking reaction. Thus, in a further aspect, the present disclosure provides a. a porous base layer, and b. a crosslinked block copolymer membrane layer that exhibits less than about 20 percent change in bubble point when exposed to one or more photolithography solvents over a 24-hour period, a method for preparing a composite membrane comprising casting a block copolymer having either a residual carbon-carbon double bond or an anthracene moiety onto the porous base layer and subjecting the block copolymer membrane layer to a crosslinking reaction. A method is provided.

[0016] Casting of the crosslinked block copolymer membrane layer onto the porous base layer can be achieved using known methodologies. For example, see "Tuning Structure and Properties of Graded Triblock Terpolymer-Based Mesoporous and Hybrid Films", W.A. Phillip et al., Nano Lett., 2011, 11, 2892-2900, which describes a methodology for forming block copolymer films using a combination of controlled solvent evaporation and nonsolvent-induced phase separation (NIPS). Generally, with respect to casting a membrane onto a glass surface and replacing it with a porous base layer, the methodologies described in the cited reference can be utilized to form a composite membrane comprising a porous base layer and a crosslinked block copolymer layer, which can then be subjected to a crosslinking reaction to obtain the membranes of the present disclosure.

[0017] Accordingly, in a further aspect, the present disclosure provides a composite membrane comprising a porous base layer and a crosslinked block copolymer layer, the composite membrane showing a change of less than about 20 percent in bubble point when exposed to one or more photolithography solvents over a 24-hour period.

[0018] The porous substrate layer can be made of any conventional natural or synthetic porous material such as a nonwoven fiber material or a porous polymer membrane. Exemplary polymers in this context include polyolefins and halogenated polymers. Exemplary polyolefins include polyethylene, polypropylene, polymethylpentene, polybutene, polyisobutylene, and copolymers of two or more of ethylene, propylene, and butylene. In a further specific embodiment, the porous substrate material comprises ultra-high molecular weight polyethylene (UPE). UPE filter materials such as UPE membranes are typically formed from resins having a molecular weight (viscosity average molecular weight) higher than about 1×10 6 ~9×10 6 Da, or in the range of 1.5×10 6 ~9×10 6 Da, such as higher than about 1×10 6 Daltons (Da). In this porous polymer-based support or substrate layer, crosslinking between polyolefin polymers such as polyethylene can be facilitated by the use of heat or crosslinking chemicals such as peroxides (e.g., dicumyl peroxide or di-tert-butyl peroxide), silanes (e.g., trimethoxyvinylsilane), or azoester compounds (e.g., 2,2'-azo-bis(2-acetoxy-propane)). Exemplary halogenated polymers include polytetrafluoroethylene (PTFE), polychlorotrifluoro-ethylene (PCTFE), fluorinated ethylene polymer (FEP), polyhexafluoropropylene, and polyvinylidene fluoride (PVDF).

[0019] Furthermore, the porous substrate layer may be composed of a polymer selected from polyimide, polysulfone, polyethersulfone, polyarylsulfone polyamide, polyacrylate, polyester, polyamide-imide, cellulose, cellulose ester, polycarbonate, or a combination thereof.

[0020] As described above, the membranes of the present disclosure can be prepared by a plurality of alternative crosslinking reactions. Thus, in another aspect, the present disclosure is a method for preparing a crosslinked block copolymer membrane, which includes treating a block copolymer membrane having residual carbon-carbon double bonds to form a crosslinked block copolymer, and the treatment is a. treatment with a sulfur compound at a temperature sufficient to induce crosslinking; and b. treatment with a thermal free radical initiator at a temperature sufficient to induce crosslinking; and c. treatment with ultraviolet light in the presence of a free radical photoinitiator; and d. treatment by electron beam irradiation and provides a method selected from the group consisting of.

[0021] In option a above, treatment with a sulfur compound such as polymeric sulfur at a temperature sufficient to induce crosslinking refers to conventional vulcanization methods for natural and synthetic rubbers as is well understood. For example, see U.S. Patent Nos. 2,560,045, 4,238,470, 7,569,639, RE25007E, 10,125,239, and 10,011,663, which are hereby incorporated by reference in their entireties.

[0022] In Option b, treatment with a thermal free radical initiator refers to the use of a thermally activated free radical initiator such as benzoyl peroxide or azobisisobutyronitrile (AIBN), which decompose at elevated temperatures to provide a free radical flux and thus enable a crosslinking reaction between carbon-carbon double bond moieties present within the polymer matrix. The block copolymer starting material can be converted into a filtration membrane and then treated, for example, with a solvent solution containing a thermally activated free radical initiator and then heated.

[0023] In Option c, treatment with a photo free radical initiator can be achieved in a similar manner by exposing a block copolymer membrane having residual carbon-carbon double bonds to a solution of a free radical initiator such as Irgacure® 2595 (Ciba) (2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone), benzophenone, or ammonium persulfate in the presence of ultraviolet light. The block copolymer starting material can be converted into a filtration membrane and then treated, for example, with a solvent solution containing a photoactivated free radical initiator and then heated.

[0024] In Option d, to promote crosslinking, a block copolymer membrane having residual carbon-carbon double bonds can be exposed to electron beam irradiation in the absence of an initiator. See, for example, "Effect of Electron Beam Radiation on Tensile and Viscoelastic Properties of Styrenic Block Copolymers", J. Wu et al., Polym. Eng. Sci., 54:2979-2988, 2014. In this regard, the dose level can be utilized within the range of 40 - 240 kGy and can be tailored to the desired level of crosslink density and the proportion of available carbon-carbon double bonds present within the polymer matrix.

[0025] Alternatively, in one embodiment of the present disclosure, the block copolymer utilized to form the filtration membrane is designed to include, in at least a portion of its composition, residues of monomeric materials containing anthracene moieties. Such polymers containing these anthracene moieties can be effectively crosslinked by subjecting the resulting block copolymer to ultraviolet light that brings about a dimerization reaction between the anthracene moieties present within the polymer matrix. Thus, in a further aspect, the present disclosure provides a method for preparing a crosslinked block copolymer membrane, wherein the membrane comprises at least one block copolymer containing residues of anthracene, and the method comprises exposing the block copolymer containing residues of anthracene to ultraviolet light.

[0026] In this way, the above methodology is considered useful for performing a crosslinking reaction between at least some of the residual carbon-carbon double bonds present within the block copolymer matrix. This crosslinking reaction is thought to necessarily result in a higher molecular weight polymer and a polymer that exhibits improved resistance to solvents such as those used in photolithography. In this regard, exemplary photolithography solvents include n-butyl acetate, isopropyl alcohol, 2-ethoxyethyl acetate, xylene, cyclohexanone, ethyl acetate, isopentyl ether, methyl-2-hydroxyisobutyrate, methyl isobutyl carbinol, methyl isobutyl ketone, isoamyl acetate, undecane, propylene glycol methyl ether, propylene glycol monomethyl ether acetate, and a mixed solution (7:3) of propylene glycol methyl ether and propylene glycol monomethyl ether acetate having a mixed ratio surface tension of 27.7 mN / m.Additional solvents that are considered to be able to be purified using the membranes of the present disclosure include ethanol, methanol, butanol, hexanol, heptanol, octanol, decanol, benzyl alcohol; amides such as N,N-dimethylacetamide, N,N-dimethylformamide, N-methyl-2-pyrrolidone, piperidine, morpholine, pyridine, diethylenetriamine, pyrrolidone, methoxyethane, tetrahydrofuran, dioxane, dimethoxyethane; esters such as n-butyl acetate, methyl acetate, ethyl acetate, propyl acetate, pentyl acetate, amyl acetate, methyl formate, ethyl formate, propyl formate, butyl formate, ethyl lactate, propyl lactate, ethylene glycol, propylene glycol, triethylene glycol, ethylene glycol monomethyl ether, propylene glycol monomethyl ether, triethylene glycol monomethyl ether, chloroform, hexane, decane, octane, cyclohexane, pentane, toluene, xylene, benzene, methyl ethyl ketone, octanone, nonanone, acetone, heptanone, hexanone, diisobutyl ketone phenylacetone, cyclohexanone, acetylacetone, propylene carbonate, acetonitrile, sulfolane, and dimethyl sulfoxide, and mixtures thereof, including mixtures with water.

[0027] As used herein, the term "block copolymer" refers to the simplest block copolymer that contains two or more linear segments, i.e., "blocks", where adjacent segments contain different constitutional units and each block has only one type of constitutional unit. However, this simple structure is not the only structure that can lead to nanoscale and mesoscale self-assembly. Such structures are referred to as complex block or copolymer architectures and can include, for example, intermediate non-repeating units (junction blocks) between blocks and various end groups at the chain termini. Even more complex block architectures and block copolymer architectures exist where at least a portion of one block, or at least a portion of one junction block, or one or more end groups have a structure or composition more complex than a linear single constitutional unit chain. Such complex architectures include, but are not limited to, periodic or random mixtures of different constitutional units in one or more blocks, graft copolymer blocks, cyclic blocks or block copolymers, gradient blocks, or crosslinked blocks. Any block copolymer architecture / topology is suitable where the incompatible segments of the block copolymer phase separate (self-assemble) into distinct domains and are processed using the disclosed methods to produce a porous block copolymer material.

[0028] Some examples of suitable blocking chemistries include, but are not limited to, poly(isobutylene), poly(isoprene), poly(butadiene), poly(propylene glycol), poly(ethylene oxide), poly(dimethylsiloxane), poly(ether sulfone), poly(sulfone), poly(hydroxystyrene), poly(methylstyrene), poly(ethylene glycol), poly(2-hydroxyethyl methacrylate), poly(acrylamide), poly(N,N-dimethylacrylamide), poly(propylene oxide), poly(styrene sulfonate), poly(styrene), poly(ethylene), poly(vinyl chloride), poly(2-(perfluorohexyl)ethyl methacrylate), poly(tetrafluoroethylene), poly(vinylidene fluoride), poly(pentafluorostyrene), poly(acrylic acid), poly(2-methylphenyl methacrylate ... poly(4-vinylpyridine), poly(3-vinylpyridine), poly(N-isopropylacrylamide), poly(dimethylaminoethyl methacrylate), poly(glycidyl methacrylate), poly(ethyleneimine), poly(lactic acid), poly(acrylonitrile), poly(methyl acrylate), poly(butyl methacrylate), poly(methyl methacrylate), poly(n-butyl acrylate), poly(amic acid), poly(isocyanate), poly(ethyl cyanoacrylate), poly(allylamine hydrochloride), or a substituted equivalent of any of the above, provided that the block copolymer as a whole has within the polymer matrix at least some carbon-carbon double bond moieties available for crosslinking reactions or has anthracene moieties that can undergo dimerization reactions, as described above.

[0029] Suitable block copolymer starting materials for producing the membranes of the present disclosure include those having a molecular weight of about 1×10 3 ~Approx. 1×10 7 M in g / mol n These include diblock, triblock, and higher order BCPs (i.e., tetrablock, pentablock, etc.). The polydispersity index (PDI) of a block copolymer is a measure of the heterogeneity of molecular size and indicates the distribution of molar mass in a BCP sample. The PDI is determined by the average molar mass (Mw ) and the number-average molar mass (M n ). The PDI of at least one embodiment of the BCP contemplated herein is in the range of about 1.0 to about 3.0.

[0030] Exemplary block copolymers useful as starting materials in the present disclosure can be found in U.S. Patent Nos. 10,711,111 and 9,527,041; and U.S. Patent Publications 2021 / 0040281, 2021 / 0370237, and 2009 / 0173694, the disclosures of which are incorporated herein by reference in their entireties.

[0031] One particular block copolymer starting material is a polymer known as poly(1,4-isoprene)-b-poly(styrene)-b-poly(vinylpyridine), which is commercially available from Polymer Source, Inc., in Quebec, Canada. [Chemical formula]

[0032] In such a structure, the residual carbon-carbon double bonds from the polymerization of isoprene monomers provide a platform for crosslinking reactions.

[0033] The block copolymers useful in the present disclosure advantageously self-organize into nanostructures and can form micelles of uniform size in the casting solution, which provides a highly ordered isoporous structure on the surface of the membrane. See, for example, U.S. Patent Publication 2014 / 0217012, which is incorporated herein by reference and describes the production of filter membranes by a combination of controlled solvent evaporation and immersion precipitation processes known as self-assembly and solvent-nonsolvent induced phase separation (SNIPS).

[0034] Furthermore, the membrane starting material can be prepared by the methodology described in U.S. Patent Publication No. 2021 / 0040281, which is hereby incorporated by reference in its entirety. In the cited methodology, the formation of the block copolymer film comprises: (a) a step of formulating a polymer solution by mixing at least one block copolymer, wherein at least one block copolymer is combined with at least one solvent; (b) a step of extruding the polymer solution onto a non-porous substrate to form a film; (c) a step of evaporating at least a portion of at least one chemical substance of the polymer solution; and (d) a step of immersing the film in a coagulation bath.

[0035] Alternatively, in the cited methodology for forming a block copolymer (either self-standing or as part of a composite), the film also comprises: (a) a step of formulating a polymer solution by mixing at least one block copolymer, wherein at least one block copolymer is combined with at least one solvent; (b) a step of extruding the polymer solution onto a non-porous substrate to form a film; (c) a step of evaporating at least a portion of at least one chemical substance of the polymer solution; (d) a step of immersing the film in a coagulation bath; and (e) a step of rinsing the block copolymer film.

[0036] The crosslinking reaction of the present disclosure can be carried out after the drying step when the underlying membrane is sufficiently stable, or, if not, the crosslinking reaction can be carried out on the membrane before drying. In this way, once dried, the crosslinked membrane substantially retains its pore structure. In this regard, the inventors believe that this crosslinking methodology provides a membrane that exhibits less than about 20 percent change, less than about 15 percent change, or less than about 10 percent change in bubble point when exposed to one or more photolithography solvents over a 24-hour period. Additionally, the crosslinked membrane is believed to exhibit improved acid / base stability. By the bubble point test method, a sample of a porous polymer filter membrane is immersed and wetted in a liquid having a known surface tension, and a gas pressure is applied to one side of the sample. The gas pressure is gradually increased. The minimum pressure at which gas flows through the sample is called the bubble point. To determine the bubble point of a porous material, a sample of the porous material is immersed and wetted in ethoxy-nonafluorobutane HFE7200 (available from 3M) at a temperature of 20 - 25 °C (e.g., 22 °C). Compressed air is used to apply a gas pressure to one side of the sample, and the gas pressure is gradually increased. The minimum pressure at which gas flows through the sample is called the bubble point.

[0037] After manufacture, the starting material membrane can be subjected to one or more of the above techniques to achieve the desired level of crosslink density within the polymer matrix. The membrane can then be dried and fabricated into the desired filter structure.

[0038] The filter membranes disclosed herein can be housed within a larger filter structure such as a multi-layer filter assembly or filter cartridge used in a filtration system. The filtration system places the filtration membrane, for example, as part of a multi-layer filter assembly or as part of a filter cartridge, within a filter housing, exposes the filtration membrane to a flow path of a liquid chemical, and passes at least a portion of the flow of the liquid chemical through the filtration membrane, such that the filtration membrane removes a certain amount of impurities or contaminants from the liquid chemical. The structure of the multi-layer filter assembly or filter cartridge includes one or more of various additional materials and structures that support the composite filtration membrane within the filter assembly or filter cartridge, allowing fluid to flow from a filter inlet, through the composite membrane (including the filter layer), and through a filter outlet, thereby enabling passage through the composite filtration membrane when passing through the filter. The filtration membrane supported by the filter assembly or filter cartridge can be of any useful shape, such as a pleated cylinder, a cylindrical pad, a (flat) cylindrical sheet without one or more pleats, and especially a pleated sheet.

[0039] An example of a filter structure that includes the filtration membrane in the form of a pleated cylinder can be prepared to include the following components, any of which can be included in the filter construct but may not be required: a rigid or semi-rigid core that supports the pleated, cylindrical, coated filtration membrane at the inner inlet of the pleated, cylindrical, coated filtration membrane; a rigid or semi-rigid cage that supports or surrounds the outside of the pleated, cylindrical, coated filtration membrane outside the filtration membrane; optional end pieces or "pucks" located at each of the ends on opposite sides of the pleated, cylindrical, coated filtration membrane; and a filter housing that includes an inlet and an outlet. The filter housing can be of any useful and desired size, shape, and material, and can preferably be made of a suitable polymeric material.

[0040] As an example, FIG. 1 shows a filter component 30 that is a product of a pleated cylindrical component 10 and an end piece 22, and other optional components. The cylindrical component 10 includes a filtration membrane 12 described herein and is pleated. The end piece 22 is coupled (e.g., “potted”) to one end of the cylindrical filter component 10. The end piece 22 may preferably be made of a melt processable polymer material. A core (not shown) may be disposed within the internal opening 24 of the pleated cylindrical component 10, and a cage (not shown) may be disposed around the outer periphery of the pleated cylindrical component 10. A second end piece (not shown) may be coupled (“potted”) to the second end of the pleated cylindrical component 30. At this time, the resulting pleated cylindrical component 30 having potted ends on two opposite sides and optional core and cage may be disposed within a filter housing, the filter housing including an inlet and an outlet, and configured such that the entire amount of fluid entering the inlet must necessarily pass through the filtration membrane 12 before exiting the filter at the outlet.

[0041] Although several exemplary embodiments of the present disclosure have been described as above, those skilled in the art will readily understand that still other embodiments can be created and used within the scope of the appended claims. Many advantages of the present disclosure targeted by this document have been described in the foregoing description. However, it will be understood that the present disclosure is merely illustrative in many respects. Of course, the scope of the present disclosure is defined in the language expressing the scope of the appended claims.

[0042] Aspect In a first aspect, the present disclosure provides a membrane comprising a crosslinked block copolymer.

[0043] In a second aspect, the present disclosure provides a membrane comprising a crosslinked block copolymer, which exhibits a change of less than about 20 percent in bubble point when exposed to one or more photolithography solvents over a 24-hour period.

[0044] In a third aspect, the present disclosure provides a film of the first or second aspect that has a thickness of about 75 microns or less.

[0045] In a fourth aspect, the present disclosure provides a film of any one of the first to third aspects, wherein the copolymer is a terpolymer.

[0046] In a fifth aspect, the present disclosure provides a film of any one of the first to fourth aspects that contains less than about 10 weight percent of a wetting agent.

[0047] In a sixth aspect, the present disclosure provides a film of the fifth aspect, wherein the wetting agent is glycerin.

[0048] In a seventh aspect, the present disclosure provides a film of any one of the first to sixth aspects that exhibits a tensile strain at break of greater than about 5 percent as determined by ASTM method D638-14.

[0049] In an eighth aspect, the present disclosure provides a film of any one of the first to seventh aspects, wherein the crosslinked block copolymer is prepared from a block copolymer having residues of anthracene.

[0050] In a ninth aspect, the present disclosure provides a composite film comprising a porous base layer and a crosslinked block copolymer layer.

[0051] In a tenth aspect, the present disclosure provides a composite film comprising a porous base layer and a crosslinked block copolymer layer, the composite film exhibiting a change of less than about 20 percent in bubble point when exposed to one or more photolithography solvents over a period of 24 hours.

[0052] In an eleventh aspect, the present disclosure provides a composite film of the ninth or tenth aspect, wherein the porous base layer is a nonwoven material.

[0053] In a 12th aspect, the present disclosure provides a composite membrane of the 9th, 10th, or 11th aspect, wherein the porous base layer is selected from a polyolefin or a halogenated polyolefin polymer.

[0054] In a 13th aspect, the present disclosure provides a composite membrane of any one of the 9th to 12th aspects, which has a thickness of less than about 400 microns.

[0055] In a 14th aspect, the present disclosure provides a composite membrane of any one of the 9th to 13th aspects, wherein the porous base layer comprises a polymer selected from polyethylene, polypropylene, polymethylpentene, polybutene, polyisobutylene, polymethylpentene, polybutene, polyisobutylene, and copolymers of two or more of ethylene, propylene, and butylene, polyimide, polysulfone, polyethersulfone, polyarylsulfone polyamide, polyacrylate, polyester, polyamide-imide, cellulose, cellulose ester, polycarbonate, or combinations thereof.

[0056] In a 15th aspect, the present disclosure provides a composite membrane of any one of the 9th to 14th aspects, wherein the crosslinked copolymer is prepared from a block copolymer having residues of anthracene.

[0057] In a 16th aspect, the present disclosure provides a filter comprising the membrane of the 1st or 2nd aspect.

[0058] In a 17th aspect, the present disclosure provides a filter comprising the composite membrane of the 9th or 10th aspect.

[0059] In an 18th aspect, the present disclosure provides a method for preparing a crosslinked block copolymer membrane, which includes treating a block copolymer membrane having residual carbon-carbon double bonds, and the treatment is a. treatment with a sulfur compound at a temperature sufficient to induce crosslinking, and b. treatment with a thermal free radical initiator at a temperature sufficient to induce crosslinking, and c. Treatment with ultraviolet light in the presence of a free radical photoinitiator, and d. Exposure to electron beam irradiation and A method is provided that is selected from the group consisting of.

[0060] In a nineteenth aspect, the present disclosure provides a method for preparing a crosslinked block copolymer membrane, wherein the membrane comprises at least one block copolymer containing residues of anthracene, and the method comprises exposing the block copolymer containing residues of anthracene to ultraviolet light.

[0061] In a twentieth aspect, the present disclosure provides the method of the eighteenth aspect, wherein the method is treatment with a sulfur compound at a temperature sufficient to induce crosslinking.

[0062] In a twenty-first aspect, the present disclosure provides the method of the eighteenth aspect, wherein the method is exposure to electron beam irradiation.

[0063] In a twenty-first aspect, the present disclosure provides the method of the eighteenth aspect, wherein the method is treatment with a thermal free radical initiator.

[0064] In a twenty-second aspect, the present disclosure provides the method of the eighteenth aspect, wherein the method is treatment with a photo free radical initiator, and the initiator is selected from (2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone) or ammonium persulfate.

[0065] In a twenty-third aspect, the present disclosure provides a. A porous base layer, and b. A crosslinked block copolymer membrane layer that exhibits less than about 20 percent change in bubble point when exposed to one or more photolithography solvents over a 24-hour period, and A method for preparing a composite membrane comprising, Casting a block copolymer having either a residual carbon-carbon double bond or an anthracene moiety onto a porous base layer and subjecting the block copolymer membrane layer to a crosslinking reaction, provides a method.

[0066] In a 24th aspect, the present disclosure a. a porous base layer, and b. a crosslinked block copolymer membrane layer that exhibits less than about 20 percent change in bubble point when exposed to one or more photolithography solvents over a 24-hour period, is a method for preparing a composite membrane comprising: casting a block copolymer having a residual carbon-carbon double bond onto a porous base layer to form a composite membrane, and including treating the block copolymer membrane having a residual carbon-carbon double bond, the treatment being i. treatment with a sulfur compound at a temperature sufficient to induce crosslinking, and ii. treatment with a thermal free radical initiator at a temperature sufficient to induce crosslinking, and iii. treatment with ultraviolet light in the presence of a free radical photoinitiator, and iv. exposure to electron beam irradiation selected from the group consisting of, provides a method.

[0067] In a 25th aspect, the present disclosure provides a method for preparing the composite membrane of the 24th aspect, wherein the method is treatment with a sulfur compound at a temperature sufficient to induce crosslinking.

[0068] In a 26th aspect, the present disclosure provides a method for preparing the composite membrane of the 24th aspect, wherein the method is exposure to electron beam irradiation.

[0069] In a 27th aspect, the present disclosure provides a method for preparing the composite membrane of the 24th aspect, wherein the method is treatment with a thermal free radical initiator.

[0070] In a 28th aspect, the present disclosure provides a method for preparing the composite membrane of the 24th aspect, wherein the method is treatment with a photo-free radical initiator.

[0071] In a 29th aspect, the present disclosure a. a porous base layer, and b. a crosslinked block copolymer membrane layer that exhibits a change of less than about 20 percent in bubble point when exposed to one or more photolithography solvents over a 24-hour period, A method for preparing a composite membrane comprising: casting a bock copolymer having a residual anthracene moiety onto the porous base layer to form a composite membrane, and treating the block copolymer containing residues of anthracene with ultraviolet light.

Claims

**Claim 1** A film comprising a crosslinked block copolymer and showing a change of less than about 20 percent in bubble point when exposed to one or more photolithography solvents over a period of 24 hours. **Claim 2** The film according to claim 1, having a thickness of about 75 microns or less. **Claim 3** The film according to claim 1 or 2, wherein the copolymer is a terpolymer. **Claim 4** The film according to any one of claims 1 to 3, containing less than about 10 weight percent of a wetting agent. **Claim 5** The film according to claim 4, wherein the wetting agent is glycerin. **Claim 6** The film according to any one of claims 1 to 5, showing a tensile strain at break of more than about 5 percent as measured by ASTM method D638-14. **Claim 7** The film according to any one of claims 1 to 6, wherein the crosslinked block copolymer is prepared from a block copolymer having residues of anthracene. **Claim 8** The film according to any one of claims 1 to 7, which is a composite film comprising a porous base layer and a layer of crosslinked block copolymer. **Claim 9** The film according to claim 8, wherein the porous base layer is a nonwoven material. **Claim 10** The film according to claim 8, wherein the porous base layer is selected from polyolefins or halogenated polyolefin polymers. **Claim 11** The film according to any one of claims 8 to 10, having a thickness of about 400 microns or less. **Claim 12** The film according to claim 8, wherein the porous base layer comprises a polymer selected from polyethylene, polypropylene, polymethylpentene, polybutene, polyisobutylene, polymethylpentene, polybutene, polyisobutylene, and copolymers of two or more of ethylene, propylene, and butylene, polyimide, polysulfone, polyethersulfone, polyarylsulfone polyamide, polyacrylate, polyester, polyamide-imide, cellulose, cellulose ester, polycarbonate, or combinations thereof. **Claim 13** A filter comprising the film according to any one of claims 1 to 12. **Claim 14** A method of using the film according to any one of claims 1 to 12, or the filter according to claim 13, comprising passing a photolithography solvent through the film. **Claim 15** The method according to claim 14, wherein the photolithography solvent is selected from the group consisting of n-butyl acetate, isopropyl alcohol, 2-ethoxyethyl acetate, xylene, cyclohexanone, ethyl acetate, isopentyl ether, methyl-2-hydroxyisobutyrate, methyl isobutyl carbinol, methyl isobutyl ketone, isoamyl acetate, undecane, propylene glycol methyl ether, propylene glycol monomethyl ether acetate, and combinations thereof.

16. A method for preparing a crosslinked block copolymer membrane, the method comprising treating a block copolymer membrane having residual carbon-carbon double bonds to form a crosslinked block copolymer.

17. The method according to claim 16, wherein the treatment is treatment with a sulfur compound at a temperature sufficient to induce crosslinking.

18. The method according to claim 16, wherein the treatment is treatment with a thermal free radical initiator at a temperature sufficient to induce crosslinking.

19. The method according to claim 16, wherein the treatment is treatment with ultraviolet light in the presence of a free radical photoinitiator.

20. The method according to claim 16, wherein the treatment is exposure to an electron beam irradiation.

21. A method for preparing a crosslinked block copolymer membrane, the method comprising exposing a block copolymer containing residues of anthracene to ultraviolet light to form a crosslinked block copolymer membrane.

22. The method according to claim 21, further comprising using treatment b, wherein the thermal free radical initiator is benzoyl peroxide or azobisisobutyronitrile.

23. The method according to claim 21, further comprising using treatment c and a free radical photoinitiator (2-hydroxy-4'-(2-hydroxyethoxy)-2-methylpropiophenone) or ammonium persulfate.

24. The method according to any one of claims 16 to 23, wherein the membrane exhibits a change of less than about 20 percent in the bubble point when exposed to one or more photolithography solvents over a period of 24 hours.

25. The method according to any one of claims 16 to 24, wherein the membrane is a composite membrane comprising a porous base layer and a layer of crosslinked block copolymer.

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