Crosslinkable and charged zwitterionic polymers and membranes comprising same

Abstract

The present disclosure is generally directed to polymeric materials designed to produce membranes having improved selectivity and fouling resistance, having a structure comprising an adjustable effective pore size (which can be reduced to e.g., lt; 1 nm), excellent fouling resistance, improved chemical and thermal stability, and ionic selectivity. In particular, the present disclosure relates to cross-linkable and charged zwitterionic polymers and membranes made therefrom for reverse osmosis applications.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of priority to U.S. Provisional Patent Application No. 63 / 364,755, filed on May 16, 2022, the disclosure of which is hereby incorporated by reference in its entirety. Technical Field

[0003] The present disclosure generally relates to cross-linkable and charged zwitterionic polymers and membranes made therefrom for use in reverse osmosis applications. Background Art

[0004] Membrane filtration is an important and promising method for water purification, recovery and reuse. Membranes of different pore sizes can be used for a wide range of purposes, from simple removal of pathogenic microorganisms to desalination by reverse osmosis (RO). Membranes also serve as an efficient, simple and scalable separation method in different industries such as food, beverage, dairy and bio / pharmaceutical industries.

[0005] Membranes with improved selectivity, or the ability to separate solutes with greater precision, can provide improvements in the economic feasibility and energy efficiency of several other processes. For example, membranes with improved selectivity between sulfate and chloride anions can change the composition of seawater and wastewater used as drilling fluids in offshore oil wells while operating at lower applied pressures. Membranes with very small pore sizes but low salt rejection can produce highly improved effluent quality for challenging wastewater streams (particularly those with high organic content, such as those from the food industry).

[0006] All of the above membrane processes are typically severely affected by fouling, which is defined as the degradation of membrane performance due to adsorption and accumulation of feed components on the membrane surface. Severe degradation of membrane permeability and changes in membrane selectivity are common. Fouling management is a significant component of the costs associated with membrane systems, requiring increased energy use, regular cleaning (involving downtime, maintenance and chemical use), and more complex processes. Summary of the invention

[0007] Provided herein are polymeric materials designed for producing membranes with improved selectivity and fouling resistance, with potential capabilities including tunable effective pore size (which can be reduced to, for example, <1 nm), excellent fouling resistance, improved chemical resistance and thermal stability, and ion selectivity.

[0008] In various embodiments, the present disclosure relates to zwitterionic polymers and membranes made therefrom.The present disclosure includes, but is not limited to, the following exemplary embodiments.

[0009] Embodiment 1: A copolymer comprising a plurality of first repeating units, wherein the repeating units are zwitterionic; a plurality of second repeating units, wherein at least some of the second repeating units each independently comprise a crosslinkable portion; and a plurality of third repeating units, wherein at least some of the third repeating units are ionizable, and the second repeating units and the third repeating units are different.

[0010] Embodiment 2: A copolymer as described in the preceding embodiments, wherein the first repeating units each independently comprise a sulfobetaine, carboxybetaine, phosphorylcholine, imidazolium alkylsulfonate, pyridinium alkylsulfonate, or carboxybetaine group.

[0011] Embodiment 3: A copolymer as described in embodiment 1 or 2 or any combination thereof, wherein the repeating units of the zwitterion are each independently formed by sulfobetaine acrylate, sulfobetaine acrylamide, carboxybetaine acrylate, carboxybetaine methacrylate, 2-methacryloyloxyethyl phosphorylcholine, acryloxyphosphorylcholine, phosphorylcholine acrylamide, phosphorylcholine methacrylamide, carboxybetaine acrylamide, carboxybetaine vinylpyridine, carboxybetaine vinylimidazole, 3-(2-vinylpyridinium-1-yl)propane-1-sulfonate, 3-(4-vinylpyridinium-1-yl)propane-1-sulfonate, sulfobetaine methacrylate or a combination thereof.

[0012] Embodiment 4: The copolymer of any one of Embodiments 1-3 or any combination thereof, wherein at least a portion of the second repeating units comprises a hydrophobic repeating unit.

[0013] Embodiment 5: The copolymer of any one of Embodiments 1-4 or any combination thereof, wherein at least a portion of the second repeating units comprises a hydrophilic repeating unit.

[0014] Embodiment 6: A copolymer as described in any one of embodiments 1 to 5 or any combination thereof, wherein the hydrophobic repeating units are independently formed by styrene, alkyl acrylate, alkyl methacrylate, alkyl acrylamide, acrylonitrile, aryl acrylate, aryl methacrylate, aryl acrylamide, allyl acrylate, allyl acrylamide, allyl methacrylamide, vinyl methacrylate, vinyl methacrylamide, vinyl acrylamide, allyl vinylbenzene (styrene derivative), cinnamate, benzophenone, isopropylthioxanthone or a combination thereof.

[0015] Embodiment 7: The copolymer of any one of Embodiments 1-6 or any combination thereof, wherein the second portion of the second repeating unit comprises a second type of hydrophobic repeating unit.

[0016] Embodiment 8: A copolymer as described in any one of Embodiments 1-7 or any combination thereof, wherein the second type of hydrophobic repeating units are each independently formed from alkyl acrylate, alkyl methacrylate, alkyl acrylamide, acrylonitrile, aryl acrylate, aryl methacrylate, aryl acrylamide, trifluoroethyl methacrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, acrylonitrile, styrene or a combination thereof.

[0017] Embodiment 9: The copolymer of any one of Embodiments 1-8 or any combination thereof, wherein at least some of the second repeating units do not comprise a cross-linkable moiety.

[0018] Embodiment 10: A copolymer as described in any one of embodiments 1-9 or any combination thereof, wherein the second repeating units that do not contain a cross-linkable portion are each independently formed from acrylate, methacrylate, acrylamide, methacrylamide, trifluoroethyl methacrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, acrylonitrile, styrene or a combination thereof.

[0019] Embodiment 11: The copolymer of any one of Embodiments 1-10 or any combination thereof, wherein the cross-linkable moiety comprises a carbon-carbon double bond.

[0020] Embodiment 12: A copolymer as described in any one of Embodiments 1-11 or any combination thereof, wherein the cross-linkable portion comprises an allyl group (CH2-CH=CH2), a vinyl group (-CH=CH2 or -CH=CH-), a vinyl ether (-O-CH=CH2) or a vinyl ester (-CO-O-CH=CH2).

[0021] Embodiment 13: A copolymer as described in any of Embodiments 1-12 or any combination thereof, wherein the cross-linkable portion is polymerized (e.g., cross-linked) by exposure to one or more of a free radical photoinitiator, electromagnetic radiation (e.g., UV light or electron beam), elevated temperature, a redox reaction, or a combination thereof.

[0022] Embodiment 14: A copolymer as described in any one of embodiments 1-13 or any combination thereof, wherein the ionizable third repeating units are each independently formed by: 3-sulfonyl methacrylate potassium salt, methacrylate, acrylate, acrylamide, styrene derivatives, which contain one or more of the following: carboxylates, carboxylic acids, sulfonates, sulfonic acids, amines, amino acids, phosphates, phosphonic acids, Borates or boric acid, or combinations thereof.

[0023] Embodiment 15: A copolymer as described in any one of Embodiments 1-14 or any combination thereof, wherein the copolymer has a molecular weight of about 10,000 to about 10,000,000 Daltons, preferably about 20,000 to about 500,000 Daltons, and more preferably about 20,000 to about 100,000 Daltons. Generally, the specific molecular weight of the copolymer will be selected to be suitable for a particular application.

[0024] Embodiment 16: A copolymer as described in any of Embodiments 1-15 or any combination thereof, wherein the first repeating unit constitutes about 5 to about 95%, preferably about 10 to about 90%, more preferably about 20 to about 80%, and even more preferably about 25 to about 75% by weight of the copolymer.

[0025] Embodiment 17: A copolymer as described in any of Embodiments 1-16 or any combination thereof, wherein the second repeating unit constitutes about 5 to about 95%, preferably about 10 to about 90%, more preferably about 20 to about 80%, and even more preferably about 25 to about 75% by weight of the copolymer.

[0026] Embodiment 18: A copolymer as described in any one of Embodiments 1-17 or any combination thereof, wherein the third repeating unit constitutes from about 5 to about 95%, preferably from about 10 to about 90%, more preferably from about 20 to about 80%, and even more preferably from about 25 to about 75% by weight of the copolymer. In general, the specific combination of monomers and their weight ranges will vary to suit a particular application.

[0027] Embodiment 19: A cross-linked copolymer network comprising the copolymer according to any one of Embodiments 1 to 18 or any combination thereof.

[0028] Embodiment 20: A thin film composite membrane comprising a porous substrate and a selective layer, wherein the selective layer comprises the cross-linked copolymer network as described in Embodiment 19.

[0029] Embodiment 21: The membrane of the preceding embodiment, wherein the average effective pore size of the porous substrate is greater than the average effective pore size of the selective layer.

[0030] Embodiment 22: The membrane of Embodiment 20 or 21, or any combination thereof, wherein the selective layer is disposed on top of the porous substrate.

[0031] Embodiment 23: The membrane of any one of Embodiments 20-22 or any combination thereof, wherein the selective layer has an average effective pore size of about 0.1 nm to about 2.0 nm.

[0032] Embodiment 24: The membrane of any one of Embodiments 20-23 or any combination thereof, wherein the selective layer has an average effective pore size of about 0.1 nm to about 1.2 nm.

[0033] Embodiment 25: The membrane of any one of Embodiments 20-24 or any combination thereof, wherein the selective layer has an average effective pore size of about 0.5 nm to about 1.0 nm.

[0034] Embodiment 26: The membrane of any one of Embodiments 20-25 or any combination thereof, wherein the selective layer has a thickness of about 10 nm to about 10 um.

[0035] Embodiment 27: The membrane of any one of Embodiments 20-26 or any combination thereof, wherein the selective layer has a thickness of about 100 nm to about 2 um.

[0036] Embodiment 28: The membrane of any one of Embodiments 20-27 or any combination thereof, wherein the thin film composite membrane repels charged solutes and salts.

[0037] Embodiment 29: A membrane as described in any of Embodiments 20-28 or any combination thereof, wherein the selective layer exhibits greater than 99% sulfate (SO4 2- ) exclusion.

[0038] Embodiment 30: A membrane as described in any of Embodiments 20-29 or any combination thereof, wherein the selective layer exhibits a sulfate (SO4 2- ) / chloride ion (Cl - ) separation factor.

[0039] Embodiment 31: A membrane as described in any of Embodiments 20-30 or any combination thereof, wherein the selective layer exhibits a sulfate (SO4 2- ) / chloride ion (Cl - ) separation factor.

[0040] Embodiment 32: The membrane of any one of Embodiments 20-31 or any combination thereof, wherein the selective layer exhibits different anion rejections for salts having the same cation.

[0041] Embodiment 33: A membrane as described in any of Embodiments 20-32 or any combination thereof, wherein the selective layer exhibits different anion rejections for salts selected from NaF, NaCl, NaBr, NaI and NaClO4.

[0042] Embodiment 34: A membrane as described in any of Embodiments 20-33 or any combination thereof, wherein the selective layer exhibits a fluoride ion (F - ) / chloride ion (Cl - ) separation factor.

[0043] Embodiment 35: A membrane as described in any of Embodiments 20-34 or any combination thereof, wherein the selective layer exhibits a fluoride ion (F - ) / chloride ion (Cl - ) separation factor.

[0044] Embodiment 36: The membrane of any one of Embodiments 20-35 or any combination thereof, wherein the selective layer exhibits differential rejection of monosaccharides and disaccharides.

[0045] Embodiment 37: The membrane of any one of Embodiments 20-36 or any combination thereof, wherein the selective layer exhibits a glucose / sucrose separation factor greater than 10.

[0046] Embodiment 38: The membrane of any one of Embodiments 20-37 or any combination thereof, wherein the selective layer exhibits a xylose / sucrose separation factor greater than 18.

[0047] Embodiment 39: The membrane of any one of Embodiments 20-38 or any combination thereof, wherein the selective layer exhibits resistance to fouling by oily emulsions.

[0048] Embodiment 40: The membrane of any one of Embodiments 20-39 or any combination thereof, wherein the selective layer is stable when exposed to chlorine bleach (eg, at pH 4).

[0049] Embodiment 41: The membrane of any one of Embodiments 20-40 or any combination thereof, wherein the selective layer exhibits size-based selectivity between uncharged organic molecules.

[0050] Embodiment 42: The membrane of any one of Embodiments 20-41 or any combination thereof, wherein the selective layer exhibits >99% rejection of neutral molecules having a hydrated diameter of about or greater than 1 nm.

[0051] Embodiment 43: A method for preparing a thin film composite membrane, comprising providing a copolymer as described in any one of Embodiments 1-18 or any combination thereof; depositing the copolymer onto a porous substrate; and activating the cross-linkable groups of the copolymer to form additional bonds therebetween.

[0052] Embodiment 44: A method for preparing a membrane as described in the previous embodiment, wherein the step of activating the crosslinkable groups of the copolymer comprises one or more of the following: exposing the membrane to a free radical photoinitiator, electromagnetic radiation, a free radical photoinitiator and a dithiol, or a combination thereof.

[0053] Embodiment 45: A method for preparing a membrane as described in Embodiment 43 or 44, or any combination thereof, wherein the step of exposing the membrane to a free radical photoinitiator comprises exposing the membrane to a solvent, the solvent containing the free radical photoinitiator and / or the free radical photoinitiator and a dithiol. Exposing the membrane to a solvent may include, for example, immersing, dipping, coating, rinsing, or otherwise wetting the target portion of the membrane (e.g., the crosslinkable groups of the copolymer).

[0054] Embodiment 46: A method for preparing a membrane as described in Embodiments 43-45 or any combination thereof, wherein the step of exposing the membrane to electromagnetic radiation includes exposing the membrane to ultraviolet light, an electron beam, or otherwise irradiating a target portion of the membrane (e.g., a cross-linkable group of the copolymer).

[0055] In general, additional processing steps, such as quenching, surface modification, cleaning, deactivation, etc., are contemplated and considered within the scope of the present invention and may be performed with different solvents, irradiation ranges, and processing times.

[0056] By reading the specific embodiments described in detail below together with the attached drawings (briefly described below), these and other features, aspects and advantages of the present disclosure will be apparent. The present invention includes any combination of two, three, four or more of the above-mentioned embodiments, as well as any combination of two, three, four or more features or elements described in the present disclosure, whether or not these features or elements are explicitly combined in the specific embodiment description herein. The present disclosure is intended to be read as a whole, so that any separable features or elements of the disclosed invention in its different aspects and embodiments should be considered to be intended to be combinable, unless the context clearly indicates otherwise. DETAILED DESCRIPTION

[0057] A family of polymer materials is disclosed that contains at least three types of repeating units: a crosslinkable monomer, a zwitterionic monomer, and an ionic or ionizable monomer. The present disclosure enables the easy preparation of reverse osmosis membranes with novel polymer chemistry. These membranes preferably have improved scaling resistance, chlorine resistance, and stability (e.g., resistance to chemical or thermal damage).

[0058] Crosslinkable monomers: A typical crosslinkable moiety is a C=C double bond, which can be polymerized upon exposure to a free radical photoinitiator, including photoinitiators activated by ultraviolet (UV) light or electron beams. This can also be achieved using thermal methods (i.e., using initiators activated at higher temperatures) or by redox reactions. The crosslinkable moiety may not be a C=C double bond and can be polymerized by exposure to UV light in the absence of a free radical initiator.

[0059] Zwitterionic monomers: used to impart water permeability and scaling resistance to the membrane selective layer.

[0060] Ionic or ionizable monomer: When a monomer is ionic, it has a net charge within a given pH range (preferably but not necessarily a wide pH range). When a monomer is ionizable, it is initially neutral but can acquire a net charge within a given pH range through certain ionization reactions (e.g., deprotonation or protonation). Ionic or ionizable monomers will be referred to herein as ionic / ionizable monomers.

[0061] The material may also contain additional hydrophobic repeating units that are not cross-linkable. The additional hydrophobic repeating units may be acrylate, methacrylate, acrylamide, methacrylamide or a styrene derivative. Some examples of additional hydrophobic repeating units include trifluoroethyl methacrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, acrylonitrile and styrene.

[0062] In general, these copolymers can be synthesized by methods well known in polymer science. If the crosslinkable groups contain C=C double bonds, such as vinyl or allyl groups, the copolymers can be synthesized using controlled radical methods that interact only with the more reactive polymerizable groups, for example, atom transfer radical polymerization (ATRP) and its variants such as atom regeneration transfer ATRP (ARGET-ATRP), nitroxide mediated polymerization (NMP) or reversible addition fragmentation transfer (RAFT) polymerization. These polymers can also be prepared using conventional free radical polymerization while carefully controlling the polymerization conditions (e.g., highly diluted solutions, low conversions).

[0063] In various embodiments, the copolymer is a statistical copolymer and may contain different types of repeating units in a roughly random order (different from blocks). In addition, the copolymer may have a mostly linear structure. In certain embodiments, the copolymer is linear. In certain embodiments, the copolymer is branched.

[0064] In various embodiments, the copolymers may have a molecular weight above 5,000 g / mol, preferably above 30,000 g / mol, and even more preferably above 100,000 g / mol.

[0065] In various embodiments, the copolymer comprises zwitterionic repeat units at a concentration between 10-90 wt%, more preferably between 20-80 wt%, and even more preferably between 25-75 wt%.

[0066] In one embodiment, all hydrophobic repeating units are cross-linkable. In another embodiment, three monomers are used: a cross-linkable monomer, a non-cross-linkable hydrophobic monomer, and a zwitterionic monomer.

[0067] In one example, allyl methacrylate (AMA) is used as a crosslinkable monomer. Other acrylate, methacrylate, acrylamide, methacrylamide, and styrene derivatives, which contain allyl (CH2-CH=CH2), vinyl (-CH=CH2 or -CH=CH-), vinyl ether (-O-CH=CH2), and vinyl ester (-CO-O-CH=CH2) groups in their side groups, are also suitable for similar treatments. These functional groups are polymerizable by free radical polymerization, but are significantly less reactive than acrylate, methacrylate, styrene, acrylamide, and methacrylamide groups, particularly in the controlled free radical polymerization methods described herein. Some possible crosslinkable monomers include, but are not limited to: allyl acrylate, allyl acrylamide, allyl methacrylamide, vinyl methacrylate, vinyl methacrylamide, vinyl acrylamide, allyl vinylbenzene (styrene derivatives), other alkenyl acrylates / methacrylates / acrylamides / styrenes (e.g., undecenyl acrylate), and monomers with other side groups containing double bonds (e.g., ethylene glycol dicyclopentenyl ether methacrylate, ethylene glycol dicyclopentenyl ether acrylate). Other monomers that can be crosslinked include acrylates, methacrylates, acrylamides, methacrylamides, and styrene derivatives, including cinnamate (C6H5CH=CHCO2), benzophenone (C6H5)2CO), and isopropylthioxanthone (C6H5). 16 H 14 OS). All three of these side groups can be crosslinked by UV treatment without the use of free radical initiators, and the last two of these side groups can potentially be used in combination with synergists such as tertiary amines.

[0068] In the same example, sulfobetaine methacrylate (SBMA) is used as the zwitterionic monomer. However, a wide range of zwitterionic monomers would be feasible. Monomers containing sulfobetaine, phosphorylcholine, and carboxybetaine groups attached to acrylate, methacrylate, acrylamide, methacrylamide, vinylpyridine, vinylimidazole, and a variety of other polymerizable groups are viable options.

[0069] In the same example, 3-sulfonyl methacrylate potassium salt (SPMA) is used as the ionic / ionizable monomer. Other examples of ionic / ionizable monomers include monomers containing carboxylates, carboxylic acids, sulfonates, sulfonic acids, amines, amino groups, phosphates, phosphonic acids, Methacrylate, acrylate, acrylamide or styrene derivatives of borate, boric acid or other ionic / ionizable groups. The ionic / ionizable groups may contain multiple ions or ionizable groups such that the charge of the molecule is greater than or equal to +2 for cations or less than or equal to -2 for anions.

[0070] If used, the non-crosslinkable hydrophobic monomer can be selected from a wide range. The homopolymer formed by the preferred monomer is insoluble in water under the operating conditions. Fluoroalkyl and alkyl, and fluoroaryl and aryl substituted acrylates, methacrylates, acrylamides and methacrylamides, styrene and its derivatives, acrylonitrile and methacrylonitrile are all feasible options for this hydrophobic monomer. In some embodiments, the homopolymer of this hydrophobic monomer has a glass transition temperature higher than 0°C, but this is not necessary. For this purpose, we have used trifluoromethyl methacrylate (TFEMA).

[0071] To form membranes, these copolymers are coated onto porous supports by methods well known in the membrane industry (eg, doctor blade coating, spray coating).After deposition, the zwitterions and ionic / ionizable groups are expected to form clusters due to Coulombic interactions.

[0072] After forming the film, the crosslinkable groups on the copolymer chains are activated to form additional bonds between them. In one embodiment, this is achieved by first exposing the film to a solvent containing a free radical photoinitiator and then exposing the film to ultraviolet light and / or an electron beam. This activates the double bonds on the copolymer, generating bonds between the polymer chains. In another embodiment, this is achieved by first exposing the film to a solvent containing a free radical photoinitiator and dithiols, then exposing the film to ultraviolet light and / or an electron beam. This activates the double bonds on the copolymer, generating bonds between the polymer chains. Dithiols are used to accelerate the crosslinking reaction rate.

[0073] Other possible cross-linking pathways may include: using no solvent during cross-linking (e.g., a photoinitiator may be added to the solution from which the copolymer is coated onto the support) and then exposing the coated film to electromagnetic radiation (e.g., UV light); using a thermal free radical initiator instead of a photoinitiator and cross-linking by exposure to elevated temperatures; using high intensity UV light without a photoinitiator; thermal cross-linking without an initiator; and / or using a redox initiator instead of a photoinitiator.

[0074] After cross-linking, the membrane selective layer has enhanced chemical and physical stability. The performance of this layer is expected to remain stable over a wider operating window, enabling its use at higher temperatures and / or with more complex feeds containing higher salt concentrations, some solvents, etc.

[0075] The cross-linking process can also be used to tune and improve the selectivity of the membrane. Specifically, if during cross-linking the membrane is exposed to solvents that preferentially swell the hydrophobic domains rather than the zwitterionic domains, the effective pore size of the membrane can be reduced to <1 nm, as low as 0.74 nm, and potentially even lower, as measured using sugar molecule exclusion.

[0076] Additional details about the manufacture of the membranes disclosed herein can be found in PCT application numbers WO2021 / 232018 and WO2020 / 231797 and the following articles: Lounder, SJ, Asatekin, A. Zwitterionic Ion-Selective Membranes with Tunable Subnanometer Pores and Excellent Fouling Resistance. Chem. Mater. 2021, 33, 12, 4408–4416 and Lounder, SJ, Asatekin, A. Interaction-Based Ion Selectivity Exhibited by Self-Assembled, Cross-Linked Zwitterionic Copolymer Membranes. Proc Natl Acad Sci USA (In Proof, 2021); the disclosures of which are incorporated herein by reference in their entirety.

[0077] Example

[0078] In order that the invention described herein may be more fully understood, the following examples are listed. The examples described in this application are used to illustrate the compounds, compositions, materials, devices and methods provided herein and should not be interpreted in any way as limiting the scope thereof.

[0079] Polymer Synthesis:

[0080] Copolymers of allyl methacrylate (AMA), sulfobetaine methacrylate (SBMA), and 3-sulfonyl methacrylate potassium salt (SPMA) were synthesized via electron transfer regeneration activator atom transfer radical polymerization (ARGET-ATRP). Table 1 summarizes the different reaction solution compositions used for successful ARGET-ATRP syntheses:

[0081]

[0082] Membrane manufacturing

[0083] The three polymers (P1, P2 and P3) listed in the table above were used to prepare TFC membranes. To prepare TFC membranes, the given polymer was first dissolved in trifluoroethanol (TFE) at 5.0 w / v% (i.e., 5 g polymer / 95 mL TFE). The solution was then passed through a syringe filter and coated onto a support membrane (UE50, Trisep) using a wire rod (Gardo, 16 gauge wire). The coated membrane was then transferred to an 80°C convection oven to evaporate the solvent.

[0084] Membrane cross-linking

[0085] The membrane disk was cut from the prepared TFC membrane sheet and equilibrated with a UV activation solution containing isopropyl alcohol (IPA) and UV activation components. To initiate the cross-linking reaction, we then irradiated the membrane disk with UV light (365 nm) for 2-20 minutes. This resulted in photopolymerization of the AMA groups and led to extensive membrane cross-linking for pore size reduction.

[0086] The UV-activated ingredients used for a given crosslinking reaction are: (1) a photoinitiator or (2) a photoinitiator and a dithiol crosslinking accelerator. The UV-activated ingredients studied are: 2-hydroxy-2-methylpropiophenone (HOMP); 2,2-dimethoxy-2-phenylacetophenone (DPMA); and 1,6-hexanedithiol (HDT). The UV-activated solution compositions are summarized in Table 2 below.

[0087]

[0088] The foregoing written description is considered sufficient to enable one skilled in the art to practice the invention. The scope of the invention is not limited by the examples provided, as the examples are intended as a single illustration of one aspect of the invention, and other functionally equivalent embodiments are also within the scope of the invention. Various modifications of the invention other than those shown and described herein will be apparent to one skilled in the art based on the foregoing description and fall within the scope of the appended claims. The advantages and purposes of the invention are not necessarily encompassed within each embodiment of the invention.

Claims

1. A copolymer comprising: a plurality of first repeating units, wherein the repeating units are zwitterionic; a plurality of second repeating units; wherein at least some of the second repeating units each independently comprise a cross-linkable moiety; and A plurality of third repeating units, wherein at least some of the third repeating units are ionizable, and the second repeating units and the third repeating units are different.

2. The copolymer of claim 1, wherein the first repeating units each independently comprise a sulfobetaine, a carboxybetaine, a phosphorylcholine, an imidazolium alkylsulfonate, a pyridinium alkylsulfonate, or a carboxybetaine group.

3. The copolymer of claim 1, wherein the zwitterionic repeating units are each independently formed from sulfobetaine acrylate, sulfobetaine acrylamide, carboxybetaine acrylate, carboxybetaine methacrylate, 2-methacryloyloxyethyl phosphorylcholine, acryloyloxy phosphorylcholine, phosphorylcholine acrylamide, phosphorylcholine methacrylamide, carboxybetaine acrylamide, carboxybetaine vinylpyridine, carboxybetaine vinylimidazole, 3-(2-vinylpyridinium-1-yl)propane-1-sulfonate, 3-(4-vinylpyridinium-1-yl)propane-1-sulfonate, sulfobetaine methacrylate, or a combination thereof.

4. The copolymer of any one of claims 1 to 3, wherein at least a portion of the second repeating units comprises a hydrophobic repeating unit.

5. The copolymer of any one of claims 1 to 3, wherein at least a portion of the second repeating units comprises a hydrophilic repeating unit.

6. The copolymer of claim 4, wherein the hydrophobic repeating units are independently formed from styrene, alkyl acrylates, alkyl methacrylates, alkyl acrylamides, acrylonitrile, aryl acrylates, aryl methacrylates, arylacrylamides, allyl acrylates, allyl acrylamides, allyl methacrylamides, vinyl methacrylates, vinyl methacrylamides, vinyl acrylamides, allyl vinylbenzene (styrene derivatives), cinnamate, benzophenone, isopropylthioxanthone, or a combination thereof.

7. The copolymer of any one of claims 1 to 6, wherein the second portion of the second repeating unit comprises a second type of hydrophobic repeating unit.

8. The copolymer of claim 7, wherein the second type of hydrophobic repeating units are each independently formed from alkyl acrylate, alkyl methacrylate, alkyl acrylamide, acrylonitrile, aryl acrylate, aryl methacrylate, aryl acrylamide, trifluoroethyl methacrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, acrylonitrile, styrene, or a combination thereof.

9. The copolymer of any one of claims 1-8, wherein at least some of the second repeating units do not comprise a cross-linkable moiety.

10. The copolymer of claim 9, wherein the second repeating units not comprising a crosslinkable moiety are each independently formed from acrylate, methacrylate, acrylamide, methacrylamide, trifluoroethyl methacrylate, methyl methacrylate, ethyl methacrylate, n-propyl methacrylate, n-butyl methacrylate, acrylonitrile, styrene, or a combination thereof.

11. The copolymer of any one of claims 1-10, wherein the cross-linkable moiety comprises a carbon-carbon double bond.

12. The copolymer of claim 11, wherein the crosslinkable moiety comprises an allyl group (CH2-CH=CH2), a vinyl group (-CH=CH2 or -CH=CH-), a vinyl ether (-O-CH=CH2) or a vinyl ester (-CO-O-CH=CH2).

13. The copolymer of any one of claims 1-10, wherein the crosslinkable moiety is polymerized (eg, crosslinked) by exposure to one or more of a free radical photoinitiator, electromagnetic radiation, elevated temperature, a redox reaction, or a combination thereof.

14. The copolymer of any one of claims 1 to 13, wherein the ionizable third repeating units are each independently formed from: 3-sulfonyl methacrylate potassium salt, methacrylate, acrylate, acrylamide, styrene derivatives, comprising one or more of: carboxylates, carboxylic acids, sulfonates, sulfonic acids, amines, amino acids, phosphates, phosphonic acids, Borates or boric acid, or combinations thereof.

15. The copolymer of any one of claims 1-14, wherein the copolymer has a molecular weight of about 10,000 to about 10,000,000 Daltons, preferably about 20,000 to about 500,000 Daltons, and more preferably about 20,000 to about 100,000 Daltons.

16. The copolymer of any one of claims 1-15, wherein the first repeating unit constitutes about 5 to about 95%, preferably about 10 to about 90%, more preferably about 20 to about 80%, and even more preferably about 25 to about 75% by weight of the copolymer.

17. The copolymer of any one of claims 1-15, wherein the second repeating unit constitutes about 5 to about 95%, preferably about 10 to about 90%, more preferably about 20 to about 80%, and even more preferably about 25 to about 75% by weight of the copolymer.

18. The copolymer of any one of claims 1-15, wherein the third repeating unit constitutes about 5 to about 95%, preferably about 10 to about 90%, more preferably about 20 to about 80%, and even more preferably about 25 to about 75% by weight of the copolymer.

19. A cross-linked copolymer network comprising the copolymer according to any one of claims 1 to 18.

20. A thin film composite membrane comprising: a porous substrate; and A selective layer comprising the cross-linked copolymer network of claim 19.

21. The thin film composite membrane of claim 20, wherein the average effective pore size of the porous substrate is greater than the average effective pore size of the selective layer.

22. The thin film composite membrane of claim 20, wherein the selective layer is disposed on top of the porous substrate.

23. The thin film composite membrane of claim 20, wherein the selective layer has an average effective pore size of about 0.1 nm to about 2.0 nm.

24. The thin film composite membrane of claim 20, wherein the selective layer has an average effective pore size of about 0.1 nm to about 1.2 nm.

25. The thin film composite membrane of claim 20, wherein the selective layer has an average effective pore size of about 0.5 nm to about 1.0 nm.

26. The thin film composite membrane of any one of claims 20-25, wherein the selective layer has a thickness of about 10 nm to about 10 um.

27. The thin film composite membrane of any one of claims 20-25, wherein the selective layer has a thickness of about 100 nm to about 2 um.

28. The thin film composite membrane of any one of claims 20-27, wherein the thin film composite membrane repels charged solutes and salts.

29. The thin film composite membrane of any one of claims 20 to 28, wherein the selective layer exhibits greater than 99% sulfate (SO4 2- ) exclusion.

30. The thin film composite membrane of any one of claims 20 to 29, wherein the selective layer exhibits a sulfate (SO4 2- ) / chloride ion (Cl - ) separation factor.

31. The thin film composite membrane of any one of claims 20 to 29, wherein the selective layer exhibits a sulfate (SO4 2- ) / chloride ion (Cl - ) separation factor.

32. The thin film composite membrane of any one of claims 20-31, wherein the selective layer exhibits different anion rejections for salts having the same cation.

33. The thin film composite membrane of any one of claims 20-32, wherein the selective layer exhibits differential anion rejection to salts selected from the group consisting of NaF, NaCl, NaBr, NaI, and NaClO4.

34. The thin film composite membrane of any one of claims 20 to 33, wherein the selective layer exhibits a fluoride ion (F - ) / chloride ion (Cl - ) separation factor.

35. The thin film composite membrane of any one of claims 20 to 33, wherein the selective layer exhibits a fluoride ion (F - ) / chloride ion (Cl - ) separation factor.

36. The thin film composite membrane of any one of claims 20-35, wherein the selective layer exhibits differential rejection of monosaccharides and disaccharides.

37. The thin film composite membrane of any one of claims 20-36, wherein the selective layer exhibits a glucose / sucrose separation factor greater than 10.

38. The thin film composite membrane of any one of claims 20-36, wherein the selective layer exhibits a xylose / sucrose separation factor greater than 18.

39. The thin film composite membrane of any one of claims 20-38, wherein the selective layer exhibits resistance to fouling by oily emulsions.

40. The thin film composite membrane of any one of claims 20-39, wherein the selective layer is stable when exposed to chlorine bleach.

41. The thin film composite membrane of any one of claims 20-40, wherein the selective layer exhibits size-based selectivity between uncharged organic molecules.

42. The thin film composite membrane of any one of claims 20-41, wherein the selective layer exhibits >99% rejection of neutral molecules having a hydrated diameter of about or greater than 1 nm.

43. A method for preparing a thin film composite membrane, comprising: Providing a copolymer as described in any one of claims 1 to 18; depositing the copolymer onto a porous substrate; and The crosslinkable groups of the copolymer are activated to form additional bonds therebetween.

44. The method of claim 43, wherein the step of activating the crosslinkable groups of the copolymer comprises one or more of: exposing the film to a free radical photoinitiator, electromagnetic radiation, a free radical photoinitiator and a dithiol, or a combination thereof.

45. The method of claim 44, wherein the step of exposing the film to a free radical photoinitiator comprises exposing the film to a solvent containing the free radical photoinitiator and / or the free radical photoinitiator and a dithiol.

46. ​​The method of claim 44, wherein the step of exposing the film to electromagnetic radiation comprises exposing the film to ultraviolet light and / or an electron beam.

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