EP4638428A1 - Heterocyclic acrylic acid derivatives as monomers for the synthesis of polymers for use in ion exchange articles - Google Patents

Abstract

The present invention relates to monomers of formula (I) having a nitrogen atom that can be protonated at relatively low pH values (e.g., less than pH 9.5 or less than pH 9), polymers containing monomeric units derived from these monomers, anion exchange separation articles having the polymers grafted to a porous substrate, and methods of using the anion separation articles to separate mixtures of materials with different ionic content are described. Advantageously, the anion exchange separation articles can be used to separate biomaterials that cannot be subjected to high pH conditions (e.g., greater than 9 or 9.5) and/or to high ionic strength conditions (e.g., greater than 0.5M or 1M).

Description

ANION EXCHANGE SEPARATION ARTICLES, METHOD OF MAKING, AND METHODS OF USING Ion exchange (IEX) chromatography is commonly used for the purification of biological species. Cation exchange (CEX) chromatography typically utilizes acidic ligands immobilized on solid supports with pKa values in the range of 0 to about 4. Anion exchange (AEX) chromatography typically uses ligands with pKa values in the range of about 9 to 12. Relatively few ligands are available with pKa values between these two ranges. Commonly used anion exchange ligands used for bio-separations have high pKa values. For example, the pKa of the strong anion exchange quaternary amine ligand is greater than 12. Weak anion exchange ligands, such as those formed from the monomers diethylaminopropylacrylamide and dimethylaminopropylacrylamide, have respective pKa values of 10.3 and 9.3. When these ligands are used for bind and elute AEX chromatographic purifications, elution of the captured biomaterial is typically accomplished using buffer solutions having elevated salt concentrations such as 0.5M or 1.0M. Elution by changing the pH is typically not possible since an eluent having a pH above the pKa of the ligand is needed. This can be a problem since many proteins, especially enzymes, cannot tolerate such high pH values. In addition, many biological species cannot tolerate high salt concentrations or low pH values such as below 3.5 or 4. For example, many enzymes, viruses, and virus-like particles (VLPs) are only stable within narrow ranges of pH and salt conditions. Further, many viruses, especially enveloped viruses, are notoriously difficult to purify because they have low or near neutral isoelectric points. Conventional IEX ligands have limited effectiveness for purification of viruses with low or near neutral isoelectric points. Summary Monomers are provided that can be used in the preparation of anion exchange separation articles. The anion exchange separation articles have ligands that are formed from monomers that have calculated pKa values that are in a range of 3.5 or 4 to 9 or 9.5. These monomers can be used to form polymers grafted to solid supports to provide anion exchange (AEX) articles that can be utilized for bio-separations under relatively mild conditions. That is, the polymers can include monomers selected to have a pKa that allows one to bind, wash, and elute (i.e., purify) within a pH and salt concentration range that maintains the stability of the target biological species. In a first aspect, a monomer of Formula (I) is provided. In Formula (I), the group R¹ is and R² is a (hetero)alkylene. The group Z is -NH-(C=O)-, -NH-(C=O)-NH-, -NH-(C=O)-NH-R³-, -(C=O)-NH-, or –(C=O)-NH-R³-, where R³ is alkylene having at least 2 catenated carbon atoms. Groups R⁴ and R⁵ are each an alkylene having at least 2 carbon atoms, wherein a sum of ring atoms in a ring group consisting of nitrogen, R⁴, Q, and R⁵ is either 6 or 7. Group Q has a single catenated atom and is -O-, -N(R⁶)-, -S-, -S(=O)-, or -S(=O)₂- with the proviso that Q is equal to -N(R⁶)- when Z is -NH-(C=O)-. Group R⁶ is hydrogen, alkyl, or (hetero)aryl, wherein the alkyl is optionally further substituted with hydroxy, alkoxy, or (hetero)aryl and wherein the (hetero)aryl is optionally further substituted with hydroxy, halo, nitro, cyano, trifluoromethyl, alkyl, or alkoxy. In a second aspect, a polymer is provided that is a polymerized product of a monomer composition comprising a monomer of Formula (I) as described in the first aspect. In a third aspect, an anion exchange separation article is provided that includes a porous substrate and a plurality of grafted polymers attached to a surface of porous substrate, wherein the grafted polymers are a polymerized product of a monomer composition comprising a monomer of Formula (I) as described in the first aspect. In a fourth aspect, a method of separating a mixture of material of different ionic content is provided. The method includes preparing or providing an anion exchange separation article as described in the third aspect. The method further includes passing a mixture of materials through the anion exchange separation article at a first pH that is sufficiently low to protonate the monomeric repeat units of the grafted polymers that are derived from the monomer of Formula (I) and at a first ionic strength value to bind at least one component of the mixture of materials to the anion exchange separation article as a bound component. As used herein, the terms “a”, “an”, “the”, and “at least one” are used interchangeably. The term “and/or” means either or both. For example, “A and/or B” means A alone, B alone, or both A and B. The term “alkyl” refers to a monovalent group that is a radical of an alkane. The alkyl group can have 1 to 32 carbon atoms, 1 to 20 carbon atoms, 1 to 12 carbon atoms, 1 to 10 carbon atoms, 1 to 6 carbon atoms, or 1 to 4 carbon atoms. The alkyl can be linear, branched, cyclic, or a combination thereof. A linear alkyl has at least one carbon atom while a cyclic or branched alkyl has at least 3 carbon atoms. The term “alkylene” refers to a divalent group that is a radical of an alkane. The alkylene group can have 1 to 32 carbon atoms, 1 to 20 carbon atoms, 1 to 12 carbon atoms, 1 to 10 carbon atoms, 1 to 6 carbon atoms, or 1 to 4 carbon atoms. The alkylene can be linear, branched, cyclic, or a combination thereof. A linear alkylene has at least one carbon atom while a cyclic or branched alkylene has at least 3 carbon atoms. The term “heteroalkylene” refers to an alkylene having one or more of the carbon atoms replaced with a heteroatom. The heteroatom is typically nitrogen (e.g., -NH-), oxygen (-O-), or sulfur (-S-). Typically, there are not two heteroatoms adjacent to each other such as in a peroxide. The term “(hetero)alkylene” refers to an alkylene, heteroalkylene, or both. The term “alkoxy” refers to a monovalent group of formula -OR^a where R^a is an alkyl as defined above. The term “aryl” refers to a monovalent group that is a radical of an aromatic carbocyclic compound. The aryl group has at least one aromatic carbocyclic ring and can have 1 to 3 optional rings that are connected to or fused to the aromatic carbocyclic ring. The additional rings can be aromatic, aliphatic, or a combination thereof. The aryl group usually has 5 to 20 carbon atoms or 6 to 10 carbon atoms. The term “heteroaryl” refers to aryl with at least one heteroatom in the ring. The term “heteroaryl” refers to an aryl having one or more of the ring carbons replaced with a heteroatom. The heteroatom is selected from nitrogen, oxygen, or sulfur typically. The ring often has 1 to 3 heteroatoms and typically has 5 or 6 ring members. The heteroaryl can have 1 to 3 optional rings that are connected to or fused to the heterocyclic ring. The additional rings can be aromatic, aliphatic, or a combination thereof and can include heteroatoms or be free of heteroatoms. The term “(hetero)aryl” refers to an aryl or heteroaryl. The term “catenated” refers to atoms in the main chain and/or ring of a compound. In the compound CH₃-CH₂-CH₂-CH(CH₃)-CH(CH₃)-CH(CH₃)-CH₂-CH₂-CH₃, for example, there are 12 carbon atoms and 9 of them are catenated. The term “grafted” is used to indicate that polymeric chains are covalently attached to the porous polymeric substrate. In most embodiments, the polymeric chains are grafted to a carbon atom in the polymeric backbone of the porous polymeric substrate. The term “graft density” refers to the millimoles of monomeric units per gram grafted to a substrate. The millimoles are calculated by dividing the mass gain by the molecular weight of the monomer and multiplying by 1000. This value is then normalized by dividing by the original mass of the substrate (grams). The graft density is expressed as millimoles of monomeric units grafted per gram of substrate (mmoles/gram). For clarity, the material that is grafted is typically a polymeric material containing a plurality of monomeric units. The term “pKa” refers to the acid dissociation constant. It indicates how easily a proton is released from a molecule. The terms “polymer” and “polymeric material” are used interchangeably and refer to materials formed by reacting one or more monomers. The terms include homopolymers, copolymers, terpolymers, or the like. Likewise, the terms “polymerize” and “polymerizing” refer to the process of making a polymeric material that can be a homopolymer, copolymer, terpolymer, or the like. The terms “in a range of” or “ranging from” are used interchangeably to refer to all values within the range plus the endpoints of the range. Detailed Description Monomers having a nitrogen atom that can be protonated at relatively low pH values (e.g., less than pH 9.5 or less than pH 9), polymers containing monomeric units derived from these monomers, anion exchange separation articles having the polymers grafted to a porous substate, and methods of using the anion separation articles to separate mixtures of materials with different ionic content are described. Advantageously, the anion exchange separation articles can be used, for example, at pH values ranging from about 3.5 or 4 to about 9 or 9.5 and at ionic strengths up to about 0.5 moles/liter (e.g., 50 milli-Siemens). That is, the pH and ionic strength can be selected to provide conditions that can be tolerated by various biomaterials of interest. The anion exchange separation article is formed by grafting a plurality of polymers (i.e., polymeric chains) onto a porous polymeric substrate that is typically a solid material. The grafted polymers contain monomeric units with nitrogen-containing groups that can function as anion exchange ligands. That is, the nitrogen-containing groups can be protonated. The nitrogen-containing monomers used to form the grafted polymers have a calculated pKa value in a range of 3.5 or 4 to 9 or 9.5 and can be deprotonated at lower pH values compared to many nitrogen-containing monomers commonly used to prepare anion exchange separation articles. The anion exchange separation article can be used in either a flow-through separation method or a bind-and-elute separation method. Monomers Monomers are provided that have a nitrogen atom that can be protonated. More particularly, the monomers are selected to have a nitrogen atom that can be protonated at a low pH and typically have a calculated pKa value in a range of 3.5 or 4 to 9 or 9.5. The monomers are of Formula (I). In Formula (I), the group R¹ is and R² is a (hetero)alkylene. The group Z is -NH-(C=O)-, -NH- -NH-, -NH- -NH- , - -NH-, or –(C=O)-NH-R³-, where R³ is alkylene having at least 2 catenated carbon atoms. Groups R⁴ and R⁵ are each an alkylene having at least 2 carbon atoms, wherein a sum of ring atoms in a ring group consisting of nitrogen, R⁴, Q, and R⁵ is either 6 or 7. Group Q has a single catenated atom and is -O-, -N(R⁶)-, -S-, -S(=O)-, or -S(=O)₂- with the proviso that Q is equal to -N(R⁶)- when Z is -NH-(C=O)-. Group R⁶ is hydrogen, alkyl, or (hetero)aryl, wherein the alkyl is optionally further substituted with hydroxy, alkoxy, or (hetero)aryl and wherein the (hetero)aryl is optionally further substituted with hydroxy, halo, nitro, cyano, trifluoromethyl, alkyl, or alkoxy. The monomers have a (meth)acryloyl group of formula CH₂=CR¹-(C=O)- where R¹ is hydrogen or methyl. The group X¹ is either -O- or -NH-. If X¹ is -O-, the monomer of Formula (I) is a (meth)acrylate but if X is -NH-, the monomer is a (meth)acrylamide. Group R² is a (hetero)alkylene. In many embodiments, R² is an alkylene such as one having 1 to 20 carbon atoms. The alkylene R² can have, for example, at least 1, at least 2, at least 3, at least 4, at least 6, at least 8, or at least 10 carbon atoms and up to 20, up to 18, up to 16, up to 14, up to 12, up to 10, up to 8, up to 6, or up to 4 carbon atoms. In other embodiments, R² is of formula -R-O-R- where each R is an alkylene having 2 to 10 catenated carbon atoms. The alkylene R can have at least 2, at least 3, at least 4 and up to 10, up to 8, up to 6, or up to 4 catenated carbon atoms. The group Z is -NH-(C=O)-, -NH-(C=O)-NH-, -NH-(C=O)-NH-R³-, -(C=O)-NH-, and –(C=O)-NH-R³-, where R³ is alkylene having at least 2 catenated carbon atoms. Suitable alkylene groups often have 2 to 10 carbon atoms such as at least 2, at least 3, at least 4 and up to 10, up to 8, up to 6, or up to 4 carbon atoms. Group Z can form hydrogen bonds, which may be beneficial for improving binding efficiency when the monomers of Formula (I) are used, for example, to form anion exchange separation articles. Although the sum of catenated atoms in R² plus Z can be as low as three for some uses of the monomers of Formula (I), the sum is preferably greater if the monomers of Formula (I) are used to form anion exchange articles. The sum preferably is at least 4, at least 5, at least 6, at least 7, at least 8, at least 9, or at least 10. The sum can be, for example, up to 20 or more, up to 18, up to 16, up to 14, up to 12, up to 10, up to 8, up to 6, or up to 5. Groups R⁴ and R⁵ are each an alkylene having at least two carbon atoms. The ring group consisting of nitrogen, R⁴, Q, and R⁵ has 6 or 7 ring members. Each group R⁴ and R⁵ typically has either 2 or 3 carbon atoms included in atoms that form the ring (e.g., catenated carbon atoms) but there can be additional carbon atoms in R⁴ and R⁵ that are not ring atoms (e.g., non-catenated carbon atoms). The sum of ring carbon atoms (i.e., catenated atoms) in R⁴ and R⁵ is either 4 or 5. The ring group consisting of nitrogen, R⁴, Q, and R⁵ is typically saturated (i.e., there are no carbon-carbon double bonds). Group Q is -O-, -N(R⁶)-, -S-, -S(=O)-, or -S(=O)₂- with the proviso that Q is equal to -N(R⁶)- when Z is -NH-(C=O)-. When Q is -O-, -S-, -S(=O)-, or -S(=O)₂-, the nitrogen atom that is part of the same ring and that is attached to group Z is selected so that it can be protonated. When Q is -N(R⁶)- , there can be one or two protonated groups in the monomer of Formula (I). Group Q has a single catenated atom. That is, group Q contributes a single ring atom (i.e., a single catenated atom) to the ring consisting of nitrogen, R⁴, Q, and R⁵. For example, in the Q group -N(R⁶)-, nitrogen is the ring atom; and in the Q groups –S(=O) and -S(=O)₂, sulfur is the ring atom. If the nitrogen bonded to group Z is part of a urea group, then the ring has a single group that can be protonated arising from the group -N(R⁶)-. That is, if Z is equal to -NH-(C=O)-, then Q is equal to - N(R⁶)-. For example, in the following monomer, which is 2-[[4-(2-hydroxyethyl)piperazine-1- carbonyl]amino]ethyl 2-methylprop-2-enoate (also referred to as IEM/N-(2-hydroxyethyl)piperazine), the nitrogen bonded to the -NH- group and this nitrogen atom is unlikely to be protonated. The other nitrogen atom in the ring, which is in a group of formula -N(R⁶)- where R⁶ is a hydroxy-substituted alkyl, is more likely to be protonated. If the nitrogen bonded to group Z is not part of a urea group (i.e., Z is not equal to -NH-(C=O)-), then the nitrogen atom bonded to group Z plus the nitrogen in the group -N(R⁶)- can be protonated. For example, in the following monomer, which is 2-[(4-methylpiperazin-1- yl)carbamoylamino]ethyl 2-methylprop-2-enoate (also referred to as IEM/1-amino-4-methylpiperazine), both nitrogen atoms in the ring attached to Z (-NH-(C=O)-NH-) is not part of a urea linkage but to a nitrogen is the ring is the group - N(R⁶)- where R⁶ is methyl (e.g., an alkyl). The group R⁶ in the Q group -N(R⁶)- is hydrogen, alkyl, or (hetero)aryl. When R⁶ is an alkyl, it can optionally be further substituted with hydroxy, alkoxy, or (hetero)aryl. When R⁶ is a (hetero)aryl, it can optionally be further substituted with hydroxy, halo, nitro, cyano, trifluoromethyl, alkyl, or alkoxy. Suitable R⁶ alkyl groups can have 1 to 10 carbon atoms such as at least 1, at least 2, at least 3, at least 4 and up to 10, up to 8, up to 6, or up to 4 carbon atoms. Suitable R⁶ aryl groups usually have six carbon atoms while R⁶ heteroaryl groups often have either 5 or 6 ring atoms with 1 or 2 of these ring atoms being a heteroatom and with the remainder ring atoms being carbon. The heteroatoms are usually nitrogen. When group R⁶ is an alkyl, it can be unsubstituted or substituted with hydroxy (-OH), alkoxy, or (hetero)aryl group. Suitable alkoxy groups for substitution are of formula -OR^a where R^a is an alkyl having 1 to 10 carbon atoms such as at least 1, at least 2, at least 3, at least 4 and up to 10, up to 8, up to 6, or up to 4 carbon atoms. Suitable (hetero)aryl groups for substitution can be an aryl group with six carbon atoms or a heteroaryl group having either 5 or 6 ring atoms with 1 or 2 of these being a heteroatom and with the remainder being carbon. The heteroatoms in the heteroaryl group are usually nitrogen. When group R⁶ is a (hetero)aryl, it can be substituted or unsubstituted with hydroxy (-OH), halo (e.g., chloro or bromo), nitro (-NO₂), cyano (-CN), trifluoromethyl (-CF₃), alkyl, or alkoxy. Suitable alkyl groups often have 1 to 10 carbon atoms such as at least 1, at least 2, at least 3, at least 4 and up to 10, up to 8, up to 6, or up to 4 carbon atoms. Suitable alkoxy groups for substitution are of formula -OR^a where R^a is an alkyl having 1 to 10 carbon atoms such as at least 1, at least 2, at least 3, at least 4 and up to 10, up to 8, up to 6, or up to 4 carbon atoms. The monomers of Formula (I) can be prepared using any suitable method. Two methods are often used. In the first method, a (meth)acrylate monomer having an isocyanato group is reacted with a cyclic compound that has a reactive -NH- or -NH₂ group. In the second method, a cyclic compound that has a reactive -NH- or -NH₂ group is reacted with an alkenylazlactone. In some embodiments, the monomers of Formula (I) can be formed using Reaction Scheme A where compound (1), which is a (meth)acrylate monomer having an isocyanato group, is reacted with a compound having a ring structure as shown in compound (2). The -NH- group in compound (2) reacts with the isocyanato group in compound (1) to form compound (3), which is a monomer with a cyclic nitrogen-containing group (i.e., the cyclic group has ring members consisting of nitrogen, R⁴, Q, and R⁵). Reaction Scheme A , , are same as Q in compounds (2) and (3) is typically -N(R⁶)-. Group Z in Formula (I) is equal to -NH-(C=O)- in compound (3). In many embodiments of compound (1), group X¹ is -O- and R² is an alkylene having 2 to 10 carbon atoms. The number of carbon atoms can be at least 2, at least 3, or at least 4 and up to 10, up to 8, up to 6, or up to 4. In some embodiments, R² has 2 or 3 carbon atoms. In some methods of making compound (3), group Q in compound (2) is -NH- and this group is protected so that it does not react with compound (1). For example, the -NH- group for Q can be protected by reacting it with Boc₂O, which is a compound of formula (CH₃)₃C-(C=O)-O-(C=O)-C(CH₃)₃, to form an intermediate group Q¹ that is -NR⁷- where R⁷ is –(C=O)-C(CH₃)₃. After reacting with compound (1), group -NR⁷- can be reacted by heating in the presence of trifluoroacetic acid to reform the -N(H)- group for Q. Such a procedure can be used, for example, if compound (2) is piperazine. Compound (2) examples include, but are not limited to, (A) N-(2-hydroxyethyl)piperazine where Q is -N(R⁶)- with R⁶ being an alkyl group substituted with a hydroxy group, (B) N-methylpiperazine where Q is -N(R⁶)- and R⁶ is an alkyl group, (C) N-phenylpiperazine where Q is -N(R⁶)- and R⁶ is an aryl group, (D) N-phenethylpiperazine where Q is -N(R⁶)- and R⁶ is an alkyl group substituted with an aryl, (E) piperazine where Q is -N(H)-, (F) N-methylhomopiperazine where Q is - N(R⁶)- and R⁶ is an alkyl, (G) 1-(2-pyridyl)piperazine where Q is -N(R⁶)- and R⁶ is a 6-membered heteroaryl with a nitrogen heteroatom, (H) 1-(2-pyrimidyl)piperazine where Q is -N(R⁶)- and R⁶ is a 6-membered heteroaryl with 2 nitrogen heteroatoms, (I) N-(4- hydroxyphenyl)piperazine where Q is -N(R⁶)- and R⁶ is an aryl group substituted with hydroxy, (J) N-(4- methoxyphenyl)piperazine where Q is -N(R⁶)- and R⁶ is an aryl groups substituted with an alkoxy, (K) N- (4-nitrophenyl)piperazine where Q is -N(R⁶)- and R⁶ is an aryl groups substituted with nitro, (L) N-(2- methoxyethyl)piperazine where Q is -N(R⁶)- and R⁶ is an alkyl substituted with an alkoxy, and (M) N- benzylpiperazine where Q is -N(R⁶)- and R⁶ is an alkyl substituted with an aryl. In other embodiments, the monomers of Formula (I) can be formed using Reaction Scheme B where compound (1), which is a (meth)acrylate monomer having an isocyanato group, is reacted with a compound having a -NH₂ group attached to a ring structure as shown in compound (4). The product is compound (5), which is a monomer. Reaction Scheme B Groups R¹, X¹, R², R⁴, R⁵, and Q in compounds (1), (4), and (5) are the same as described above. Group Z in Formula (I) is equal to -NH-(C=O)-NH- in compound (5). Compound (4) examples include, but are not limited to, (A) 1-amino-4-methylpiperazine where Q is -N(R⁶)- with R⁶ being an alkyl, (B) 1-amino-4-phenylpiperazine where Q is -N(R⁶)- with R⁶ being an aryl, and (C) 1-amino-4-cyclopentylpiperazine where Q is -N(R⁶)- with R⁶ being an alkyl (i.e., cyclic alkyl). In yet other embodiments, the monomers of Formula (I) can be formed using Reaction Scheme C where compound (1), which is a (meth)acrylate monomer having an isocyanato group, is reacted with a compound having a NH₂-R³- group attached to a ring structure as shown in compound (6) to produce compound (7) that is a monomer. Reaction Scheme C , , are same as Z in Formula (I) is equal to -NH-(C=O)-NH-R³- in compound (7). Group R³ is an alkylene and often has 2 to 10 carbon atoms. For example, R³ has at least 2, at least 3, at least 4, or at least 6 carbon atoms and can have up to 10, up to 8, up to 6, up to 4, or up to 2 carbon atoms. Compound (6) examples include, but are not limited to, (A) N-(2-aminoethyl)morpholine where Q is -O- and R³ is an alkylene, (B) N-(3-aminopropyl)morpholine where Q is -O- and R³ is an alkylene, (C) N-(2-aminoethyl)thiomorpholine-1,1-dioxide where Q is -S(O₂)- and R³ is an alkylene, (D) N-(3- aminopropyl)thiomorpholine-1,1-dioxide where Q is -S(O₂)- and R³ is an alkylene, (E) N-(2- aminoethyl)thiomorpholine where Q is -S- and R³ is an alkylene, (F) N-(2-aminoethyl)morpholine where Q is -O- and R³ is an alkylene, (G) N-(3-aminopropyl)thiomorpholine-1-oxide where Q is -S(O)- and R³ is an alkylene, (G) N-(2-aminoethyl)thiomorpholine-1-oxide where Q is -S(O)- and R³ is an alkylene, (H) N-(3-aminopropyl)thiomorpholine where Q is -S- and R³ is an alkylene, and (I) 1-(3-aminopropyl)-4- methylpiperazine where Q is -N(R⁶)-, R⁶ is an alkyl, and R³ is an alkylene. In still other embodiments, the monomers of Formula (I) can be formed using Reaction Scheme D where compound (8), which is an alkenylazlactone, is reacted with a compound (6) having a NH₂-R³- group attached to a ring structure to produce compound (9) that is a monomer. Compound (6) is the same as described above for use in Reaction Scheme (C). Reaction Scheme D Groups R¹, R³, R⁴, R⁵, and Q in compounds (8), (6), and (10) are the same as described above. Group R² is typically an alkylene such as, for example, -C(CH₃)₂- or -C(CH₃)₂CH₂-. Group Z in Formula (I) is equal to -(C=O)-NH-R³- in compound (9). Suitable compound (6) examples are described above for Reaction Scheme C. In still additional embodiments, the monomers of Formula (I) can be formed using Reaction Scheme E where compound (8), which is an alkenylazlactone, is reacted with a compound (4) having a NH₂- group attached to a ring structure to produce compound (10) that is a monomer. Reaction Scheme E Group R² . (I) is equal to -(C=O)-NH- in compound (10). Suitable compound (4) examples are described above for Reaction Scheme B. While the sum of catenated atoms in the groups R² and Z can be as low as three, the combined groups preferably have at least 4 catenated atoms, especially when the monomers of Formula (I) are used in the formation of anion exchange separation articles. The sum of catenated atoms in R² and Z determines the length of the spacer group between alkenyl group (CH₂=CR¹- group) and a nitrogen atom that can be protonated. Typically, the spacer group has at least 5 catenated atoms but R² and Z are often selected to provide a longer spacer length when the monomers of Formula (I) are used in the formation of anion exchange separation articles. Groups R² and Z are often selected to provide a spacer group that has at least 6, at least 7, or at least 8 catenated atoms. In some embodiments, the spacer length is at least 9, at least 10, at least 12 atoms and up to 20, up to 18, up to 16, up to 14, or up to 12 catenated atoms. A longer spacer group or a larger sum of catenated atoms in groups R² and Z tends to enhance binding with other materials. That is, monomeric units with a longer spacer length tend to function better in anion exchange separation methods. The method of counting the catenated atoms is shown in the monomer below. For this compound, which is 2- ethyl 2-methylprop-2-enoate (referred to herein as IEM/N-phenylpiperazine), there are 9 catenated atoms between the alkenyl group and the ring nitrogen that can protonated. A nitrogen atom that is part of a urea linkage, as is the case of the nitrogen atom at the position 7 in the compound above, is typically not one that can be protonated. It is the nitrogen at position 10 that can be protonated in this compound. However, for the following compound below, which is 2-(3- (referred to herein as IEM/N-(3-aminopropyl) protonated. The monomers are often selected to have a calculated pKa value in a range of 3 to 9.5 or in a range of 3.5 or 4 to 9 or 9.5. In some embodiments, the calculated pKa is at least 3.5, at least 4.0, at least 4.5, at least 5.0, at least 5.5, at least 6.0, at least 6.5, at least 7.0, at least 7.5, or at least 8.0 and up to 9.5, up to 9.0, up to 8.5, up to 8.0, up to 7.5, up to 7.0, up to 6.5, or up to 6.0. The calculated pKa values can be used to predict what monomers are likely to be suitable for separation of various mixtures of materials such as those containing biomaterials. The method and software used to calculate the pKa value are provided in the Examples section below. The calculations can be used to quickly assess whether the monomer has a pH within an acceptable range before synthesis of the polymeric chains and preparation of an anion exchange separation article. The estimates of error in calculation of the pKa value based on Hammett-Taft methods are often dependent on the structural similarity of a novel material to those present in the model database. Estimations are useful for biological applications as the error is usually smaller than the range of acceptable pH values for the application. Thus, the calculated pKa values allow for rapid selection of a limited number of potential ligands for evaluation for use in a particular separation in a desired pH range. This selection can result in substantial time-savings as opposed to the random synthesis and evaluation of a large ligand library. Literature articles that provide information about the calculation of pKa values include, for example, J. R. Greenwood et al., "Towards the comprehensive, rapid, and accurate prediction of the favorable tautomeric states of drug-like molecules in aqueous solution", Journal of Computer-Aided Molecular Design, 2010, 24, 591-604 and J. C. Shelley et al., "Epik: a software program for pK_a prediction and protonation state generation for drug-like molecules", Journal of Computer-Aided Molecular Design, 2007, 21, 681-691. Articles with grafted polymers Articles can be prepared that have a plurality of polymeric chains extending from a surface of a porous polymeric substrate. The polymeric chains are formed from monomers of Formula (I). These articles can be used as anion exchange separation articles. The polymeric chains can be homopolymers formed exclusively of monomers of Formula (I) or copolymers formed from a mixture of monomers of Formula (I) with other monomers that are not of Formula (I). The other monomers in the mixture are often hydrophilic monomers that are not ionic. The polymeric chains in the articles are often grafted to a porous polymeric substate that is a solid. The term “solid” in reference to the porous polymeric substrate means that the substrate is not a liquid and is not dissolved in a solution. Small particles suspended in a liquid are not considered to be dissolved in the liquid. That is, a suspension is not considered to be a solution herein and the suspended particles are solids as the term is used herein. In many embodiments, however, the solid substrate is not a small particle but is selected to have a larger form such as those described further below. The pores of the porous polymeric substrate can have any desired average size. In some embodiments, the pores are macro-porous, mesoporous, microporous, or a mixture thereof. As used herein, the term “macro-porous” refers to a polymeric substrate having pores with diameters greater than 50 nanometers, the term “meso-porous” refers a polymeric substrate having pores with diameters in a range of 2 nanometers to 50 nanometers, and the term “micro-porous” refers to a material having pores with diameters less than 2 nanometers. The terms “solid porous polymeric substrate”, “porous polymeric substrate”, “polymeric substrate”, “substrate”, and similar variations can be used interchangeably herein. The porous polymeric substrate can have any desired size, shape, and form. For example, the porous polymeric substrate can be in the form of particles, fibers, films, non-woven webs, woven webs, membranes, sponges, or sheets. In some examples, the polymeric substrate is a porous membrane or a porous non-woven web. To prepare large separation articles or many separation articles and for ease of manufacturing, the polymeric substrate can be in the form of or formed from a roll such as a roll of a film, non-woven web, woven web, membrane, sponge, or sheet. This allows the use of roll-to-roll processing to prepare the separation articles. The porous polymeric substrate can include a single layer or multiple layers of the same or different polymeric materials. The porous polymeric substrate is often formed from a thermoplastic material. Suitable thermoplastics include, but are not limited to, polyolefins, poly(isoprenes), poly(butadienes), fluorinated polymers, chlorinated polymers, polyamides, polyimides, polyethers, poly(ether sulfones), poly(sulfones), poly(vinyl acetates) and copolymers thereof such as poly(ethylene)-co-poly(vinyl acetate), polyesters such as poly(lactic acid), poly(vinyl alcohol) and copolymers thereof such as poly(ethylene)–co-poly(vinyl alcohol), poly(vinyl esters), poly(vinyl ethers), poly(carbonates), polyurethanes, poly((meth)acrylates) and copolymers thereof, and combinations thereof. Suitable polyolefins for the porous polymeric substrate include poly(ethylene), poly(propylene), poly(1-butene), copolymers of ethylene and propylene, alpha olefin copolymers (such as copolymers of ethylene or propylene with 1-butene, 1-hexene, 1-octene, and/or 1-decene), poly(ethylene-co-1-butene), poly(ethylene-co-1-butene-co-1-hexene), poly(butadiene) and copolymers thereof, and combinations thereof. Suitable fluorinated polymers for the porous polymeric substrate include poly(vinyl fluoride), poly(vinylidene fluoride), copolymers of vinylidene fluoride (such as poly(vinylidene fluoride-co- hexafluoropropylene)), copolymers of chlorotrifluoroethylene (such as poly(ethylene-co- chlorotrifluoroethylene)), and combinations thereof. Suitable polyamides for the porous polymeric substrate include various nylon compositions such as, for example, poly(iminoadipoyliminohexamethylene), poly(iminoadipoyliminodecamethylene), polycaprolactam, and combinations thereof. Suitable polyimides include poly(pyromellitimide), and combinations thereof. Suitable poly(ether sulfones) for the porous polymeric substrate include poly(diphenylether sulfone), poly(diphenylsulfone-co-diphenylene oxide sulfone), and combinations thereof. Suitable copolymers of vinyl acetate for the porous polymeric substrate include copolymers of ethylene and vinyl acetate as well as terpolymers of vinyl acetate, vinyl alcohol, and ethylene. In some embodiments, the porous polymeric substrate is a porous membrane having an average pore size (average longest diameter of the pore) that is often greater than 0.1 micrometer to minimize size exclusion separations, minimize diffusion constraints, and maximize surface area and separation. Generally, the average pore size can be in the range of 0.1 to 10 micrometers. For example, the average pore size is at least 0.2, at least 0.4, at least 0.6, or at least 0.8 micrometers and up to 8, up to 6, up to 4, or up to 2 micrometers. The porous polymeric substrate can be a macro-porous membrane such as a thermally induced phase separation (TIPS) membrane. TIPS membranes are often prepared by forming a solution of a thermoplastic material and a second material above the melting point of the thermoplastic material. Upon cooling, the thermoplastic material crystallizes and phase separates from the second material. The crystallized material is often stretched. The second material is optionally removed either before or after stretching. Macro-porous membranes are further described in U.S. Patent Nos.4,539,256 (Shipman), 4,726,989 (Mrozinski), 4,867,881 (Kinzer), 5,120,594 (Mrozinski), 5,260,360 (Mrozinski), and 5,962,544 (Waller, Jr.). Some exemplary TIPS membranes include poly(vinylidene fluoride) (PVDF), polyolefins such as poly(ethylene) or poly(propylene), vinyl-containing polymers or copolymers such as ethylene- vinyl alcohol copolymers and butadiene-containing polymers or copolymers, and (meth)acrylate- containing polymers or copolymers. TIPS membranes including PVDF are further described in U.S. Patent No.7,338,692 (Smith et al.). In some embodiments, the porous polymeric substrate can include a nylon macro-porous film or sheet (for example, a macro-porous membrane), such as those described in U.S. Patent Nos.6,056,529 (Meyering et al.), 6,267,916 (Meyering et al.), 6,413,070 (Meyering et al.), 6,776,940 (Meyering et al.), 3,876,738 (Marinaccio et al.), 3,928,517 (Knight et al.), 4,707,265 (Barnes, Jr. et al.), and 5,458,782 (Hou et al.). In other embodiments, the porous polymeric substrate can be a nonwoven web, which can include nonwoven webs manufactured by any of the commonly known processes for producing nonwoven webs. As used herein, the term “nonwoven web” refers to a fabric that has a structure of individual fibers or filaments that are randomly and/or unidirectionally interlaid in a mat-like fashion. For example, the fibrous nonwoven web can be made by wet laid, carded, air laid, spunlaced, spunbonding, or melt-blowing techniques, or combinations thereof. Spunbonded fibers are typically small diameter fibers that are formed by extruding molten thermoplastic polymer as filaments from a plurality of fine, usually circular capillaries of a spinneret, with the diameter of the extruded fibers being rapidly reduced. Melt-blown fibers are typically formed by extruding molten thermoplastic material through a plurality of fine, usually circular, die capillaries as molten threads or filaments into a high velocity, usually heated gas (for example, air) stream, which attenuates the filaments of molten thermoplastic material to reduce their diameter. Thereafter, the melt-blown fibers are carried by the high velocity gas stream and are deposited on a collecting surface to form a web of randomly dispersed, melt-blown fibers. Any of the nonwoven webs can be made from a single type of fiber or from two or more fibers that differ in the type of thermoplastic polymer and/or thickness. Further details of manufacturing methods of useful nonwoven webs have been described by Wente in “Superfine Thermoplastic Fibers,” Indus. Eng. Chem., 48, 1342 (1956) and by Wente et al. in “Manufacture of Superfine Organic Fibers,” Naval Research Laboratories Report No.4364 (1954). The nonwoven web substrate may optionally further comprise one or more layers of scrim. For example, either or both major surfaces of the nonwoven web may each optionally further comprise a scrim layer. The scrim, which is typically a woven or nonwoven reinforcement layer made from fibers, is included to provide strength to the nonwoven web. Suitable scrim materials include, but are not limited to, nylon, polyester, fiberglass, polyethylene, polypropylene, and the like. The average thickness of the scrim can vary but often ranges from about 25 to about 100 micrometers, preferably about 25 to about 50 micrometers. The scrim layer may optionally be bonded to the nonwoven article. A variety of adhesive materials can be used to bond the scrim to the nonwoven. Alternatively, the scrim may be heat-bonded to the nonwoven web. The porosity of nonwoven substrates is typically characterized by properties such as fiber diameter, or basis weight, or solidity, rather than by pore size. The fibers of the nonwoven substrate are typically microfibers having an effective fiber diameter of at least 0.5, 1, 2, or even 4 micrometers and at most 15, 10, 8, or even 6 micrometers, as calculated according to the method set forth in Davies, C. N., “The Separation of Airborne Dust and Particles,” Institution of Mechanical Engineers, London, Proceedings 1B, 1952. The nonwoven substrate preferably has a basis weight in the range of at least 5, 10, 20, or even 50 g/m²; and at most 800, 600, 400, 200, or even 100 g/m². The minimum tensile strength of the nonwoven web is about 4.0 Newtons. It is generally recognized that the tensile strength of nonwoven substrates is lower in the machine direction than in the cross-web direction due to better fiber bonding and entanglement in the latter. Nonwoven web loft is measured by solidity, a parameter that defines the solids fraction in a volume of web. Lower solidity values are indicative of greater web loft. Solidity (α) is a unitless fraction typically represented by: α = m_f ÷ ρ_f × L_nonwoven where m_f is the fiber mass per sample surface area, ρ_f is the fiber density, and L_nonwoven is the nonwoven thickness. Solidity is used herein to refer to the nonwoven substrate itself and not to the functionalized nonwoven substrate. When a nonwoven substrate contains mixtures of two or more kinds of fibers, the individual solidities are determined for each kind of fiber using the same L_nonwoven and these individual solidities are added together to obtain the web's solidity, α. The polymeric chains grafted to the porous polymeric substrate can be a homopolymer or copolymer (e.g., the term “copolymer” refers to a polymeric material having at least two different monomeric units). The polymeric chains are often homopolymers of the monomers of Formula (I) to prepare polymers with high binding capacity for the materials desired to be captured. That is, the polymeric chains can contain up to 100 weight percent of first monomers of Formula (I) based on the total weight of monomers used to form the polymeric chains. In some embodiments, other monomers (second monomers) can be copolymerized with the first monomers to adjust the binding capacity and/or to achieve other desired properties of the polymeric chains. Any suitable second monomer can be used but they are typically hydrophilic monomers. For example, they are often water soluble or water miscible. The amount of the first monomer of Formula (I) can be, for example, in a range of 10 to 100 weight percent or 20 to 100 weight percent based on the total weight of monomeric units in the polymeric chain. The amount can be at least 10, at least 20, at least 30, at least 40, at least 50, at least 60, at least 70, at least 75, at least 80, at least 85, at least 90, or at least 95 weight percent and up to 100, up to 99, up to 98, up to 97, up to 95, up to 90, up to 85, up to 80, or up to 75 weight percent based on the total weight of monomeric units in the polymeric chain. Higher amounts of the first monomer tend to increase the binding capacity for various target compounds such as biomaterials. In many embodiments, the amount of the fist monomer of Formula (I) is in a range of 80 to 100, 85 to 100, 90 to 100, or 95 to 100 weight percent based on the total weight of monomeric units. The optional second monomer in the polymeric chain can be, for example, a hydrophilic monomer to adjust the degree of hydrophilicity imparted to the substrate or to adjust the charge density of the anion exchange separation article. The hydrophilic monomer has an ethylenically unsaturated group and a hydrophilic group such as, for example, a hydroxyl group, ether group, or amido group. Suitable hydrophilic monomers include, for example, acrylamide, dimethylacrylamide, hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, ethoxyethylmethacrylate, diethyleneglycolmethylether methacrylate, 2-hydroxyethylacrylamide, N-vinylpyrrolidone, and the like, and combinations thereof. Other optional second monomers include those that have more than one ethylenically unsaturated group. This types of second monomers are typically water soluble and are used in only relatively small amounts to impart a degree of branching and/or relatively light crosslinking to a resulting copolymer. For example, the amount of these multifunctional monomers having more than two ethylenically unsaturated groups may be present in an amount ranging from 0.1 to 25 weight percent, based upon the total weight of monomers in the polymerizable composition. The amount can be at least 0.1, at least 0.2, at least 0.5, or at least 1.0 weight percent and up to 25, up to 20, up to 15, up to 10, up to 5, up to 4, up to 3, up to 2, or up to 1 weight percent. Although crosslinking monomers can be used and can be beneficial for some applications, they tend to reduce binding capacity for some biomaterials. Examples of suitable crosslinking monomers include, but are not limited to, poly(ethyleneglycoldi(meth)acrylate, methylenebisacrylamide, 3-acryloyloxy-2-hydroxypropyl methacrylate, glyceroldimethacrylate, glyceroldiacrylate, diacryloylpiperazine, and 1,2- ethylenebisacrylamide. The total amount of the second monomer can be up to 80 weight percent of the monomers used to form the polymeric chain. Lower amounts of the second monomer typically enhance the binding capacity for various target compounds such as protein biomaterials. The amount, if present, is usually equal to 100 minus the weight percent of the first monomer of Formula (I) based on the total weight of monomers in the polymerizable composition. In some embodiments, the polymerizable composition contains 10 to 90 weight percent of the first monomer of Formula (I) and 90 to 10 weight percent of the second hydrophilic monomer. For example, the polymerizable composition can contain 20 to 90 weight percent of the first monomer and 80 to 10 weight percent of the second monomer, 10 to 80 weight percent of the first monomer and 90 to 20 weight percent of the second monomer, 30 to 90 weight percent of the first monomer and 70 to 10 weight percent of the second monomer, 30 to 80 weight percent of the first monomer and 70 to 20 weight percent of the second monomer, 30 to 70 weight percent of the first monomer and 70 to 30 weight percent of the second monomer, 40 to 90 weight percent of the first monomer and 60 to 10 weight percent of the second monomer, or 50 to 90 weight percent of the fist monomer and 50 to 10 weight percent of the second monomer. The polymeric chains are grafted onto the porous polymeric substrate. Any suitable method of grafting can be used. In many embodiments, a Type II photoinitiator is combined with the monomer composition to form a reaction mixture. Upon exposure of the reaction mixture to ultraviolet radiation, the Type II photoinitiator abstracts a hydrogen atom from the porous polymeric substrate resulting in the generation of free radicals on the porous polymeric substrate. The free radicals react with the monomers present in the composition resulting in the formation of polymeric chains grafted to the porous polymeric substrate. The polymeric chains are often grafted to a carbon atom in the backbone of the polymeric material contained in the porous polymeric substrate. Type II photoinitiators are typically aromatic ketone compounds. Examples include, but are not limited to, benzophenone, carboxybenzophenone (e.g., 3-carboxybenzophenone), 4-(3- sulfopropyloxy)benzophenone sodium salt, Michler’s ketone, benzil, anthraquinone, 5,12- naphthacenequinone, aceanthracenequinone, benz(A)anthracene-7,12-dione, 1,4-chrysenequinone, 6,13- pentacenequinone, 5,7,12,14-pentacenetetrone, 9-fluorenone, anthrone, xanthone, thioxanthone, 2-(3- sulfopropyloxy)thioxanthen-9-one, acridone, dibenzosuberone, acetophenone, and chromone. The ultraviolet (UV) light used to generate free radicals on the porous polymeric substrate can be provided by various light sources such as light emitting diodes (LEDs), black lights, medium pressure mercury lamps, etc., or a combination thereof. The actinic radiation (e.g., UV radiation) can also be provided using higher intensity light sources such as those available from Fusion UV Systems Inc. The ultraviolet light sources can be relatively low light intensity sources such as blacklights that provide generally 10 mW/cm² or less (as measured in accordance with procedures approved by the United States National Institute of Standards and Technology as, for example, with a UVIMAP UM 365 L-S radiometer manufactured by Electronic Instrumentation & Technology, Inc., in Sterling, VA) over a wavelength range of 280 to 400 nanometers. Alternatively, relatively high light intensity sources such as medium pressure mercury lamps can be used that provide intensities generally greater than 10 mW/cm², preferably between 15 and 450 mW/cm². The exposure time can be up to about 30 minutes or even longer. In another method useful for generating free radicals on a surface of the porous polymeric substrate, the substrate itself is selected to be photoactive and no Type II photoinitiator is needed. The monomer composition is exposed to actinic radiation, which is typically in the ultraviolet region of the electromagnetic spectrum. Upon exposure to the actinic radiation, the polymeric substrate absorbs enough energy that some of its covalent bonds are broken, resulting in the generation of free radicals that can react with the monomers to form polymeric chains. Examples of photoactive polymeric substrates include polysulfones and poly(ether sulfones). Other photoactive polymeric substrates often contain an aromatic group such as, for example, homopolymers and block copolymers of poly(methylphenylsilane) and various polyimides based on benzophenone tetracarboxylic dianhydride. In other methods for generating free radicals on a surface of the polymeric substrate, ionizing radiation is used rather than a Type II photoinitiator and/or UV radiation. As used herein, the term “ionizing radiation” refers to radiation that is of a sufficient dose and energy to form free radical reaction sites on the surface and/or in the bulk of the polymeric substrate. The radiation is of sufficient energy if it is absorbed by the polymeric substrate and results in the cleavage of chemical bonds in the substrate and the formation of free radicals. The ionizing radiation is often beta radiation, gamma radiation, electron beam radiation, x-ray radiation, plasma radiation, or other suitable types of electromagnetic radiation. Preferably, ionizing radiation is conducted in an inert environment to prevent oxygen from reacting with the radicals. In many embodiments of this process, the ionizing radiation is electron beam radiation, gamma ray radiation, x-ray radiation, or plasma radiation because of the ready availability of suitable generators. Electron beam generators are commercially available such as, for example, the ESI ELECTROCURE EB SYSTEM from Energy Sciences, Inc. (Wilmington, MA, USA) and the BROADBEAM EB PROCESSOR from E-beam Technologies (Davenport, IA, USA). Gamma ray radiation generators are commercially available from MDS Nordion that use a cobalt-60 high energy source. For any given type of ionizing radiation, the dose delivered can be measured in accordance with ISO/ASTM52628-13, “Standard Practice for Dosimetry in Radiation Processing,” by ASTM International (West Conshohocken, PA). By altering the extractor grid voltage, beam diameter, exposure time, and distance from the irradiation source, various dose rates can be obtained. Multiple polymeric chains are grafted to the porous polymeric substrate. The term “ligand density” refers to the millimoles of monomeric units per gram grafted to a substrate. The millimoles are calculated by dividing the mass gain by the molecular weight of the monomer and multiplying by 1000. This value is then normalized by dividing by the original mass (grams) of the porous polymeric substrate. The ligand density (mmoles/gram) is expressed as millimoles of monomeric units grafted per gram of substrate. For clarity, the material that is grafted is typically a polymeric material containing a plurality of monomeric units. When the substrate is a membrane, the anion exchange separation articles often have a ligand density of about 0.02 to about 3 mmoles/gram or even higher. The graft density can be at least 0.02, at least 0.05, at least 0.1, at least 0.2, at least 0.5, or at least 1 mmoles/gram and up to 3, up to 2.5, up to 2, up to 1.5, up to 1, up to 0.8, up to 0.7, or up to 0.5 mmoles/gram. The weight gain is calculated from the equation [100 (Weight 2 – Weight 1) ÷ Weight 1] where Weight 1 is the weight of the substrate and Weight 2 is the weight of the substrate with grafted polymers attached. The weight gain can be in a range of 1 to 85 weight percent or even higher. The amount, can be, for example, at least 1, at least 2, at least 5, at least 10, at least 15, at least 20, at least 25, at least 30, at least 35, at least 40, at least 45, or at least 50 weight percent and up to 85, up to 80, up to 75, up to 70, up to 65, up to 60, up to 55, up to 50, up to 45, up to 40, up to 35, or up to 30 weight percent. When the substrate is a nonwoven or fibrous substrate, the weight gain upon grafting can often be higher than that of membrane substrates. The weight gain can be in a range of 20 to 400 weight percent or even higher. The amount can be, for example, at least 20, at least 50, at least 100, at least 150, at least 200, at least 250, or at least 300 weight percent and up to 400, up to 350, up to 300, up to 250, up to 200, up to 150, up to 100, up to 75, or up to 50 weight percent. For example, the weight gain can be in a range of 100 to 400, 100 to 300, or 100 to 200 weight percent. Method of separating a mixture of materials using the anion exchange separation article The anion exchange separation article can be used to separate a mixture of materials having different ionic content. The anion exchange separation article is the same as described above. The method includes passing a mixture of materials through the anion exchange separation article at a first pH that is sufficiently low to protonate the monomeric repeat units of the grafted polymers that are derived from the monomer of Formula (I) and at a first ionic strength value to bind at least one component of the mixture of materials to the anion exchange separation article as a bound component. The first pH is selected to protonate at least a portion of the monomeric repeat units of the grafted polymers that are derived from a monomer of Formula (I). The portion that is protonated is often at least 5, at least 10, at least 20, at least 30, at least 40, at least 50, or at least 60 mole percent and up to 100, up to 95, up to 90, up to 80, up to 70, up to 60, up to 50, up to 40, or up to 30 mole percent. The pH can be optimized using experimental approaches known to those skilled in the art and/or as demonstrated in the Examples section below. If desired, the proportion of protonated monomer units can be calculated by first determining the actual pKa of the anion exchange separation article by potentiometric titration, then substituting the pKa and the pH values into the Henderson-Hasselbalch equation to calculate the ratio of protonated to unprotonated units. Typically, the pH is selected so that it is lower than the pKa value of the monomer of Formula (I) used in the preparation of the grafted polymers that are attached to the porous polymeric substrate. If the pH is lower than the pKa value, the monomeric units derived from the monomers of Formula (I) will be positively charged. Under these lower pH conditions, the grafted polymers can bind to negatively charged species. If the pH is increased above the pKa value, the monomeric units derived from the monomers of Formula (I) in the grafted polymers are neutralized, and the bound materials can be released. The monomers of Formula (I) often have a calculated pKa value ranging from about 3.5 or 4 to about 9 or 9.5. Thus, the composition of the grafted polymers can be adjusted to optimize the pKa value for separation of different mixtures. That is, the composition of the grafted polymers and the pH can be adjusted to either (a) bind the materials of interest and not the impurities or (b) bind the impurities and not the materials of interest. As noted above, the pH can be adjusted so that the materials of interest but not impurities are retained upon passage of a sample through the anion exchange separation article. After passage of the sample, the anionic separation article optionally can be washed to remove any residual impurities. The materials of interest can then be released from the anion exchange separation article by increasing the pH and/or increasing the ionic strength of the composition passing through the anion exchange separation article. This method can be referred to as a bind and release (i.e., elute) process. In some embodiments of the bind and release process, the pH and/or the ionic strength can be increased gradually or in a stepwise manner to further separate a mixture of bonded materials. Alternatively, the pH can be adjusted so that impurities are retained but the materials of interest are not retained upon passage of a sample through the anion exchange separation article. This method can be referred to as a flow-through separation process. The retained impurities can be released from the anion exchange separation article, if desired, after passage of the materials of interest by increasing the pH and/or increasing the ionic strength of the composition passing through the anion exchange separation article. Removing the retained impurities allows the anion exchange separation article to be used again for separating other material mixtures. Alternatively, the impurities are not released, and the anion exchange separation article is discarded after use. In this instance, the anion exchange separation device can be referred to as a single-use device. Many materials that are desirable to separate are biological materials that have an isoelectric point (pI). At pH values above their pI value, the biomaterials are net negatively charged and can bind to the positively charged grafted polymers; however, at pH values below their pI value, the biomaterials are net positively charged and will not be attracted to the positively charged grafted polymers. Examples of biological materials that can be bound include, but are not limited to, proteins, nucleic acids, nucleic acid fragments, cells, viruses, and virus-like particles. The anion exchange separation devices described herein are well suited for the separation of many biological materials that cannot tolerate high pH conditions (e.g., pH 10, 11, or greater depending on the biological material) or low pH conditions (e.g., pH 5, 4, or below depending on the biological material) and/or high salt concentrations (e.g., 0.5 M or higher such as 1.0 M) that are commonly used in many current anion exchange separation articles. The monomers of Formula (I) can be used to form grafted polymers on the anion exchange separation article that can be used under pH conditions less then pH 11 or pH 10 such as in the range of pH 3.5 or 4 to 9 or 9.5. For example, the pH can be down to 3.5 or even lower, down to 4, down to 4.5, down to 5.0, down to 5.5, down to 6.0, down to 6.5, down to 7, down to 7.5, or down to 8 and up to 11 or even higher, up to 10.5, up to 10, up to 9.5, up to 9, up to 8.5, up to 8, up to 7.5, up to 7, up to 6.5, up to 6, up to 5.5 or up to 5. Additionally, these anion exchange separation articles can bind and elute biological materials at salt concentrations less than or equal to 0.5 M such as in the range of 0.01 M to less than 0.5 M. The concentration can be, for example, at least 0.01, at least 0.02, at least 0.05, at least 0.07, at least 0.1, at least 0.15, or at least 0.2 and up to 0.5 M, up to 0.45 M, up to 0.4 M, up to 0.35 M, up to 0.3 M, up to 0.25 M, up to 0.2 M, up to 0.15 M, up to 0.1 M, or up to 0.05 M. The salt concentration is often expressed based on the conductivity. For example, the conductivity is often less than or equal to 50 mS/cm (milliSiemens/centimeter) such as in a range of 1 to 50 mS/cm. That is, the conductivity can be at least 1, at least 2, at least 3, at least 5, or at least 10 mS/cm and up to 50, up to 40, up to 30, up to 20, up to 10, or up to 5 mS/cm. Non-grafted polymers with monomeric units derived from monomers of Formula (I) Polymers can be formed from the monomers of Formula (I) that are not grafted to a porous polymeric substate as described above. The polymers can be homopolymers or copolymers with additional monomeric units not of Formula (I). For example, the polymers can be prepared to be soluble in a polar solvent and, if desired, to be coated onto a substrate that is either porous or non-porous. The polymerization process can be carried out using any known method. In most polymerization processes, a radical initiator is used that can be either a thermal initiator or a photoinitiator. In many embodiments a photoinitiator is used. Useful photoinitiators include, but are not limited to, benzoin ethers such as benzoin methyl ether and benzoin isopropyl ether, substituted acetophenones such as 2, 2-dimethoxyacetophenone available as IRGACURE 651 photoinitiator (Ciba Specialty Chemicals), 2,2 dimethoxy-2-phenyl-l-phenylethanone available as ESACURE KB-1 photoinitiator (IGM Resins, Charlette, NC), 1-[4-(2- hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one available as IRGACURE 2959 (Ciba Specialty Chemicals), dimethoxyhydroxyacetophenone, substituted a-ketols such as 2- methyl-2-hydroxy propiophenone, aromatic sulfonyl chlorides such as 2-naphthalene-sulfonyl chloride, and photoactive oximes such as 1-phenyl-1,2-propanedione-2-(O-ethoxy-carbonyl)oxime. Other useful photoinitiators include, for example, hydrogen-abstracting (Type II) photoinitiators such as benzophenone, 4-(3-sulfopropyloxy)benzophenone sodium salt, Michler’s ketone, benzil, anthraquinone, 5,12-naphthacenequinone, aceanthracenequinone, benz(A)anthracene-7,12-dione, 1,4- chrysenequinone, 6,13-pentacenequinone, 5,7,12,14-pentacenetetrone, 9-fluorenone, anthrone, xanthone, thioxanthone, 2-(3-sulfopropyloxy)thioxanthen-9-one, acridone, dibenzosuberone, acetophenone, and chromone. Examples of suitable thermal initiators include peroxides such as benzoyl peroxide, dibenzoyl peroxide, dilauryl peroxide, cyclohexane peroxide, methyl ethyl ketone peroxide, hydroperoxides (for example, tert-butyl hydroperoxide and cumene hydroperoxide), dicyclohexyl peroxydicarbonate, t-butyl perbenzoate, 2,2-azo-bis(isobutyronitrile), and the like or combinations thereof. Examples of commercially available thermal initiators include initiators available from Chemours (Wilmington, Delaware) under the VAZO trade designation including VAZO 67 (2,2'-azo-bis(2-methylbutyronitrile)), VAZO 64 (2,2'-azo-bis(isobutyronitrile)), and VAZO 52 (2,2'-azo-bis(2,2-dimethylvaleronitrile)), as well as from Elf Atochem North America (Philadelphia, PA) under the trade designation LUCIDOL 70 (benzoylperoxide). The initiator can be used in an amount effective to initiate free radical polymerization of the monomer(s). Such amount will vary depending upon, for example, the type of initiator and polymerization conditions utilized. The initiator generally can be used in amounts ranging from about 0.01 part by weight to about 5 parts by weight, based upon 100 parts total monomer. The polymerization solvent can be essentially any solvent that can substantially dissolve (or, in the case of emulsion or suspension polymerizations, disperse or suspend) the monomer(s) (and comonomer(s), if used). In many embodiments, the solvent can be water or a water/water-miscible organic solvent mixture. The ratio of water to organic solvent can vary widely, depending upon monomer solubility. With some monomers of Formula (I), the ratio can be greater than 1:1 (volume/volume) water to organic solvent such as greater than 5:1, greater than 7:1, or even greater than 10:1. If desired, a higher proportion of organic solvent (even up to 100 percent) can be used such as when the organic solvent is an alcohol. Any such water-miscible organic solvent preferably has no groups that would retard polymerization. In some embodiments, the water-miscible solvents can be protic group-containing organic liquids such as the lower alcohols having 1 to 4 carbon atoms, lower glycols having 2 to 6 carbon atoms, and lower glycol ethers having 3 to 6 carbon atoms and 1 to 2 ether linkages. In some embodiments, higher glycols such as poly(ethylene glycol) can be used. Specific examples include methanol, ethanol, isopropanol, n-butanol, t-butyl alcohol, ethylene glycol, methoxyethanol, ethoxyethanol, propoxyethanol, butoxyethanol, methyl carbitol, ethyl carbitol, and the like, and combinations thereof. In other embodiments, non-protic water-miscible organic solvents can be used. Such solvents include aliphatic esters (for example, methoxyethyl acetate, ethoxyethyl acetate, propoxyethyl acetate, butoxyethyl acetate, and triethyl phosphate), ketones (for example, acetone, methyl ethyl ketone, and methyl propyl ketone), and sulfoxides (for example, dimethyl sulfoxide). The monomer concentration in the polymerization solvent can vary, depending upon various factors including, but not limited to, the nature of the monomer or monomers, the extent of polymerization desired, the reactivity of the monomer(s), and the solvent used. Typically, the monomer concentration can range from about 0.1 to about 60 weight percent or even higher based on the total weight of monomers and solvent. For example, the monomer concentration can be at least 0.1, at least 0.5, at least 1, at least 2, at last 5, at least 10, at least 15, at least 20, at least 25, or at least 30 weight percent and up to 60, up to 55, up to 50, up to 45, up to 40, up to 35, up to 30, up to 25, or up to 20 weight percent based upon the total weight of monomer and solvent. Any of the optional second monomers described above for the grafted polymers can be included in the reaction mixture used to form the non-grafted polymer. The time and temperature used for the polymerization reaction using a thermal initiator can be any amount that is used in the art. Likewise, the time and radiation sources suitable for use with a photoinitiator can be any amount that is used in the art. An aqueous monomer mixture optionally can be formulated with relatively high levels of multifunctional (crosslinking) monomers or co-monomers (for example, from about 5 percent (%) by weight up to about 90 weight percent, based upon the total weight of monomer(s) and co- monomer(s)) and polymerized as a suspension or dispersion in a nonpolar, immiscible organic solvent, optionally in the presence of added porogen(s), to produce crosslinked, porous particles comprising monomeric units derived from the monomers of Formula (I). Such methods are described, for example, in U.S. Patent Nos.7, 098,253 (Rasmussen et al.), 7, 674,835 (Rasmussen et al.), 7,647,836 (Rasmussen et al.), and 7, 683,100 (Rasmussen et al.). Examples Calculation of pKa The pKa values were calculated using the EpiK pKa prediction tool with the Maestro GUI, both obtained from Schrödinger LLC (New York, NY). Computations were performed on the monomeric species with Maestro version 2021-4 set to “Sequential pKa Values” with H₂O as the solvent to a pH of 9 and allowed tautomerization. Hammett and Taft relations were used by the EpiK pKa prediction tool to predict protonation states based on functional group structure and sensitivity to perturbations from the rest of the molecule. The model is empirically driven and trained on a combination of publicly reported pKa values and proprietary internal measurements performed by Schrodinger. The Hammett and Taft Equation (Equation 1) assumes that each chemical group has a base pKa ( ^^ ^^_^ ^{^}) that is then modulated by a correction factor ( ^^ ^^, Equation 2) as well as a perturbility term ( ^^) for the target constituent group and influence constants ( ^^) for other substituent groups in the molecule. Equation 1 ^^ ^^_^ ൌ ^^ ^^_^ ^{^} ^ CF െ ∑_^ ^^_^ ∑_^ ^^_^ Equation 2 ^{^ౄ^} ^^ ^^ In the equations, ^^_ୌ^ denotes the number of from an acidic molecule while ^^_ୌୖ represents the number of ways to is an adjustment term for aliphatic rings. Uncertainty for the pKa value is calculated from the uncertainties of ^^ ^^_^ ^{^} and ^^. Novel molecules with low coverage for ^^ ^^_^ ^{^} and ^^ have a default uncertainty of 2.0 pKa units. The calculated pKa values for some representative monomers of the disclosure are provided in Table 1. Table 1. Monomers and Calculated pKa Values pKa Monomer Structure Abbreviated Monomer Name Value +/- IEM/N-phenylpiperazine 3.61 1.6 IEM/N-(2- p_{yrimidyl)piperazine} ^{3.79 0.86} IEM/N-(2- aminoethyl)thiomorpholine- 3.81 1.04 1,1-dioxide IEM/N-(4- h_{ydroxyphenyl)piperazine} ^{4.33 1.6} IEM/N-(3- aminopropyl)thiomorpholine- 1,1-dioxide 4.7 1.4 O CH₃ IEM/N-(4- O H N _meth ^{4.87 2.22} N N _{oxyphenyl)piperazine} O O IEM/N-(4- n_{itrophenyl)piperazine} ^{5.67 1.6} IEM/N-(2- aminoethyl)thiomorpholine- 6.12 1.04 1-oxide V^DM/N-(2- a_{minoethyl)morpholine} ^{6.66 0.67} IEM/N-(2-pyridyl)piperazine 6.67 1.12 IEM/N-phenethylpiperazine 6.83 2.22 IEM/N-(2- a_{minoethyl)morpholine} ^{6.83 0.67} IEM/N-(3- aminopropyl)thiomorpholine- 7.01 1.04 1-oxide IEM/N-(2- h_{ydroxyethyl)piperazine} ^{7.02 2.22} VDM/N-(3- a_{minopropyl)morpholine} ^{7.04 0.67} IEM/N-(2- m_{ethoxyethyl)piperazine} ^{7.21 2.22} IEM/N-(3- a_{minopropyl)morpholine} ^{7.42 0.67} IEA/N-methylpiperazine 7.46 2.22 IEM/N-methylpiperazine 7.46 2.22 IEM/N-(2- _{aminoethyl)thiomorpholine} ^{7.58 1.04} IEM/N-benzylpiperazine 7.69 2.22 IEM/1-amino-4- 7.96 2.22 methylpiperazine & & 5.30 2.22 IEM/1-(3-aminopropyl)-4- 8.03 2.22 methylpiperazine & & 8.31 2.22 IEM/piperazine 8.36 0.7 IEM/N-(3- _{aminopropyl)thiomorpholine} ^{8.46 1.04 IEM/N-} m_{ethylhomopiperazine} ^{9.44 0.8} Materials N-(2-hydroxyethyl)piperazine, 1-amino-4-methylpiperazine, N-phenethylpiperazine, 1-(2- pyridyl)piperazine, 1-(2-pyrimidyl)piperazine, and ethylenediaminetetraacetic acid (EDTA) were obtained from Alfa Aesar, Ward Hill, MA. N-(2-aminoethyl)morpholine and N-(3-aminopropyl)morpholine were obtained from TCI America, Portland, OR. N-phenylpiperazine, N-methylpiperazine, 2-hydroxyethylmethacrylate (HEMA), 2-morpholinoethane-1- sulfonic acid, 3-morpholinopropane-1-sulfonic acid, tris(hydroxymethyl)aminomethane, N-cyclohexyl-2- aminoethane-1-sulfonic acid, and 4-hydroxy-TEMPO were obtained from the Sigma-Aldrich Company, St. Louis, MO. Phosphate buffered saline (PBS, 1X), Dulbecco’s Modified Eagle Medium (DMEM), trypan blue (0.4% solution), and fetal bovine serum (FBS) were obtained from ThermoFisher Scientific, Waltham, MA. 1-Boc-piperazine was obtained from Oakwood Chemical, Estill, SC. 2-Vinyl-4,4-dimethylazlactone (VDM) was obtained from SNPE, Inc., Princeton, NJ, and redistilled before use. 2-Isocyanatoethylmethacrylate (IEM, Karenz MOI) and 2-isocyanatoethylacrylate (IEA, Karenz AOI) were from Showa Denko KK, Tokyo, Japan. 3-Carboxybenzophenone was obtained from the Sigma-Aldrich Company. A solution of 3- carboxybenzophenone, sodium salt (C-BP) (0.033 g/mL) was prepared by dissolving 3- carboxybenzophenone in 1M sodium hydroxide and diluting with deionized water. Method 1. Preparation of Polymer Grafted Membranes Grafting solutions (5 grams each) of monomers were prepared at various monomer concentrations in deionized water, based on the measured % solids of the monomer solution. Each monomer solution also contained 3-carboxybenzophenone, sodium salt (62.5 microliters of a 0.033 g/mL aqueous solution). For each grafting solution, a nylon membrane substrate (#080ZN, reinforced nylon 6,6 membrane, 0.8 micrometer nominal pore size, obtained from the 3M Company, St. Paul, MN) was placed on a sheet of polyester film, and sufficient grafting solution was pipetted onto the top surface of the substrate to completely wet the substrate. The coating solution was allowed to soak into the substrate for about 1 minute, and then a second sheet of polyester film was placed on top of the substrate. A 2.28 kg cylindrical weight was rolled over the top of the resulting three-layer sandwich to squeeze out excess coating solution. Ultraviolet (UV)-initiated grafting was conducted by irradiating the sandwich using a UV stand (Classic Manufacturing, Inc., Oakdale, MN) equipped with 18 bulbs (Sylvania RG240W F40/350BL/ECO, 10 above and 8 below the substrate, 1.17 meters (46 inches) long, spaced 5.1 cm (2 inches) on center), with an irradiation time of 15 minutes. The polyester sheets were removed and the resulting grafted membrane was placed in a polyethylene bottle. The bottle was filled with 0.9% saline solution, sealed and placed on a laboratory bottle roller for 30 minutes to wash off any residual monomer or ungrafted polymer. The saline solution was poured off and replaced with deionized water for an additional 30 minutes of washing. Washing was repeated with fresh 0.9% saline solution for 30 minutes, followed by 30 minutes of washing with deionized water (2 times). Following the wash steps, the polymer grafted membrane was air dried. Graft density of the polymer grafted membrane was estimated based on mass gain. Method 2. Bovine Serum Albumin (BSA) Static (Equilibrium) Binding Capacity Method Individual disks (16 mm diameter) of polymer grafted membranes were die-punched from sheets of polymer grafted membranes. A single disk was placed in a 5 mL centrifuge tube that contained 4.5 mL of bovine serum albumin (product no. A-7906, Sigma-Aldrich) prepared at a concentration of about 4 mg/mL in a buffer solution selected to have a pH of 5.0, 6.0, 7.0, 8.0, or 9.0. Each centrifuge tube was capped and tumbled overnight (typically 14 hours) on a rotating mixer. The resulting supernatant solution was analyzed using a UV-VIS spectrometer at 280 nm (with background correction applied at 325 nm). The static binding capacity for each disk was determined by comparison to the absorption value of the supernatant solution to the absorbance value of the starting BSA solution, and the results are reported in mg/mL (i.e., mg of BSA bound to membrane/mL of membrane volume) and reported as the average of three replicates. All the buffer solutions were prepared using deionized water. The pH 5.0 buffer was acetate buffer (10 mM). The pH 6.0 buffer was MES (2-morpholinoethane-1-sulfonic acid) buffer (25 mM). The pH 7.0 buffer was MOPS (3-morpholinopropane-1-sulfonic acid) buffer (10 mM). The pH 8.0 buffer was TRIS (tris(hydroxymethyl)aminomethane) buffer (25 mM). The pH 9.0 buffer was CHES (N- cyclohexyl-2-aminoethane-1-sulfonic acid) buffer (20 mM). The buffer solutions were prepared by mixing appropriate amounts of the acid and base form of the buffer salt to attain the desired pH. Recipes for the preparation of each individual buffer were determined using the ‘Calculator for pH Buffers’ software tool provided on the website of the Centre for Proteome Research at the University of Liverpool (website: www.liverpool.ac.uk/pfg/Tools/BufferCalc/Buffer.html). For higher ionic strengths, the appropriate amount of sodium chloride was added. Method 3. Preparation of Filtration Capsules Plastic filtration capsules were used for testing some of the grafted membranes. Each capsule consisted of a sealed, circular housing. The capsule housing was prepared from two halves (upper and lower halves) which were mated and sealed together at the perimeter after a grafted membrane was inserted in the internal cavity of the lower housing. Fluid inlet and vent ports were located on the upper portion of the housing and a fluid outlet port was located on the lower portion of the housing. The outlet port was centered in the middle of the lower housing surface. Experimental capsules were prepared as follows. A single disk (15.9 mm diameter) of grafted membrane was placed in the bottom of the lower housing and overlayed with two polypropylene rings (15.9 mm outer diameter, 13.9 mm inner diameter, 1.3 mm thickness) and a silicone gasket (15.9 mm outer diameter, 9.5 mm inner diameter, 3 mm thickness). The upper and lower housings were mated together and ultrasonically welded using a Branson 20 kHz Ultrasonic welder (Model 2000xdt, Emerson Electric Company, St. Louis, MO) to form a finished filtration capsule. The overall outer diameter of the finished capsule was about 4.3 cm and the overall height including inlet, outlet, and vent ports was about 4.8 cm. The effective filtration area of the capsule was 1.0 cm² and the bed volume of the media was 0.3 mL. Method 4. Preparation of 96-well Centrifugation Testing Apparatus for Membrane Samples Two 7.5 mm disks of grafted membrane (prepared as described in Method 1) were inserted into each well of a 96-well EMPORE Filter plate (product no.6065, 3M Company) in which the original solid phase extraction material was previously removed. The filter disks were held in place by a plastic O-ring of the appropriate dimension to provide a robust seal, such that when phosphate buffered saline (PBS, 1X) was applied to the top of the membrane layers in each well, no liquid flowed through the membrane when the plate was placed on a horizontal surface for 10 minutes. In operation, flow of liquid through the membranes was achieved by centrifugation of the plate. Method 5. Preparation of Phi6 Virus Stock Culture Phi6 bacteriophage (DSMZ 21518) was obtained from the DSMZ German Collection of Microorganisms and Cell Cultures, Braunschweig, Germany. The virus culture was produced by inoculating 100 mL of tryptic soy broth (Hardy Diagnostics, Santa Maria, CA) plus 5 mM magnesium sulfate with 1.5 mL of Pseudomonas syringae (DSMZ 21482) host bacteria overnight culture. The culture was grown at 25 °C with shaking at 210 revolutions per minute (rpm) for 2 hours. The culture was then inoculated with 10⁹ plaque forming units (pfu) of Phi 6 virus. The inoculated culture was grown for an additional 3 hours at 25 °C with shaking at 210 rpm. Cells were removed by centrifugation at 3700 x g and the supernatant was filtered through a 0.2 micron PES membrane filter. Method 6. Determination of Phi6 Virus Concentration by Plaque Assay Phi6 virus samples were serially diluted (10-fold). Molten tryptic soy top agar (2.5 mL of tryptic soy broth with 5 mM MgSO4 and 0.9% agar) was mixed with 50 microliters of Pseudomonas syringae host bacteria overnight culture and 100 microliters of diluted Phi 6 virus. The mixture was poured on top of a standard tryptic soy agar plate and incubated overnight at 25 °C. Following incubation, the plaque- forming units (pfu) were counted. The number of pfu was correlated with virus particle number. The virus particle concentration (particles/mL) was calculated from the pfu count adjusted for dilution. Method 7. Preparation of Phi6 Virus Stock from Agar Plates An overnight culture of Pseudomonas syringae (DSMZ 21482) was prepared by picking a single colony into 5-7 mL of liquid tryptic soy broth and incubating in a shaking incubator (210-250 rpm) overnight at 25 °C. A 50 microliter aliquot of the overnight culture broth was added to molten soft tryptic soy top agar (5 mL of tryptic soy broth with 5 mM MgSO₄ and 0.75% agar). The molten agar was poured on top of a standard tryptic soy agar plate and allowed to solidify. Stock Phi6 bacteriophage (100 microliters, DSMZ PN21518) at 1E+09 pfu/mL was spread on top of the solidified top agar plate and allowed to incubate at room temperature overnight at room temperature (approximately, 22-25 °C). The produced virus was harvested from the agar by scraping the layer of top ager from the plates into a 50 mL conical tube, adding 20 mL of phage storage buffer (50 mM NaHPO₄, 22 mM KH₂PO₄, 85.5 mM NaCl, 1 mM MgSO₄, 1 mM CaCl₂), and vortexing for 15-30 minutes to release the virus into the buffer. The mixture is then centrifuged at 3000 x g for 15 minutes and filtered through a 0.2 um PES membrane. Method 8. Determination of Phi6 Virus Concentration by Surface Spotting Method Phi6 virus samples were serially diluted (10-fold) in a 96 well plate (down to a 100,000x dilution). Molten soft tryptic soy top agar supplemented with MgSO₄ (5 mL of tryptic soy broth with 5 mM MgSO₄ and 0.9% agar) was mixed with 50 microliters of Pseudomonas syringae host bacteria overnight culture and poured on top of a standard tryptic soy agar plate. After the agar is solidified, 3 microliters of each dilution were spotted onto the surface of the prepared plate in an array. The plates were incubated overnight at 25 °C. Following incubation, the virus was quantified by counting particle forming units in the 3 microliter spot at the highest dilution where plaques were countable. The virus particle concentration (particles/mL) was calculated from the pfu count adjusted for dilution. Method 9. Preparation and Characterization of Lentivirus Culture Lentivirus containing a GFP reporter gene was produced in LV-MAX Viral production suspension cells (product no. A35347, ThermoFisher Scientific) provided with the GIBCO LV-MAX Lentiviral Production System (product no. A35684, ThermoFisher Scientific). The cells were transfected with pLenti-GFP control vector (product no. CALTV-400, Cell Biolabs San Diego) and LV-MAX lentiviral packaging mix plasmids (product no. A43237, ThermoFisher Scientific) according to the manufacturer’s instructions for the LV-MAX Lentiviral Production System. Cells were maintained in LV-MAX culture medium consisting of GIBCO LV-MAX Production Medium (product no. A3583402, ThermoFisher Scientific) supplemented with GIBCO penicillin-streptomycin (product no.15140122, ThermoFisher Scientific) at the recommended 1X concentration. Cell density and viability of LV-MAX suspension cells were estimated by manual counting of trypan blue stained cell samples using a hemacytometer. The lentivirus containing supernatant was harvested on day 3 post transfection by centrifugation of the culture at 1300 x g for 15 minutes, followed by filtration of the supernatant through a 0.45 micron filter PES filter (product no.295-4545, ThermoFisher Scientific). Method 10. Determination of Lentivirus Titer Lentivirus titer was determined using a titration assay for transducing units/mL (TU/mL). LentiX-293T cells (product no.632180, Takara Bio USA, Mountain View, CA) were maintained in Dulbecco’s Modified Eagle Medium (DMEM) supplemented with 10% by volume fetal bovine serum (FBS) and GIBCO penicillin-streptomycin and seeded at a density of 10,000 cells/well in a black-walled 96-well culture plate. After cells had attached, test samples were serially diluted in culture medium supplemented with polybrene at 8 micrograms/mL (product no. TR1003G, Sigma-Aldrich) and the medium for the cells was removed and replaced with medium containing the serial dilutions. The plates were then centrifuged at 900 x g for 30 minutes, followed by incubation for 96 hours, at which time the “% GFP positive cells” were determined using a BioTek Cytation 5 Imaging reader (Agilent Technologies, Santa Clara, CA). Settings and gain for the GFP channel and focal point were adjusted for the plate/cells used. All plates were scanned on the same day with the same settings. Wells with a “% GFP positive cells” reading between 1% and 20% were used to calculate the titer according to the equation TU/mL = [Fraction of GFP positive cells]*[10,000 cells seeded/well]/[mL of original viral sample added to well]. Method 11. Determination of DNA concentration DNA was extracted from the collected samples using a 96 well format DNA extraction kit (product no. D100W, Cygnus Technologies, Southport, NC) according to the manufacturer’s instructions. Extracted DNA was then quantified by fluorescence using a QUANT-IT PICOGREEN dsDNA Assay Kit (product no. P7589, ThermoFisher Scientific) according to the manufacturer’s instructions. Method 12. Measurement of Conductivity and pH Conductivity and pH measurements were made using a calibrated Orion Star A215 pH/Conductivity Benchtop Multiparameter Meter (ThermoFisher Scientific). The instrument was calibrated for conductivity measurements using Oakton 1.413 mS/cm and 12.88 mS/cm standard solutions (Cole-Parmer, Vernon Hills, IL). The instrument was calibrated for pH measurements using ORION pH 4.01, 7.00, and 10.01 standard solutions (ThermoFisher Scientific). Example 1. Preparation of 2-[[4-(2-hydroxyethyl)piperazine-1-carbonyl]amino]ethyl 2-methylprop-2-enoate (IEM/N- (2-hydroxyethyl)piperazine) N-(2-hydroxyethyl) into a 250 mL round- bottomed flask equipped with a magnetic stirrer. Deionized water (50 mL) was added and the stirred mixture was placed in an ice-water bath under a slow nitrogen purge. An aliquot (100 microliters) of 4- hydroxy-TEMPO solution (10,000 ppm in deionized water) was added and the solution was stirred for 10 minutes followed by the addition of IEM (3.5 mL). The solution was then stirred for 15 minutes followed by the addition of 3.5 mL of IEM (total amount of IEM = 7.0 mL, 0.05 mole). The mixture was stirred for 15 minutes and then removed from the ice-water bath. Concentrated hydrochloric acid was then added by dropwise addition with stirring to obtain a solution pH 6.0 as measured by pH paper. The cloudy solution was filtered to give 2-[[4-(2-hydroxyethyl)piperazine-1-carbonyl]amino]ethyl 2- methylprop-2-enoate as a clear, colorless filtrate with a % solids of 23.95%. ¹H-NMR (D₂O): δ 1.74 (s, 3H), 3.13 (m, 6H), 3.33 (t, 2H), 3.51 (broad m, 4H), 3.76 (t, 2H), 4.09 (t, 2H), 5.55 (s, 1H), 5.95 (s, 1H). Percent solids was determined using an Ohaus moisture balance (Model Number MB35, obtained from the Ohaus Corporation, Parsippany, NJ). A sample of the aqueous monomer solution was acidified to a pH of about 1 with 0.1 N HCl and then titrated with 0.1 N NaOH to provide an experimental pKa estimation of 6.8 for IEM/N-(2-hydroxyethyl)piperazine. Example 2. Preparation of 2-[(4-methylpiperazine-1-carbonyl)amino]ethyl 2-methylprop-2-enoate (IEM/N- The general procedure as with the exception that N-(2- hydroxyethyl)piperazine was replaced with N-methylpiperazine (5.00 grams, 0.05 mole). The resulting filtrate of 2-[(4-methylpiperazine-1-carbonyl)amino]ethyl 2-methylprop-2-enoate had 21.65% solids. ¹H- NMR (D₂O): δ 1.73 (s, 3H), 2.71 (s, 3H), about 3.0 (broad, 8H), 3.32 (t, 2H), 4.08 (t, 2H), 5.54 (s, 1H), 5.94 (s, 1H). Example 3. Preparation of 2-(2-morpholinoethylcarbamoylamino)ethyl 2-methylprop-2-enoate (IEM/N-(2- aminoethyl)morpholine) The general procedure with the exception that N-(2- hydroxyethyl)piperazine was replaced with N-(2-aminoethyl)morpholine (6.51 grams, 0.05 mole). The resulting filtrate of 2-(2-morpholinoethylcarbamoylamino)ethyl 2-methylprop-2-enoate had 23.55% solids. ¹H-NMR (D₂O): δ 1.75 (s, 3H), 3.07 (t, 2H), 3.19 (broad s, 4H), 3.28 (t, 2H), 3.35 (t, 2H), 3.80 (broad s, 4H), 4.07 (t, 2H), 5.56 (s, 1H), 5.96 (s, 1H). Example 4. Preparation of 2-(3-morpholinopropylcarbamoylamino)ethyl 2-methylprop-2-enoate (IEM/N-(3- aminopropyl)morpholine) The general procedure d with the exception that N-(2- hydroxyethyl)piperazine was replaced with N-(3-aminopropyl)morpholine (7.21 grams, 0.05 mole). The resulting filtrate of 2-(3-morpholinopropylcarbamoylamino)ethyl 2-methylprop-2-enoate had 23.75% solids. ¹H-NMR (D₂O): δ 1.74 (s and m, 5H), 3.00 (m, 2H), 3.04 (t, 2H), 3.15 (broad s, 4H), 3.27 (t, 2H), 3.79 (broad s, 4H), 4.05 (t, 2H), 5.55 (s, 1H), 5.96 (s, 1H). Example 5. Preparation of 2-[(4-methylpiperazin-1-yl)carbamoylamino]ethyl 2-methylprop-2-enoate (IEM/1-amino- 4-methylpiperazine) The general procedure as with the exception that the total amount of IEM used was 3.5 mL (0.025 mole) and the N-(2-hydroxyethyl)piperazine was replaced with 1-amino-4-methylpiperazine (2.88 grams, 0.025 mole). The resulting filtrate of 2-[(4-methylpiperazin-1- yl)carbamoylamino]ethyl 2-methylprop-2-enoate had 23.1% solids. ¹H-NMR (D₂O): δ 1.75 (s, 3H), 2.77 (s overlapping another absorption, 5H), 3.02 (broad d, 2H), 3.12 (broad t, 2H), 3.32 (t, 2H), 3.39 (broad d, 2H), 4.11 (t, 2H), 5.56 (s, 1H), 5.96 (s, 1H). Example 6. Preparation of 2-[(4-phenylpiperazine-1-carbonyl)amino]ethyl 2-methylprop-2-enoate (IEM/N- phenylpiperazine) N-phenylpiperazine (4.05 into a 250 mL round-bottomed flask equipped with a magnetic stirrer. Diethyl ether (75 mL) was added and the stirrred mixture was placed in an ice-water bath under a slow nitrogen purge. The mixture was stirred for 10 minutes. IEM (3.5 mL) was added by pipette and the mixture was stirred for 75 minutes. The colorless precipitate that formed was filtered and dried to give 5.3 grams of 2-[(4-phenylpiperazine-1-carbonyl)amino]ethyl 2-methylprop- 2-enoate. ¹H-NMR (CDCl₃): δ 1.96 (s, 3H), 3.18 (m, 4H), 3.53 (m, 4H), 3.59 ((q, 2H), 4.31 (t, 2H), 5.00 (broad t, 1H), 5.61 (s, 1H), 6.14 (s, 1H), 6.92 (m, 3H), 7.28 (m, 2H). Example 7. Preparation of 2-[[4-(2-phenylethyl)piperazine-1-carbonyl]amino]ethyl 2-methylprop-2-enoate (IEM/N- phenethylpiperazine) N-phenethylpiperazine into a 250 mL round-bottomed flask equipped with a magnetic stirrer. and the stirred mixture was placed in an ice-water bath under a slow nitrogen purge. The mixture was stirred for 10 minutes. IEM (3.5 mL) was added by pipette. The mixture was stirred for 10 minutes. A second portion of IEM (3.5 mL) was added by pipette and the mixture was stirred for 30 minutes. The reaction mixture was then poured into a separatory funnel. A 50 mL portion of 1N HCl was added to the funnel and the funnel was shaken. The funnel was placed in a stand to allow the mixture to separate into 3 layers. The lower layer was discarded, and the remaining layers were separated by collecting into two vessels. NMR analysis indicated that both layers contained the desired product. The layers were combined, and 50 microliters of 4-hydroxy-TEMPO solution (10,000 ppm in deionized water) was added. A majority of the dichloromethane was removed by rotary evaporation to provide a clear, light yellow aqueous solution of 2-[[4-(2-phenylethyl)piperazine-1-carbonyl]amino]ethyl 2-methylprop-2-enoate with a pH 4-5 (measured with pH paper) and % solids of 21.6%. ¹H-NMR (D₂O): δ 1.73 (s, 3H), 2.86 (broad s, 2H), 2.92 (m, 2H), 3.07 (broad s, 2H), 3.24 (m, 2H), 3.32 (t, 2H), 3.42 (broad s, 4H), 3.92 (broad s, 2H), 4.07 (t, 2H), 5.54 (s, 1H), 5.95 (s, 1H), 7.17 (m, 3H), 7.23 (m, 2H). Example 8. Preparation of 2-(piperazine-1-carbonylamino)ethyl 2-methylprop-2-enoate (IEM/piperazine) 1-Boc-piperazine (18.6 a 250 mL round-bottomed flask equipped with a magnetic stirrer. Dichloromethane (75 mL) was added, and the stirred mixture was placed in an ice-water bath under a slow nitrogen purge. The mixture was stirred for 10 minutes. IEM (3.5 mL) was added by pipette and the mixture was stirred for 1 minute, followed by the addition of a second portion of IEM (3.5 mL). Two additional 3.5 mL portions of IEM were added spaced at 5 minutes intervals (total of 14 mL of IEM added in 4 equal portions). The resulting mixture was stirred for 30 minutes and then the solvent was removed by rotary evaporation to give the BOC-protected IEM/piperazine intermediate as a colorless solid (33.5 grams). ¹H-NMR (CDCl₃): δ 1.39 (s, 9H), 1.87 (s, 3H), 3.28 (m, 4H), 3.35 (m, 4H), 3.47 (q, 2H), 4.21 (t, 2H), 5.12 (broad t, 1H), 5.53 (s, 1H), 6.06 (s, 1H). BOC-protected IEM/piperazine intermediate (5.0 grams) was placed into a round-bottomed flask, dissolved in about 5 mL of trifluoroacetic acid, and then heated at 50 ^oC for 1 hour. The flask was placed on a rotary evaporator at 50 ^oC for 90 minutes to provide 2-(piperazine-1-carbonylamino)ethyl 2- methylprop-2-enoate containing some residual trifluoroacetic acid. ¹H-NMR (CD₃OD): δ 1.91 (s, 3H), 3.19 (t, 4H), 3.45 (t, 2H), 3.64 (t, 4H), 4.21 (t, 2H), 5.61 (s, 1H), 6.10 (s, 1H). The residue was dissolved in 20 mL deionized water to provide an approximately 0.5 M monomer solution that was used for membrane grafting. Example 9. Preparation of 2-[(4-methyl-1,4-diazepane-1-carbonyl)amino]ethyl 2-methylprop-2-enoate (IEM/N- The general procedure as with the exception that N-(2- hydroxyethyl)piperazine was replaced with N-methylhomopiperazine (5.71 grams, 0.05 mole). The resulting filtrate of 2-[(4-methyl-1,4-diazepane-1-carbonyl)amino]ethyl 2-methylprop-2-enoate had 22.45% solids. ¹H-NMR (D₂O): δ 1.69 (m, 2H), 1.71 (s, 3H), 2.08 (s, 3H), 2.37 and 2.41 (2 m, 4H), 3.20 (m, 2H), 3.28 (m, 4H), 4.05 (t, 2H), 5.52 (s, 1H), 5.93 (s, 1H). Example 10. Preparation of 2-[(4-methylpiperazine-1-carbonyl)amino]ethyl prop-2-enoate (IEA/N-methylpiperazine) N-methylpiperazine (2.0 into a 50 mL round-bottomed flask equipped with a magnetic stirrer. Dichloromethane (20 mL) was added and the stirred mixture was placed in an ice-water bath under a slow nitrogen purge. The mixture was stirred for 10 minutes. IEA (2.56 mL) was added by pipette and the mixture was stirred for 15 minutes to provide 2-[(4- methylpiperazine-1-carbonyl)amino]ethyl prop-2-enoate as a solution in dichloromethane. ¹H-NMR (CDCl₃): δ 2.22 (s, 3H), 2.31 (t, 4H), 3.30 (t, 4H), 3.46 (q, 2H), 4.20 (t, 2H), 4.93(broad t, 1H), 5.79 (dd, 1H), 6.07 (dd, 1H), 6.36 (dd, 1H). Example 11. Preparation of 2-methyl-N-(2-morpholinopropyl)-2-(prop-2-enoylamino)propenamide (VDM/N-(3- aminopropyl)morpholine) O H _O The general procedure as described in Example 4 was followed with the exception that IEM was replaced with VDM (6.95 g). The resulting filtrate of VDM/N-(3-aminopropyl)morpholine had 23.2 % solids. ¹H-NMR (D₂O): δ 1.29 (s, 6H), 1.73 (p, 2H), 2.89 (m, 2H), 3.05 (broad s, 4H), 3.11 (t, 2H), 3.76 (broad s, 4H), 5.58 (d, 1H), 5.99 (d, 1H), 6.11 (dd, 1H). Example 12. Preparation of 2-(4-(pyridin-2-yl)piperazine-1-carboxamido)ethyl methacrylate (IEM/N-(2- pyridyl)piperazine) A suspension of 1-(2- in 30 mL of water was cooled to 0 °C. IEM (3.46 mL, 24.5 mmol) a period of 3 minutes. A white solid formed. After stirring for 20 minutes, the white solid was isolated by filtration and washed with several portions of water. The solid was transferred to a crystallizing dish and allowed to air dry for several days to give 6.62 g of 2-(4-(pyridin-2-yl)piperazine-1-carboxamido)ethyl methacrylate as a white solid.¹H NMR (500 MHz, CD₃OD) δ 8.07-8.14 (m, 1 H) 7.59 (ddd, J=8.7, 7.1, 2.0 Hz, 1 H) 6.84 (d, J=8.7 Hz, 1 H) 6.71 (dd, J=6.7, 5.4 Hz, 1 H) 6.14 (s, 1 H) 5.61-5.68 (m, 1 H) 4.24 (t, J=5.7 Hz, 2 H) 3.53 (s, 8 H) 3.49 (t, J=5.7 Hz, 2 H) 1.94 (s, 3 H). Example 13. Preparation of 2-(4-(pyrimidin-2-yl)piperazine-1-carboxamido)ethyl methacrylate (IEM/N-(2- pyrimidyl)piperazine) A suspension of 1-(2- in 25 mL of water was cooled to 0 °C. IEM (3.10 mL, 21.9 mmol) was added to the stirred solution over a period of 3 minutes. A white solid formed. An additional 25 mL of water was added, and the mixture was stirred for 15 minutes. The white solid was isolated by filtration and washed with several portions of water. The solid was transferred to a crystallizing dish and allowed to air dry overnight to give 6.11 g of 2-(4-(pyrimidin-2- yl)piperazine-1-carboxamido)ethyl methacrylate as a white solid.¹H NMR (500 MHz, CD₃OD) δ 8.35 (d, J=4.8 Hz, 2 H) 6.63 (t, J=4.8 Hz, 1 H) 6.14 (s, 1 H) 5.65 (m, 1 H) 4.24 (t, J=5.7 Hz, 2 H) 3.81 (m, 4 H) 3.49 (m, 6 H) 1.95 (m, 3 H). Example 14. Preparation of 2-methyl-N-(4-methylpiperazin-1-yl)-2-(prop-2-enoylamino)propanamide (VDM/1-amino-4-methylpiperazine) The general procedure as with the exception that the IEM was replaced with VDM (1.5 mL, . of 2-methyl-N-(4-methylpiperazin- 1-yl)-2-(prop-2-enoylamino)propanamide had 21.85% solids. ¹H-NMR (D₂O): δ 1.22 (s, 6H), 2.70 (s, 3H), 3.5-2.5 (br. m, 8H), 5.50 (d, 1H), 5.92 (d, 1H), 6.06 (dd, 1H). Example 15. Nylon membranes were grafted with a monomer solution of Example 1 (IEM/N-(2- hydroxyethyl)piperazine) or Example 2 (IEM/N-methylpiperazine) according to the procedure described in Method 1. Each membrane was coated and grafted with a single monomer solution at a concentration of 0.25 M, 0.375 M, or 0.5 M. The grafted membranes were evaluated for BSA binding (mg/mL) at pH 6.0, pH 7.0, and pH 8.0 according to the procedure of Method 2. The results are reported in Table 2. The results in Table 2 show that the polymer grafted membrane prepared from the IEM/N-(2- hydroxyethyl)piperazine monomer (calculated pKa of 7.02) lost about 40% of its binding capacity for BSA when the pH of the buffer was increased from pH 6.0 to pH 7.0 and >80% of its capacity when the pH was increased from pH 6.0 to pH 8.0. In contrast the polymer grafted membrane prepared from the IEM/N-methylpiperazine monomer (calculated pKa of 7.46) lost only about 20% of its binding capacity for BSA when the pH of the buffer was increased from pH 6.0 to pH 7.0 and >80% of its capacity when the pH was increased from pH 6.0 to pH 8.0. Table 2. Monomer BSA Binding Capacity (mg/mL) Calculated Monomer used Concentration Graft Density Monomer for Grafting in Grafting (mmol/g) pH 6.0 pH 7.0 pH 8.0 pKa Solution (M) Example 1 7.02 0.25 0.25 39 25 7 Example 1 7.02 0.375 0.36 59 36 NT Example 1 7.02 0.5 0.58 87 56 NT Example 2 7.46 0.25 0.30 52 45 9 Example 2 7.46 0.375 0.48 84 67 NT Example 2 7.46 0.5 0.68 110 89 NT NT = Not Tested Example 16. A polyethersulfone membrane (MacroPES with nominal pore size 5 microns, obtained from the 3M Company) was grafted using the monomer of Example 1 (IEM/N-(2-hydroxyethyl)piperazine, pKa 7.02) with a 0.75 M monomer concentration, irradiation time of 20 minutes, and no photoinitiator (C-BP) included in the grafting solution. The resulting grafted membrane had a graft density of 1.04 mmol/g. The grafted substrate was tested for static BSA binding capacity at pH 6.0 in MES buffer according to the procedure of Method 2. The static BSA binding capacity was 114 mg/mL. The supernatant BSA solution was decanted from the centrifuge tube and the membrane disks were sequentially washed 3 times with 4.5 mL of fresh MES buffer (pH 6.0). Each washing procedure was for 30 minutes using a rotary mixer. The final wash buffer was decanted from the centrifuge tube and the bound BSA was eluted from a disk by adding 4.5 mL of TRIS buffer having a pH of 8.0 and tumbling the centrifuge tube for 30 minutes. The eluate was assayed for BSA concentration and the measured BSA concentration was then used to calculate an eluted Binding Capacity (BSA eluted binding capacity = 119 mg/mL). The results show that BSA protein was bound to the membrane using buffer at near neutral pH and then quantitatively eluted from the membrane via a mild adjustment of the eluent pH. Example 17. Nylon membranes were grafted with a monomer solution selected from Example 3 (IEM/N-(2- aminoethyl)morpholine), Example 4 (IEM/N-(3-aminopropyl)morpholine), Example 5 (IEM/1-amino-4- methylpiperazine), Example 7 (IEM/N-phenethylpiperazine), or Example 8 (IEM/piperazine) according to the procedure described in Method 1. Each membrane was coated and grafted with a single monomer solution at a concentration of 0.375 M, 0.5 M, or 0.625 M. The grafted membranes were evaluated for BSA binding capacity (mg/mL) at pH 5.0, pH 6.0, pH 7.0, pH 8.0 and pH 9.0 according to the procedure of Method 2. The results are reported in Table 3. Table 3. Calculate Monomer Graft BSA Binding Capacity (mg/mL) Monomer d concentratio Density used for pH pH pH pH pH Monomer n in Grafting (mmol/g Grafting 5.0 6.0 7.0 8.0 9.0 pKa Solution (M) ) Example 6.83 0.375 0.38 97 60 48 16 NT 3 Example 6.83 0.5 0.61 137 102 109 43 NT 3 Example 6.83 0.625 0.79 143 124 151 62 NT 3 Example 7.42 0.5 0.51 NT 107 83 41 NT 4 Example 7.96 0.625 0.15 NT NT 46 30 9 5 Example 6.83 0.5 0.84 32 9 11 5 NT 7 Example 8.36 0.25 0.36 NT 81 66 NT NT 8 Example 8.36 0.5 0.80 NT 137 125 74 48 8 NT = Not Tested Example 18. Nylon membranes were grafted with a 0.5 M monomer solution of Example 1 (IEM/N-(2- hydroxyethyl)piperazine) or Example 2 (IEM/N-methylpiperazine) according to the procedure described in Method 1. The grafted membranes were evaluated for BSA binding capacity (mg/mL) according to the procedure of Method 2 at pH 7.0 using MOPS buffer solutions of varying ionic strengths. The ionic strengths of individual MOPS buffer solutions were adjusted to 50 mM and 150 mM by the addition of sodium chloride. The results are reported in Table 4. Table 4. BSA Binding Capacity (mg/mL) Monomer Calculated Graft MOPS MOPS Buffer MOPS Buffer (pH used for Monomer Density Buffer (pH (pH 7.0, Ionic 7.0, Ionic Strength = Grafting pKa (mmol/g) 7.0, no NaCl Strength = 50 150 mM added) mM) Example 7.02 0.58 56 31 13 1 Example 7.46 0.68 89 58 28 2 Example 19. Two buffer solutions were prepared and designated as Buffer A and Buffer B. Buffer A was 25 mM MES buffer (pH 6.0) and Buffer B was 25 mM MES buffer (pH 6.0) that contained 1M NaCl. A test sample of BSA (0.56 grams of BSA in 50 millilters of Buffer A) was prepared and then filtered using a 0.22 micron PES membrane filter (STERIFLIP Sterile Disposable Vacuum Filter Unit, MilliporeSigma, Burlington, MA). A nylon membrane was grafted with a monomer solution of Example 1 (IEM/N-(2- hydroxyethyl)piperazine, calculated pKa of 7.02) according to the procedure described in Method 1. The graft density was 0.36 mmol/g. Six 25 mm disks of the grafted membrane were stacked in a chromatography module with the stack of disks held in place using o-rings. The exposed disk frontal surface area was 284 mm². The module contained a straight, cylindrical polycarbonate body with a cap attached to one end of the body. The cap contained an inlet port and a vent port. The opposite end contained an outlet port with a stopcock. A finished module was attached to an AKTA avant chromatography system (Cytiva, Marlborough, MA) equipped with UV/VIS (280 nm absorbance setting) and conductivity detectors. The module was flushed with 5 mL of Buffer A at a flow rate of 1 mL/minute. Next, the BSA test sample was pumped through the module at a flow rate of 0.5 mL/minute, followed by 20 mL of Buffer A at a flowrate of 1 mL/minute to wash the membrane stack. In a final elution step, BSA was eluted from the membrane stack by pumping 20 mL of a 0-100% Buffer B:Buffer A gradient (i.e., the gradient was from 100% Buffer A to 100% Buffer B based on volume) at a flow rate of 1 mL/minute. BSA bound to the grafted membrane stack eluted at a buffer conductivity of ≥1 mS/cm. Example 20. The procedure of Example 19 was followed with the exception that the test sample was β- lactoglobulin from bovine milk (product no. L3908, Sigma-Aldrich) in 50 mL of Buffer A. β- lactoglobulin bound to the grafted membrane stack eluted at a buffer conductivity of ≥1 mS/cm. Example 21. Three buffer solutions were prepared using 50 mM TRIS buffer with the pH adjusted to 6.0, 7.0, or 8.0 and the conductivity adjusted to 5 mS/cm. The pH values were adjusted using either 1N HCl or 1N NaOH. The conductivity value was adjusted by adding 5M sodium chloride. Phi6 virus challenge solutions with virus concentrations listed in Table 5 were prepared by spiking each buffer solution with Phi6 virus stock culture described in Method 5. Filtration Capsules were prepared according to the procedure of Method 3 using a nylon membrane that had been grafted with a monomer solution of Example 1 (IEM/N-(2-hydroxyethyl)piperazine) according to the procedure described in Method 1. The grafted membrane had a graft density of 0.25 mmol/g. Each Phi6 virus challenge solution (7 mL) was pumped through an individual capsule at 0.5 mL/minute. The resulting filtrate was collected. The input challenge solution and the filtrate sample were measured for Phi6 content using the plaque assay described in Method 6. The log reduction values (LRV) from filtration were calculated by comparing the Phi6 virus concentrations of the filtrate samples to the Phi6 virus concentrations in the corresponding input challenge solutions before filtration (Equation 3). The results are reported in Table 5. The results show that a substantial amount of Phi 6 enveloped virus was bound to the grafted membrane when the challenge solution had a pH of 6.0-7.0. However when the challenge solution had a pH value of 8.0, the Phi6 virus flowed through the grafted membrane with almost no Phi6 virus bound to the grafted membrane. ^{Equation 3:} L_{RV ൌ log10^ ୡ୭୬ୡ^୬^୰ୟ^୧୭୬୭^ ^୧୰^^ ୧୬ ^ୟ୫୮୪^ ୠ^^୭୰^ ^୧୪^୰ୟ^୧୭୬ ^୮^^/୫^^ ୡ୭୬ୡ^୬^୰ୟ^୧୭୬୭^ ^୧୰^^ ୧୬ ^୦^ ^୧୪^୰ୟ^^ ^୮^^/୫^^ ]} Table 5. Monomer Calculated pH of Phi6 Virus Concentration LRV for Phi6 Virus used for Monomer Challenge of Challenge Solution using Filtration Grafting pKa Solution (pfu/mL) Capsule Example 1 7.02 6.0 4.0E+08 3.85 Example 1 7.02 7.0 2.9E+08 4.12 Example 1 7.02 8.0 4.9E+08 0.21 Example 22. The procedure described in Example 21 was followed using 50 mM TRIS buffer solutions with the pH adjusted to a pH of 7.0, 7.25, 7.5, 7.75, or 8.0 and the conductivity adjusted to 5 mS/cm to prepare the Phi6 virus challenge solutions. The results are reported in Table 6. The results show that a portion of the Phi 6 enveloped virus was bound to the grafted membrane when the challenge solution had a pH of 7.0-7.5. However, when the challenge solution had a pH value of 7.75 - 8.0 the Phi6 virus flowed through the membrane with almost no Phi6 virus bound to the grafted membrane. Table 6. Monomer Calculated pH of Phi6 Virus Concentration LRV for Phi6 Virus used for Monomer Challenge of Challenge Solution using Filtration Grafting pKa Solution (pfu/mL) Capsule Example 1 7.02 7.0 2.60E+04 2.41 Example 1 7.02 7.25 6.70E+04 2.83 Example 1 7.02 7.5 4.84E+04 2.68 Example 1 7.02 7.75 3.10E+04 0.01 Example 1 7.02 8.0 1.90E+04 0.12 Example 23. The procedure described in Example 21 was followed using 50 mM TRIS buffer solutions with the pH adjusted to a pH of 7.0 and the conductivity adjusted to 10, 12.5, 15, 17.5, or 20 mS/cm to prepare the Phi6 virus challenge solutions. Filtration Capsules were prepared according to the procedure of Method 3 using a nylon membrane that had been grafted with a monomer solution of Example 1 (IEM/N- (2-hydroxyethyl)piperazine) according to the procedure described in Method 1. The grafted membrane had a graft density of 0.36 mmol/g. The results are reported in Table 7. The results show that a majority of the Phi 6 enveloped virus was bound to the grafted membrane when the challenge solution had a conductivity of 10 mS/cm. However, the binding of Phi6 virus to the grafted membrane decreased substantially when the conductivity of the challenge solution was increased to 12.5 - 20 mS/cm. Table 7. Challenge Solution LRV for Phi6 Monomer Calculated Phi6 Virus Viruses using used for Monomer Conductivity pH Concentration Filtration Grafting pKa (mS/cm) (pfu/mL) Capsule Example 7.02 10 7.0 5.90E+07 4.99 1 Example 7.02 12.5 7.0 3.80E+07 0.68 1 Example 7.02 15 7.0 7.10E+07 0.19 1 Example 7.02 17.5 7.0 5.20E+07 0.18 1 Example 7.02 20 7.0 6.40E+07 0 1 Example 24. Calf thymus DNA challenge solutions were prepared by dissolving 20 micrograms/mL of calf thymus DNA (Sigma-Aldrich Company) in either 50 mM TRIS buffer (pH 7.0, 10 mS/cm) or 50 mM TRIS buffer (pH 8.0, 10 mS/cm). Filtration Capsules were prepared according to the procedure of Method 3 using a nylon membrane that had been grafted with a monomer solution of Example 1 (IEM/N- (2-hydroxyethyl)piperazine) according to the procedure described in Method 1. The grafted membrane had a graft density of 0.36 mmol/g. Each DNA challenge solution (8mL) was pumped through an individual capsule at 0.5 mL/minute. The resulting filtrate was collected in four separate 2 mL fractions (i.e., Fractions 1-4). DNA concentrations (micrograms/mL) of challenge solutions before and after filtration were determined with UV spectroscopy by measuring the 260 absorbance and subtracting the background absorbance of the buffers. The results are reported in Table 8. The results show that the grafted membrane bound substantial amounts of DNA when the challenge solution with a pH of 7.0 was used (i.e., only small amounts of DNA were recovered in the filtrate fractions). However, when the challenge solution of pH 8.0 was used, the DNA in the challenge solution did not bind to the membrane (i.e., most of the DNA was recovered in the filtrate fractions). It is believed that elevated level of DNA in 4^th filtrate fraction from the pH 7.0 challenge solution occurred because the capacity of the grafted membrane was exceeded. Table 8. Monomer Calculated Challenge Solution DNA used for Monomer ^Conductivit Fraction Collected Concentration Grafting pKa _pH ^y (_{mS/cm) micrograms/mL} Challenge Solution b_{efore Filtration} ^17.4 1 1.8 E^{xample 1 7.02 7.0 10} 2 0.5 3 0.9 4 5.8 Challenge Solution b_{efore Filtration} ^19.6 1 19.6 E^{xample 1 7.02 8.0 10} 2 18.7 3 19.0 4 18.8 Example 25. Membrane Grafted with IEM/N-methylpiperazine:HEMA Copolymer (75:25 Molar Ratio) Nylon membranes were grafted with a single comonomer solution containing Example 2 (IEM/N-methylpiperazine, calculated pKa of 7.46) and 2-hydroxyethylmethacrylate (HEMA) according to the procedure described in Method 1. The total monomer concentration of the solution was 0.35 M and the molar ratio of the monomers in the solution was 75:25 IEM/N-methylpiperazine:HEMA. The graft density was 0.30 mmol/g. Example 26. Membrane Grafted with IEM/N-methylpiperazine:HEMA Copolymer (50:50Molar Ratio) Grafted membranes were prepared according to the procedure described in Example 25 with the exception that the molar ratio of the monomers in the solution was 50:50 IEM/N- methylpiperazine:HEMA and the graft density was 0.20 mmol/g. Example 27. Membrane Grafted with IEM/N-methylpiperazine:HEMA Copolymer (25:75Molar Ratio) Grafted membranes were prepared according to the procedure described in Example 25 with the exception that the molar ratio of the monomers in the solution was 25:75 IEM/N- methylpiperazine:HEMA and the graft density was 0.12 mmol/g. Example 28. Membrane Grafted with IEM/N-methylpiperazine:HEMA Copolymer (75:25 Molar Ratio) Grafted membranes were prepared according to the procedure described in Example 25 with the exception that the total monomer concentration of the solution was 0.50 M, the molar ratio of the monomers in the solution was 75:25 IEM/N-methylpiperazine:HEMA and the graft density of was 0.53 mmol/g. Example 29. A 96-well EMPORE Filter plate was modified with grafted membranes of Example 2 (IEM/N- methylpiperazine, pKa 7.46) and Examples 25-27 (including HEMA as copolymer) as described in Method 4. Two disks of the same type of grafted membrane were added to a well and 9 wells were prepared for each type of grafted membrane. The membrane disks of Example 2 had a graft density of 0.375 mmol/g. A 500 microliter aliquot of 20 mM TRIS-Acetate Buffer (with 100 mM of NaCl added, pH 7.4) was added to each well. The pH of the buffer was adjusted using acetic acid. The EMPORE plate was placed on top of a 96 well 2 mL deep-well collection plate and the plate assembly was centrifuged at 1000 x g for 10 minutes using an ALLEGRA 25R Centrifuge (Beckman Coulter, Indianapolis, IN). The flowthrough collected in the collection plate was discarded. A challenge solution of Phi6 virus was prepared by diluting the Phi6 virus stock sample (prepared according to Method 7) 100- fold with the TRIS-acetate buffer to achieve a titer of about 1E+07 pfu/mL. A 300 microliter aliquot of the challenge solution was added to each well of the EMPORE plate and then the assembly was centrifuged at 1000 x g for 10 minutes. Next, the EMPORE plate was removed from the collection plate and transferred to the top of a new collection plate. Three separate elution buffers were prepared by adjusting the pH of a 20 mM TRIS-acetate buffer to either pH 8.0, pH 8.5, or pH 9.0 with HCl. A 2-step procedure was used to elute Phi6 virus from the grafted membranes. In the first step, a 300 microliter aliquot of a single elution buffer was added to 3 wells of each type of grafted membrane (n=3 for each elution buffer) and the plate was centrifuged at 1000 x g for 10 minutes. In the second step, a second 300 microliter aliquot of the same elution buffer used in the first step was added to each well and the plate was centrifuged at 1000 x g for 10 minutes. The collected flowthrough samples of elution buffer were analyzed for Phi6 virus content using the procedure of Method 8. The results are presented in Table 9 as the mean percent of Phi6 virus recovered from the challenge solution with standard deviation (SD). Table 9. Molar Ratio of IEM/N- Mean Percent of Phi6 Virus Recovered using Elution Grafted methylpiperazine to Buffers Membrane HEMA in Grafting pH 8.0 Elution pH 8.5 Elution pH 9.0 Elution Solution Buffer Buffer Buffer 8.6% 15.08% 50.5% Example 2 100:0 (SD = 12.1%) (SD = 12.9%) (SD = 86.1%) 60% 67.5% 45.0% Example 25 75:25 (SD = 26.0%) (SD = 13.0%) (SD = 30.0%) 25% 17.5% 3.25% Example 26 50:50 (SD = 24.1%) (SD = 4.3%) (SD = 0.4%) 0.14% 1.65% 0.025% Example 27 25:75 (SD = 0.2%) (SD = 2.5%) (SD = 0.04%) Example 30. A Clarified lentivirus cell culture challenge solution (about 1.25E+06 TU/mL lentivirus) was prepared according to Method 9 and spiked with about 1E+09 pfu/mL Phi6 virus (prepared according to Method 7) at a 1:1000 dilution. The pH of the clarified culture was 7.05 and the conductivity was 10 mS/cm. A 96-well EMPORE Filter plate was modified with grafted membrane of Example 28 (prepared using a grafting solution with a 75:25 IEM/N-methylpiperazine:HEMA molar ratio). The EMPORE plate was placed on top of a 96 well 2 mL deep-well collection plate and 500 microliters of 1X phosphate buffered saline (PBS) was added to each well. The plate assembly was then centrifuged at 1000 x g for 5 minutes with the collected PBS discarded. Next, 500 microliters of the clarified challenge solution (containing both Phi6 virus and lentivirus) was applied to each well, followed by centrifugation at 1000 x g for 5 minutes. The collected liquid was discarded. A series of 20 elution buffers were prepared from 10 mM PBS having a pH of either 7.25, 7.5, 7.75, 8.0, or 8.25 and a conductivity of 10, 20, 30, or 40 mS/cm. For each elution buffer, the pH was adjusted using 1N HCl and the conductivity was adjusted using NaCl. A 500 aliquot of a single elution buffer was added to each of 3 wells (n=3), followed by centrifugation of the plate at 1000 x g for 5 minutes. The collected samples of elution buffer were analyzed for lentivirus (TU/mL), Phi6 virus (pfu/mL), and DNA (nanograms/mL (ng/mL)) content according to the procedures of Methods 8-11. The results are presented in Tables 10-12 as the mean concentration value with standard deviation (SD). The results presented in Tables 10-12, show that the elution conditions of the method can be optimized to provide purified virus with reduced DNA content. Eluting material bound to the grafted membrane with buffer solutions having a pH of 7.25-7.75 and conductivity of 20 mS provided filtrates with significant amounts of lentivirus and Phi6 virus and only low levels of DNA. Table 10. Mean Lentivirus Recovered (TU/mL) with Standard Deviation (SD) at Elution Conductivity Buffer pH and Conductivity (mS/cm) pH 7.25 pH 7.5 pH 7.75 pH 8.0 pH 8.25 1.00E+04 1.31E+04 1.00E+04 1.00E+04 6.43E+05 10 (SD = (SD = (SD = (SD = (SD = 0.00E+00) 5.29E+03) 0.00E+00) 0.00E+00) 6.89E+04) 5.97E+04 9.19E+04 2.52E+05 1.15E+05 6.02E+05 20 (SD = (SD = (SD = (SD = (SD = 8.15E+02) 2.73E+04) 1.15E+05) 8.03E+03) 9.24E+04) 5.66E+05 9.73E+05 7.04E+05 1.15E+06 1.24E+06 30 (SD = (SD = (SD = (SD = (SD = 2.90E+05) 4.34E+05) 4.50E+05) 5.19E+05) 5.89E+05) 7.34E+05 9.10E+05 6.25E+05 1.02E+06 1.81E+06 40 (SD = (SD = (SD = (SD = (SD = 1.92E+05) 1.24E+05) 2.57E+05) 3.92E+05) 7.16E+05) Table 11. Mean Phi6 Virus Recovered (CFU/mL) with Standard Deviation (SD) at Conductivity Elution Buffer pH and Conductivity (mS/cm) pH 7.25 pH 7.5 pH 7.75 pH 8.0 pH 8.25 3.33E+02 2.22E+02 2.22E+02 5.33E+03 2.33E+06 10 (SD = (SD = (SD = (SD = (SD = 0.00E+00) 9.62E+01) 0.00E+00) 1.01E+04) 1.17E+06) 5.00E+06 3.00E+06 3.67E+06 3.11E+06 1.67E+06 20 (SD = (SD = (SD = (SD = (SD = 1.92E+05) 1.84E+06) 2.80E+06) 3.33E+06) 1.92E+05) 3.44E+06 2.44E+06 3.44E+06 4.44E+06 3.56E+06 30 (SD = (SD = (SD = (SD = (SD = 1.17E+06) 2.17E+06) 6.67E+05) 1.92E+05) 6.94E+05) 2.44E+06 3.89E+06 3.78E+06 6.00E+06 6.22E+06 40 (SD = (SD = (SD = (SD = (SD = 1.84E+06) 6.67E+05) 9.62E+05) 1.92E+05) 1.92E+06) Table 12. Mean DNA Recovered (ng/mL) with Standard Deviation (SD) at Elution Buffer Conductivity pH and Conductivity (mS/cm) pH 7.25 pH 7.5 pH 7.75 pH 8.0 pH 8.25 1.8 2.0 3.1 3.4 92.1 10 (SD = 0.2) (SD = 1.0) (SD = 2.6) (SD = 1.2) (SD = 10.2) 5.2 10.2 27.1 169.1 215.1 20 (SD = 1.0) (SD = 0.5) (SD = 11.6) (SD = 7.8) (SD = 17.3) 199.8 234.0 235.9 240.0 239.4 30 (SD = 2.8) (SD = 8.5) (SD = 14.6) (SD = 6.5) (SD = 8.2) 232.6 260.6 243.8 255.8 255.4 40 (SD = 7.7) (SD = 17.0) (SD = 32.9) (SD = 5.8) (SD = 6.2) Example 31. A MAX EFFICIENCY DH5α Competent Cells Kit (catalog no.18258012, ThermoFisher Scientific) was used to clone pUC19 DNA according to the manufacturer’s instructions. The kit contained MAX EFFICIENCY DH5α competent cells, pUC19 DNA, and S.O.C medium. The E. coli cell culture was grown at 37 °C and agitated at 200 rpm for 18 hours. The pUC19 DNA was purified using a Qiagen QIAprep Spin Miniprep Kit (Qiagen, Germantown, MD) according to the manufacturer’s instructions. Nylon membranes were grafted with the monomer solution of Example 1 (IEM/N-(2-hydroxyethyl)piperazine having a calculated pKa of 7.02) according to the procedure described in Method 1. The graft density was 0.36 mmol/g. An EMPORE 96-well filter plate was prepared according to Method 4 with the exception that only a single disk was added to each well. Three individual solutions of TE buffer (TE buffer = 50 mM TRIS buffer supplemented with 10 mM ethylenediaminetetraacetic acid (EDTA)) were prepared having a pH of either 7.0, 8.0, or 9.0. Two individual solutions of 50 mM MES buffer were prepared having a pH of either 5.0 or 6.0. The pH of the buffer solutions was adjusted using 1N HCl or 1N NaOH. A 150 microliter aliquot of a single buffer solution was added to each of 3 wells (n=3 for each buffer solution). The EMPORE plate was placed on top of a 96 well 2 mL deep-well collection plate and the plate assembly was centrifuged at 1500 rpm for 5 minutes. The flowthrough liquid collected in the collection plate was discarded. The EMPORE plate was then placed on top of a new collection plate. A 150 microliter aliquot of pDNA (about 100 nanograms/microliter) dissolved in buffer was added to each well of the EMPORE plate. The pH of the pDNA solution added to a well was selected to match the pH of the initial 150 microliter aliquot of buffer solution added to the well. The plate assembly was then centrifuged at 2000 rpm for 2 minutes. The collected flowthrough samples were analyzed to determine the percent of bound pDNA using a NanoDrop Microvolume Spectrophotometer (ThermoFisher Scientific) at an absorbance setting of 260 nm. Analysis of the flowthrough samples showed that greater than about 80% of the pDNA was bound to the grafted membranes when buffers at pH values of 5.0-8.0 were used, but only about 3% of the pDNA was bound to the grafted membrane when buffer at pH 9.0 was used. pDNA was subsequently eluted from the grafted membranes by sequentially adding 100 microliter aliquots of buffer solution to each well. The pH of each subsequent aliquot in the sequence was increased by 1.0 pH unit. After adding each aliquot, the plate was centrifuged, and the resulting flowthrough samples were analyzed for pDNA as described above. The process was repeated until a buffer of pH of 9.0 was used as the eluent. Irrespective of the initial buffer pH, the largest percentage of pDNA was recovered from the grafted membranes using the pH 9.0 elution buffer. The mean percent recovery of pDNA (n=3) in the collected samples is reported in Table 13 with standard deviation (SD).

Table 13. Mean Percent of pDNA Recovered based on pH of the Elution Buffer Initial pH of pDNA pH 5.0 pH 6.0 Ph 7.0 pH 8.0 pH 9.0 Solution ** 5_.0 ^19.4% 0.7% 0.4% 0.5% 30.7% (SD = 8.1%) (SD = 0.9%) (SD = 0.6%) (SD = 0.7%) (SD = 5.2%) 6^{.0 NT 5.4%**} 0.9% 2.3% 45.6% (_{SD = 2.5%)} (SD = 1.3%) (SD = 0.4%) (SD = 3.0%) 7^{.0 NT NT 7.0%**} 2.3% 72.4% (_{SD = 3.7%)} (SD = 0.2) (SD = 4.1%) 8^{.0 NT NT NT 14.1%**} 74.9% (_{SD = 3.6%)} (SD = 2.2%) 9^{.0 NT NT NT NT 97.0%**} (_{SD = 4.2%)} NT = Not Tested ** = initial flowthrough sample

Claims

What is claimed is: 1. A monomer of Formula (I) wherein R¹ is hydrogen or X¹ is -O- or -NH-; R² is a (hetero)alkylene; Z is -NH-(C=O)-, -NH-(C=O)-NH-, or -NH-(C=O)-NH-R³-, -(C=O)-NH-, and –(C=O)-NH-R³-, where R³ is alkylene having at least two catenated carbon atoms; R⁴ and R⁵ are each an alkylene having at least 2 carbon atoms, wherein a sum of ring atoms in a ring group consisting of nitrogen, R⁴, Q, and R⁵ is either 6 or 7; Q is -O-, -N(R⁶)-, -S-, -S(=O)-, or -S(=O)₂- with the proviso that Q is equal to -N(R⁶)- when Z is -NH-(C=O)-; and R⁶ is hydrogen, alkyl, or (hetero)aryl, wherein the alkyl is optionally further substituted with hydroxy, alkoxy, or (hetero)aryl and wherein the (hetero)aryl is optionally further substituted with one or more hydroxy, halo, nitro, cyano, trifluoromethyl, alkyl, or alkoxy.

2. The monomer of claim 1, wherein the monomer has a calculated pKa value in a range of 3.5 or 4 to 9 or 9.5.

3. The monomer of claim 1, wherein a sum of catenated atoms in group R² plus group Z is equal to at least 4.

4. A polymeric material comprising a first monomeric unit derived from a monomer of Formula (I) according to any one of claims 1 to 3.

5. The polymeric material of claim 4, further comprising second monomeric unit not derived from a monomer of Formula (I), wherein the second monomeric unit is hydrophilic.

6. The polymeric material of claim 5, wherein the polymeric material comprises 10 to 90 mole percent of the first monomeric unit and 90 to 10 mole percent of the second monomeric unit.

7. An anion exchange separation article comprising: a solid porous polymeric substrate; and a plurality of grafted polymers attached to a surface of the porous substrate, wherein the grafted polymers are polymerized products of a monomer composition comprising a first monomer of Formula (I) wherein R₁ is hydrogen or X¹ is -O- or -NH-; R² is a (hetero)alkylene; Z is -NH-(C=O)-, -NH-(C=O)-NH-, or -NH-(C=O)-NH-R³-, -(C=O)-NH-, and –(C=O)-NH-R³-, where R³ is alkylene having at least two catenated carbon atoms; R⁴ and R⁵ are each an alkylene having at least 2 carbon atoms, wherein a sum of ring atoms in a ring group consisting of nitrogen, R⁴, Q, and R⁵ is either 6 or 7; Q has a single catenated atom and is -O-, -N(R⁶)-, -S-, -S(=O)-, or -S(=O)₂- with the proviso that Q is equal to -N(R⁶)- when Z is -NH-(C=O)-; and R⁶ is hydrogen, alkyl, or (hetero)aryl, wherein the alkyl is optionally further substituted with hydroxy, alkoxy, or (hetero)aryl and wherein the (hetero)aryl is optionally further substituted with one or more hydroxy, halo, nitro, cyano, trifluoromethyl, alkyl, or alkoxy.

8. The anion exchange separation article of claim 7, wherein a sum of catenated atoms in group R² plus group Z is equal to at least 4 for the monomer of Formula (I).

9. The anion exchange separation article of any one of claims 7 or 8, wherein the monomer of Formula (I) has a calculated pKa value in a range of 3.5 or 4 to 9 or 9.5.

10. The anion exchange separation article of any one of claims 7 to 9, wherein the monomer composition further comprises a second monomer that is hydrophilic but not of Formula (I).

11. The anion exchange separation article of claim 10, wherein the monomer composition comprises 10 to 90 mole percent of the first monomeric unit and 90 to 10 mole percent of the second monomeric unit.

12. The anion exchange separation article of any one of claims 7 to 11, wherein each of the plurality of grafted polymers are grafted to a carbon atom of the solid porous polymeric substrate.

13. The anion exchange separation article of any one of claims 7 to 12, wherein the porous polymeric substrate comprises particles, fibers, a film, a non-woven web, a membrane, a sponge, or a sheet.

14. A method of separating a mixture of materials of different ionic content, the method comprising: a) preparing or providing an anion exchange separation article comprising a solid porous polymeric substrate; and a plurality of grafted polymers attached to a surface of porous substrate, wherein the grafted polymers are polymerized products of a monomer composition, the first monomer being of Formula (I) wherein R₁ is hydrogen or X¹ is -O- or -NH-; R² is a (hetero)alkylene; Z is -NH-(C=O)-, -NH-(C=O)-NH-, or -NH-(C=O)-NH-R³-, -(C=O)-NH-, and –(C=O)-NH-R³-, where R³ is alkylene having at least two catenated carbon atoms; R⁴ and R⁵ are each an alkylene having at least 2 carbon atoms, wherein a sum of ring atoms in a ring group consisting of nitrogen, R⁴, Q, and R⁵ is either 6 or 7; Q has a single catenated atom and is -O-, -N(R⁶)-, -S-, -S(=O)-, or -S(=O)₂- with the proviso that Q is equal to -N(R⁶)- when Z is -NH-(C=O)-; R⁶ is hydrogen, alkyl, or (hetero)aryl, wherein the alkyl is optionally further substituted with hydroxy, alkoxy, or (hetero)aryl and wherein the (hetero)aryl is optionally further substituted with one or more hydroxy, halo, nitro, cyano, trifluoromethyl, alkyl, or alkoxy; and (b) passing a mixture of materials through the anion exchange separation article at a first pH that is sufficiently low to protonate monomeric repeat units of the grafted polymers that are derived from the monomer of Formula (I) and at a first ionic strength value to bind at least one component of the mixture of materials to the anion exchange separation article as a bound component.

15. The method of claim 14, further comprising: (c) optionally passing a washing solution though the anion exchange separation article; and (d) passing an eluent composition through the anion exchange separation article at a second pH that is equal to or greater than the first pH and/or at a second ionic strength value that is greater than the first ionic strength value, wherein the eluent removes the bound component from the anion exchange separation article.

16. The method of claim 14 or 15, wherein a sum of catenated atoms in R² plus Z is equal to at least 4.

17. The method of any one of claims 14 to 16, wherein both the first pH and the second pH are in a range of 3.5 or 4 to 9 or 9.5.

18. The method of any one of claims 14 to 17, wherein the first ionic strength and the second ionic strength are less than or equal to 0.5 moles/liter and/or less than or equal to 50 milli-Siemens.

19. The method of any one of claims 14 to 18, wherein the mixture of materials comprises proteins, nucleic acids, nucleic acid fragments, cells, viruses, or virus-like particles.

20. The method of any one of claims 14 to 19, where the method is a flow-through method or a bind- and-elute method.