See also Graft or Side Chains/extenders/linkers (Reactive Monomers) 

The carrier or substrate which is covered in another section (i.e., polysaccharide, polypeptide or silica) is modified by a synthetic polymer which is covalently bonded to the substrate through surface reacstive groups of the substrate, for example, surface hdyroxy groups of the polysaccharides, surface amino groups of the polypeptides and surface hydroxy or SiOH groups of the silica. The polymer which modifies the substrate is either a homopolymer or copolymer. An essential feature of the polymerizable compound is that it must contain a group capable of covalently bonding with the surface reactive group of the substrate (coupling group) and also contain either an ionizable chemical group or a group capable of transformation to an ionizable chemical group which provides the ionic exchange (ion exchange group)  (Hous, US 4,639,513). 

There are four main types of ion exchange resins differing in their functional groups: strongly acidic (typically, sulfonic acid groups, e.g., sodium polystyrene sulfonate or polyAMPS); strongly basis (quaternary amino groups, for example, trimethylammonium groups, elg. polyAPTAC); weakly acidic (mostly, caroxylic acid groups); weakly basis (primary, secondary, and/or ternary amino groups, e.g., polyethylene amine). There are also specialized types: chelating resins (iminodiacetic acid, thiourea and many others)/ Bill (US Patent Applicaiton No: 14/365,449, published as 10/364268).

Methods of Coupling the Polymer to the Carrier/Substrate

Different methods for immobilization of functional groups include physical adorption (non-covalent bridges such as ionic and hydrogen bonds, hydrophobic interactions and van der Walls forces), immobilization via reactive groups, aminopropyltriethoxysilan e bridges, glutaraldehyde, or bis(sulfosuccinimidyl) suberate activation, or via aldehyde groups, phosphoramidite groups, peptide groups, binding through biotin or avidin, protein A or G, attachment via metal-carrying media such as chelate-forming iminodiacetate groups, copper ions, nickel ions, ferric or ferrous ions, zinc ions, magnesium ions, coavlent attachment of oxidized groups as for example to oxidize the carbohydrate moieites in an antibody’s Fc region with periodate to form aldehyde groups, which are then chemically bound to hydrozide-activated solid supports such as agarose. (WO 02/085519).

The polymerizable compound may have a group capable of reacting with a hydroxy group of the polysaccharide with the formation of a covalent bound. Such polymerizable compounds are defined for example in US 4,070,348 to Kraemer. Hydroxy reactive groups are preferably activated carobxy groups known from peptide chemistry or O-alkylating agents such as alkyl halide or epoxide groups such as acrylic and methacrylic anydrides. The polymerizable compound may be one whcih does not react directly with hydroxy groups of the polysaccharide but rather are covalently coupled to the polysaccharide indirectly, via a bridge compound. This is the case when  a polysaccharide of the carrier is first chemically activated as by oxidation and reacted with a compound having as for example an epoxy group ro a vinyl groups.  When the substrate to be modified is a polypeptide then the comonomer conatins vinyl unsaturation to promote polymerization and or copolymerization and also contains a coupling group which is capable of covalently bonding to the polypeptide cahin through amino  gropus of the polypeptide chain. Typical groups capable of so reacting include glycidyl groups such as glydicyl acrylate and methacrylate and N-methylol groups such as N-acrylamide. When the substrate to be modified is silica or a siliceous material, then comonomer contains both vinyl unsaturation for polymerization purpsoes and a group capable of coupling to the hydroxy or SiOH surface groups. Typical monomers include the glycidyl group contianing monomers with glycidyl acrylate and methacrylate preferred.  The polymeriable comonomer will vary depending on the ultimate use of the carrier and may contain any of the well known ionizable chemical groups such as compounds containing a viny or vinylidine group and a carboxylic acid, a carboxylate salt, a carboxylate ester, a carboxylic acid amide, a secondary or tertiary amine, a quaternary ammonium, a sulfonic acid, a sulfonic acid ester, a sulfonamide, a phosphorice or phsophonic acid or a phosphoramide group. (Hou, US 4,639,513). 

Types of Functional Groups/Ligands

1. Anion-Exchange Groups:

Anionically dissociating groups which can be immobilized include quaternary ammonium salts and primary, secondary and tertiary amino or amido groups such as an amino group, a methylamino group a  diethylamino group.

2. Cation-Exchange Groups:

Cationically dissociating groups which can be immobilized include carboxyl group, a sulfone group, a phosphate group, a sulfoethyl group, a phosphomethyl group and a carbomethyl group (WO 02/085519).

Cation exchange groups are roughly divided into a weak cation exchange group such as a carboxyl group and a strong cation exchange group such as a sulfonic acid group. An adsorbent haivng a weak cation exchange group has a drawback in that the surface charge of the adsorbent changes as the pH of the mobil phase changes, with the result that a binidng capacity to a protein such as an antibody changes. Accordingly, if an adsorbent having a weak cation exchange group is used for separation of an antibody, the reproducibility of the separation becomes poor and the recovery rate of the antibody may decrease. (Koguma, US9643173)

Sulfone/sulphonate ligands (S groups): Sulphonate ligands, known as S groups, are commonly used strong cation-exchange groups. In some cases, cush exchangers are named by the group formed by the functional group and its linker to the carrier; for example SP cation exchangers are S groups linked by propyl to the carrier (WO2007027139).

S groups can for example be introduced into at least a part of reactive functional groups (e.g., hydroxyl groups) possessed by a porous cellulose gel.  Matsumoto (US 13/201,647) describes such a procedure. First, a sulfonation agent such as sodium 3-chloro-2-hydroxypropanesulfonate and sulfonic acid having epoxide such as 1,2-epoxyethanesulfonic acidis put into a reaction container. Next, the dried porous cellulose gel is added to the sulfonation agent to cause a reaction.  

 Axen (WO2007/027139) also discloses manufacturing a chromatography materix by providing a polysacharide carrier having OH group and reacting the hydroxyl groups with vinyl sulphonate to provide a sulphonate-functionalized cation exchanger.  In one embodiment, a bifunctional cross-linking agent having one active site and one inactive site to the polysacharide carrier having an OH group is added such that the hydroxyl groups of the polysaccharide reactive with the active site of the cross-linking agent. After the polysaccharide solution is geled by cooling, the inactive site of the cross-linking agent is activated such that it can react with hydroxyal groups of the polysaccharide gel to cross linke the gel. Then the remaning hydroxyl groups are reacted with vinyl sulphonate to provide the sulfphonated-functionalized (S-functionalized) cation exchanger. In another embodiment, extenders may be provided between the carrier and ligand (see ligand extenders).

Koguma (US 9643173) discloses a temperature responsive absorbent prepared by immobilizing a copyolymer containing at least N-isoproylacrylamide to a base material surface. N-isopropylacrylamide (Poly(N-isopropylacrlamide) is known to have a lower limit critical temperature of 32C. The carrier introduced into the surface of the polymer greatly changes surface physical properties such as hydrophilicity/hydrophobicity at a critical termpature. Therefore, if this is grafted or applied as a coating to the surface of a packinga getn for chromatography, sample retenetivity can be obtianed depndent upon the temperature. As a result, retention behavior can be controlled by temperature whihout chaning the compoisiton of an elute. The copolymer has at least a strong cation exchange group in an amount of 0.01 to 5 mol% relative to N-isopropylacrylamide. The absorbent is produce by a surface graft polymerization method using a reaction solution containing a monomer having a strong cation group such as sulfonic acid group or a precursor of a strong cation exchange group in a ratio of 001 to 5 mol % relative to N-isopropylacrylamidel. 

Ishihara (US 14/435456) discloses a cation media for purifying an antibody which has a strong cation monomer unit (examples include for Formula I:  2-acrylamide-2-methylpropanesulfonic acid, 2-acrylamideethane sulfonic acid, 2-methacrylamide-2-methylpropanesulfonic acid and 2-methacrylamideethane sulfonic acid; examples for a Formula II include 3-sulfopropyl methacrylate and 2-sulfoethyl methacrylate. ) and a neutral monomer unit or weak cation monomer unit (examples of a neutral monomer include N,N-dimethylacrylamide, N,N-diethalacrylamide, N-tert-butylacrylamide, N-iso-propylacrylamide, acrylamide, N-(methoxymethl)methacrylamide and N-(iso-butoxymethl)methacrylamide) (example of a weak cation monomer unit include acrylic acid, methacrylic acid, sodium acrylate, potassium acrylate, sodium methacrylate and potassium methacrylate).  Examples the comibnation include 2-acrylamide-2-methylpropanesulfonic acid and N,N-dimethylacrylamide OR  2-acrylamide-2-methylpropanesulfonic acid and acrylic acid. Specific examples of crosslinked cellulose partciles that can be used  include a porous cellulose gel.