Grafted Cation-Exchange Resins

Tentacular cation exchangers are predominantly used for the following separation problems  

Base matrix material Ethylvinylbenzene 55% cross-linked with divinylbenzene Ethylvinylbenzene 55% cross-linked with divinylbenzene 

Protein binding capacity per mL volume 6 mg lysozyme 3 mg lysozyme 

Typical buffers Sodium and potassium salts of phosphate, MES, Tris Sodium and potassium salts of phosphate, MES, Tris 

Solvent compatibility 80% MeCN, acetone 80% MeCN, acetone 80% MeOH 

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Guerra and Palla ° have recently prepared some unique graft copolymers by reacting polystyryl anions (living polymer) with EMA copolymer. This general reaction is being explored to produce new cation-exchange resins. 

A new cation exchange resin, obtained by grafting sulphonic acid groups onto porous silica, has been shown to possess catalytic activity comparable to that of polystyrene sulphonic acid for the hydrolysis of oligosaccharides. 

Rates, Equilibria. Figure 2 illustrates results from the three methods of heterophase esterifrcation where linoleic acid is grafted to equal equivalents of the pendant carbinol groups in poly(styrene-co-allyl alcohol), PSAA-1. The methods include esterifications conduct in w/o microemulsion catalyzed by DBS A, in dispersion catalyzed by an acidic cation exchange resin and, finally, in a w/o emulsion catdyzed either by DBSA with water as an aqueous phase or by NaDBSA with 7.4N H2SO4 as an aqueous phase. In all runs about 46 wt % toluene was present as a... 

Figure 2. Time-conversion plots for the grafting of linoleic acid to PSAA-1 in o/w emulsion, o/w microemulsion and in a dispersion of an acidic cation exchange resin. O Amberlyst s/1 dispersion, 80 C, 830 meq H / kg. w/o emulsion, NaDBSA/7.4 N H2SO4, 80 C, 83 meq/kg NaDBSA. V w/o emulsion, NaDBSA/H2S04, 25 C, 83 meq/kg NaDBSA. t w/o microemulsion, 25 C, DBSA 87 meq/kg, no added aqueous phase. DBSA, 87 meq/kg, 25°C, in w/o aqueous emulsion.

The same authors " prepared copoly(vinyl alcohol-styrenesulfonic acid) resins which catalyze the hydrolysis of cubohydrates, among them dextrin and sucrose. Also, cation-exchanger membranes (from radiochemical grafting of styrene followed by reaction with chlorosulfonic add) were patented for the hydrolysis of dextrin to D-glucose. The results discussed may be useful for introducing subtle modifications into dextrins already prepared. A review on modified (converted) starches appeared in 1987. 

Other milestones are grafting by radical, cationic, anionic and coordinative polymerization use of semisynthetic and synthetic polymers as ion exchange resins " and catalysts which, in some cases, mimic and even surpass the efficiency of enzymes and solid phase peptide synthesis by Merrifield and Letsinger. ... 

The properties and performance of a commercial weak-acid resin column (Dionex CS12) have been described [41]. The substrate is a highly cross-linked, macroporous ethylvinylbenzene-divinylbenzene polymer with a bead diameter of 8 pm, a pore size of 6 nm, and a specific surface area of 3(X) m /g. In a second step, this substrate was grafted with another polymer containing carboxylate groups. The exchange capacity is listed as 2.8 mequiv/column for a 250 mm x 4 mm i.d. column. With this column, simple eluents such as hydrochloric or methanesulfonic acid can be used to separate mono- and divalent cations rapidly and efficiently under isocratic conditions. 

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