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Poly(methyl methacrylate) (PMMA) microspheres carrying poly(ethylene imine) (PEI) were prepared for the removal of heavy-metal ions (copper, cadmium, and lead) from aqueous solutions with different amounts of these ions (50 -600 mg/L) and different pH values (3.0 -7.0). Ester groups in the PMMA structures were converted to imine groups in a reaction with PEI as a metal-chelating ligand in the presence of NaH. The adsorption of heavy-metal ions on the unmodified PMMA microspheres was very low [3.6 mol/g for Cu(II), 4.6 mol/g for Cd(II), and 4.2 mol/g for Pb(II)]. PEI immobilization significantly increased the heavy-metal adsorption [0.224 mmol/g for Cu(II), 0.276 mmol/g for Cd(II), and 0.126 mmol/g for Pb(II)]. The affinity order of adsorption (in moles) was Cd(II) Ͼ Cu(II) Ͼ Pb(II). The adsorption of heavy-metal ions increased with increasing pH and reached a plateau value around pH 5.5. Their adsorption behavior was approximately described with the Langmuir equation.

Microporous poly(2-hydroxyethyl methacrylate) (pHEMA) membrane was prepared by UV-initiated photopolymerization. The spacer arm (i.e., hexamethylene diamine) was attached covalently and then invertase was immobilized by the condensation reaction of the amino groups of the spacer arm with carboxyl groups of the enzyme in the presence of carbodiimides. The values of the Michael's constant K m of invertase were significantly larger (ca. 2.5 times) upon immobilization, indicating decreased affinity by the enzyme for its substrate, whereas V max was smaller for the immobilized invertase. Immobilization improved the pH stability of the enzyme as well as its temperature stability. Thermal stability was found to increase with immobilization and at 70°C the half times for the activity decay were 12 min for the free enzyme and 41 min for the immobilized enzyme. The immobilized enzyme activity was found to be quite stable in repeated experiments.

A new "grafting from" strategy based on surface-initiated atom transfer radical polymerization (ATRP) was first used for the preparation of a polymer-based ion-exchange support for HPLC. The most important property of the proposed method is to be applicable for the synthesis of any type of ion exchanger in both the strong and the weak forms. Monodisperse, porous poly(glycidyl methacrylate-co-ethylene dimethacrylate), poly(GMA-co-EDM) particles 5.8 mum in size were synthesized by "modified seeded polymerization". Poly(dihydroxypropyl methacrylate-co-ethylene dimethacrylate), poly(DHPM-co-EDM) particles were then obtained by the acidic hydrolysis of poly(GMA-co-EDM) particles. The ATRP initiator, 3-(2-bromoisobutyramido)propyl(triethoxy)silane was covalently attached onto poly(DHPM-co-EDM) particles via the reaction between triethoxysilane and diol groups. In the next stage, the selected monomer carrying strong cation exchanger groups, 3-sulfopropyl methacrylate (SPM), was polymerized on the initiator-immobilized particles via surface-initiated ATRP. The degree of polymerization of SPM (i.e., length of polyionic ligand) on the particles was precisely controlled by adjusting ATRP conditions. Poly(SPM)-grafted poly(DHPM-co-EDM) particles obtained with different ATRP formulations were tried as chromatographic packing in the separation of proteins by ion-exchange chromatography. The proteins were successfully separated with higher column yields with respect to the previously proposed materials. The plate heights between 100 and 150 mum were achieved with the column packed with the particles carrying the shortest poly(SPM) chains. The plate height showed no significant increase with increasing flow rate in the range of 0.5-16 cm/min.

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