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.
A single-stage swelling and polymerization method was proposed for the synthesis of monodisperse porous poly(vinyl acetate-co-divinylbenzene) [poly(VAc-co-DVB)] particles with different VAc/DVB feed ratios. The particles obtained with the VAc/DVB feed ratio of 50:50 v/v had a narrow pore size distribution exhibiting a sharp peak at 30 nm. Based on this distribution the mean pore size and the specific volume were determined as 12 nm and 1.39 mL/g, respectively. The specific surface area of poly(VAc-co-DVB) particles was found to be 470 m2/g. These properties make poly(VAc-co-DVB) particles a promising support for potential HPLC applications. Poly(vinyl alcohol-co-divinylbenzene) [poly(VA-co-DVB)] particles were then obtained by the basic hydrolysis of poly(VAc-co-DVB) particles. The hydroxyl groups on poly(VA-co-DVB) particles have a suitably reactive functionality for surface grafting or derivatization protocols aiming at synthesizing various HPLC packings. The examination of poly(VA-co-DVB) particles by confocal laser scanning microscopy showed the homogeneous distribution of hydroxyl functionality in the particle interior. As a starting point, the chromatographic performance of plain material, poly(VAc-co-DVB) particles produced with VAc/DVB feed ratio of 50:50 (v/v) was tested by a commonly utilized chromatographic mode, reversed phase chromatography. Poly(VAc-co-DVB) particles were successfully used as packing material in the RP separation of alkylbenzenes with resolutions higher than 1.5. Theoretical plate numbers up to 17 500 plates/m were achieved. No significant change both in the chromatographic resolution and column efficiency was observed with increasing flow rate. The chromatography showed that poly(VAc-co-DVB) particles were a suitable starting material for the synthesis of chromatographic packings for different modes of HPLC.
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