Thermoresponsive copolymer brushes possessing quaternary amine groups for strong anion-exchange chromatographic matrices

A thermoresponsive copolymer incorporating a quaternary amine group, poly(N-isopropylacrylamide-co-3-acrylamidopropyl trimethylammonium chloride (APTAC)-co-tert-butylacrylamide), was conjugated to the surface of silica beads through surface-initiated atom transfer radical polymerization. Prepared copolymer- and copolymer brush-modified beads were characterized by CHN elemental analysis, X-ray photoelectron spectroscopy, gel permeation chromatography, and observation of phase transition profiles. Phase transition profiles of the prepared copolymer indicated that 5 mol % APTAC is suitable for enabling thermally modulated property changes in the copolymer. Chromatographic elution behaviors of adenosine nucleotides and proteins were observed using prepared beads as chromatography matrices. Higher retention time of adenosine nucleotides and strong protein adsorption behavior were observed compared with those on beads with tertiary amine groups, because of the strong basic properties. Therefore, copolymer brush modified beads will be useful as thermoresponsive ion-exchange chromatographic matrices.