Copolymerization of acrylic acid and 2-hydroxyethyl methacrylate onto poly(N-vinylpyrrolidone):: Template influence on comonomer reactivity

The copolymerization of acrylic acid and 2-hydroxyethyl methacrylate in aqueous solution is investigated by means of High Performance Liquid Chromatography (HPLC), The reactivity ratios of the two monomers are determined by the method of Kelen-Tudos. Acrylic acid showed a preferential tendency to cross-polymerisation while 2-hydroxyethyl methacrylate tends to auto-propagate. The characterization of the copolymer obtained in the absence of the template indicates that comonomeric units are distributed along the polymeric chain with a higher 2-hydroxyethyl methacrylate/acrylic acid ratio with respect to the feed composition. In the presence of the template (poly(N-vinylpyrrolidone)), the reaction rate and the reactivity ratio of acrylic acid increase while the same quantities decrease for the other comonomer. This experimental evidence suggests the presence of a stronger interaction between acrylic acid and the template. The approach used to study the system could be an useful model to investigate the mechanism of molecular recognition in aqueous (natural) environments.