Synthesis and solution properties of thermosensitive hydrophilic imidazole-based copolymers with improved catalytic activity

Abstract

We report the synthesis of two new hydrophilic random copolymers prepared by free radical polymerization of 1-(2-methacryloyloxyethyl carbamoyloxy-2-ethyl) imidazole and N-isopropylacrylamide in 5:95 (IMU-NIPAm-5) and 10:90 (IMU-NIPAm-10) molar ratios and the study of their characteristic thermo-responsive properties in aqueous solution. Accordingly, the lower critical solution temperature (LCST) is higher for IMU-NIPAm-10 (36 °C) than for IMU-NIPAm-5 copolymer (33 °C), illustrating that LCST depends on the ratio of the imidazole-based segment present in the final copolymer. Above these values, stable micelles with a collapsed core (hydrophobic PNIPAM) and a stabilizing corona (hydrophilic imidazole-based segments) were observed. Moreover, their catalytic activity in the hydrolysis of p-nitrophenyl acetate (NPA) was also determined, with activity higher than the predicted ones. Chemically efficiency, simplicity of experimental procedures and biocompatibility of both components support the use of these synthetic polymers as potential substitutes of natural enzymes.