Thermo- and pH-Responsive Gradient and Block Copolymers Based on 2-(2-Methoxyethoxy)ethyl Methacrylate Synthesized via Atom Transfer Radical Polymerization and the Formation of Thermoresponsive Surfaces

A series of gradient and block copolymers, based on 2-(2-methoxyethoxy)ethyl methacrylate (MEO(2)MA) and tertbutyl acrylate ((t)BA), were synthesized by atom transfer radical polymerization (ATRP) in a first step. The MEO(2)MA monomer leads to the production of thermosensitive polymers, exhibiting lower critical solution temperature (LCST) at around room temperature, which could be adjusted by changing the proportion of (t)BA in the copolymer. In a second step, the tert-butyl groups of (t)BA were hydrolyzed with trifluoroacetic acid to form the corresponding block and gradient copolymers of MEO(2)MA and acrylic acid (AA), which exhibited both temperature and pH-responsive behavior. These copolymers showed LCST values strongly dependent on the pH. At acid pH, a slightly decrease of LCST with an increase of AA in the copolymer was observed. However, at neutral or basic conditions, ionization of acid groups increases the hydrophilic balance considerably raising the LCST values, which even become not observable over the temperature range under study. In the last step, these carboxylic functionalized copolymers were covalently bound to biocompatible and biodegradable films of poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) [P(HB-co-HHx)] obtained by casting and, previously treated with ethylenediamine (ED) to render their surfaces with amino groups. Thereby, thermosensitive surfaces of modified P(HB-co-HHx) could be obtained. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 690-700, 2011