Low temperature aqueous living/controlled (RAFT) polymerization of carboxybetaine methacrylamide up to high molecular weights

Abstract

Among the class of zwitterionic polymers poly(carboxybetaine)s (poly(CB)s) are unique, emerging as the only ultra-low fouling materials known allowing the preparation of biosensors, fouling resistant nanoparticles, and non-adhesive surfaces for bacteria. Poly(carboxybetaine methacrylate) and poly(carboxybetaine acrylamide) have been prepared via atom transfer radical polymerization (ATRP), however a polymerization with living characteristics has not been achieved yet. Herein, the first successful living/controlled reversible addition fragmentation transfer (RAFT) polymerization of (3-methacryloylamino-propyl)-(2- carboxy-ethyl)-dimethyl-ammonium (carboxybetaine methacrylamide) (CBMAA-3) in acetate buffer (pH 5.2) at 70 and 37 °C is reported. The polymerization afforded very high molecular weight polymers (determined by absolute size exclusion chromatography, close to 250 000 g · mol -1 in less than 6 h) with low PDI (<1.3) at 70 °C. The polymerization was additionally carried out at 37 °C allowing to achieve yet lower PDIs (1.06 1.15) even at 90% conversion, demonstrating the suitability of the polymerization conditions for bioconjugate grafting. The living character of the polymerization is additionally evidenced by chain extending poly(CBMAA-3) at 70 and 37 °C. Block copolymerization from biologically relevant poly[N-(2-hydroxypropyl)methacrylamide] macroCTAs was additionally performed. The first living/controlled polymerization of a carboxybetaine monomer is presented. Aqueous RAFT polymerization of carboxybetaine methacrylamide at 70 or 37°C affords high molecular weight polymers (up to 250000 g·mol -1) with low PDI in less than 6h. Block copolymers with the bio-relevant poly(2-hydroxypropyl methacrylamide) are additionally prepared. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.