Synthesis of superhydrophilic Gradient-Like Copolymers: Kinetics of the RAFT copolymerization of methacryloyloxyethyl phosphorylcholine with PEO methacrylate

Abstract

Brush copolymers containing PEO side chains and zwitterionic units of 2-methacryloyloxyethyl phosphorylcholine (MPC) were synthesized by RAFT copolymerization with an especial attention to compositional microstructure of the copolymers. Two complementary methods – size exclusion chromatography (SEC) and 1H NMR spectroscopy – were used to study the kinetics of the RAFT copolymerization of MPC (M1) and the macromonomer poly(ethylene oxide) methyl ether methacrylate with medium-length PEO chain (PEOMEMA, M2) in methanol–water mixed solutions. Analysis of the reaction mixtures by the two methods allowed concluding that in mixed solutions of methanol and water, every molecule of MPC carries about 15 molecules of water as an integral part of the monomer. Monomer reactivity ratios calculated by the method of Meyer and Lowry were r1 = 2.48 and r2 = 0.40. The dependences of the copolymer composition on monomer conversion determined experimentally and calculated by the terminal model of free-radical copolymerization differed significantly, demonstrating the specific impact of the mechanism of RAFT on the distribution of copolymer compositions. The copolymers p(MPC-co-PEOMEMA) possessed strongly expressed gradient microstructure, and were characterized by moderately low dispersity (Ð < 1.3). The copolymers showed evident superhydrophilicity with a water contact angle of about 7° and, like pMPC, exhibited cononsolvency in water–ethanol mixed solutions.