Well-defined graft copolymers of tert-butyldimethylsilyl methacrylate and poly(dimethylsiloxane) macromonomers synthesized by RAFT polymerization

Abstract

Graft copolymers of hydrolyzable tert-butyldimethylsilyl methacrylate (TBDMSiMA) and low surface energy poly(dimethylsiloxane) methacrylate of 1000 g mol⁻¹ (PDMSMA1k) and 5000 g mol⁻¹ (PDMSMA5k) were synthesized by the RAFT process, using 2-cyanoprop-2-yl-dithiobenzoate (CPDB) as a chain transfer agent, at 70 °C, in xylene. The homopolymerizations of each monomer were first studied, demonstrating their control by the RAFT process. Simultaneous copolymerizations of TBDMSiMA and PDMSMA led to gradient graft copolymers as demonstrated by the determination of monomer reactivity ratios by the Jaacks method. Sequential polymerizations led to diblock or blocky graft copolymers depending on the order of addition of each monomer. All the copolymerizations were controlled by the RAFT process with molecular weight values close to the theoretical values, together with monomodal and narrow distributions (PDI < 1.2). The graft copolymers exhibited two glass transition temperatures, corresponding to the PDMS- and pTBDMSiMA-enriched phases, respectively. The PDMS side chain distribution and length were shown to be significant parameters influencing the thermal behavior of the copolymers, their low surface energy and their erosion properties in artificial seawater. These latter properties make these graft copolymers suitable for applications as binders for self-polishing/fouling release hybrid antifouling coatings.