Synthesis of microsequential methylvinylsiloxane-dimethylsiloxane copolymers by nonequilibrium copolymerization

Nonequilibrium anionic ring-opening copolymerization of 1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane (V-4) with hexamethylcyclotrisiloxane (D-3) was examined as a route to methylvinyl-dimethylsiloxane microsequential copolymers. The copolymerization was carried out in toluene and was initiated with Me3SiCH2Li using DMSO as the promoter. Distribution of siloxane units obtained from kinetic analysis based on first-order Markovian statistics was compared with that found from analysis by Si-29 NMR spectroscopy. Results showed that although chain transfer and back-biting play some role in this system, the kinetics of copolymerization may be described to a reasonable approximation by the first-order Markov model. (C) 1998 John Wiley & Sons, Inc.