Special features of the polymerization process in the formation of network polyorganosiloxanes

Abstract The anionic copolymerization of octamethylcyclotetrasiloxane (OMSTS) and 2,2,4,4,6,6-hexamethyl-8,8,10,10-tetraphenylspiro-(7,5)-hexasiloxane (spirocycle) is studied. Plots are obtained for the increase in viscosity, conversion of octamethylcyclotetrasiloxane, and the yield of gel fraction as a function of time for various concentrations of initiator and different amounts of added spirocycle. Plots of the kinetic curves are given in Avrami coordinates and the effect of the spirocycle to cyclotetrasiloxane and spirocycle to initiator ratios on the induction period and on the kinetic parameter p is indicated. Two schemes for the copolymerization reaction are proposed, which assume the formation of a cardosiloxane polymer, which undergoes a subsequent transition into a three-dimensional network structure, with formation of a network polymer in accordance with a microgel mechanism.