Mechanism of chain propagation and termination in the polymerization-exchange reactions of synthesis of polydimethylsilazasiloxanes

A study was made of the mechanism of propagation and termination of macromolecules in anionic copolymerization of octamethylcyclotetrasiloxane and N,N′-(hydroxydimethylsilyl)tetramethylcyclodisilazane by controlling the variation of MW of the system undergoing polymerization and of the polymers formed. It was shown that polymerization is complicated by regrouping by the cyclodisilazane and subsequent reactions of condensation. With a high diol content the role of condensation reactions is considerable and the process take place basically as equilibrium polymerization. With a reduction in diol concentration, transition takes place to non-equilibrium polymerization.