RING-OPENING POLYMERIZATION OF CYCLIC ORGANOSILICON COMPOUNDS - RECENT PROGRESS

A novel initiator, i.e. trimethylsilylmethyllithium has been successfu lly used for the ring opening polymerization of cyclosiloxanes in tolu ene, in the presence of the cryptand [211]. Suitable conditions have b een found in which monomodal distributions of molecular weights of pol ysiloxanes are observed by GPC, even in the case of D4 and 1,3,5,7-tet ramethyl-1,3,5,7-tetravinyl cyclotetra siloxane (D4Vi) polymerizations . Moreover, kinetics of propagation and of formation of cyclosiloxanes can be followed by Si-29 or C-13 NMR spectroscopy on living polymer s olutions. The rate of propagation of hexaethylcyclotrisiloxane is 120 times lower than that of the corresponding dimethylated analog D3, und er the same conditions.