Mechanism for the formation of poly(phenylsilsesquioxane)

Poly(phenylsilsesquioxane) with molecular weight of 1400 was synthesized by hydrolysis of phenyltrichlorosilane, followed by condensation of the resulting hydrolyzates in the presence of a catalytic amount of hydrochloric acid in methyl isobutyl ketone. The progress of dehydration of the hydrolyzates leading to poly(phenylsilsesquioxane) was monitored by Si-29 NMR spectroscopy. Dehydration of cis-(1,3,5,7-tetrahydroxy)-1,3,5,7-tetraphenylcyclooctasiloxane as a model compound was also investigated by the Si-29 NMR technique. The mechanism for the formation of poly(phenylsilsesquioxane) is discussed.