Polycondensation using hydrosilylation: a tool for preparing tailor-made polysiloxanes with anchoring groups

The synthesis of copolymers composed of dimethylsiloxane segments (DMS) of different lengths, regularly separated by one bisphenol A unit (BPA) is des cribed. This was achieved by performing hydrosilylation of 2,2'-diallyl BPA with hydride terminated polydimethylsiloxanes in the presence of Pt(0) cat alyst. The influence of several factors, including the control of the [Si-H ]/[double bond] ratio and the protection of the -OH groups, on the molecula r weight distribution of the polymers is described. Side reactions, such as the isomerization of the double bond and the O-silylation were studied by H-1 and Si-29 n.m.r. As expected, there is a strong influence of the DMS se gment length and of the presence of H-bonding interactions on the thermal p roperties of the resulting polymers. (C) 2000 Elsevier Science Ltd. All rig hts reserved.