Synthesis, characterization and thermal properties of SiH and SiOH terminated hybrid polysiloxanes

Silalkylene polysiloxanes, also called 'hybrid' polysiloxanes, are polysilo xanes including an alkyl spacer between two silicon atoms. So far, several studies had been performed on hybrid polysiloxanes with perfluoroalkyl spac ers. The present study focuses on hybrid polysiloxanes with alkyl spacers - CnH2n- (called SiOHT PSX). Their synthesis is described, and the influence of the size of the spacer on the thermal behavior of these SiOHT PSX has be en evaluated. The synthesis of SiH terminated hybrid oligosiloxanes (SiHT P SX) with different sizes was performed via a new route: polyhydrosilylation of octadiene with tetramethyldisiloxane (TMDS), The theoretical control of the average number molecular weights ((M) over bar (n)) was achieved by ad ding an excess of one of the difunctional compounds (TMDS in this case). Th ese (M) over bar (n) are discussed and compared to the experimental (M) ove r bar (n) determined by H-1 NMR. The influence of the size of the SiHT PSX on its thermal behavior was studied and considered in parallel with the hom ologue SiOHT PSX, The SiOHT PSXs synthesized may be considered as choice el astomers since they exhibit a low glass transition temperature (T-g) and ex cellent thermal resistance. The SiHT PSXs exhibit lower T-g but they show a lower thermal resistance. However, they may be used as performing precurso rs for the synthesis of block copolymers.