Degradative side reactions in the syntheses of exactly alternating silarylene-siloxane polymers

Summary Four principal synthetic methods for preparation of exactly alternating silarylene-siloxane polymers: the chlorosilane, the acetoxysilane, the aminosilane and the ureidosilane polymerization reactions, were compared under equivalent experimental conditions. As indicated earlier, polymers with considerably different molecular weights were obtained. The highest molecular weight polymer resulted from the ureidosilane reaction, while the lowest ones were obtained from the chlorosilane and the acetoxysilane routes. Because thorough precautions were taken to ensure equally favorable conditions in all preparations, these results seem to support a hypothesis that the latter two reactions are limited by the occurrence of degradative desilytation side reactions which are inherent to the nature of these polymerization systems.Dedicated to Professor Dragutin Fle on the occasion of his 70th birthday