Preparation and Orthogonal Polymerizations of 1-Hydrido-1-vinyldimethylsiloxy-3,3,5,5-tetramethylcyclotrisiloxane

1-Hydrido-1-vinyldimethylsiloxy-3,3,5,5-tetramethylcyclotrisiloxane ( IV ) was prepared by reaction of tetramethyldisiloxane-1,3-diol and 1,1-dichloro-1-hydrido-3,3-dimethyl-3-vinyldisiloxane ( III ). Ring-opening polymerization of IV catalyzed by either triflic acid or dilithium diphenylsilanediolate yields high molecular weight poly[1-hydrido-1-vinyldimethylsiloxy-3,3,5,5-tetramethyl-1,3,5-trisiloxanylene] ( V ), which has an exceptionally low T g . On the other hand, hydrosilylation polymerization of IV catalyzed by the 1,3-divinyltetramethyldisiloxane platinum complex (Karstedt catalyst) gives high molecular weight alt -copoly(3,3,5,5-tetramethylcyclotrisiloxane-1,1-ylene/2,2-dimethyl-1-oxa-2-sila-1,4-butanylene) ( VI ). The structures of V and VI were confirmed by IR, 1 H, 13 C, and 29 Si NMR spectroscopy as well as by elemental analysis. Differences in the microstructure of V, formed by acid- or base-catalyzed ring opening of IV, were detected by 29 Si NMR. The molecular weight distributions of V and VI were determined by GPC. The thermal stability and glass transition temperatures of V and VI were measured by TGA and DSC, respectively. As expected, these polymers are easily cross-linked.