Thermally Stable Silphenylene Vinyl Siloxane Elastomers and Their Blends

Abstract

Vinyl-substituted silphenylene siloxane elastomers (VSPSEs) with variable vinyl content were synthesized using the disilanol−diaminosilane polycondensation method. High molecular weight elastomers were obtained by using carefully purified monomers. The polymers were characterized by gel permeation chromatography, differential scanning calorimetry (DSC), and thermogravimetric analyses (TGA). Analysis by 29Si NMR established that the samples have exactly alternating chemical structures. VSPSEs have low glass transition temperatures (Tg's) ranging from −26 to −63 °C. Substitution of the methyl group on silicon with phenyl increases the Tg as well as the TGA residues in both air and nitrogen. TGA experiments showed that the VSPSEs synthesized in this study have the highest degradation temperatures reported so far. The TGA residues at 900 °C increased to 70% in nitrogen and 57% in air as the vinyl content increased. Furthermore, remarkable isothermal weight losses were shown by the VSPSEs. For example, the ela...