Novel Diacetylinic Aryloxysilane Polymers: A New Thermally Cross-Linkable High Temperature Polymer System

A new diacetylinic polymer was prepared through polycondensation of 4,4'-buta-1,3-diyne-1,4-diyldiphenol and dichlorodiphenylsilane. This aromatically substituted siloxane polymer contained thermally cross-linkable diacetylene links in the mainchain. FTIR, Raman, and C-13 NMR analysis confirmed the diethynyl group was present in the polymer. DSC analysis showed the polymer had a T-g of 130 degrees C, and a strong exothermic cure peak at 260 degrees C. Parallel plate rheological testing through monitoring of changes in viscosity confirmed the polymer crosslinked during heating. After curing above 260 degrees C, the polymer vitrified, with no detectable T-g observed on subsequent reheating. The activation energy of thermally initiated curing of the diacetylene groups was estimated to be 120 +/- 17 kJ/mol from DSC data using the Ozawa Flynn Wall method. TGA analysis in nitrogen starting from uncured polymer showed a 5% weight loss temperature of 541 degrees C and a pyrolysis yield of 82% at 800 degrees C.