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 ¹³C NMR analysis confirmed the diethynyl group was present in the polymer. DSC analysis showed the polymer had a T_g of 130 °C, and a strong exothermic cure peak at 260 °C. Parallel plate rheological testing through monitoring of changes in viscosity confirmed the polymer cross-linked during heating. After curing above 260 °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 °C and a pyrolysis yield of 82% at 800 °C.