Synthesis and thermal curing of liquid unsaturated polysilsesquioxane and its mechanical and thermal properties

Abstract The liquid unsaturated polyhedral oligomeric silsesquioxane (PMPOSS) has been successfully synthesized via the hydrolysis-condensation reaction of phenyltrimethoxysilane (PTMS) and methacryloxypropyl trimethoxysilane (MPS). The structures of PMPOSS were confirmed by FTIR, NMR, and MALDI-TOF MS, indicating eight cage structures with different ratios of phenyl and methacryloxypropyl appeared. After that, the PMPOSS was diluted with different concentrations of styrene to explore the best curing formula. The bending test results demonstrated PMPOSS diluted by 20 wt% styrene (PMPOSS20) possessed good mechanical properties, however, PMPOSS0 (self-polymerization of PMPOSS) had the lower values of peak-HRR, THR, TSR, and peak-SD, which were reduced by 44.4%, 21.7%, 49.1%, and 33.8% in comparison to PMPOSS20, respectively. In addition, pyrolysis products were analyzed in detail by TGA-FTIR and Py-GC-MS. The results showed that large amounts of inflammable organic compounds were released from PMPOSS20 caused by the polystyrene fragments and methacryloxypropyl.