Preparation, Optical, and Heat Resistance Properties of Phenyl-Modified Silicone Gel

A series of Si-H- or Si-Vi-terminated, branched and linear oligomers containing Me₂SiO segments were prepared by equilibrium polymerization or non-equilibrium polymerization initiated by living anions, respectively. These oligomers were used to improve the defects of concentrated crosslinking points and the high hardness of crosslinked products when using phenyltris(dimethylsiloxy)silane or 1,1,5,5-tetramethyl-3,3-diphenyl trisiloxane as crosslinking agents in the preparation of silicone gel. NMR, FT-IR, and GPC characterized the structure and molecular weight information of the prepared oligomers. The effects of equilibrium polymerization and the anionic non-equilibrium ring-opening polymerization methods on the structure of oligomers were investigated in detail, together with the structure, the molar ratio of SiH to SiVi, and the phenyl content on the thermal properties and the transmittance retention yield of the silicone gel. The introduction of phenyl groups increases the glass transition temperature of silicone gel from -121.29 °C to -117.71 °C when the phenyl content increased from 0.88 wt% to 3.17 wt%. Meanwhile, the thermal decomposition temperature of silicone gel at 10% weight loss in the N₂ atmosphere increased from 440.5 °C to 480.0 °C. When the SiH/SiVi molar ratio is close to 1.0, the transmittance retention yield of the prepared silicone gel using Si-Vi-terminated phenyl T-shaped polysiloxane as the matrix and α, ω-dimethylsiloxyl-terminated PDMS as the crosslinking agent could reach 88.9% after 25 min of UV irradiation.