Double-Decker Silsesquioxane-Grafted Polysilsesquioxane Hybrid Films as Thermal Insulation Materials
Takashi Hamada, Sakino Takase, Arata Tanaka, Kenta Okada, Susumu Mineoi, Akira Uedono, Joji Ohshita
Abstract
The development of thermal insulators possessing high thermal insulating properties and thermal stability is desired for realizing a sustainable society. In polysilsesquioxanes (PSQs), which are promising as next-generation thermal insulation materials, the introduction of cross-linking units allows improving the thermal insulating properties through formation of intramolecular void spaces. However, this is usually accompanied by a loss of transparency and stability. To circumvent this issue, the hydrosilylation reaction between hydrodimethylsilylated oligomethylsilsesquioxane and vinyl-functionalized double-decker silsesquioxane (vinyl-DDSQ), which is a highly thermally stable unit, was conducted to obtain aggregation-free DDSQ-grafted PSQ films. The high miscibility of the double-decker silsesquioxane (DDSQ) molecule allowed introducing a high amount of vinyl-DDSQ, and colorless and transparent DDSQ-grafted PSQ films were obtained without aggregation of DDSQ molecules. The thermal diffusivities of the DDSQ-grafted PSQ films decreased from 1.21 × 10–7 to 1.02 × 10–7 m2/s with increasing the DDSQ amount from 5 to 25 mol %. Although a similar trend was observed for the previously reported polyhedral oligomeric silsesquioxane-containing hybrid films, the hardness of the DDSQ-grafted PSQ films decreased with increases in the vinyl-DDSQ content, and their thermal stability was higher (over 400 °C), with higher 5% mass loss temperature and 10% mass loss temperature values of 438–463 °C and 495–523 °C, respectively. Therefore, the high thermal insulating properties and thermal stability of the DDSQ-grafted PSQ films render them promising materials for next-generation thermal insulators.