Thermal Insulating Property of Silsesquioxane Hybrid Film Induced by Intramolecular Void Spaces

Key points of this research results

  • The hydrosilylation of dimethylhydrosilyl-terminatedoligomethylsilsesquioxane and caged
    octavinylsilsesquioxane (Vinyl-POSS) gave ethylene-bridged PSQ films containing POSS units.
  • The resultant ethylene-bridged PSQ film containing 5 wt% Vinyl-POSS unit exhibited low density and thermal diffusivity. The film was colorless and transparent, and showed high thermal stability.
  • Positron annihilation lifetime measurements indicated the enhanced hole volume for the POSS-containing PSQ films, compared to the PSQ films that contained no POSS units, reported previously, thereby improving the thermal insulating property of the PSQ films.

Outline

Organic/inorganic hybrid polymers are extensively studied with regard to the application as heat insulators. Polysilsesquioxane (PSQ) films with ethylene-bridged silicon atoms are of particular interest because of their enhanced thermal insulations due to intramolecular void spaces. In this work, the hydrosilylation of dimethylhydrosilyl-terminated oligomethylsilsesquioxane and caged octavinylsilsesquioxane (Vinyl-POSS) was examined.

The resultant ethylene-bridged PSQ film containing 5 wt% Vinyl-POSS units exhibited lower density and thermal diffusivity (1.19 g/cm3 and 1.21 × 10–7 m2/s). The film was colorless and transparent, and showed high thermal stability with a 5% weight loss temperature and a 10% weight loss temperature of 382 and 453 °C, respectively. Positron annihilation lifetime measurements indicated the enhanced hole volume for the POSS-containing PSQ films, compared to the PSQ films that contained no POSS units, reported previously.

The results clearly demonstrate that the thermal insulating property of the PSQ films was improved by the formation of intramolecular void spaces surrounding the POSS units, offering important hints for the molecular design of PSQ-based high-performance heat insulating materials.


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