Crack- and Shrinkage-Free Ethylene-Bridged Polysilsesquioxane Film Prepared by a Hydrosilylation Reaction

Abstract

With the aim of developing an improved strategy for the preparation of ethylene-bridged polysilsesquioxanes as thermal insulator materials, this paper describes the synthesis of a crack- and shrinkage-free ethylene-bridged polysilsesquioxane film by the hydrosilylation reaction of hydrodimethyl-silylated oligomethylsilsesquioxane (MSQ-SiH) and dimethylvinyl-silylated oligomethylsilsesquioxane (MSQ-SiVi) in the presence of Karstedt’s catalyst. Polysilsesquioxane precursors were prepared by the sol–gel reaction of triethoxymethylsilane and the successive capping reaction with chlorodimethylsilane and chlorodimethylvinylsilane. The obtained ethylene-bridged polysilsesquioxane film showed lower density and thermal diffusivity (1.13 g/cm3 and 1.15 × 10–7 m2/s, respectively) than a polymethylsilsesquioxane film (1.34 g/cm3 and 1.36 × 10–7 m2/s, respectively). As a result of the introduction of the SiCCSi ethylene bridge, the thermal insulation property of the polysilsesquioxane film was enhanced.

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

“…The chemical structure of Vinyl-POSS was confirmed by 1 H and 29 Si nuclear magnetic resonance (NMR) spectra, which were in good agreement with the literature values . For the preparation of the hybrid film by hydrosilylation reaction with Vinyl-POSS, we followed our previously reported procedure using hydrodimethyl-silylated oligomethylsilsesquioxane (MSQ-SiH) with M w = 760 and M w / M n = 1.37, which was also prepared as reported in our previous paper . A white turbid slurry of MSQ-SiH and 5 wt % Vinyl-POSS was obtained using a rotation/revolution vacuum mixer, and it was mixed again to obtain a homogeneous slurry after the addition of platinum (0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane (Karstedt’s catalyst).…”

“…A white turbid slurry of MSQ-SiH and 5 wt % Vinyl-POSS was obtained using a rotation/revolution vacuum mixer, and it was mixed again to obtain a homogeneous slurry after the addition of platinum (0)-1,3-divinyl-1,1,3,3-tetramethyldisiloxane (Karstedt’s catalyst). Subsequently, the cross-linked gel film was prepared via the hydrosilylation reaction by heating at 80, 120, and 140 °C for 1 h, respectively, and then at 160 °C for 4 h. As reported in a previous paper, MSQ-SiH has one silyl group on each repeating unit . The molar ratio of MSQ-SiH and Vinyl-POSS was estimated to be approximately 50:1, i.e., vinyl groups in Vinyl-POSS reacted with 6–8 times the number of hydrosilyl groups in MSQ-SiH to complete the transformations of vinyl groups to ethylene linkages.…”

“…We previously reported an ethylene-bridged polysilsesquioxane film prepared by the hydrosilylation reaction, which exhibited lower thermal diffusivity and density than a polymethylsilsesquioxane film due to the formation of the ethylene-bridged structure . Interestingly, the thermal diffusivity and density of the ethylene-bridged polysilsesquioxane film decreased with an increase in the amount of the SiCCSi bonds, namely, the thermal insulating property of the ethylene-bridged polysilsesquioxane film was enhanced by the presence of intramolecular void spaces.…”

“…Very recently, we found that an ethylene-bridged polysilsesquioxane film prepared by hydrosilylation reaction shows enhanced thermal insulating property due to the formation of intramolecular void spaces . Compared with a polymethylsilsesquioxane film, the ethylene-bridged polysilsesquioxane film exhibits low density and thermal diffusivity, indicating the formation of intramolecular void spaces around the SiCCSi bonds.…”

Ethylene-bridged polysilsesquioxane/hollow silica particle hybrid film for thermal insulation material

“…Indeed, recently, we reported the preparation of ethylene-bridged polysilsesquioxane (EBPSQ) film by hydrosilylation reaction, and their ethylene-bridged structure improved the thermal insulating property. 21 To further enhance the thermal insulating properties, we conceived to introduce HSPs containing a hollow cavity into EBPSQ film. Furthermore, because of its excellent thermal properties, EBPSQ is a suitable base polymer for preparing a composite film containing HSPs.…”