Syntheses of Dumbbell-Shaped Trifluoropropyl-Substituted POSS Derivatives Linked by Simple Aliphatic Chains and Their Optical Transparent Thermoplastic Films

Dumbbell-shaped trifluoropropyl-substituted C2-linked POSS (POSS-DE), C3-linked POSS (POSS-DP), and C6-linked POSS (POSS-DH) were prepared by corner-capping of hepta(3,3,3-trifluoropropyl)tricycloheptasiloxane trisodium silanolate (F7-Na) with 1,2-bis(trichlorosilyl)ethane, 1,3-bis(trichlorosilyl)propane, and 1,6-bis(trichlorosilyl)hexane, respectively. The structures of these obtained compounds were confirmed by H-1, C-13, and Si-29 NMR spectra and MALDI-TOF MS analysis. In the case of POSS-DP and POSS-DH, spin coating of hexafluorobenzene solutions and subsequent baking at 100 degrees C for 3 min gave optical transparent films. POSS-DE, however, formed opaque whitish films. Refractive indices of the transparent films were in the range of 1.38 to 1.39, which were the same as those of the corresponding random silsesquioxanes prepared by baking at 250 degrees C. POSS-DP and POSS-DH are regarded as low temperature processing low refractive materials. Thermal stabilities of the dumbbell-shaped POSS derivatives were higher than that of allylhepta(3,3,3-trifluoropropyl)-T8-silsesquioxane (POSS-F7A1). Both the glass transition and melting temperatures Of the dumbbell-shaped POSS derivatives were observed by DSC analysis.