Organic–inorganic hybrid materials XI. Characterization and degradation of hydrogen-bonded acidic fluorinated poly(siloxane-amideimide-silica) hybrids

Abstract

Hydrogen-bonded acidic fluorinated poly(siloxane-amideimide-silica) hybrid materials (FPSAI–SiO 2) were obtained using the sol-gel technique by polycondensation of tetramethoxysilane (TMOS) in diethoxysilane-terminated amic acid solution. IR, 29Si- and 13C-NMR spectroscopy and thermogravimetric analysis (TGA) were used to study hybrids containing various proportions of TMOS. The abundant Q 4 structures implied that in the absence of HCl the degree of condensation of TMOS was enhanced by hydrogen-bonded acidic fluorinated poly(siloxane amideimide). The microstructure and chain mobility of the hybrids were investigated by measurements of the spin-lattice relaxation time in the rotating frame ( T H 1ρ) and the time constant for energy exchange between 1H and 29Si spin systems ( T SiH). The results suggested that the rate of polarization transfer in FPSAI–SiO 2 hybrids was dependent on the local motion. On the other hand, the spin-diffusion path length ( L) in FPSAI–SiO 2 hybrids was around 3.6 nm. The apparent activation energy ( E a) for degradation of the hybrids was studied by the van Krevelen method. The E a values of the FPSAI–SiO 2 hybrids in thermal degradation decreased with increasing silica content, whereas those for thermo-oxidative degradation were almost unchanged.