Hydrolysis and condensation of fluorine containing organosilicon

Abstract To generate sol–gel film from the hydrolysis and condensation reaction of fluorine containing organosilicon monomers, 3-trifluoromethylphenyltriethoxysilane (TFSI), 3, 5-bistrifluoromethylphenyltriethoxysilane (BTFSI) and pentafluorophenyltriethoxysilane (PFSI) were synthesized. The reactivity of each monomer was investigated by 1 H-NMR spectroscopy in the presence of a confirmed concentration of hydrochloric acid, water and hexafluorobenzene. According to the integration ratio of ethanol/ethoxy peak for all monomers, the ethoxy groups were almost remained constant during some period and then disappeared very quickly. PFSI showed higher reactivity than TFSI and BTFSI at the same reaction condition. The clear film was easily fabricated by spin coating and crosslinked at 270 °C for 2 h. The cured films showed good chemical resistance and thermal stability until 398 °C. At 1.55 μm wavelength, the refractive indices and birefringences of the sol–gel films were in the range of 0.0005–0.0009 and 0.0031–0.0034, respectively, depending on feed ratio of TFSI or BTFSI and PFSI.