Synthesis of novel highly heat-resistant fluorinated silane coupling agents

Abstract

Novel fluorinated silane coupling agents with a biphenyl structure, C n F 2 n+1 (C 6H 4) 2 CH 2CH 2Si(OCH 3) 3 ( n = 4, 6, and 8), were synthesized with the aim to improve the heat-resistance, oxidation-resistance, and acid-resistance of the surface modified with a common fluorinated silane coupling agent. Alcohols, Rf (C 6H 4) 2 CH(OH)CH 3, were obtained by reducing the intermediates, Rf (C 6H 4) 2 COCH 3, the products of the reaction of 4-acetyl-4′-bromobiphenyl with perfluoroalkyl iodides in the presence of copper powder. The reaction of the alcohols with phosphorus tribromide gave olefins, Rf (C 6H 4) 2 CH CH 2, which were then allowed to react with tetramethoxysilane in the presence of hexachloroplatinate(IV) catalyst to yield novel fluorinated silane coupling agents with a biphenyl structure. The coupling agents with four and six carbon atoms in their fluorocarbon chains were obtained as a colorless liquid while that with 8 carbon atoms was a white gel. Evaluations were made of the coupling agents using surfaces modified with them in terms of water contact angles, heat-resistance, oxidation-resistance, and acid-resistance. The agents behaved similarly to the conventional fluorinated silane coupling agents with respect to water contact angles, oxidation-resistance, and acid-resistance, whereas the former showed an extremely higher heat-resistance (up to 350 °C). In addition, C 6H 5 C 6H 4 CH 2CH 2Si(OCH 3) 3 and CH 3 (C 6H 4) 2 CH 2CH 2Si(OCH 3) 3 with no fluoroalkyl group were synthesized and the heat-resistance of glass surfaces modified with these compounds was examined.