Synthesis of novel highly heat-resistant fluorinated silane coupling agents

Novel fluorinated silane coupling agents with a biphenyl structure, CnF2n+1-(C6H4)(2)-CH2CH2Si(OCH3)(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-(C6H4)(2)-CH(OH)CH3, were obtained by reducing the intermediates, Rf-(C6H4)(2)-COCH3, 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-(C6H4)(2)-CH=CH2, 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 degrees C). In addition, C6H5-C6H4-CH2CH2Si(OCH3)(3) and CH3-(C6H4)(2)-CH2CH2Si(OCH3)(3) with no fluoroalkyl group were synthesized and the heat-resistance of glass surfaces modified with these compounds was examined. (c) 2006 Elsevier B.V. All rights reserved.