Synthesis of Trimethoxy-type Silane Coupling Agents Containing Two Fluorocarbon Chains and Surface Modification of Glass

Abstract

Trimethoxy-type silane coupling agents each containing two fluorocarbon chains in the molecule, RfCH₂CH₂OCOCH [Si (OCH₃) ₃] CH₂COOCH₂CH₂Rf [Rf=CF₃ (CF₂) n, n=3, 5, 7, or (CF₃) ₂CF (CF₂) _m, m=2, 4, 6, 8], were prepared by the hydrosilylation of trimethoxysilane with the corresponding di [2- (perfluoroalkyl) ethyl] maleate, RfCH₂CH₂OCOCH=CHCOOCH₂CH₂Rf, in the presence of hydrogen hexachloroplatinate (IV). Surface modification of glass was carried out using these agents. The contact angles θ (°) of water and oleic acid on a modified glass surface indicated the coupling agents to have high capacity for causing modification. Although high oxidation resistance was observed on glass surfaces modified with the silane coupling agents containing two longer fluorocarbon chains, rapid contact angle reduction was observed for glass surfaces modified with the silanes containing shorter fluorocarbon chains. This feature was compared with trimethoxy-type silane coupling agents containing a fluorocarbon chain, C_nF_2n+1 CH₂CH₂Si (OCH₃) ₃ Owing to ester hydrolysis of the silane coupling agents, acid resistance on modified glass surfaces was not very high.