Surface Chemistry of Amphiphilic Polysiloxane/Triethyleneglycol-Modified Poly(pentafluorostyrene) Block Copolymer Films Before and After Water Immersion

Abstract

New amphiphilic block copolymers Si-EFSx composed of a poly(dimethyl siloxane) (Si) block and a poly(4-(triethyleneglycol monomethyl ether)-2,3,5,6-tetrafluorostyrene) (EFS) block are synthesized by atom transfer radical polymerization (ATRP) starting from a bromo-terminated Si macroinitiator. Similarly, new hydrophobic block copolymers Si-FSy consisting of an Si block and a poly(pentafluorostyrene) (FS) block are prepared for comparison. X-ray photoelectron spectroscopy (XPS) analysis on block copolymer films reveals that the Si block is concentrated at the polymer–air interface, while the EFS block is located in the layers underneath. The same polymer films undergo a marked surface reconstruction after immersion in water for 7 d, as probed by XPS. This phenomenon involves the exposure of the hydrophilic oxyethylenic chains to contact water. Such surface reconstruction is even more drastic when an amphiphilic block copolymer is dispersed in a cross-linked poly(dimethyl siloxane) matrix film.