Effect of solvent evaporation rate on surface composition in fluoro-copolymer/acrylate-copolymer blend films

The relationship between the surface composition and the rate of solvent evaporation (R) in blend films of poly(vinylidene fluoride-co-hexafluoroacetone) (P(VDF-HFA)) and poly(2-ethylhexyl acrylate-co-acrylic acid-co-vinyl acetate) (P(2EHA-AA-VAc)) has been investigated. P(VDF-HFA), a low-surface tension component, was concentrated on the surface when R was relatively high. In contrast, when R was relatively low, P(2EHA-AA-VAc), a low-density component, was concentrated on the surface. Therefore, it is speculated that the factors dominating surface enrichment in polymer blends were changed from surface tension differences to density differences between the components when R was decreased. In addition, the affinity between components and substrate strongly affects the dominant factors determining the surface composition. (C) 2001 Society of Chemical Industry.