Surface composition of siloxane‐containing polymers

X‐ray photoelectron spectroscopy was used to study relationships between the surface and bulk composition in block copolymers and blends of poly(dimethyl‐siloxane), poly(bisphenol A sulfone) and poly(bisphenol A carbonate). In all cases the polymer surfaces were highly enriched in siloxane. At a fixed siloxane concentration in the bulk the highest enrichment was observed in the blends of homopolymers and the lowest in the copolymers. It was found that the addition of small quantities of a siloxane‐rich copolymer to another copolymer having a lower siloxane content may reduce the surface siloxane concentration of the latter. This unusual surface behavior was explained by the formation of an over‐layer in which the macromolecules of the siloxane‐rich copolymer are oriented nearly parallel to the sample surface.