Surfaces of polymer blends: X‐ray photoelectron spectroscopy studies of polystyrene/poly(vinyl methyl ether) blends

摘要

The surface compositions of polystyrene (PS)/poly(vinyl methyl ether) (PVME) blends have been investigated using x‐ray photoelectron spectroscopy (XPS). The XPS results demonstrate that there are significant differences between the composition of the surfaces (e.g., outmost ∼6 nm) and the bulk of both miscible and immiscible blends. The surfaces of PS/PVME films dip‐coated from either toluene or trichloroethylene solutions are found to be enriched in PVME. An additional enrichment in the PVME content of the surface is also observed when miscible PS/PVME blends are phase separated by heating them above the lower critical solution temperature. The average composition profile of a miscible 50/50(w) blend has been obtained by angular‐dependent XPS measurements. This experiment suggests that the enrichment is the result of a concentration gradient rather than a monolayer coating. These results are discussed in terms of the surface free energies of PS and PVME and the degree of mixing in the surface layer.