SURFACE STUDIES ON MULTICOMPONENT POLYMER SYSTEMS BY X-RAY PHOTOELECTRON-SPECTROSCOPY - POLYSTYRENE - POLY(ETHYLENE OXIDE) DIBLOCK COPOLYMERS

X-ray photoelectron spectroscopy (XPS) is a surface characterization technique capable of providing detailed information about the structure and bonding of molecules in the solid state. In this study, we have used XPS to elucidate the surface topography and copolymer composition of a series of polystyrenepoly (ethylene oxide) diblock copolymer thin films at the polymer-air interface. These copolymers undergo microphase separation when solvent cast into films. The XPS results clearly indicate that the copolymer compositions of the surfaces (e.g., outermost ~50 Å) are significantly different from the overall bulk compositions. Surface excesses of polystyrene are observed in all copolymer films cast from chloroform, ethylbenzene, and nitromethane. Angular dependent XPS studies [XPS((θ)] support a model for the topography of the copolymer surfaces that has isolated domains of each homopolymer at the surface appearing thick on the XPS scale of ~ 50 Å with a fractional area coverage proportional to the mole percent bulk composition of the copolymers. © 1979, American Chemical Society. All rights reserved.