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

Angular-dependent X-ray photoelectron spectroscopy, XPS (6), was used to determine the surface compositions and topographies of a series of PEO/PS/PEO triblock copolymer films cast from chloroform. The results indicate that the PS concentration at the air-polymer interface is substantially higher than the known bulk concentration of PS and that the copolymer surfaces are laterally inhomogeneous, i.e., there are isolated domains of PS and PEO residing at the surface. Furthermore, the molar composition of the surface corresponds to the surface area occupied by each component. A comparison of these results on triblock copolymers with those found earlier on the PS/PEO diblock copolymers indicates these two systems have remarkably similar surface compositions and topographies. This study has, for the first time, shown that data from XPS(0) measurements can provide information bearing on the question of phase-separation behavior in multicomponent polymer systems. Our results on the triblock copolymers suggest that the components in the copolymers are partially miscible in the surface region and that this miscibility is a result of electronic interactions between the PEO and PS blocks in the copolymers. © 1979, American Chemical Society. All rights reserved.