SURFACE SEGREGATION IN BLENDS OF POLYSTYRENE AND DEUTERATED POLYSTYRENE

Surface-enhanced Raman scattering (SERS) has been used to investigate surface segregation in blends of high molecular weight polystyrene (PS) and deuterated polystyrene (DPS) following annealing at temperatures above the upper critical solution temperature (UCST). Blends of PS and DPS (both having molecular weight 1 950 000) were spin-coated onto silicon substrates from toluene solutions and annealed at 200-degrees-C for various times. Silver island films were then evaporated onto the blend films and SERS spectra were obtained. The relative intensities of the bands near 1015 and 975 cm-1, which were characteristic of PS and DPS, respectively, were used to determine the relative amounts of PS and DPS at the surface of the blend films. Before annealing, the composition of the surface regions of the blends was similar to that of the bulk. However, after annealing, DPS segregated to the surface and the extent of surface segregation was related to the amount of DPS in the blends.