COMBINED TIME-OF-FLIGHT SECONDARY-ION MASS-SPECTROMETRY AND X-RAY PHOTOELECTRON-SPECTROSCOPY STUDY OF THE SURFACE SEGREGATION OF POLY(METHYL METHACRYLATE) (PMMA) IN BISPHENOL-A POLYCARBONATE PMMA BLENDS

Phase segregation at the surface of Bisphenol A polycarbonate (PC) and poly(methyl methacrylate) (PMMA) blends is studied by X-ray photoelec tron spectroscopy (XPS) and time-of-flight secondary ion mass spectrom etry (ToF SIMS). Blends with different compositions were solution-cast ed onto silicon wafers with dichloromethane (CH(2)CL(2)) as the mutual solvent. A sharp PMMA segregation is observed at the surface of the b lends. In fact, the quantitative analysis of the XPS data shows that t he PMMA surface molar concentration increases first steeply with the P MMA bulk concentration (the surface concentration reaches 70% of PMMA for a 2.5% bulk concentration), and then it continues to increase slow ly and saturates for a 38.8% hulk concentration. The ToF SIMS results show that PC remains detected even for high PMMA surface concentration . A semiquantitative ToF SIMS analysis is also presented, which correl ated with the XPS results and confirmed the segregation even if matrix effects are detected when the surface concentration of each polymer i s comparable. The segregation is explained by the difference of surfac e tension between the two polymers. The surface morphology is also sam pled by the ToF SIMS imaging mode, but no contrast is detected althoug h optical images reveal a two-phase system in the bulk.