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

Abstract

Phase segregation at the surface of Bisphenol A polycarbonate (PC) and poly(methyl methacrylate) (PMMA) blends is studied by X-ray photoelectron spectroscopy (XPS) and time-of-flight secondary ion mass spectrometry (ToF SIMS). Blends with different compositions were solution-casted onto silicon wafers with dichloromethane (CH(2)CL(2)) as the mutual solvent. A sharp PMMA segregation is observed at the surface of the blends. In fact, the quantitative analysis of the XPS data shows that the PMMA surface molar concentration increases first steeply with the PMMA bulk concentration (the surface concentration reaches 70% of PMMA for a 2.5% bulk concentration), and then it continues to increase slowly 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 correlated with the XPS results and confirmed the segregation even if matrix effects are detected when the surface concentration of each polymer is comparable. The segregation is explained by the difference of surface tension between the two polymers. The surface morphology is also sampled by the ToF SIMS imaging mode, but no contrast is detected although optical images reveal a two-phase system in the bulk.