Phase Separation and Dewetting Induced Surface Pattern in PS/PMMA Blend Films

The pattern evolution of phase separation and dewetting of PS/PMMA blend thin films at 160 °C were observed by optical video microscopy and atomic force microscopy (AFM). The results show that the PMMA wetting component is driven toward the substrate, and the PS dewetting component is driven toward the surface by pressure caused by phase separation and wetting. At the late stage of the process, irregular shapes of PS islands evolve into round droplets. A cross-section of the interface between the PS and PMMA after phase separation was observed by AFM for the first time. This shows that the PS component extends considerably into the PMMA substrate layer and a trench was observed inside and outside the PMMA rim, respectively. This confirms the notion of a deformable interface between the two materials.