Phase Evolution of PS/PMMA Blend Films Between Two Parallel Rigid Plates With Nano-Scale Gap

We present the phase evolution of PS/PMMA blend film strongly confined between two parallel rigid plates with identical surface energies and a gap distance ranging from 50 nm ~100 nm. This symmetrical configuration is achieved by pressurizing a spun-cast PS/PMMA film on a silicon wafer against another silicon wafer. In the absence of pressurization, phase inversion process occurred on both substrates, with PMMA wetting both substrates and PS breaking into correlated droplets. The phase inversion was completely suppressed by pressurizing the plates, as the pressure overcame the capillary pressure of confined PS domains.