Phase separation of PS/PVME blend films induced by capillary force

The phase behavior of a miscible PS/PVME (80/20, w/w) blend film in a confined geometry has been investigated at the annealing temperature much lower than the low critical solution temperature (LCST) of the blend. When the annealing temperature (52 °C) is near the glass transition temperature of the blend (51.2 °C), PVME-rich phase at the air–film surface under a microchannel forms smaller protrusion. When the annealing temperature is increased to 70 °C, the protruding stripes, which are almost developed, are mainly composed of the mobile PVME-rich phase. These results reveal that the capillary force lead to the enrichment of PVME-rich phase at the air–polymer interface of a PDMS microchannel, that is, the capillary force lithography (CFL) can induce the phase separation of PS/PVME blend films.