Domain size effects on the thermal properties of PS/PMMA blends

Polystyrene/poly(methylmethacrylate) blends (PS/PMMA) are phase-separated materials and remain so even at elevated temperatures. Blends of PS/PMMA with 40:60, 50:50 and 60:40 wt.% ratio were prepared with PS showing glass transition (Tg) at 64 deg. C and PMMA at Tg = 119 deg. C. The constituents were mixed using three different methods: melt-mixing, casting from solution and spin-casting. The thermal properties of the blends were studied using thermogravimetry (TG) and temperature modulated differential scanning calorimetry (TMDSC). Insights into the morphology of phases were obtained by atomic force microscopy (AFM) using intermittent contact mode. The melt-mixing blends have domain sizes larger than a micron and the casting and spin-casting materials are submicron phase-separated. AFM indicated the co-continuous phase arrangement of spin-casting samples at 140 deg. C. TMDSC showed an increase of interfacial content along with a decrease in the difference between the glass transitions of the phase-separated materials when the preparation varies from melt-mixed to casting