Thermodynamic phase behavior was studied for polymer dispersed liquid crystal (PDLC) films consisting of blends of different thermoplastics such as poly (bisphenol A carbonate) (PC), poly(methylphenylsiloxane) (PMPLSi), poly(styrene-b-ethylene oxide) (PSEO) block copolymer, and low-molecular weight 4'-(hexyloxy)-4-biphenyl-carbonitrile (HOBC) liquid crystals. The phase diagrams of these PDLC systems were built up using thermal transitions determined by differential scanning calorimetry (DSC), transmission optical microscopy (TOM), and dynamic mechanical analysis (DMA). Final morphology of these PDLC films generated by temperature induced phase separation was monitored by TOM. The final morphology of HOBC blends with PC, PSEO, or PMPLSi could be modified by controlling the relative compositions resulting in PDLC systems with small and narrow size-distribution of nematic droplets, suitable for use in thermo-optical devices. (C) 2008 Wiley Periodicals, Inc.