Thermal induced phase separation of E7/PMMA PDLC system

The phase behaviour of thermoplastic polymer-dispersed liquid crystal system is studied with particular emphasis on the various transitions that occur within the system. The extent of plasticization of the polymer(polymethyl methacrylate) by the low molecular weight liquid crystal(E7) along with the several transitions of the LC(Liquid Crystal) are determined by modulated DSC. Optical microscopy was used to construct the temperature versus composition phase diagram. Our study indicates the existence of a limiting temperature of 40 degrees C around which the PMMA matrix turns glassy irrespective of the initial composition within the phase separated region, suggesting the intersection of the glass transition curve with the coexistence curve. A slight depression of the N-I(Nematic to isotropic) transition of the LC is observed with increasing composition of PMMA whereas the S-M(Smectic to Nematic) transition and the T-g (Glass transition temperature) of the LC remain unaffected. The one phase mixture remains isotropic until phase separation at a lower temperature where the LC rich domains become nematic. The growth of LC rich domains is studied as a function of temperature and time.