Phase transition studies of polymer-liquid crystal composite using dielectric and optical transmittance techniques

Dielectric properties of polymer-liquid crystal composite comprised of the polymer poly(methyl methacrylate) and low-molecular mass liquid crystal, cholesteryl palmitate are investigated in the frequency range from 1 kHz to 10 MHz and in the temperature range of 27-120°C. The dielectric permittivity and dielectric loss shows substantial changes with the addition of polymer. The significant feature is that the pure liquid crystal exhibits broad absorption, showing dielectric relaxation in the range of 10 - 100 kHz whereas the composite shows relaxation peaks at 10 MHz. The percentage optical transmittance of pure liquid crystal and composite have also been measured and compared to study its phase transition behavior. The smectic phase observed in the pure liquid crystal is suppressed on formation of polymer composites. The mass spectrometry measurement does not show any abduct formation between the pure liquid crystal and the composite. POLYM. COMPOS. © 2008 Society of Plastics Engineers