Photopyroelectric Measurements of Thermal Parameters over Phase Transitions in Polymer/Liquid Crystals Systems

The photopyroelectric technique (PPE) has been used to investigate phase transitions in polymer/liquid crystal systems. The sensitivity of measurements has allowed the detection of the transition from biphasic regions to isotropic single phase state. Thermal diffusivity and specific heat changes that occur over this phase transition have been measured by using the PPE technique in the back detection configuration with a new normalisation procedure. Equilibrium phase diagrams of these systems have been established on the basis of data recorded from the amplitude and phase of the PPE signal.