Thermal Properties and Order Parameter for Model Compounds of Liquid Crystalline Polymers

Abstract

The thermal behavior and order parameter of two kinds of model compounds for liquid crystalline polyesters were studied by DSC and ESR spin probe methods, respectively. The transition temperatures for the twin model compounds which composed of structural sequences with a mesogen-flexible chain-mesogen demonstrated a dramatic odd-even alternation as increasing the number of methylene unit in the central flexible part. Both melting (Tm) and isotropization (Ti) temperatures for the twin model compounds with an even number of methylene lengths were higher than those with an odd number of methylene lengths. The strong alternation in the isotropization entropy change(ΔSi) and in the order parameter (S) were also observed in these twin compounds with variable spacer lengths. However, an inverse alternation regarding with the number of methylene length was found in Si and S for the azobenzene type of twin models which are composed of the inverse order of atoms in the ester linkage comparing with that of the cyanostilbene type of twin models.