PVT Analysis of Chain Molecules Exhibited Crystal-Liquid Crystal-Isotropic Phase Transition-Orientational Order Dependence of Intramolecular Interaction Potentials and Limitation of Mean-Field Theory

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The effects of volume dependence of thermal-pressure coefficient on the estimation of constant-volume transition entropy (ΔS_m)_v were investigated by the analysis of PVT data of main-chain dimer compounds, the amount (approximately 10%) being reasonably small. The PVT analysis suggested that about 65% of the transition entropy arises from (ΔS_m)_v corresponding to the variation in the conformational distribution of the spacer. We pointed out that the order-disorder characteristics inherent in the primary structure of the flexible spacer are precisely controlled in order to develop the LC mesophase.The intermolecular interaction potentials such as ε=-η/V^m have been widely adopted in conventional mean-field theories of liquids including molten polymers. Here η is defined as a mean-field parameter representing the strength of the interaction field and the parameter m is often set equal to unity in the conventional treatment of liquid. In the analysis of PVT data, m approaches unity only … More within a narrow range of temperature. This results suggested that the conventional form of the potential in the above-mentioned is only valid within a certain limited range of temperature and volumes in both isotropic and nematic LC phases.Vibrational analyses were performed on dimer liquid crystals having a diethylene glycol spacer such as CN-φφ-(OCH_2CH_2)_2O-φφ-CN(CBE2). The specific IR active modes in CBE2 were found to show the frequency shift resembled in the qualitatively shape of nematic order parameter, while other vibrations remain unaltered. It is considered that the selective coupling between intramolecular vibration and the liquid crystalline order is relative to the intrinsic symmetry of the modes.Screw-sense inversion behaviors of a-helical polyaspartate differ substantially depending on the chemical structure of the ester group at the side-chain terminals. The cause of such phenomenological difference among polymers has been investigated by constructing the phase diagram as a function of solvent composition and temperature. Less