Crystallization of a Nonracemic Chiral Main-Chain Liquid Crystalline Polyester Confined by Its Smectic Layer Structure

摘要

A nonracemic chiral main-chain liquid crystalline polyester [PET(R)-7] has been synthesized using condensation reaction of an AB type monomer. Multiple phase transitions have been found during cooling and heating at different rates in differential scanning calorimetry measurements. Wide-angle X-ray diffraction (WAXD) experiments have shown that the phase transition sequence is from a highly ordered smectic phase -SmC (139℃) - SmA (199℃) ― TGBA (206℃) ― isotropic with increasing temperature. It has been found that the smectic layer structure can confine the orientation of the crystalline phase developed therein. The c-axis of crystals is along the layer normal of the smectic phase from which they grow. An interesting observation is that macroscopic LC quasi-monodomains can be obtained by applying a mechanical external field and a single crystal-like macroscopic crystalline domain can be grown in the SmC phase.