Phase Transformations in Chiral Non-racemic Main-chain Liquid Crystalline Polyesters Involving Double-twist Helical Crystals

It is for the first time the double-twisted helical single lamellar crystals were observed in a series of synthetic chiral non-racemic main-chain liquid crystalline polyesters. Phase structure and transition behaviors were investigated. Multiple liquid crystalline phases were found including the twisted grain boundary phase. During crystallization, the chain molecules kept their memory of the primary and secondary chiral structures, and transferred to the tertiary chiral structure. The hierarchies of these chiralities in different length scales were also discussed. Chiralities in Different Length Scales Chirality in molecules has generated profound new phase structures, transition behaviors and specific optical and electric properties in low molecular mass liquid crystals, biomacromolecules and synthetic polymers.1-5 In polymer systems, due to their long chain nature, chirality can be defined in different length scales forming the chirality “hierarchies” as shown in Figure 1.6 Asymmetrical chiral centers introduced into a polymer backbone, which is a primary chiral structure (configurational chirality), usually result in helical Case study Molecular Spectroscopy Authors Christopher Y. Li1 Shi Jin2 Xin Weng2 Dong Zhang2 Feng Bai2 John Z. Zhang2 Frank W. Harris2 Liang-Chy Chien3 Bernard Lotz4 Stephen Z. D. Cheng2 1 Department of Materials Science and Engineering Drexel University Philadelphia, PA 2 The Maurice Morton Institute and Department of Polymer Science The University of Akron Akron, OH 3 Liquid Crystal Institute Kent State University Kent, OH 4 Institute Charles Sadron Strasbourg, France