Inherently Flexible Thermotropic Main Chain Polymeric Liquid Crystals

Abstract

Phase behavior (isotropic—nematic transition, disorder in the crystal) and order of chains in the mesophase (orientational and conformational) are investigated in the homologous series of polymers and corresponding Siamese twin models. Results from the following experiments are presented: DSC (normal and high pressure), polarizing microscopy, broad line NMR (PMR and DMR), small angle X-ray and neutron scattering, induced magnetic birefringence and melt rheology. Influence of chain length, spacer length and parity, temperature and concentration in nematic solutions on nature and level of order is discussed. Molecular segregation by chain length in the nematic—isotropic biphase is considered in relation to its impact on morphology of the isotropic, nematic and solid phases. This series provides a model system for characterization of inherently flexible main chain PLCs formed by alternating mesogens and spacers. Such PLCs are easily processable materials with potentially high levels of micro and macroorder.