X Ray Diffraction Study of Thermotropic Liquid- Crystalline Main-Chain Polyesters and Diester Model Compounds

Abstract

Two nematic liquid-crystalline polyesters were examined by x-ray diffraction following quenching from the nematic temperature in a magnetic field of 15 tesla. It was not possible to quench an aligned nematic glass; instead a polycrystalline phase showing some preferred orientation or an unoriented nematic glass was produced. Fibers drawn from the nematic melts yielded monodomain nematic diffraction patterns with one resembling that of a fiber (crystalline) photograph while the other showed good nematic alignment which could be enhanced slightly by annealing. A series of Siamese-twin dieater model compounds also were examined at their respective nematic temperatures in a magnetic field of 2,000 gauss as well as in their crystalline phase at room temperature. All displayed well-aligned nematic monodomains above the crystalli- zation point.