Pressure-Induced Crystal Modification of A Thermotropic Polyester

Abstract

It was found that a crystal polymorph of a thermotropic polyester, poly(4,4′-dioxy-2,2′-dimethylazox- ybenzene dodecanedioyl) (labeled as DDA-9), is formed by cooling it from the nematic liquid crystal phase under hydrostatic pressures of 100 MPa. The crystal modification is stable under atmospheric pressure. The sample has a larger density and a higher crystal melting point than those of the DDA-9 polyester formed under normal pressure.

Key Words:

• thermotropic polyester
• nematic phase
• crystal modification
• high pressures
• wide-angle X-ray diffraction