RELAXATIONS IN LIQUID-CRYSTALLINE POLY(TETRAETHYLENE OXIDE TEREPHTHALOYL-BIS-4-OXYBENZOATE)

The relaxation behavior of poly(tetra ethylene oxide terephthaloyl-bis-4-oxybenzoate), PTETOB, was analyzed by thermally stimulated depolarization currents, TSDC, and dynamic mechanical techniques, DMTA, and the results compared with those obtained by differential scanning calorimetry, thermo-optical analysis, and x-ray diffraction. In the low temperature region, -173-30 degrees C, three main transitions were observed and assigned to the gamma relaxation, the glass transition of the mesophase and the glass transition temperature of the amorphous material. The complex behavior observed in the range 110-160 degrees C was assigned to a crystal-crystal transition which competed with the formation of a mesophase and afterward the formation of a smectic A mesophase. At higher temperatures, was observed the transition from the smectic A mesophase to a nematic one, prior to the isotropization temperature. In the TSDC experiments the formation of a permanent electret was detected and the charges trapped in the mesophase were canceled only at the isotropization temperature. (C) 1995 John Wiley and Sons, Inc.