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 depolari zation currents, TSDC, and dynamic mechanical techniques, DMTA, and th e results compared with those obtained by differential scanning calori metry, thermo-optical analysis, and x-ray diffraction. In the low temp erature region, -173-30 degrees C, three main transitions were observe d and assigned to the gamma relaxation, the glass transition of the me sophase and the glass transition temperature of the amorphous material . The complex behavior observed in the range 110-160 degrees C was ass igned to a crystal-crystal transition which competed with the formatio n 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 det ected and the charges trapped in the mesophase were canceled only at t he isotropization temperature. (C) 1995 John Wiley and Sons, Inc.