Relaxations in liquid crystalline poly(tetraethylene oxide terephthaloyl-bis-4-oxybenzoate) |
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Authors: | M A Gmez C Marco J M G Fatou N Suarez E Laredo A Bello |
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Institution: | M. A. Gómez,C. Marco,J. M. G. Fatou,N. Suarez,E. Laredo,A. Bello |
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Abstract: | 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 calcrimetry, thermo-optical analysis, and x-ray diffraction. In the low temperature region, ?173–30°C, three main transitions were observed and assigned to the γ 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°C was as signed 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. © 1995 John Wiley & Sons, Inc. |
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Keywords: | liquid crystals thermotropic polyesters relaxations phase transitions mesophases dielectric relaxations thermally stimulated depolarization current experiments |
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