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Thermally stimulated depolarization current investigations of copolyesteramide (Vectra B 950) polymer liquid crystal

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Quamara J. K. , Mahna S. K. , Garg S.

tom Vol. 28, No. 3

679--691

Thermally stimulated depolarization current (TSDC) characteristics of copolyesteramide (Vectra B950), a polymer liquid crystal having a monomeric composition of 60/20/20 mol % of 6-hydroxy-2 -naphthoic acid (HNA), terethalic acid (TA) and 4-aminophenol (AP) were investigated in the tempera-ture range 20-250 °C in function of polarizing temperature (80-190 °C), polarizing field (2.77-13.88 kV/cm), polarization time (0.5-2 h) and storage time (1 - 100 h). The TSDC spectra in general comprise four maxima, namely ß', ß, ?, and ? with their respective locations around 30°C, 110 °C, 160 °C and 220 °C. The ß peak was attributed to the dipolar nature of the carbonyl group (> C = O) present in HNA and TA non liquid crystalline phase of Vectra B, whereas the ß' peak is due to the dipolar nature of the ester group. The ? peak was assigned to a space charge trapping mechanism. A major contribution towards ? relaxation comes from interfacial polarization arising from liquid crystalline phase inVectra B. A high temperature of the ? relaxation is associated with the onset of melting due to the movement of large segmental groups of liquid crystalline phase.