The dielectric constant (ε') and dielectric loss (ε‫)״‬ of pristine and C 5+ (70 MeV) ion irradiated samples of the PEEK have been investigated with the variation of temperature at different frequencies (100 Hz, 1 kHz, 10 kHz and 100 kHz). The maxima are obtained around 170 o C in dielectric constant (ε') vs. temperature (T) curve. This relaxation is linked with the movement of ketone (>C=0) dipoles linked to the main chain. The irradiation of polymers increases the orientational polarization due to increase in number of dipoles with fluence. The increase in dielectric constant (ε') and dielectric loss (ε'') is attributed to chain scissioning at higher fluence which results in an increase of free radicals and unsaturations.

The dielectric relaxation behavior of thermotropic liquid crystal copolyester of 73% of p-hydroxy-benzoic acid (HBA) and 27% of 2-hydroxy-6-naphthoic acid (HNA) (Vectra-A) at poling temperature 80°C has been studied using thermally stimulated depolarization current (TSDC) technique in the temperature range from 15°C to 250°C. The TSD currents were obtained for different polarizing fields ranging from 3.8 kV/cm to 19.2 kV/cm. TSD current spectra in the temperature range from 15°C to 250°C show three current maxima around 25°C, 110°C, and 220°C. The maxima around 25°C and 110°C correspond to characteristic dipolar relaxations β and α, respectively. The peak around 220°C is due to space charge effects named as δ-relaxation. The various relaxation parameters like activation energy (U), relaxation strength , preexponential factor , the quantity of charge released (Q) and concentration of trap for β- and α-relaxations at polarizing temperature 80°C for different polarizing fields were evaluated using Bucci-Fieschi fit. The linear variation between activation energy and natural logarithm of preexponential factor indicates the presence of compensation effect for dipolar relaxations of Vectra-A under present poling conditions.

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The most significant advantage of studying the charge storage mechanism of Vectra-A, Liquid Crystal Copolyester through Dielectric Spectroscopy (DS) is their complex structure, which can be physically or chemically tailored for specific applications which make it suitable for charge storing devices like Micro-Electro-Mechanical Systems (MEMS). The variation of dielectric constant (ε') and dielectric loss (ε'') in the temperature interval (25 o C to 250 o C) for pristine samples of Vectra-A at different frequencies (1 kHz to 1 MHz) have been investigated.

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