Dielectric behaviour and AC conductivity of LiCF3SO3 doped H-chitosan polymer films

Abstract

H-chitosan that exhibited solubility in THF was prepared by acyl modification of chitosan. Films of H-chitosan containing LiCF3SO3 were prepared by the solution cast technique. The effect of salt concentration on the frequency-dependent dielectric properties of H-chitosan: LiCF3SO3 complexes were investigated by impedance spectroscopy, in the temperature range from 243 to 373 K. The dielectric properties and ac conductivity of the samples prepared have been analyzed. The dielectric constant increases sharply with temperature in the low frequency region. At higher frequencies, the effect of temperature on the dielectric constant is negligible. The values of dielectric constant were also found to increase with increasing conductivity of the samples. The imaginary part, Mi of electrical modulus shows the formation of dispersion peak. Relaxation times for the ionic charge carriers were extracted from the loss tangent maximum peak at various temperatures. The plot of relaxation times as a function of temperature shows Arrhenius type behaviour. The ac conductivity was found to obey the universal power law and as the temperature increases, the feature of σ(θ) α θn is more predominant. The temperature dependence of the power law exponent n is reasonably interpreted by the overlapping large polaron tunneling (OLPT) model.