Conductivity and dielectric relaxation in various polyvinyl alcohol/ammonium salt composites

Abstract

We studied electrical conductivity and dielectric relaxation in polyvinyl alcohol/ammonium chloride and polyvinyl alcohol/ammonium acetate composite films. Infrared absorbance showed the presence of H-bonding interaction between the salt and the polymer. X-ray diffraction showed the reduction of the grain size of ordered regions in the polymer matrix after adding salt. Thermo gravimetric analysis (TGA) showed water wt% content between 4.2 and 5.8%. Differential Scanning Calorimetry (DSC) showed the decrease of the glass transition due to retained water indicating its plasticizer effect. The ac conductivity studied in the frequency range from 10−1 Hz to 1 MHz and the temperature range from 10 to 150°C is described by the universal law of Jonsher characterizing the charge transport in disordered materials. With NH4Cl inclusion, the dc conductivity showed a higher value in the vicinity of 4% but with NH4CH3CO2 the dc conductivity decreases monotonically by increasing the salt amount. By using the dielectric permittivity and dielectric modulus we detected three relaxation processes which we attributed to electrode/sample polarization, alpha relaxation and conductivity relaxation respectively.