Conductivity and transport studies of plasticized chitosan-based proton conducting biopolymer electrolytes

This paper focuses on the conductivity and transport properties of chitosan-based solid biopolymer electrolytes containing ammonium thiocyanate (NH₄SCN). The sample containing 40 wt% NH₄SCN exhibited the highest conductivity value of (1.81 ± 0.50) × 10⁻⁴ S cm⁻¹ at room temperature. Conductivity has increased to (1.51 ± 0.12) × 10⁻³ S cm⁻¹ with the addition of 25 wt% glycerol. The temperature dependence of conductivity for both salted and plasticized systems obeyed the Arrhenius rule. The activation energy (E_a) was calculated for both systems and it is found that the sample with 40 wt% NH₄SCN in the salted system obtained an E_a value of 0.148 eV and that for the sample containing 25 wt% glycerol in the plasticized system is 0.139 eV. From the Fourier transform infrared studies, carboxamide and amine bands shifted to lower wavenumbers, indicating that chitosan has interacted with NH₄SCN salt. Changes in the C–O stretching vibration band intensity are observed at 1067 cm⁻¹ with the addition of glycerol. The Rice and Roth model was used to explain the transport properties of the salted and plasticized systems. (paper)