Effect of plasticization on the conductivity and dielectric properties of starch–chitosan blend biopolymer electrolytes infused with NH4Br

The present work examines the effect of plasticization on the conductivity and dielectric properties of starch–chitosan blend biopolymer electrolytes. Initial Fourier transform infrared (FTIR) spectroscopy analysis of the hydroxyl band recorded 3280 cm−1 for starch and 3354 cm−1 for chitosan. The FTIR spectrum of starch–chitosan blend films shows that the hydroxyl band shifted to 3288 cm−1, indicating interaction between pure starch and chitosan. Different concentrations of ammonium bromide (NH4Br) were then added to the blend solution and stirred until complete dissolution. The homogeneous solutions were then placed onto different plastic Petri dishes, where they were left to dry. The highest conductivity value of (9.72 ± 0.95) × 10−5 S cm−1 was obtained with addition of 35 wt% NH4Br. Addition of 30 wt% ethylene carbonate increased the conductivity value to (1.44 ± 0.51) × 10−3 S cm−1. The plots of dielectric constant, er, against frequency for both plasticized and unplasticized systems show non-Debye behaviour. The temperature dependence of the power law exponent for the highest conducting sample in the unplasticized system follows the small polaron hopping model while the conduction mechanism of the highest conducting sample in the plasticized system can be represented by the quantum mechanical tunnelling model.