Conductivity studies of biopolymer electrolytes based on chitosan incorporated with NH4Br

A polymer electrolyte system based on chitosan complexed with ammonium bromide (NH4Br) salt was prepared by the solution cast technique. 30 wt% NH4Br added electrolyte gave a room temperature conductivity of (4.38 +/- 1.26) x 10(-7) S cm(-1) and increased to (2.15 +/- 0.47) x 10(-4) S cm(-1) with addition of 40 wt% glycerol. The dependence of the conductivity on temperature proves that both chitosan-NH4Br and chitosan-NH4Br-glycerol systems are Arrhenian. The activation energy (E-a) value for 70 wt% chitosan-30 wt% NH4Br film is 0.31 eV and the E-a value for 42 wt% chitosan-18 wt% NH4Br-40 wt% glycerol film is 0.20 eV. The carboxamide band at 1640 cm(-1) and the amine band at 1549 cm(-1) in the spectrum of pure chitosan film shifted to 1617 and 1516 cm(-1), respectively, in the spectrum of 70 wt% chitosan-30 wt% NH4Br film, indicating the occurrence of complexation between polymer and salt. The band at 1024 cm(-1) in the pure chitosan film spectrum, which corresponds to the C-O stretching vibration, shifted to lower wavenumbers on addition of salt. A new band appears at 997 cm(-1) on addition of 40 wt% glycerol.