Bifunctional ionic liquid in conductive biopolymer based on chitosan for electrochemical devices application

Abstract

Conductive polymer based on chitosan has been successfully prepared via solution casting technique with ionic liquid 1-butyl-3-methylimidazolium acetate ([Bmim][OAc]). [Bmim][OAc] plays two important roles in the conduction of chitosan: i) charge carrier and ii) plasticizer in this system. Appearance of new peaks and shifting of several characteristic peaks in the FTIR spectra signify the strong interactions between chitosan and [Bmim][OAc]. XRD diffractograms showed an increase in the amorphous region as the weight percentage (wt.%) of [Bmim][OAc] increases. SEM observations have proven the smoother surface morphology of the plasticized chitosan. The enhancement in the ionic conductivity (σ), is observed as the wt.% of [Bmim][OAc] increases. The highest σ achieved is (2.44±0.41)×10−3Scm−1 measured at ambient temperature (298K) and the corresponding activation energy is 0.2961eV. The temperature dependence of conductivity is Arrhenian in the studied temperature range and achieved σ of (7.60±0.62)×10−3Scm−1 at 70°C. The increase in the ionic conductivity is related to the decrease of glass transition temperature (Tg) as proven by the DSC analysis. High electrochemical stability of 3.4V was achieved of the highest conducting electrolyte by means of linear sweep voltammetry (LSV). Transference number measurement confirms that ions predominate the conduction of electrolyte with 0.75 ion transference number.