Hexanoyl chitosan that exhibited solubility in tetrahydrofuran was prepared by acyl modification of chitosan. Films of hexanoyl chitosan-based polymer electrolyte were prepared by the technique of solution casting. Ethylene carbonate, propylene carbonate, and diethyl carbonate with different dielectric constants were employed as the plasticizing solvents and lithium trifluoromethanesulfonate (LiCF3SO3) was used as the salt. The importance of dielectric constant affecting conductivity and transport properties of hexanoyl chitosan:LiCF3SO3 electrolytes have been examined in the present study. An enhancement in the ionic conductivity has been found on plasticization, and the magnitude of conductivity increment strongly depended on the dielectric constant of the plasticizer. Transport properties such as activation energy and charge carrier concentration have been calculated to obtain information that may be used to elucidate the mechanism of conductance. In addition to conductivity studies, thermal studies and transference number measurements were performed to correlate the phase structure and diffusion phenomena to the conductivity behavior of hexanoyl chitosan-based polymer electrolyte. (c) 2006 Wiley Periodicals, Inc.