Study of the conductivity and side chain mobility of a comb-like polymer electrolyte using the dynamic mechanical method

Abstract

Using poly(styrene- co-maleic anhydride) as a backbone and poly(ethylene glycol) methyl ether (PEGME) with different molecular weights as side chains, three comb-like polymers and their Li salt complexes were synthesized. The dynamic mechanical properties and conductivities were investigated. Results showed that the polymer electrolytes possess two glass transitions: α-transition and β-transition, and the temperature dependence of the ionic conductivity shows WLF (Williams–Landel–Ferry) behavior. Based on the time–temperature equivalence principle, a master curve was constructed by selecting T β as reference temperature. The values of the WLF parameters ( C 1 and C 2) were obtained and were found to be almost independent of the length of the PEGME side chain and the content of Li salt. By reference to T 0=50°C, the relation between log τ c and c was found to be linear. The master curves are displaced progressively to higher frequencies as the molecular weight of the side chain is increased. The relation between log τ n and the molecular weight of the side chain is also linear.