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

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 Tβ as reference temperature. The values of the WLF parameters (C1 and C2) 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 T0=50°C, the relation between log τc 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 τn and the molecular weight of the side chain is also linear.