Acetic acid-doped poly(ethylene oxide)-modified poly(methacrylate): a new proton conducting polymeric gel electrolyte

A proton conducting polymeric gel membrane was first developed from poly(ethylene oxide)-modified poly(methacrylate) (PEO-PMA) containing poly(ethylene glycol) dimethylether (PEGDE). Acetic acid (HAc) was doped by immersing the polymeric film directly in the aqueous solution of HAc. Characterization by FT-IR, XRD and AC conductivity measurements were carried out on the film electrolytes consisting of different gel compositions. The ionic conductivity of the membrane showed a sensitive variation with the immersion time and concentration of the acid in the doping solution through the changes in the contents of acid and water in the gel. The ionic conductivity also depended on the PEGDE content in the polymer. The proton conductivity was 6.2×10 −4 S cm −1 at 20 °C and 1.0×10 −3 S cm −1 at 80 °C for the gel prepared from HAc concentration of 3.0 mol l −1. The temperature dependence of the conductivity was found to be consistent with Arrhenius-type relationship at a temperature range from 20 to 80 °C, except for the films with low PEGDE contents. The apparent activation energy for the proton conduction was in the range of 5–30 kJ mol −1, depending on the HAc concentration and the polymer matrix composition. The FT-IR spectra of the polymeric membranes showed that HAc does not protonate the carbonyl or ester groups of the polymer matrix, but interacts with them by the hydrogen bonding interaction or weak molecular interactions.