Gelification of liquid–polymer systems: a valid approach for the development of various types of polymer electrolyte membranes

Large interest is presently devoted to the development of gel membranes and to their use in advanced-design, plastic-like electrochemical devices. In our laboratory, we have demonstrated the validity of this approach for the case of lithium ion conducting membranes, e.g., membranes formed by the immobilization of mixed organic solutions of lithium salts in a polymer matrix (PM). Relevant examples are membranes formed by the gelification of a LiPF6 ethylene carbonate–dimethyl carbonate (EC–DMC) solution into a poly(acrylonitrile) (PAN) matrix. In this paper, in addition to reporting the characteristics of some selected examples of lithium membranes, we demonstrate that the gel approach can be extended to other ion-conducting membranes. In particular, we report the properties of new types of protonic membranes formed by the inclusion of mixed solvent solution of an organic acid in a poly(methylmetacrylate) (PMMA) matrix. The results confirm that the gel-forming procedure, so far mainly addressed to the fabrication of lithium-conducting membranes, may indeed be extended to other ionic polymer systems.