Conductive properties of polymer diacrylates incorporating solutions of lithium salts: Part II. Model of ionic transport in the gel in relation with the polymer network structure

Gamma butyrolactone (BL) or BL/LiN(CF3SO2)2 (LiTFSI) solutions were incorporated in the polymer network of 1,3-butanediol diacrylate (BDD) or tetraethylene glycol diacrylate (TEG) polymerized under UV irradiation with about 1 wt.% of benzoı̈n methyl ether as initiator. The evolution of the ionic conductivity, determined by ac impedance technique, with both gel composition and temperature, is related to the ions–solvent and ions–polymer interactions, assuming a cubic lattice structure for the polymer network. The decrease in conductivity from the “free” liquid phase to the incorporated liquid phase is due to both a dynamic equilibrium of solvation of ions between the solvent and the polymer, and, for the “free” ions, a drastic decrease in their mobility because of long-range interactions with the polymer. These interactions are quantified in terms of a “fixation equilibrium constant” and a “microscopic viscosity” relative to ion mobility in the gel. In addition, the moving of ions is not straight in the gel and a tortuosity coefficient in relation with the gel composition is defined.