The application of acrylic monomers with acidic groups to the synthesis of proton-conducting polymer gels

Novel proton-conducting gels suitable for electrochromic applications were prepared by the co-polymerisation of 2-acrylamido-2-methyl-1-propane sulfonic acid (AMPSA) and ethylene glycol methacrylate phosphate (EGMP) either with methyl methacrylate (MMA), glycidyl methacrylate (GMA) or 2-hydroxyl ethyl methacrylate (HEMA) in polar aprotic solvents, such as propylene carbonate (PC), ethylene carbonate (EC) or N,N-dimethylformamide (DMF). The gels obtained, were characterised by impedance spectroscopy, FT-ir and Raman spectroscopies and DSC experiments. Electrochemical stability was studied by voltammetry from which it can be concluded that the investigated gels do not show any appreciable electroactivity over a range of potentials (−1.2 to +1.2V). The electrolytic properties of the resulting gel electrolytes are affected by the polymer matrix content, type and concentration of the acidic component, i.e., AMPSA or EGMP as well as the type of solvent used as plasticizer. The highest conductivities reached values of respectively 1.5×10−3 and 6.7×10−4 S cm−1 at room temperature for AMPSA- and EGMP-based electrolytes. These were achieved for DMF-plasticized samples. All EGMP-based systems had lower conductivities than AMPSA-based systems. The use of PC–DMF, EC–DMF or PC–EC–DMF solvent mixtures, on the other hand, improves adhesion to a glass substrate and resistance to the influence of traces of water. We found that the poly(AMPSA-co-MMA)–PC–DMF (30 wt.% polymer) and poly(AMPSA-co-HEMA)–PC–EC–DMF (20 wt.% polymer) systems are the most promising for electrochromic applications.