Ion transport in single anion conducting polymer networks

Network polymer electrolytes offer promising to provide both mechanical strength and ionic conductivity, but few fundamental studies have been performed on such structures. Here, single anion conducting networks were synthesized via radical copolymerization of an anionic methacrylate, PEG methacrylatem and a dimethacrylate crosslinker as study system. The effects of cation chemistry, crosslink density and comonomer side chain length will be discussed. Dielectric spectroscopy was performed to study segmental relaxation, ionic conductivity, and their relation. Calorimetric T_gs remained nearly constant over the crosslink density range of 1% to 40%, while dielectric T_g, defined at the dielectric relaxation time equal to 10^-4 s, increased with crosslink density up to 20 K over this range. Angell plot (conductivity vs. T_g/T) shows that calorimetric T_gs do not explain the effect of crosslink density while conductivity collapsed on a dynamic T_g normalized plot. Walden plots (relaxation time vs. conductivity) suggested conductivity was strongly coupled with segmental movement. Other analysis based on dielectric spectroscopy were also performed. Static dielectric constant and the number density of simultaneously conducting ions were also showed to be affected by crosslink density. Our work may provide a guide in design polymer electrolytes for ion-transport applications, including polymer electrolytes for electrochemical energy storage.