Ionic polymer actuators using poly(ionic liquid) electrolytes

[Display omitted] •Poly(ionic liquid) (polyIL) networks were prepared via free radical polymerization.•The polyILs have either imidazolium or –[SO2NSO2CF3]− structure in their side chains as the fixed charge.•Ionic polymer actuators with the polyIL network electrolyte layer showed a characteristic performance depending on the fixed charge on the network. In this work, poly(ionic liquid) (polyIL) polymer electrolytes were prepared by the free radical copolymerization of IL monomers with a plasticizing monomer having poly(ethylene glycol) (PEG) side chain. The IL monomers, i.e., the polycation and polyanion precursors, were 1-[(3-methacryloyloxy)propyl]-3-methylimidazolium bis(trifluoromethanesulfonyl)amide ([C3mim-MA][TFSA]) and 1-methyl-3-propylimidazolium N-[3-(methacryloyloxy)propylsulfonyl]-N-(trifluoromethanesulfonyl)amide ([C3mim][TFSA-MA]), respectively. The ionic conductivities of the polyIL polymer electrolytes increased with a decrease in the weight fraction of the ionic monomer owing to the plasticizing effect of the PEG side chain, whereas the mechanical strength simultaneously decreased due to a lowering in the glass transition temperature of the electrolytes. The ionic conductivities of the electrolytes were 10−6–10−7 S cm−1 at room temperature. Ionic polymer actuators were fabricated using the polyILs as an electrolyte layer by sandwiching the electrolyte membrane with two carbon electrodes. The displacement behavior depended entirely on the fixed charge on the polymer chain.