Imidazolium-Containing ABA Triblock Copolymers as Electroactive Devices

Two-step reversible addition–fragmentation chain transfer (RAFT) polymerization and two subsequent postpolymerization modification steps afforded well-defined ABA triblock copolymers featuring mechanically reinforcing polystyrene outer blocks and 1-methylimidazole-neutralized poly­(acrylic acid)-based central blocks. Size exclusion chromatography and ¹H NMR spectroscopy confirmed predictable molecular weights and narrow distributions. The ionic liquid (IL) 1-ethyl-3-methylimidazolium trifluoromethanesulfonate ([EMIm]­[OTf]) was incorporated at 30 wt % into polymeric films. Thermogravimetric analysis, differential scanning calorimetry, and dynamic mechanical analysis determined the thermomechanical properties of the polymers and polymer–IL composites. Atomic force microscopy, small-angle X-ray scattering (SAXS), and transmission electron microscopy (TEM) determined surface and bulk morphologies, and poly­(Sty-<i>b</i>-AA­(MeIm)-<i>b</i>-Sty) exhibited a change from packed cylindrical to lamellar morphology in SAXS upon IL incorporation. Electrochemical impedance spectroscopy determined the in-plane ionic conductivities of the polymer–IL membranes (σ ∼ 10^–4 S/cm). A device fabricated from poly­(Sty-<i>b</i>-AA­(MeIm)-<i>b</i>-Sty) with 30 wt % incorporated IL demonstrated mechanical actuation under a low applied voltage of 4 V