Enhanced electromechanical response of ionic polymer actuators by improving mechanical coupling between ions and polymer matrix

Poly[(vinylidene difluoride)-co-(chlorotrifluoroethylene)] (P(VDF-CTFE)) and P(VDF-CTFE)/poly(methyl methacrylate) (PMMA) cross-linked blends were exploited as ionic electroactive polymer (i-EAP) actuators with electrolyte ionic liquid 1-ethyl-3-methylimidazolium trifluoromethanesulfonate [C ₂mim][TfO] for the first time. Compared to the traditional i-EAPs that are based on Nafion or Aquivion (Hyflon) ionomers, i-EAP actuators made with P(VDF-CTFE) and P(VDF-CTFE)/PMMA polymers exhibited remarkably enhanced actuation strain and significantly reduced electrical capacitance. The increase in the strain-charge ratio ε/C indicates that this improvement is a direct result of improved elastic coupling between the [C ₂mim][TfO] electrolyte and the polymer matrix. As a result, an order-of-magnitude improvement in electromechanical energy conversion efficiency is achieved for both P(VDF-CTFE) and P(VDF-CTFE)/PMMA polymer-based actuators, which makes them promising polymer matrices for i-EAP actuators.