Experimental study of Nafion- and Flemion-based ionic polymer-metal composites (IPMCs) with ethylene glycol as solvent

Ionic polymer-metal composites (IPMCs) consist of a perfluorinated ionomer membrane (usually Nafion(R) or Flemion(R)) plated on both faces with a noble metal such as gold or platinum and neutralized with a certain amount of counterions that balance the electrical charge of anions covalently fixed to the membrane backbone. IPMCs are electroactive materials that can be used as actuators and sensors. Their electrical-chemical-mechanical response is highly dependent on the cations used, the solvent, the amount of solvent uptake, the morphology of the electrodes, and other factors. With water as the solvent, the applied electric potential must be limited to less than 1.3V at room temperature, to avoid electrolysis. Moreover, water evaporation in open air presents additional problems. These and related factors limit the application of IPMCs with water as the solvent. Ethylene glycol has a viscosity of about 16 times that of water at room temperature, and has a greater molecular weight. It is used as an anti-freeze. Like water, it consists of polar molecules and thus can serve as a solvent for IPMCs. We present the results of a series of tests on both Nafion- and Flemion-based IPMCs with ethylene glycol as the solvent, and compare these with the results obtained using water. IPMCs with ethylene glycol as their solvent have greater solvent uptake, and can be subjected to relatively high voltages without electrolysis. They can be actuated in open air for rather long time periods, and at low temperatures. They may be good actuators when high-speed actuation is not necessary.