An equivalent circuit model for ionic polymer-metal composites and their performance improvement by a clay-based polymer nano-composite technique

Ionic Polymer-Metal Composite (IPMC) is a new class of polymeric material exhibiting large strain with inherent soft actuation. The observed motion characteristics of an IPMC subjected to an electric field is highly nonlinear. This is believed to be due primarily to the particle electrodes on the IPMC surface, which is inherently both capacitive and resistive due to particle separation and density. Knowing that the value of resistivity and capacity can be manipulated by the number of metal platings applied to the IPMC, the force response of an IPMC when subjected to an imposed electric field is due to the interaction of an array of capacitors and resistors along with ionic migration. In this effort we attempt to incorporate a capacitive and resistive model into the linear irreversible thermodynamic model. The advantages of using such a model are (i) the possible dynamic predictability of the material itself in connection with capacitive responses; and (ii) the realization of capacitive and resistive effect arising from the particle electrodes and the base polymer, respectively. The behavior of the proposed model can explain typical experimentally obtained values well. Also, an experimental effort to improve the properties of the base polymer was carried out by a novel nanocomposite technique. The experiment results on the current/voltage (I/V) curves indicate that the starting material of ionic polymer-metal composites (IPMCs) can be optimized to create effective polymer actuators.