Ionic polymer metal composite (IPMC) was prepared by electroless plating method on NafionTM film. In this study, the effect of reduction temperature of electroless plating process was examined on the impedance, surface resistivity, and IPMC performance. At high first reduction temperature OH- anions appears to penetrate deep into the negatively charged polymer membrane and produce in-depth Platinum (Pt) deposition with low impedance. The second reduction temperature greatly affects the surface morphology of Pt electrodes and surface resistivity. Low impedance and surface resistivity result in better performance of IPMC in terms of tip displacement, tip force, and rate of response. The Platinum electrode of IPMC was post-treated by additional gold (Au) coating employing ion coater or dc sputter. It was observed that coarse and large Au polycrystals with the size of 0.5 - 2.5 μm were formed on Pt layer in the case of dc sputtering, whereas ion coating produced much smaller Au polycrystals filling the gaps between Pt polycrystals effectively. The IPMC treated by ion coating demonstrated the improved actuation behavior.
Incorporation of small amounts (3-7 wt%) of nanoparticles such as layered silicate (MMT), silica, and carbon nanotube (CNT) may greatly alter important mechanical and electrical properties of NafionTM matrix. These fillers can be easily modified and functionalized to implement unique properties of IPMC. Our recent study indicates that Nafion/MMT, Nafion/silicates composites can be prepared with nano-scale dispersion. Most of IPMCs based on Nafion nanocomposite exhibit improved displacements and blocking forces compared to pure NafionTM based IPMC. Due to the barrier property and hygroscopic nature of silicates, water loss of IPMC under dc voltage is greatly reduced, which prolong the service life of IPMC. In the case of Nafion / layered silicate nanocomposite, however, response is slow due to the barrier effect of the clay platelet; while in Nafion / silica and Nafion / CNT systems, response rate is comparable with that of conventional IPMC. Improvement in mechanical properties and relaxation was achieved without any significant loss of important properties.