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.
The degradation mechanism of ionic polymer metal composites (IPMCs) containing hydrophobic ionic liquids has been investigated. The ionic liquid was mixed with ethylene glycol in order to obtain high solvent uptake. The actuation response of the IPMCs with the mixed solvent was faster than that with only ethylene glycol. During the actuation durability tests under an AC square wave input, the IPMCs suffered from liquid squeezing-out problem, resulting in lower solvent concentration inside the IPMCs and hence poor actuation response. The degradation development of the IPMCs was influenced by the applied AC frequency. The tip displacement and the electric current were used to study the degradation development under AC electric field. Tin layer of polyurethane was applied on the IPMC surface to minimize the squeezing problems. The degradation was not significant observed after being subjected to 3V square wave input for more than 20 hours. However, the conductivity of the coated IPMCs was lower than that of the uncoated ones.
Manufacturing and characterization of ionic polymer metal composites (IPMCs) with silver as electrodes have been investigated. Tollen's reagent that contains ion Ag(NH3)2+ was used as a raw material for silver deposition on the surfaces of the polymer membrane Nafion"R". Two types of inner solvents, namely common water based electrolyte solution (LiOH 1N) and ionic liquid were used and investigated. Compared to IPMCs with platinum electrodes, silver-plated IPMCs with water electrolyte showed higher conductivity. The actuation response of silver-plated IPMCs with the water based electrolyte was faster than that of platinum IPMCs. However, the silver electrode was too brittle and severely damaged during the solvent exchange process from water to ionic liquid, resulted in high resistance and hence very low 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.
Ion exchange polymer metal composites (IPMC) are electro-active actuators that show large deformation in the presence of low applied voltage. Perfluorosulfonic acid membrane, Nafion, is one of the most widely studied materials for this purpose. Experimental studies were carried out on the bending behavior of Nafion-based IPMCs containing various solvents and cation species. Various counter cations of sulfonate groups in the membrane were obtained by soaking the composite membrane in aqueous salt solutions. The salts used in ion exchange process include LiOH, NaOH, Cu(NO3)2, Co(NO3)2. Ion-exchange capacity of the IPMC was measured by ICP. In the case of cationic effect the Li-form IPMC demonstrated an immediate and efficient deformation behavior at 1 DC V, while divalent cuprous cation containing IPMC exhibited the larger tip displacement at an elevated electric potential. A threshold electric driving force appears to be required for cations with large hydration and high volume. IPMCs were also prepared by soaking in various transport media. The solutions were prepared by adding 1 mole of NMP, DMF, DMSO, and PEG 200 in water. The feasibility of D2O was also investigated. Addition of organic polar solvents in water decreases the dielectric constant of medium, which subsequently reduces the dissociation of ion pairs. Among the various solutions the heavy water, D2O and DMSO/water (1 Mole/L) mixture demonstrated unusually stable tendency in terms of electrolysis.
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