Characteristics and performance of ionic polymer–metal composite actuators based on Nafion/layered silicate and Nafion/silica nanocomposites

Incorporation of a small amount (3–10 wt.%) of nanoparticulates such as layered silicate (montmorillonite) or fumed silica, forming a nanocomposite, may greatly alter the mechanical and electrical properties of the Nafion matrix. These nanocomposites were used as polyelectrolytes for preparation of ionic polymer–metal composites (IPMCs) employing an electroless plating method. In the case of Nafion/silica nanocomposite-based IPMCs, additional metal cations were incorporated via a silylation reaction of silica using an organosilane. Experimental results showed that the water loss of the nanocomposite-based IPMCs was significantly reduced due to the barrier property of layered silicate and the hygroscopic nature of fumed silica. In addition, finer and denser Pt grains were formed on the surface of the nanofiller-containing IPMCs as observed by SEM, resulting in a higher current density when subjected to an electric field. As a consequence of these factors, compared to a pure Nafion-based IPMC, these nanocomposite-based IPMCs exhibited larger blocking forces due to the increased water and cation content and better surface coverage of the Pt electrode. IPMC containing 10 wt.% modified silica displayed nearly three times the blocking force with two times the displacement and a more rapid response under an applied electric voltage than that of a Nafion-based IPMC.