Characteristics of ionic polymer–metal composite with chemically dopedTiO2 particles

Abstract

Many studies have investigated techniques to improve the bending performance of ionicpolymer–metal composite (IPMC) actuators, including ‘doping’ of metal particles in thepolymer membrane usually by means of physical processes. This study is mainly focused onthe characterization of the physical, electrochemical and electromechanical properties ofTiO2-doped ionic polymer membranes and IPMCs prepared by the sol–gel method,which results in a uniform distribution of the particles inside the polymermembrane. X-ray and UV–visible spectra indicate the presence of anatase-TiO2 in the modifiedmembranes. TiO2-doped membranes (0.16 wt%) exhibit the highest level of water uptake. Theglass transition temperature of these membranes, measured using differentialscanning calorimetry (DSC), increases with the increase of the amount ofTiO2 inthe membrane. Dynamic mechanical analysis (DMA) demonstrated that the storage modulus of driedTiO2-doped ionic polymer membranes increases as the amount ofTiO2 inthe membrane increases, whereas the storage modulus of hydrated samples is closely related to thelevel of water uptake. Electrochemical impedance spectroscopy (EIS) shows that the conductivity ofTiO2-doped membranes decreases with increasingTiO2 content in spite of an internal resistance drop in the samples. Above all, bending deflection ofTiO2-doped IPMCdecreased with higher TiO2 content in the membrane while the blocking force of each sample increased with the higherTiO2 content. Additionally, it was determined that the lifetime of IPMC is strongly dependenton the level of water uptake.