Actuation increase in polypyrrole bilayer by photo-activated dopants

A new methodology to increase the polypyrrole (PPy) bilayer actuation displacement is presented, based on photo-activated dopants generating secondary charges. Two dopants, dodecyl benzenesulfonate (DBS) and the photo-active dopant 2-diazo-1-naphthol-5-sulfonic acid (DNSA), were compared in this study. PPy/DBS, PPy/DBS-DNSA and PPy/DNSA bilayers on polyethylene terephthalate were formed and their actuation properties in aqueous electrolyte were investigated applying cyclic voltammetry and square wave potential steps. Exposure to solar irradiation increased PPy/DBS-DNSA and PPy/DNSA bilayer bending displacements by two and three times, respectively, accompanied by increased charge density during the reversible redox cycles. UV-vis and Fourier transform infrared (FTIR) measurements were also performed to follow the photo reaction of the photo-active dopants.