Effects of monomer and electrolyte concentrations on actuation of PPy(DBS) bilayers

Bilayers of gold-coated Kapton and polypyrrole doped with dodecylbenzenesulfonate PPy(DBS), were prepared electrochemically, and their bending movement was studied under electrochemical stimulation. The effects on actuation of monomer and electrolyte concentration during deposition, as well as electrolyte concentration during subsequent electrochemical cycling, are presented. Lowering the pyrrole concentration decreased hysteresis, somewhat increased actuator speed, and unexpectedly eliminated the so-called capacitive current above the oxidation peak. Neither pyrrole nor electrolyte concentration in the deposition solution affected the extent of movement, despite the fact that the former strongly impacted the cyclic voltammograms. The cyclic voltammograms were, therefore, not predictive of the extent of bending, and strain could not be significantly improved by altering the concentration of either monomer or salt in the deposition solution. Raising the deposition electrolyte concentration, and in particular raising it with respect to the pyrrole concentration, did increase the movement to charge ratio, making the actuators more efficient.