Bending of polyelectrolyte membrane platinum composites by electric stimuli Part II. Response kinetics

In previous papers, it was reported that a solid polymer electrolyte membra ne-platinum (SPM-Pt) composite bent in response to electric stimuli. In thi s paper, a model, in which electric fields can induce mechanical deformatio n in the SPM via electrokinetically induced pressure gradients, was applied to the kinetics of the bending response. In order to compare the theoretic al model with the experimental result, simultaneous measurement was carried out with the displacement and the electrochemical properties for the compo sites prepared from membranes of different thickness in various kinds of sa lt solution. The curvature response was simulated by the empirical equation s having one characteristic time. The characteristic time was linearly prop ortional to the square of the thickness of the membrane. The parameter whic h means curvature per unit charge was linearly proportional to the reciproc al of the square of the membrane thickness, and the water transference coef ficient of the membrane of various ionic forms. The results support the the oretical model. In addition to the electrokinetic effect, the model include s the effect of the interfacial stress between the Pt electrode and the SPM . The bending behavior after the characteristic time can be explained succe ssfully by the model including the interfacial effect. (C) 2000 Elsevier Sc ience S.A. All rights reserved.