ELECTROCHEMICALLY-INDUCED CHEMOMECHANICAL BENDING OF BILAYERED ION-EXCHANGE MEMBRANES

A bilayered ion-exchange membrane consisting of poly(styrene-co-4-viny lpyridinium ion) (anion-exchange membrane) and a gel-like mixture of p oly(vinyl alcohol) and poly(acrylic acid) (cation-exchange membrane) w as prepared. The bilayered membrane strip, one end of which is fixed, is placed between two carbon electrodes in a cell which contains KCl s olution of 0.01 mol/kg(-1) molality. If the electric field is applied from the cation-exchange layer side to the anion-exchange layer side, the cation-exchange layer becomes the K+ form and is elongated. On the contrary, if the electric field is reversed, dissociation of water in to H+ and OH- occurs at the interface between the two layers. Conseque ntly, the carboxyl group becomes the acid form, resulting in contracti on of the layer. The anion-exchange layer, which contains a strong bas e group, becomes either the Cl- form or the OH- form with changing the electric field, but there is no detectable change in volume. Thus if the electric field applied to the membrane is periodically reversed, p eriodical bending of the bilayered membrane is observed.