Bending direction of Ag-plated IPMC containing immobile anions and/or cations

Abstract

One of IPMCs, Ag-plated Selemion CMV containing –SO 3H atomic groups, exhibited bending under a voltage. Its bending curvature heavily depended on the total charge given to it. The way in which the charge was given to Ag-plated Selemion CMV did not matter, as the bending curvature was always proportional to the charge quantity, as long as the environmental humidity was maintained constant. Such a proportionality was observed even for Ag-plated NEOSEPTA CMB containing –SO 3H atomic groups. Even Ag-plated Selemion AMV and NEOSEPTA AHA both of which contained amino groups instead of –SO 3H atomic groups bent in the same direction as Ag-plated Selemion CMV and NEOSEPTA CMB after long application of voltage. Furthermore, it was observed that Ag-plated amphoteric NEOSEPTA BP-1E containing both –SO 3H and amino groups exhibited bending in the same direction as Ag-plated NEOSEPTA CMB. Hence, the sign of the charge of mobile and immobile ions contained in the ion exchange membrane did not appear to matter for determining the bending direction of IPMC. It was speculated that Ag layers played a central role for the bending induction of IPMC, and the ion exchange membrane per se must played primarily a role of current mediator and has almost nothing to do with determining the bending direction of IPMC.