PROPERTIES OF ION-EXCHANGE MEMBRANES COMBINED ANISOTROPICALLY WITH CONDUCTING POLYMERS .2. RELATIONSHIP OF ELECTRICAL POTENTIAL GENERATION TO PREPARATION CONDITIONS OF COMPOSITE MEMBRANES

Preparation and properties of cation-exchange membranes with which polypyrrole had been combined anisotropically were studied in detail. When one side of a cation-exchange membrane in the ferric ion form contacted an aqueous pyrrole solution for a given period, pyrrole polymerized easily and quickly and formed a polypyrrole layer in the membrane matrix beginning from the membrane surface. The polypyrrole layer was so tight that pyrrole molecules could not permeate it in 50 h of exposure. X-ray microanalysis of a cross section of the membrane revealed its anisotropic structure. During this oxidative polymerization of pyrrole, more than 90% of the ferric ions in the membrane phase were reduced to ferrous ions. On the surface of the membrane opposite the polypyrrole layer was a cation-exchange membrane layer that contained ferric ions, while most of the membrane contained ferrous ions. When this composite membrane was held tightly between two platinum plates, a electrical potential was observed because of Fe2+-Fe3+ redox reactions. To confirm this further, a ferric ion form of a cation-exchange membrane and a cation-exchange membrane in which polypyrrole had been impregnated from both surfaces were clamped together tightly between two platinum plates and placed into pure water to hydrate the membranes. A higher electrical potential was observed when compared with the composite membrane.