Ion exchange membrane studies began as basic and academic research and have grown to today's huge membrane technology. From finding ion exchange phenomena in soil, it has taken about 170 years, and following studies of membrane phenomena in biological cell membranes about 80 years have passed.

Today, ion exchange membranes are essential in industry and daily human life. Initially, membranes were mainly applied to electrodialysis to concentrate and desalinate salt solutions to prepare drinking water and salt. In 1972, the perfluorocarbon ion exchange membrane was developed and provided a new era of applications. The chlor-alkali membrane process using perfluorocarbon ion exchange membranes is the most energy saving electrolysis method, is without pollution problems, and produces a highly pure product. The membrane resulted in a large technical revolution. Composites of ion exchange membranes and electrodes (membrane electrode assembly: MEA), in which the membrane is used as a solid polymer electrolyte, have provided new applications: water electrolysis to produce hydrogen gas using only pure water as the feed, and production of oxidizing agents such as O ₃, H ₂O ₂, etc.; fuel cells. Especially, the proton electrolyte fuel cell (PEFC) and direct methanol fuel cell (DMFC) are expected to be significant electric power generators for automobiles and stationary electric power generators in the near future.

With expansion of their use, unsolved problems of the membrane and requirements have arisen over about half a century. Some of them are:

1. There are no stable anion exchange groups in strong alkali...