CATION-EXCHANGE MEMBRANE, FLUORINE-CONTAINING POLYMER, METHOD FOR PRODUCING FLUORINE-CONTAINING POLYMER, AND ELECTROLYZER

To provide a fluorine-containing polymer that achieves both of low resistivity and high heat stability, which have been thought to be mutually contradictory properties, a cation-exchange membrane having the fluorine-containing polymer, and an electrolytic cell having the cation-exchange membrane.SOLUTION: A cation-exchange membrane has a fluorine-containing polymer having a tetrafluoroethylene unit (A) and a perfluoroethylene unit (B) having a carboxylic acid ion exchange group, and having a main chain terminal structure (T) represented by the formula (1) (where, m and n each denote any integer satisfying m≥2, n≥0, 2m-n≥1).SELECTED DRAWING: Figure 1 【課題】従来相反する低い抵抗率及び高い熱安定性を両立する含フッ素系重合体、該含フッ素系重合体を含む陽イオン交換膜、該陽イオン交換膜を備える電解槽を提供する。【解決手段】テトラフルオロエチレン単位（Ａ）とカルボン酸型イオン交換基を有するパーフルオロエチレン単位（Ｂ）とを含有し、かつ、下記式（１）で表される主鎖末端構造（Ｔ）を有する含フッ素系重合体を含む、陽イオン交換膜。【化１】（式（１）中、ｍ及びｎは、ｍ≧２、ｎ≧０、２ｍ−ｎ≧１を満たす任意の整数を表す。）【選択図】図１