POLYMER ELECTROLYTE MEMBRANE, ELECTROLYTE MEMBRANE WITH CATALYST LAYER USING THE SAME, MEMBRANE ELECTRODE COMPOSITE, POLYMER ELECTROLYTE FUEL CELL, AND WATER ELECTROLYSIS TYPE HYDROGEN GENERATOR

To achieve a polymer electrolyte membrane having excellent proton conductivity even in low humidity conditions and also having excellent mechanical strength and chemical stability.SOLUTION: There is provided a polymer electrolyte membrane comprising a block copolymer having one or more, respectively, of ionic segments and non-ionic segments. The block copolymer has an ion exchange capacity (meq/g) of more than 2.0 and less than 3.1, the polymer electrolyte membrane has a co-continuous phase separation structure, an average period size (nm) of the co-continuous phase separation structure as observed by a transmission electron microscope is less than 110 nm, and the average period size (nm) and the ion exchange capacity (meq/g) of the co-continuous phase separation structure satisfy a relationship, average period size (nm)/ion exchange capacity (meq/g)≥21.SELECTED DRAWING: None 【課題】低加湿条件下においても優れたプロトン伝導性を有し、機械強度および化学的安定性にも優れた高分子電解質膜を実現すること。【解決手段】イオン性セグメントと、非イオン性セグメントと、をそれぞれ一個以上有するブロック共重合体を含む高分子電解質膜であって、前記ブロック共重合体が、イオン交換容量（ｍｅｑ／ｇ）が２．０を超え３．１未満であり、前記高分子電解質膜が共連続相分離構造を有し、透過電子顕微鏡によって観察される前記共連続相分離構造の平均周期サイズ（ｎｍ）が１１０ｎｍ未満であり、前記共連続相分離構造の平均周期サイズ（ｎｍ）と前記イオン交換容量（ｍｅｑ／ｇ）が平均周期サイズ（ｎｍ）／イオン交換容量（ｍｅｑ／ｇ）≧２１の関係を満たすことを特徴とする高分子電解質膜。【選択図】なし