Abstract: A polymer electrolyte membrane which exhibits superior high-temperature operability and a fuel cell and the like comprising the polymer electrolyte membrane are provided. In an aspect, the present invention relates to a polymer electrolyte membrane comprising a polymer electrolyte and having a first surface and a second surface, wherein the water vapor permeability coefficient from the first surface of the polymer electrolyte membrane to the second surface which is measured in a state where the first surface is exposed to a humidified environment of a temperature of 85° C. and a relative humidity of 20% and the second surface is exposed to a non-humidified environment of a temperature of 85° C. and a relative humidity of 0% is equal to or higher than 7.0×10?10 mol/sec/cm, and the breaking stress at a temperature of 80° C. and a relative humidity of 90% is equal to or greater than 20 MPa.

Abstract: The present invention provides a polyarylene-based copolymer including a plurality of segments having an ion exchange group and a plurality of segments having substantially no ion exchange group, wherein at least one of the segments having an ion exchange group includes a polyarylene structure, the polystyrene-equivalent weight-average molecular weight of the segments having an ion exchange group is from 10,000 to 250,000, and the ion exchange capacity of the polyarylene-based copolymer is 3.0 meq/g or more.

Abstract: A polymer electrolyte composition comprising a component (A) defined below, and at least one kind of a component (B) selected from the group consisting of a component (B1) defined below and a component (B2) defined below: (A) a polymer electrolyte; (B1) a compound having a degree of affinity for platinum of 10% or more; and (B2) a compound having at least two kinds of atoms having an unshared electron pair, selected from the group consisting of a nitrogen atom, a phosphorus atom, and a sulfur atom in the molecule.

Abstract: An object of the present invention is to provide an ion-conductive composition that has proton conductivity over a wide temperature range, including the intermediate and high temperature range of 100° C. and higher, and an ion-conductive composite material such as ion-conductive membrane prepared from the composition. The composite ion-conductive material comprises the ion-conductive composition of the present invention, and the ion-conductive composition includes an ion-conductive polymer and ion-conductive inorganic solid material.

Abstract: To provide a polymer electrolyte membrane with excellent radical resistance, a polymer electrolyte composition for the polymer electrolyte membrane, and further a polymer electrolyte type fuel cell using the polymer electrolyte membrane. [1] A polymer electrolyte composition comprising the following component (a), (b) and (c): (a) a polymer electrolyte having a strong acid group, (b) a compound having at least one group containing a pentavalent phosphorous atom, and (c) an antioxidant [2] The polymer electrolyte composition described in the above [1], wherein the component (b) comprises a copolymer expressed by the following formula (6): wherein Z represents a sulfonyl group or a carbonyl group. Ar represents a divalent aromatic group, R1 and R2 represent a hydrogen atom or a monovalent organic group. [3] A polymer electrolyte membrane obtained using the polymer electrolyte composition of the above [1] or [2]. [4] A fuel cell composed of the polymer electrolyte membrane described in the above [3].