To provide a membrane electrode assembly which can suppress cracking of the catalyst layers.

The membrane electrode assembly of the present invention is a membrane electrode assembly comprising an anode having a catalyst layer containing a proton-conductive polymer, a cathode having a catalyst layer containing a proton-conductive polymer, and a polymer electrolyte membrane disposed between the anode and the cathode, wherein the proton-conductive polymer contained in the catalyst layer of at least one of the anode and the cathode is a polymer (H) having units containing a cyclic ether structure and sulfonic acid-type functional groups, and the polymer electrolyte membrane contains a porous material containing a fluorinated polymer, and a fluorinated polymer (S) having sulfonic acid-type functional groups.

The disclosed technology relates to esterified and/or ether containing polymers derived from itaconic acid that are free of the less reactive tri-substituted vinyl monomers (e.g., citraconic acid or mesaconic acid) that may be used, for example, as builders in detergent applications, such as in the personal and home care market.

The disclosed technology relates to esterified and/or ether containing polymers derived from itaconic acid that are free of the less reactive tri-substituted vinyl monomers (e.g., citraconic acid or mesaconic acid) that may be used, for example, as builders in detergent applications, such as in the personal and home care market.

To provide a method for fractionating a liquid composition, which is excellent in separability of the liquid composition. This method for fractionating a liquid composition comprises discharging, from a discharge port of a filling nozzle, a liquid composition containing a solvent and a polymer having ion exchange groups, and fractionating a predetermined amount of the liquid composition, characterized in that the temperature of the liquid composition is controlled so that the average tan δ1 of the liquid composition when discharged from the discharge port of the filling nozzle becomes to be at most 1.00.

To provide a method for fractionating a liquid composition, which is excellent in separability of the liquid composition. This method for fractionating a liquid composition comprises discharging, from a discharge port of a filling nozzle, a liquid composition containing a solvent and a polymer having ion exchange groups, and fractionating a predetermined amount of the liquid composition, characterized in that the temperature of the liquid composition is controlled so that the average tan δ1 of the liquid composition when discharged from the discharge port of the filling nozzle becomes to be at most 1.00.

Provided are a polymer composition that can suppress bubbling during membrane formation and peeling of a laminated membrane and an ion-exchange membrane. The polymer composition is a polymer composition including: a fluorine-containing copolymer including a unit (a) derived from a perfluorovinyl compound having a side chain having an ionic group and a unit (b) derived from a fluoroolefin; and a low molecular weight compound (a) having a functional group represented by —COOX (X is H, NH.sub.4, or a monovalent metal ion), wherein a content of the low molecular weight compound (a) is 600 ppm or less based on a mass of the polymer composition.

Provided are a polymer composition that can suppress bubbling during membrane formation and peeling of a laminated membrane and an ion-exchange membrane. The polymer composition is a polymer composition including: a fluorine-containing copolymer including a unit (a) derived from a perfluorovinyl compound having a side chain having an ionic group and a unit (b) derived from a fluoroolefin; and a low molecular weight compound (a) having a functional group represented by —COOX (X is H, NH.sub.4, or a monovalent metal ion), wherein a content of the low molecular weight compound (a) is 600 ppm or less based on a mass of the polymer composition.

Disclosed are: an ionomer dispersion having high dispersion stability while also containing high content of ionomer solids, thus optimizing the ionomer morphology in a polymer electrolyte membrane to allow both the ion conductivity and durability of the polymer electrolyte membrane to be improved; a method for producing the ionomer dispersion; and a polymer electrolyte membrane produced using the method.

Disclosed are: an ionomer dispersion having high dispersion stability while also containing high content of ionomer solids, thus optimizing the ionomer morphology in a polymer electrolyte membrane to allow both the ion conductivity and durability of the polymer electrolyte membrane to be improved; a method for producing the ionomer dispersion; and a polymer electrolyte membrane produced using the method.

Provided is a method for producing polytetrafluoroethylene, which includes polymerizing tetrafluoroethylene in an aqueous medium in the presence of a nucleating agent and a polymer (I) containing a polymerization unit (I) based on a monomer represented by the general formula (I) to obtain polytetrafluoroethylene:

CX.sup.1X.sup.3═CX.sup.2R(—CZ.sup.1Z.sup.2-A.sup.0).sub.m  (I)

wherein X.sup.1 and X.sup.3 are each independently F, Cl, H, or CF.sub.3; X.sup.2 is H, F, an alkyl group, or a fluorine-containing alkyl group; A.sup.0 is an anionic group; R is a linking group; Z.sup.1 and Z.sup.2 are each independently H, F, an alkyl group, or a fluorine-containing alkyl group; and m is an integer of 1 or more.