TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The (per)fluoro sulfonyl fluoride polymer comprises repeating monomeric units derived from: (A) at least one ethylenically unsaturated (per)fluoro monomer free from (-SO2F) groups; and (B) at least one (per)fluoro vinyl ether comprising at least one (-SO2F) group. Alternatively, the (per)fluoro sulfonyl fluoride polymer in the -SO2F form comprises repeating monomeric units derived from: (A') at least one 2-8C perfluoro olefin; (B') at least one sulfonyl fluoride perfluoro vinyl ether, where (B') is a sulfonyl fluoride perfluoro vinyl ether of formula F2C=CF-O-CF2-CF2-SO2F. The component (B) is a sulfonyl fluoride perfluoro vinyl ether of formula F2C=CF-O-CF2-CF2-SO2F. The polymer particles form an aqueous latex. The polymer particles of the aqueous latex have a size of 10-300 nm. The aqueous latex is obtainable throughout an emulsion or micro-emulsion polymerization process involving the copolymerization of the monomers (A) and (B). The aqueous suspending medium comprises the liquid suspending medium of the latex. Preferred Composition: The catalyst-polymer liquid dispersion (LD) is free from the liquid suspending medium of the latex or organic solvent; and further comprises at least one viscosity modifier. The weight amount of the catalyst particles, polymer particles and the aqueous suspending medium forms at least 96 wt.% based on the total weight of the liquid dispersion (LD). The dispersion (LD) consists of: (i) catalyst particles, (ii) polymer particles consisting of at least one (per)fluoro sulfonyl fluoride polymer in the -SO2F form, (iii) an aqueous suspending medium, and (iv) optionally, at least one viscosity modifier. Preferred Method: In the method (M3) for preparing the catalyst coated membrane (CCM), the membrane provided in step (a2) is a film consisting of at least one (per)fluoro sulfonyl fluoride polymer in the -SO2F, SO3H or SO3M form. EXAMPLE - A catalyst-polymer liquid dispersion was prepared. A mixture of demineralized water (11.5 l), sulfonyl fluoride perfluoro vinyl ether (having formula: CF2=CF-O-CF2-CF2-SO2F) (A1) (980 g), and water solution containing 5 wt.% of the fluorinated surfactant CF2ClO(CF2CF(CF3)O)n(CF2O)mCF2COOK (average mol. wt. 521)(where n/m = 10), was stirred at 540 rpm and heated to 60degreesC. A water solution (150 ml) containing potassium persulfate (6 g/l) was added. The pressure in the autoclave was maintained at 13 bar while feeding tetrafluoroethylene (TFE) (1000 g). Once the addition of TFE was completed, (A1) (175 g) was further added. During the polymerization reaction, additional amounts of TFE and (A1) were fed (175 g (A1) for every 200 g of TFE). After an overall polymerization reaction time of 248 minutes and the addition of a total amount of TFE of 4000 g, the polymerization was interrupted by stopping the stirring, cooling and venting the unreacted TFE. The aqueous latex of polymer particles in the -SO2F form thus obtained had a polymer concentration of 28 wt.%. The aqueous latex was kept under nitrogen bubbling for 16 hours to eliminate the residual unreacted monomers, and it was stored. TANAKA (RTM: Pt on carbon (Pt/C) catalyst containing 50 wt.% of platinum) (4 g) was dispersed in 300 ml of water, heated to 80degreesC and stirred until the solid was completely wetted and a slurry was obtained. The slurry was then sonicated for 30 minutes at 80degreesC. The aqueous latex of the perfiuoro sulfonyl fluoride polymer produced in the previous step was added dropwise with a rate of 1 drop every 3 seconds until a ratio of 3:1 between the catalyst and the polymer added was reached. The slurry was stirred further for 60 minutes, filtered on paper filters. The filtered solid was then washed, dried and grinded until obtaining a smooth powder consisting of particles of catalyst and polymer in the -SO2F form (5.3 g). The obtained powder (4 g) was dispersed in water solution (40 g, pH 7) containing 4000 ppm of Carbopol (RTM: viscosity modifier) (the pH value of the solution was adjusted by diluted aqueous KOH) to obtain the catalyst-polymer liquid dispersion. A catalytic ionomeric ink was prepared using the dispersion, and a catalyst coated membrane (test) was prepared using the ionomeric ink. A fuel cell was set up using the catalyst coated membrane and run for 8 hours, then cell temperature was raised to 90degreesC and the voltage values at different current densities were recorded. For comparison, a previously described catalyst membrane (control) was used and voltage values were also recorded. At the following current densities, the voltage values at different current densities for (test)/(control) were as follows: at current density of 1.2 A/cm2: (567/533) mV; at 0.8: (712/632) mV; at 0.2: (827/788) mV; and at 0: 943/937 mV. The results demonstrated that the test membrane showed better voltage/current balance than the control, when used in a fuel cell.