TECHNOLOGY FOCUS - POLYMERS - Preparation: No general preparation given. Preferred Components: The ion-conducting copolymer comprises ion conducting arylene segment comprising ion conducting group, and non-ion conducting elastomeric segment. The elastomeric segment comprises butadiene, isoprene, styrene, acrylonitrile and/or ethylene monomers, preferably styrene/butadiene/styrene block copolymer, styrene/isoprene block/styrene block copolymer, random styrene/butadiene copolymers, tapered styrene/butadiene rubber, microblock styrene/butadiene rubber, random styrene/isoprene copolymer, tapered styrene/isoprene rubber, random styrene/butadiene/isoprene, styrene-ethylene/butylene-styrene block copolymer, styrene-ethylene/butylene block copolymer, styrene- ethylene/propylene-block copolymer, styrene-ethylene/propylene-styrene block copolymer, styrene-ethylene/propylene-ethylene block copolymer, styrene- ethylene/butylene-ethylene block copolymer, styrene-ethylene/styrene block copolymer, ethylene-ethylene/butylene block copolymer, ethylene-ethylene/butylene/styrene block copolymer (hydrogenated BR-SBR block copolymer), ethylene-ethylene/butylene/styrene-ethylene block copolymer (hydrogenated BR-SBR-BR block copolymer), ethylene-ethylene/butylene-ethylene block copolymer or partially or fully hydrogenated polymers and copolymers. An ion conducting membrane comprises a polymer electrolyte membrane having adhesion promotion layer in contact with surfaces (a) and/or (b). The adhesion promotion layer comprises the ion conducting polymer. A catalyst coated membrane comprises the polymer electrolyte membrane in which all or portion of opposing surfaces comprises a catalyst layer. A membrane electrode assembly comprises polymer electrolyte membrane, catalyst layer (a1) and adhesion promotion layer. The polymer electrolyte membrane comprises ion conducting polymer (i) on the surfaces. The catalyst layer (a1) comprises ion conducting polymer (ii) and catalyst. The adhesion promotion layer is in contact with surface of polymer electrolyte membrane and catalyst layer. The adhesion promotion layer comprises an ion conducting adhesive copolymer comprising the ion conducting copolymer. The ion conducting polymers (i or ii) comprises a polyarylene segment. The polyarylene segment of ion conducting adhesive copolymer comprises polyarylene segment of said first or said second ion conducting polymers. The ion conducting polymer of formula (I) is preferably of formula (II).r=10-500, preferably 70-80;x=mole fraction of monomer containing sulfonic acid moieties, which is 0.3 or more, preferably 1;z=1-100;andy=2-500, preferably 19-40.Preferred Properties: The adhesion promotion layer has thickness of 200-5000 nm. The adhesion of catalyst layer to polymer electrolyte membrane via adhesion promotion layer is more that the adhesion of electrode to polymer electrolyte membrane without adhesion promotion layer. Preferred Composition: The adhesive composition further comprises inorganic particles. Preferred Definitions:    ISC=(((Ar 1-T-) i-Ar 1-X-) a(power)m(Ar 2-U'-Ar 2-X-) b(power)n((Ar 3-V'-) j-Ar 3-X-) c(power)o(Ar 4-W'-Ar 4-X-) d(power)p);    Ar 1-Ar 4=aromatic moieties;    T,U',V',W'=linking moieties;    X=-O- or -S-;    i,j=1 or more;    a-d=mole fractions, in which a and/or b is more than 0 and sum of a, b, c and d is 1;and    m-p=integers indicating the number of different oligomers or monomers in the copolymer.    At least one of Ar 1or Ar 2comprises an ion conducting group. At least one of Ar 1, Ar 2, Ar 3and Ar 4comprises cyclohexylidene bisphenol monomer or benzophenone monomer comprising ion conducting group.    EXAMPLE - Carboxy-terminated butadiene oligomer of formula (1) (in g) (12) having molecular weight of 4000 was dissolved in toluene (100), added to phosphorus pentachloride (1.7), stirred at 80 degrees C for 2 hours and toluene was removed, to obtain acyl chloride-terminated butadiene oligomer of formula (2). 4,4'-Difluorobenzophenone (11.055), 4,4'-difluorobenzophenone-3,3'-disodium sulfonate (9.169) and cyclohexylidene bisphenol (18.452) were dissolved in dimethyl sulfoxide (200) and toluene (100) with potassium carbonate (10.929). The reaction mixture was heated at120-170 degrees C for 8 hours and cooled, to obtain fluoro-terminated sulfonated oligomer intermediate. Then, 4-aminophenol (0.80) and toluene (200) were to the reaction mixture, heated at 120-170 degrees C for 8 hours and cooled, to obtain amino-terminated sulfonated oligomer of formula (3). Acyl chloride-terminated butadiene oligomer (13.82) and amino-terminated sulfonated oligomer (5.52) were dissolved in toluene (20) and N,N-dimethylformamide (20) and stirred at 170 degrees C for 16 hours under nitrogen, to obtain ion-conducting copolymer of formula (II).    r=20-200.