TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Composition: The block (B) contains oxygen-containing repeating structural unit of formula (II or III). The block (A) further contains carbonyl group-containing structural units of formulae (IV,V).R2-R5=H or proton acid group, preferably -CnH2n-SO3Z, -CnH2n-PO2Z2 or -CnH2n-COOZ, and at least one of R2-R5 is proton acid group;n=0-10;Z=H, Na or K;i,j,k,m=0 or 1;R6=same as R1;A3-A8=same as A1;Y=group of formula (c) or group of formula (b);R7,R8=H or proton acid group;andX=group of formula (a) or group of formula (b)Hydrogen atom of aromatic ring in formulae (II,III) is optionally substituted by proton acid group, -F, -CF3, -Si(CH3)3, -OSi(CH3)3 or -CN. Hydrogen atom of aromatic ring in formula (IV) is optionally substituted by -CmH2m+1 (where m is 1-10), -F or -CF3. Hydrogen atom of aromatic ring in formula (V) is not substituted. Alcohol is directly used for fuel in fuel cell. EXAMPLE - 3,3'-carbonyl bis(6-fluorobenzene sulfonic acid sodium) (in g) (14.7802), 2,2-bis(4-hydroxy phenyl) propane (9.9877) and anhydrous potassium carbonate (5.8) were heated at 140degreesC, and dimethyl sulfoxide (99) and toluene (40) were added. The mixture was reacted, and precipitated product was washed with acetone and dried at 150degreesC. An oligomer containing proton acid group (sulfonic acid sodium salt group) directly bonded to aromatic ring and not having alkyl group directly bonded to aromatic ring was obtained. The obtained oligomer had reduced viscosity of 0.2 dl/g. 4,4'-difluoro benzophenone (14.183), 3,3',5,5'-tetramethyl-4,4'-dihydroxy diphenyl methane (14.4197), anhydrous potassium carbonate (10.76), dimethyl sulfoxide (114) and toluene (46) were added and heated at 140degreesC for 4 hours. The mixture was reacted for 4 hours. The resulting reaction mixture was washed with acetone and distilled water, filtered and dried, to obtain crosslinkable proton conductive block copolymer (46.2) having sulfonic acid sodium salt group was obtained with yield of 93.5%. The obtained block copolymer had reduced viscosity of 1.45 dl/g. A proton conduction film having methanol permeability of 0.54 micronsol/cm2.minute, water absorption of 11%, proton conductivity of 0.011 S/cm and ion exchange group equivalent of 770 g/mol, was formed using the obtained crosslinkable proton conductive block copolymer.