TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Composition: The fuel cell contains mixture of 1-6C organic compound and water as fuel. The ionic group is chosen from sulfonic acid group, sulfonimide group, sulfate group, phosphonic acid group, phosphoric acid group and carboxylic acid, preferably sulfonic acid group contained in an amount of 0.5-3 mmol/g.    TECHNOLOGY FOCUS - POLYMERS - Preferred Unit: The structural unit of formula (P1) is preferably of formula (P2), which is optionally substituted. The polymer (I) further contains structural unit of formula (P5).X1=divalent bond or divalent organic group;Y1=-CO-, -SO2-, or -P(Rp)O-;Rp=organic group;M1,M2=H, metal cation or ammonium cation;anda,b=1-4. Preferred Definitions:    Q1,Q2=perfluoro alkyl group;    X1=groups of formulae (P3,P4);and    Ar1=groups of formulae (P6-P8).    Z1=H, alkyl or aryl, preferably phenyl;    Z2=direct bond, methylene group, -CO-, -SO2-, O or S, preferably direct bond;    Z3=-CO- or -SO2-;    Z4=O, S or NRn;and    Rn=organic group.    EXAMPLE - Grignard reagent prepared from 5-bromo-2-fluorobenz trifluoride and magnesium was reacted with trimethoxy boron, to obtain 4-fluoro-trifluoromethyl phenyl boric acid. 4-fluoro-trifluoromethyl phenyl boric acid (in g) (67) and p-dibromobenzene (31) were reacted in toluene/water medium in presence of sodium carbonate and palladium tetraphenyl phosphine, to obtain diphenyl monomer. Potassium carbonate (3.5), 4,4'-dihydroxy tetraphenyl methane (7.1), difluoro monomer (1.6) and sulfonated difluoro monomer (8.1) were polymerized at 190degreesC in N-methyl-2-pyrrolidone. The obtained polymer was reprecipitated with water, to obtain polymer having weight average molecular weight of 220000 and sulfonic acid group density of 1 mmol/g after proton substitution. The obtained polymer was dissolved in N-methyl-2-pyrrolidone and spread on glass substrate. Subsequently, the polymer solution was heat-processed at 325degreesC for 10 minutes under nitrogen, to obtain polymeric electrolytic film with thickness of 33 microns. The film had excellent methanol cross over inhibitory effect, high proton conductivity and excellent heat-resistant methanol property.