TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Composition: The nickel compound is nickel halide and complex of nitrogen-containing bi-dentate ligand and zinc. The content of nickel compound is 0.01-5 mol with respect to 1 mol monomers in monomer composition.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Composition: The dihalo sulfo compound (VI) is preferably of formula (VII), (VIII) or (IX). The arylene dihalide compound (XII) is preferably of formula (XIV). The arylene diboronic acid compound (XIII) is preferably of formula (XV).    TECHNOLOGY FOCUS - POLYMERS - Preparation (claimed): A monomer composition containing polyarylene dihalide of formula: X-(Ar1)n-X (X) which does have ion exchange group and dihalo sulfo compound of formula: X-Ar2-X (VI) is polymerized, and converting group of formula: -S(=O)(=O)-OM into sulfo group (a).X=halo;OM=-OM1 or -O-M2+;M1=1-20C alkyl;andM2+=alkali-metal cation or cation of ammonium compound.Preferred Process: The monomer composition is polymerized in presence of nickel compound. The polyarylene dihalide (X) is obtained by carrying out coupling reaction of arylene dihalide compound of formula: X-Ar3-X (XII) and arylene diboronic acid compound of formula: B(-R1O)(-R1O)-Ar4-B(-OR1)(-OR1) (XIII) in presence of palladium catalyst.Ar3,Ar4=Ar1;andR1=H or 1-20C alkyl.Preferred Composition: The repeating unit (I) is preferably of formula (i). The repeating unit (III) is preferably of formula (ii). The polyarylene dihalide compound (X) is preferably of formula (XI).R=substituent A;g=0-4;j=1-4;m=0-3;andj+m=1-4. EXAMPLE - 13 g 4,4'-Dichloro-2,2'-bis(trifluoromethyl)-biphenyl, 17.8 g 2,2'-bis(trifluoromethyl)-4,4'-biphenyl diboronic acid bis(pinacol), 30.7 g potassium phosphate, 221 g toluene and 26.5 g water were mixed, argon gas was blown in at 25 degrees C for 30 minutes, and stirred. 0.16 g Palladium acetate and 0.59 g phosphorus compound were added into resultant mixture and reacted at 90 degrees C for 6 hours in nitrogen atmosphere. The obtained reaction mixture was cooled to 25 degrees C. 360 g Water and 670 g ethyl acetate were added to resultant mixture, and liquid separation was carried out. An oil layer was removed and washed using sodium hydrogencarbonate and 5% water. 1000 g Tetrahydrofuran was added into obtained mixture, and heated at 50 degrees C. Solid content of the reaction mixture was separated. 23.9 g Obtained crude products was concentrated and dried, to obtain (2,2'-bis(trifluoromethyl)-4,4'-biphenylene)dichloride with yield of 97.8%, weight average molecular weight (Mw) of 17400, and number average molecular weight (Mn) of 8600.