TECHNOLOGY FOCUS - POLYMERS - Preferred Composition: The polyelectrolyte is aromatic polyelectrolyte containing ion exchange group and having repeating units chosen from formulae: -(Ar1-Z-Ar2-X)- (1a), -(Ar3-Z'-Ar4-X'-Ar5(-Y'-Ar6)p-X')- (2a), -((Ar7)q-X"(-Ar8)r-X")- (3a) and/or -(Ar9)- (4a), or polyelectrolyte having repeating unit which does not contain ion exchange group and has structure chosen from formulae: -(Ar11-Z-Ar12-X)- (1b), -(Ar13-Z'-Ar14-X'-Ar15(-Y'-Ar16)p'-X')- (2b), -((Ar17)q-X"(-Ar18)r'-X")- (3b) and/or -(Ar19)- (4b).Ar1-Ar9,Ar11-Ar19=optionally substituted arylene group;Z,Z'=-SO2- or -CO-;X,X',X"=-O- or -S-;Y'=-C(Ra)(Rb)-;p=0, 1 or 2;q,r=1, 2 or 3;p'=1 or 2;q',r'=1, 2 or 3;andRa,Rb=1-10C alkyl, 1-10C alkoxy, 5-8C cycloalkyl, 1-20C acyl, 6-18C aryl, 6-18C aryloxy (all optionally substituted), or H.Ar1 and/or Ar2, Ar3-Ar6, Ar7 and/or Ar8 and Ar9 have aromatic ring directly bonded with ion exchange group. Ra, Rb may mutually combine to form optionally substituted non-aromatic ring system. The polyelectrolyte is block copolymer, random copolymer and/or graft copolymer containing multiple types of repeating units, preferably block copolymer or random copolymer comprising block (A) having ion exchange group and block (B) which does not have ion exchange group. The block (A) has optionally substituted aromatic ring in the principal chain and ion exchange group directly coupled to the aromatic ring. The block (A) is of formula: -(Ar9)m- (4a') and the block (B) is chosen from formulae: -(Ar11-Z-Ar12-X)n- (1b), -(Ar13-Z'-Ar14-X'-Ar15(-Y'-Ar16)p'-X')n- (2b) and/or -((Ar17)q'-X"(-Ar18)r'-X")n- (3b).Ar9,Ar11-Ar18=arylene group optionally substituted by 1-10C alkyl, 2-20C acyl, 1-10C alkoxy, 6-18C aryl or 6-18C aryloxy;andn=5 or more.The polyelectrolyte has sulfonic acid group as ion exchange group. The high molecular compound is contained in an amount of 0.1-25 weight parts with respect to 100 weight parts of the polyelectrolyte. The N-hydroxy imide structural unit is residue obtained after removing hydrogen atom from cyclic compound of formula (5 or 7), and the structural unit is of formula (6 or 8).Q=-CRcRd-, -O- or -S-;j=0-2;andR1-R4,Rc,Rd=1-10C alkyl, 1-10C alkoxy, 5-8C cycloalkyl, 1-20C acyl, 6-18C aryl, 6-18C aryloxy (all optionally substituted), H, hydroxyl, carboxyl, nitro, amino or cyano group.When j is 0, a single bond is represented and R1-R4 are not cyano and/or nitro. When j is 1 or 2, R1-R4, Rc and Rd may combine to form optionally substituted aromatic or non-aromatic ring. The high molecular compound contains repeating unit containing N-hydroxy imide structure and repeating unit which does not contain N-hydroxy imide structure of formula: -(C(R5)(R6)-C(R7)(R8))- (9) or -(Ar21)- (10).R5-R8=1-10C alkyl, 1-10C alkoxy, 5-8C cycloalkyl, 1-20C acyl, 6-18C aryl, 6-18C aryloxy (all optionally substituted), H, hydroxyl, carboxyl, nitro, amino, cyano or carbonyl group;andAr21=optionally substituted arylene.