TECHNOLOGY FOCUS - POLYMERS - Preparation (Claimed): Preparation of the polyelectrolyte involving either: polymerizing monomers of formulae (I), (II) and (III) to give the polymerization product of formula (Ia), where the mol factions of monomers are such that: I=50%, II=((1-I)-III)), and III=((1-I)-II)) (preferably II=0.01-0.49 mol fraction and III=0.01-0.49 mol fraction); polymerizing monomers of formulae (I), (IV) and (III') to give the polymerization product of formula (Ib), where the mol factions of monomers are such that: I=50%, IV=((1-I)-III')), and III'=((1-I)-IV)); polymerizing monomers of formulae (I), (II') and (V) to give the polymerization product of formula (Ic), where the mol factions of monomers are such that: I=50%, II'=((1-I)-V)), and V=((1-I)-II)); polymerizing monomers of formulae (I), (II), (III') and C'-Rc-Ra(Rb-B')2-Rb-B' (VI) to give the polymerization product of formula (Id), where the mol factions of monomers are such that: I=50%, II=((1-I)-(III'+VI), III'=((1-I)-(II+ VI)), and VI=((1-I)-(II+III')); or polymerizing monomer of formula (I) to give the polymerization product of formula (Ie). In the process, ion-exchange and solvent-exchange is used to convert the neutralized polyelectrolyte to the H+ form. (Structures (I)-(III), WO2008076637A1-001) (Structure (Ia), WO2008076637A1-002) (Structures (IV) and (III'), WO2008076637A1-003) (Structure (Ib), WO2008076637A1-004) (Structures (II') and (V), WO2008076637A1-005) (Structure (Ic), WO2008076637A1-006) (Structure (Id), WO2008076637A1-007) (Structure (Ie), WO2008076637A1-008)A'=leaving group capable of eliminating from the monomer by nucleophilic attack including F, Cl, Br, I, nitro or fluorosulfonate;B'=nucleophilic group such as alcohol, metal alkoxide, amine, thiol, metal thiolate or metal carbanion;R=electron-withdrawing group which is also hydrolytically and free-radical attack stable such as sulfone, ketone, thioketone, phosphine or phosphine oxide;R'=R or another hydrolytically-stable and free radical-stable group such as bond, disubstituted alkane, disubstituted perfluoroalkane, ether, thioether or (alkyl)amine;R''=R', R or another hydrolytically-stable and free radical-stable group such as bond, disubstituted alkane, disubstituted perfluoroalkane, ether, thioether or (alkyl)amine;W'=sulfonate, phosphonate or carboxylate;Z'=H, sulfonate, phosphonate or carboxylate;Y'=Group capable of cross-linking i.e. alcohol, amine, vinylic or alkyl halide;R1=hydrolytically-stable and free radical-stable group such as bond, disubstituted alkane, disubstituted perfluoroalkane, ether, thioether or (alkyl)amine;Ra=carbon atom, alkane, perfluoroalkane, cycloalkane, aryl or other hydrolytically and free-radical-stable group capable of bearing at least 3 additional groups;Rb=alkyl, cycloalkyl, perfluoroalkyl, aryl, benzyl or other hydrolytically and free-radical-stable group;Rc=Rb or another group selected from those listed for group Rb;C'=H, alkyl, cycloalkyl, perfluoroalkyl, aryl, benzyl or other hydrolytically and free-radical-stable group;X=additional aryl-backbone polymer chain containing additional branching monomers (branching points) VI;X'=X or H;m=(n+p)=0.5;n=0.01-0.49;p=0.01-0.49;m1=(n1+p1+q1)=0.5;n1=0.01-0.48;p1=0.01-0.48;q1=0.01-0.48.Provided that: when group Z' is hydrogen, post-polymerization reaction is performed to introduce a group W' onto the ring; if groups Z' on monomer II' are hydrogen, then conversion to acidic groups W' is by sulfonation; if Rc is Rb, then C' is B'; and if Rc is Rb, then C' is B' and X' is X. The groups Z' and Y' are bound to any open position on each aromatic ring, either ortho or meta to groups R, R', R'' with one group (Z' or Y') per aromatic ring. The groups B' on monomer IV is bound to the naphthalenic ring at any position (1-8), not occupied by a group W', and groups W' on monomer IV is bound to the naphthalenic ring at any position (1-8), not occupied by a group B' (preferably groups B' on monomer IV are bound at the 4 and 5-positions, and groups W' at the 2 and 7-positions). The groups B' on monomer V is bound to any ring position not occupied by group Y'. The group Y' on monomer V is bound to any ring position not occupied by groups B'. Preferred Polyelectrolyte: The polyelectrolyte contains related aryl groups on the polymer backbone and possessing at least one repeat unit, where one repeat unit is substituted at 1-49% with sulfonate functional groups and the same or a different unit is substituted at 1-49% with crosslinkable groups. The aryl units comprise aryl-ether units. The polyelectrolyte contains at least two different monomeric units; sulfonated naphthyl diols; and 3,5-dihydroxybenzyl alcohol as a diol and/or as the cross-linkable group. The polyelectrolyte is formed from a single monomer bearing acidic and cross-linkable groups. The polyelectrolyte has a leaving group monomer (50 mol.%), and a nucleophilic monomer (50 mol.%), where up to 50 mol.% of nucleophilic monomer units comprises cross-linkable monomer. The polyelectrolyte is of formula (I). The polyelectrolyte is in the form of a neutral salt, organic quaternary ammonium salt, tetrabutylammonium salt, or acid. Preferred Film: The film comprises a separator in a fuel cell. EXAMPLE - Dichlorodiphenylsulfone (108 g) was added to a round bottom flask and dissolved in fuming sulfuric acid (210 mL). Following dissolution of the majority of the sulfone, the contents were heated at 110 degrees C for 16 hours under N2. After work up, 4,4'-dichloro-3,3'-disulfonatodiphenyl sulfone disodium salt (SDCDPS) (169.17 g) was obtained. SDCDPS (8.75 g), bisphenol A (3.07 g), and 2,2'-diallylbisphenol (1.04 g) were added to a multineck flask and dissolved in a mixture (2.66 g) of N,N'-dimethylacetamide (80 mL)/PhMe.K2CO3 (40 mL) was added and after work up, corresponding polymer (2.43 g) was obtained.