TECHNOLOGY FOCUS - POLYMERS - Preferred Grafted Chain: The grafted chains may be homo- or copolymeric, preferably copolymeric. A monomer of formula (III) is preferably grafted in addition to (I) and (II).D = H, F, CF3, CF2H, CF=CF2, SO2F or SO3-M; andM = counterionPreferred Polymer: A portion of the polymer comprises at least one (preferably at least two, preferably different) ion exchange substituent(s), The ion-exchange substituents are sulfonate or sulfonic acid. 50% of the monomer units in the grafted chains have ion-exchange substituent(s) per monomer unit. The grafted chains comprise an anion and a cation exchange group.Preferred Membrane: The membrane is an ion-exchange membrane, which is substantially gas permeable. When used for an electrochemical fuel cell, the base film is less than 100 micronsm thick.Preferred Preparation (M): For the preparation of (M), when A1 and B1 = aryl groups of monocyclic or fused polycyclic heteroaromatics having at least one nitrogen, PRR' or P(OR)(OR'), and A2 and B2 = H, then the method further comprises alkylating or benzylating a portion of the nitrogen or phosphorus.Preferred Preparation (M1): In the preparation of (M1), the method further comprises the introduction of a sulfonate group, a portion of which is subsequently converted to a substituent which is deactivating with respect to desulfonation. For the introduction of a quaternary ammonium groups when A1 and B1 both = PRR' or P(OR)(OR'), then the method comprises the introduction of a nitro group into at least a portion of the grafted monomer units, and converting a portion of them to quaternary ammonium groups. Optionally, the phosphine or phosphite groups are converted to an ion exchange substituent. Preferred Definitions:    Either:    At least one of A1 and A2 = H, with the other does not equal H. At least one of B1 and B2 = H, with the other does not equal H.    Or    A1 or B1 = lower alkyl or cyclic alkyl; and    A2 or B2, respectively = A1 or H.    Or    A1 = aryl groups, preferably fused polycyclic aromatic groups with two fused ring (most preferably biphenyl), or a (preferably monocyclic) heteroatomic aryl where the heteroatoms are N, O and/or S, and preferably containing at least two heteroatoms, one of which is an N-alkylated or N-benzylated nitrogen; and    A2 = H.    Or    A1 = PRR', or P(OR)(OR'); and    A2 = H.    Or    A1 or B1 = Me or CH(X)Ph;    X = F, Me or Ph and;    A2 or B2, respectively = A1 or H.    Or    A1 or B1 = Me; and    A2 or B2, respectively = Me or H.    Or    A1 or B1 = para-Me; and    A2 or B2, respectively = H, preferably where at least a portion of the grafted chains are crosslinked, and the base film is a polyethylene/tetrafluoroethylene copolymer.    EXAMPLE - Membrane Preparation: A 2 mm thick, 7 x 7 inch piece of Tefzel (RTM; polyethylene/tetrafluoroethylene) film was irradiated with a high energy electron beam (5 Mrad, 60 kW) in an inert atmosphere. The irradiated film was kept at -30 degrees C in an inert atmosphere prior to use. The membrane was then exposed to neat, degassed para-methyl-alpha,beta,beta-trifluorostyrene (p-Me-TFS) at 50 degrees C for 60 hours. The p-Me-TFS grafted film was removed, washed with toluene, and dried at 60 degrees C. The % graft (increase in weight of the film after grafting) was 35%.    Sulfonation Of The Membrane: The grafted membrane was then immersed in a sulfonating solution comprising liquid sulfur trioxide (30 g) and 1,1,2,2-tetrachloroethane (70 g) for 2 hours at 70 degrees C. The resulting ion-exchange membrane was washed with water and dried at 60 degrees C, to give an equivalent weight of 821 g/mol and a water content of 18% at room temperature.    Use Of Membrane In Fuel Cell: The membrane was bonded to two catalyzed carbon fiber paper electrodes to form a membrane electrode assembly having a total platinum catalyst loading of 8 mg/cm2. The assembly was tested at 110 degrees C with a fuel of 0.4M aqueous methanol solution at a reactant inlet pressure of 3.02 bara for oxidant and fuel. The reaction stoichiometries = 2.0 oxidant and 3.0 methanol. The drawing shows the polarization plots of voltage as a function of current density.