NOVELTY - Heterocycle substituted hydroquinone derivatives or their salts are new.    USE - In the preparation of aromatic polyether copolymer; polymer or copolymer (claimed); as electrolytes in high temperature proton exchange membrane (PEM) fuel cells; in the preparation and application of MEA on proton exchange membrane fuel cell (PEMFC) type single cells.    ADVANTAGE - The polymer exhibits good mechanical properties, high thermal and oxidative stability, high doping ability and high conductivity values. The copolymer containing the compound exhibits excellent film forming properties, high glass transition temperature up to 270degrees C and high thermal and oxidative stability up to 480degrees C.    DETAILED DESCRIPTION - Heterocycle substituted hydroquinone derivatives of formula (I) or their salts are new.R=3-pyridyl, 2-pyridyl, 4-pyridyl, pyrimidin-5-yl or pyrimidin-2-yl.    INDEPENDENT CLAIMS are included for the following:    (1) preparation of compound (I);    (2) an aromatic polyether copolymer of formula (II);    (3) an aromatic polyether polymer of formula -(O-T2-O-X2)n- (III) or its salt;    (4) preparation of the polymer or copolymer involving: polycondensing monomers at high temperature under conditions such that the polymer or copolymer is formed; or reacting an aromatic difluoride with the compound (I);    (5) a blend of copolymers or homopolymers prepared by mixing a dimethyl acetamide solution of the polymer and a dimethyl acetamide solution of the copolymer in a predetermined ratio;    (6) a composition comprising a slurry mixture of the polymer and/or copolymer and a polar aprotic solvent;    (7) preparation of a catalyst involving: a) depositing a layer of the composition by calendaring, screen printing or spraying on a hydrophobic layer; and b) drying and sintering the layer deposited in step (a), thereby preparing the catalyst; and    (8) a layered membrane electrode assembly comprising: a substrate layer; a gas diffusion layer; and a reaction layer.    X2 and Y2=-T1-SO2-T1-, -T1-CO-T1-, -T1-P(O)(Ph)-T1- or 2,3,5,6,2',3',5',6'-octafluoro-biphenyl-4,4'-diyl;    T1=1,4-phenylene;    A=-CH2, -CF2, phenyl or absent;    T2=1,4-phenylene (substituted on 2-position by R and on 5-position by R).