NOVELTY - Polymer comprising fluorinated cyclobutyl moiety, protogenic group and aryl/aliphatic moiety is new.    USE - In polymer membrane electrode (claimed) and fuel cell membranes.    ADVANTAGE - Unlike random copolymers, the sulfonated perfluorocyclobutane block copolymer can self-assemble into certain morphologies where the hydrophobic chain segment aggregates to form a hydrophobic domain, and the hydrophilic sulfonated chain segment aggregates to form a hydrophilic domain. Since each block copolymer has at least one hydrophobic chain segment and at least one hydrophilic chain segment, the hydrophobic domains and the hydrophilic domains formed by the block copolymer are linked together through the polymer chains. The hydrophobic domains and hydrophilic domains are linked together through strong covalent bonds. Such morphology feature of the block copolymer can greatly restrict the water swelling of the hydrophilic domain in a high humidity environment. In a similar manner, the morphology also restricts shrinkage and collapse of the hydrophilic domain in a relatively dry environment. This morphological feature makes the sulfonated perfluorocyclobutane block copolymer an improved material for proton conductive membranes and binders in membrane electrode assemblies in fuel cells. The sulfonated perfluorocyclobutane block copolymer can improve the fuel cell performance especially under low humidity and high operating temperatures. The physical morphology formed from the block copolymer, for example, may range from lamellar, bi-continuous, rod, sphere, and fibrous shapes, depending on processing conditions and specific structures of the polymer chain. The hydrophilic domain formed from sulfonated perfluorocyclobutane ether chain segment forms a continuous phase across the membrane. Such morphology allows high ionic conductivity across the membrane. The hydrophobic domain of the perfluorocyclobutane block copolymer may assemble into a continuous or discontinuous phase.    DETAILED DESCRIPTION - Polymer comprising polymer segment of formula (E1(Z1)d)-P1-Q1-P2 (I) and segment of formula E2-P3-Q2-P4 (II), is new.    Z1=protogenic group;    E1=aromatic containing moiety;    E2=unsulfonated aromatic-containing or aliphatic-containing moiety;    X=-OH, halo, ester, or -NH-SO2-R4;    d=number of Z1 attached to E1;    P1-P4=absent, -O-, -S-, -SO-, -CO-, -SO2-, -NR1H-, NR2-, or -R3-;    R2=1-25C alkyl, 1-25C aryl or 1-25C arylene;    R3=1-25C alkylene, 1-25C perfluoroalkylene, perfluoroalkyl ether, alkylether, or 1-25C arylene;    R4=trifluoromethyl, 1-25C alkyl, 1-25C perfluoroalkylene, 1-25C aryl, or another E1 group;    Q1, Q2=fluorinated cyclobutyl moiety.