TECHNOLOGY FOCUS - POLYMERS - Preparation (claimed): Preparation of a poly(2,6-dimethyl-1,4-phenylene oxide)-polyethylene oxide (PXE-PEO) block copolymer involves:(A) dissolving PXE in dried solvent to form a first solution;(B) adding phosphazene base (t-BuP4) solution to the first solution to form a second solution;(C) stirring the second solution;(D) adding ethylene oxide (EO) to the second solution to form a third solution;(E) stirring the third solution; and(F) precipitating the third solution in hexane non-solvent for the polymer.No metal is used in the preparation. Preferred Compounds: The softening temperature of the second domains is greater than or equal to 200 (preferably greater than or equal to 210, especially greater than or equal to 220) degrees C. The first polymers and the second polymers form block copolymers (P1), each block copolymer comprises the first polymer as a first block and the second polymer as a second block. The first blocks are selected from polyethers, polyamines, polyimides, polyamides, alkyl carbonates, polynitriles, polysiloxanes, polyphosphazines, polyolefins, and/or polydienes. The first blocks comprise comb polymers that have a backbone and pendant groups. The backbones are selected from polysiloxanes, polyphosphazines, polyethers, polydienes, polyolefins, polyacrylates, and/or polymethacrylates. The pendants are selected from oligoethers, substituted oligoethers, nitrile groups, sulfones, thiols, polyethers, polyamines, polyimides, polyamides, alkyl carbonates, polynitriles, and/or other polar groups. The second blocks are selected from poly(phenylene oxide), poly(2,6-dimethyl-1,4-phenylene oxide) (PXE), poly(phenylene sulfide), poly(phenylene sulfide sulfone), poly(phenylene sulfide ketone), poly(phenylene sulfide amide), and polysulfone. The polymer is a compound of formula -(Ar-X)a-((CH2)n-CH(R5)-O-)b- (I). The polymer (I) further comprises an additional group of formula -(Ar-X-)c- (II). The additional group attached to the polymer (I) forms a triblock polymer of formula -(Ar-X)a-((CH2)n-CH(R5)-O-)b-CH(R5)-(CH2)n-(X-Ar)c- (III). The polymer comprises: an ionically-conductive phase; and a structural phase where the structural phase has a softening temperature of greater than or equal to 190 degrees C; and the phases form a microphase separated domain structure. The structural phase comprises PXE. The ionically-conductive phase and the structural phase are formed block copolymers, where an association of first blocks forms the ionically-conductive phase and an association of second blocks forms the structural phase. The polymer comprises: an association of several block copolymer chains each comprising: at least one ionically conducting block; and at least one PXE block immiscible with the ionically conducting block; where the chains are arranged in an ordered nanostructure comprising a continuous matrix of: first domains defined by an association of the ionically-conductive blocks; and second domains defined by an association of PXE blocks.X=not defined;Y1=keto, sulfo, isopropylidene, hexafluoroisopropylidene, amido, or O;R1-R5=H, (halo)alkyl, alkenyl, aryl, siloxanyl, or alkyl (containing O and S ether bonds);n=1-10;a-c=10-90. EXAMPLE - To a solution of poly(2,6-dimethyl-1,4-phenylene oxide) (PXE) (mol. wt. 50 K) (2 g) in dried tetrahydrofuran (THF) (60 ml), a solution of phosphazene base (t-BuP4) in benzene (0.15 ml, 0.5 M) was added, and the mixture was stirred at 50 degrees C for 24 hours under an inert atmosphere. Ethyleneoxide (EO) (6 ml) was added to the mixture, and stirred at 45 degrees C for 48 hours. After cooling to 25 degrees C, the mixture was precipitated in hexane, filtered, washed and dried to obtain PEO-PXE polymer (having PEO:PXE ratio of 68:32) (5.2 g) as white solid.