TECHNOLOGY FOCUS - ELECTRICAL POWER AND ENERGY - Preferred Domain: The ion conductive domain forms a continuous phase and the non-ion conductive domain forms a matrix phase. The ion conductive domain and the non-ion conductive domain form a lamellar structure. The ion conductive domain including the segment (a1) forms a cylindrical structure i.e. a three-dimensional network structure in the microphase separation structure.    TECHNOLOGY FOCUS - POLYMERS - Preferred Components: The triblock copolymer has at least one of an aliphatic hydrocarbon and an alicyclic hydrocarbon as a main chain. Preferred Membrane: In the membrane, the ion conductive domain including the segment (a1) forms a continuous phase and a non-ion conductive domain including the segment (b1) forms a matrix phase. EXAMPLE - Copper(I) bromide (2.34 mmol) was mixed with hexamethyltriethylenetetramine (2.34 mmol), dimethyl 2,6-dibromoheptanedionate (2.34 mmol), and tert-butyl acrylate (tBA) (234 mmol) in dimethylformamide (DMF). The dissolved oxygen in the mixture was replaced with nitrogen. The mixture was allowed to react at 70 degrees C while monitoring the monomer conversion through gas chromatography. The reaction was stopped by quenching the reaction mixture with liquid nitrogen. The resultant poly-tert-butyl-acrylate(PtBA) had number average molecular weight (Mn) of 11600 and weight average molecular weight (Mw)/Mn of 1.20. Then, the obtained ptBA (0.261 mmol) having bromine at both ends, copper(I) bromide (0.522 mmol), hexamethyltriethylenetetramine (0.522 mmol), and styrene monomer (156.5 mmol) were mixed and the mixture was subjected to replacement by nitrogen. The mixture was allowed to react at 100 degrees C. The reaction was stopped by quenching with liquid nitrogen. Then, the resulting polymer was purified by reprecipitation into methanol, to obtain polystyrene-PtBA-polystyrene triblock copolymer with Mn of 40100 and Mw/Mn of 1.42. Next, the obtained block copolymer was mixed with trifluoroacetic acid (5 equivalents to t-butyl group) at room temperature in chloroform to form (polystyrene)-(polyacrylic acid)--(polystyrene) (PSt-PAA-PSt) triblock copolymer (p1). (p1) was dissolved in DMF, sodium hydride (5 equivalents relative to carboxylic acid) and 1,3-propanesultone (20 equivalents relative to carboxylic acid), were added and heating under reflux to give (polystyrene)-(3-sulfonyl-propylacrylate)-polystyrene block copolymer, where weight fraction of 3-sulfonyl-propylacrylate (i.e. ion conductive segment) was 0.281 and weight fraction of polystyrene (non-ion conductive) was 0.719.