TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Compounds: The sulfonating agent is a concentrated sulfuric acid.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Conditions: It is given that 0.6less than or equal toXless than or equal to0.9, 0.02less than or equal toYless than or equal to0.3, and 0.03less than or equal toZless than or equal to0.25. Preferred Compounds: The repeating unit A is a repeating unit derived from vinyl-containing aromatic compound monomer (2). The repeating unit B is a repeating unit derived from nitrogen-containing heterocyclic compound monomer having vinyl group. The nitrogen-containing heterocyclic compound monomer is compound (3). The repeating unit C is a repeating unit derived from cross-linking agent comprising a compound having vinyl group of greater than or equal to2, the compound being compound (4) or compound of formula -(CH2=CH)n-R7 (5). The vinyl-containing aromatic compound monomer is consisting of styrene, 4-methylstylene, 4-methylchlorostyrene, 4-methoxystyrene, 1-vinylnaphthalene, 2-vinylnaphthalene, 9-vinylanthracene, 4-vinylbiphenylene, indene, or acenaphthylene. The nitrogen-containing heterocyclic compound monomer having the vinyl group is consisting of 2-vinylpyridine, 3-vinylpyridine, 4-vinylpyridine, 1-vinylimidazole, 9-vinylcarbazole, 5-vinylpyrimidine, 6-vinylpurine, 4- and 5-vinylquinoline, 4- and 5-vinylisoquinoline, 3-vinylpyrazole, 1-vinylindazole, 2-vinylpyrazine, hydrosulfate, hydrochloride, and hydrosulfate, hydrochloride, or their organic sulfonate. The cross-linking agent comprising the compound having the vinyl group of greater than or equal to2 is consisting of divinylbenzene, bisvinylphenylethane, bisphenoxyethane, bisvinylphenoxybutane, bisvinylphenoxyhexane, 4,4'-divinylbiphenylene, divinylsulfone, or trivinylbenzene. The vinyl group-having aromatic compound monomer is consisting of ethyl styrenesulfonate, styrenesulfonamide, styrenesulfonephenylamide, styrenesulfonic acid anhydride, 4-styrenesulfonylhalide, vinylnaphthalenesulfonate ester, vinylanthracenesulfonate ester, or vinylbiphenylenesulfonate ester. The monomer mixture solution contains a monomer of Formula (6). Preferred Methods: The electrolytic membrane is obtained by hydrolyzing a precursor polymer and being protonated. Preferred Compositions: The cross-linked electrolyte in the electrolytic membrane is 20-90 wt.% and the structural component (1) is greater than or equal to50 wt.%.    TECHNOLOGY FOCUS - POLYMERS - Preferred Compounds: The porous membrane substrate comprises high molecular material consisting of polyethylene, polypropylene, polyimide, polyamidimide, polyvinylidene fluoride, or polytetrafluoroethylene. EXAMPLE - About 0.834 g of styrene and 0.106 g of 2-vinylpyridine were mixed with 0.204 g of a cross-linking agent and 11 mg of benzoyl peroxide (BPO) to prepare a monomer composition. A polyethylene porous membrane placed on a support was impregnated with the monomer composition, and a protective film was closely applied to it, followed by polymerizing for 20 minutes while applying pressure. After delaminating the protective film and the support, the synthesized membrane was reacted for 10 minutes in concentrated sulfuric acid at 105degreesC, and then dipped in 18 N sulfuric acid solution, followed by washing with pure water till the washing solution became neutral to prepare an electrolytic membrane.