TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Component: The styrene sulfonic acid salt is an alkali metal salt. The chloride is thionyl chloride. The inorganic base aqueous solution is an aqueous solution of an alkali metal hydroxide. The acidic aqueous solution comprises hydrochloric acid or sulfuric acid aqueous solution.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Component: The styrene sulfonic acid salt is an alkali metal salt. The chloride is thionyl chloride. The inorganic base aqueous solution is an aqueous solution of an alkali metal hydroxide. The acidic aqueous solution comprises hydrochloric acid or sulfuric acid aqueous solution.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Component: The radical initiator is an azo-based compound or a peroxide-based compound. The azo-based compound is azobisisobutyronitrile. The peroxide-based compound includes benzoyl peroxide, cumyl peroxide, t-butyl peroxide, or lauryl peroxide. The solvent comprises dimethylformamide, benzene, toluene, xylene, ethylbenzene, or methylethylketone for radical polymerization.    TECHNOLOGY FOCUS - POLYMERS - Preferred Method: The step of preparing the styrene monomer having the sulfonyl chloride group comprises reacting a p-styrene sulfonic acid salt with a chloride to prepare p-styrene sulfonyl chloride. The step of changing the sulfonyl chloride group involves treating the styrene-based polymer having the sulfonyl chloride with an inorganic base aqueous solution to change the sulfonyl chloride into a SO3M group (where M is alkali metal); and reacting the styrene-based polymer having the SO3M group with an acidic aqueous solution to prepare the styrene-based polymer having the sulfonic acid group. The polymerization is carried out using a radical initiator and a solvent. Preferred Component: The polymer or sulfonated polystyrene is of formula (I or II).R1-R5=H, halo, alkyl, aryl, or halogenated aryl;R6=CO2R';R'=H or alkyl;l,m,n=polymerization degrees, preferably 30-70, 30-70, or 10-20. EXAMPLE - 1 g (4.9 mmol) p-Styrene sulfonyl chloride, 0.5 g (4.8 mmol) styrene, and 35 mg (0.21 mmol) alpha, alpha-azobisisobutyronitrile were dissolved in 1.5 ml butanone, and air was removed using nitrogen followed by sealing. The resultant solution was placed at 70degreesC and polymerization was carried out for 3 hours to obtain a 4-styrene sulfonyl chloride-styrene copolymer. The reaction mixture was cooled to room temperature and poured into methanol slowly to obtain a white precipitate. This precipitate was filtrated and dried in a vacuum oven to obtain 1.2 g white powder. Using this product, a polymer electrolyte membrane was prepared.