TECHNOLOGY FOCUS - POLYMERS - Preparation (Claimed): Preparation of polysulfone-based copolymer of formula (I), comprises: reacting a substituted phenol compound of formula (II) and substituted phenyl compound of formula (III) to give substituted phenoxy compound of formula (IV); reacting (IV) and a nitrate-based compound to give substituted nitro-phenoxy compound of formula (V); reducing (V) to give substituted amine-phenoxy compound of formula (VI); and connecting side chains to (VI) to obtain (I).X5, X6 = halo; andr = 1-5000.Preferred Components: The ratio of m to n is 1:9-9:1. The weight average molecular weight of the polysulfone-based copolymer is 10000-200000. EXAMPLE - Polysulfone polymer solution was obtained by dissolving reduced polysulfone (1 g) in dichloromethane (10 ml) under nitrogen atmosphere. Ammonium nitrate (0.18 g) and trifluoroacetic anhydride (2.2 ml) were added to the polysulfone polymer solution and refluxed for 24 hours at 40 degrees C. Then the refluxed mixed solution was treated with methanol (300 ml) to obtain nitrated polysulfone. Nitrated polysulfone (1 g) was dissolved in chloroform (10 ml) under a nitrogen atmosphere to get polymer solution. Sodium iodide (0.1 g) and stannous chloride (3 g) were completely dissolved in a solution of hydrochloric acid (4.78 ml) and glacial acetic acid (2.38 ml), and then the mixture was slowly added to the polymer solution while stirring for 4 hours at 80 degrees C. While stirring the polymer solution, methanol (1 ml) was slowly added to it and the resultant was precipitated in methanol including 10% hydrochloric acid to obtain reduced polysulfone. The reduced polysulfone (0.5 g) was dissolved in dimethylacetamide (10 ml) and sodium methoxide (0.219 g) was added to it and reacted for 1 hour, followed by reacting with propanesultone (0.217 ml) for 7 hours at 70 degrees C. The reacted mixture was precipitated in acetone, and cleaned to obtain polysulfone including a sulfonated side chain polymer of formula (IA), (where m is 0.45, n is 0.55, and the weight average molecular weight is 70000).