Novel triazene-based polysulfone, poly 4-(4-aminophenylsulfonyl)diazobenzene, was synthesized from 4-[(4-aminobenzene)sulfonyl]aniline (Dapsone) in the presence of sodium nitrite/silica sulfuric acid system, under solvent-free conditions, and also in aqueous media to compare their polymerization process and the products. The structures of the obtained polymers under the two conditions were characterized for the first time in this investigation by several analytical and spectroscopic methods such as FT-IR, 1H-NMR, UV-vis, thermogravimetric and differential thermal analyses, gel permeation chromatography, mass spectrometry, and CHN micro-elemental analysis. The results showed that both polymerization processes had made the same product; nevertheless, the solvent-free conditions afforded silica-coated poly 4-(4-aminophenylsulfonyl)diazobenzene. In another study, the ability of the silica-coated polymer, to remove some usual applied water-soluble dyes by spectrophotometric detection, was measured in which cationic structure dyes such as Rhodamine B and Cationic blue 41 were preferably adsorbed. (c) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013