The thermochemical transformation of electrostatically formed complexes of methyl orange (MO) with polycations containing primary amine groups such as ammonium salts afforded new polymers with a high concentration of covalently bound 4-N,N-dimethylaminoazobenzene groups in the side chain. Poly(allylamine hydrochloride) and poly(beta-aminoethylene acrylamide hydrochloride) were employed as support polycations for MO. The transformation of sulfonate-ammonium ion pairs into sulfonamide bonds, via heating at an elevated temperature, was supported by the polymer properties before and after the thermal treatment. The polymer structure changes were monitored with elemental analysis, Fourier transform infrared, H-1 NMR, and ultraviolet-visible absorption spectroscopy, and thermogravimetric analysis. The spacer length between the backbone and azobenzene structures used as side chains strongly influenced the polymer properties before and after the heat-induced reaction. (c) 2006 Wiley Periodicals, Inc.