Introducing an additional functionality to chitosan, novel chitosan-based materials were synthesized. The reactions of tosylchitosan with ammonia, ethylenediamine, and hexamethylenediamine have been studied, and the chemisorption behavior of a typical acid dye (Cl Acid Orange 7) onto the resulting polymers has been evaluated. Thiol groups were introduced to the above chitosan derivatives having additional amino group at the C-6 position, and the chemisorption behavior of Hg2+ ion onto the resulting polymers was measured and compared with that of N-thioacetylchitosan. The successful synthetic reaction was demonstrated by the infrared spectroscopic measurements. It has been confirmed that the abilities of the chitosan derivatives with additional amino groups to the chemisorption of an acid dye were significantly high, and that the saturation value of the chemisorption amount of CI Acid Orange 7 toward one of 2'-aminoethylaminodeoxychitosans was significantly high as 6.16 mol/kg. The results also showed that the saturation amounts of Hg2+ ion chemisorption were larger with the increase in the thiol group content of the chitosan derivatives with the thiol groups. (c) 2007 Wiley Periodicals, Inc.