Chloromethylated polystyrene was chemically modified through alkylation of pyridylazo-beta-naphthol (PAN) in the presence of a phase-transfer catalyst. The chemical modification was achieved through O-alkylation as well as N-alkylation of PAN, leading to formation of polymer-supported quaternary ammonium salt in the latter case. Both types of a polymer-supported PAN moiety were detected by FTIR spectroscopic analysis. The complexation behavior of the polymer-supported PAN as an ion-exchanger toward some metal ions was studied. Thermogravimetric and differential thermogravimetric analyses data were used to study the kinetics of the thermal decomposition process of the ion-exchanger. Some thermodynamic parameters for the ion-exchanger were calculated by applying the rate theory of the first-order reaction.