In this study, primary modification of polystyrene (PS) was carried out with maleic anhydride using the FriedelCrafts reaction. Its secondary modification was realized through esterification of modified polystyrene (MPS) containing a carboxyl group with various alcohols in the presence of Amberlyst-36 as a heterogeneous catalyst. The heterogeneous catalyst gave moderate yields, whereas the reaction catalyzed by a homogeneous catalyst did not occur. The amount of carboxyl groups in the structure of MPS and unreacted carboxyl groups in the structure of the esterified MPS (EMPS) was found by using a chemical titration method for the determination of esterification yield. Some important reaction parameters were assigned to optimize the esterification process. FT-IR, 1H NMR, and thermogravimetric studies indicate that the esterification reaction was successfully realized for each alcohol in the presence of the heterogeneous catalyst. The results demonstrated that both the acylation reaction and esterification reaction can be carried out to obtain a significantly functionalized polymer. (c) 2012 Wiley Periodicals, Inc. Adv Polym Techn 32: E451E461, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.21292