Dimethyl 2,6-anthracene dicarboxylate is used as a comonomer in the synthesis of functional copolymers that are subject to modification with Diels-Alder reactions. The formation of poly(ethylene terephthalate-co-2,6-anthracenate), containing less than 20 mol % of the anthracene-2,6-dicarboxylate structural units, provides materials that are tractable and soluble. The anthracene units of the copolymers undergo Diels-Alder reactions with N-substituted maleimides. The grafting of Nalkylmaleimides affords soluble, hydrophobic polymers, whereas grafting with maleimide-terminated poly(ethylene glycol) affords hydrophilic polymers. Because this reaction proceeds below the melting point of the copolymers, the procedure can be applied to thin films, whereby the surface properties are modified.