The substrate specificity in solvolysis reactions of p-nitrophenyl alkanoates 2 (n = 2-18) catalyzed by 4-(dialkylamino)pyridine-functionalized polymer 1 can be controlled by the concentration of 1 in 50:50 (v/v) methanol-aqueous phosphate buffer solution at pH 8.0 and 30 degrees C. Below 1.0 x 10(-5) unit mol L-1, macromolecule 1 exhibits substrate specificity for 2 (n = 14). As the concentration of 1 increases to 2.5 x 10(-5) unit mol L-1, the substrate preference changes from 2 (n = 14) to 2 (n = 12). The substrate specificity changes again from 2 (n = 12) to 2 (n = 10) when the concentration of 1 increases further to 7.5 x 10(-5) unit mol L-1. The control of substrate specificity by polymer catalyst concentration is believed to be unprecedented for catalysis of ester solvolysis.