Novel water-soluble polyesters with pendant carboxylic groups were synthesized by polycondensation of ethylenediaminetetra-acetic acid (EDTA) dianhydride and diethylenetriamine-penta-acetic acid (DTPA) dianhydride with poly(ethylene glycol)s of different chain-lengths. Two experimental approaches (polycondensation using various solvents and in the melt) were studied, and melt condensation was found to give higher yields of polyesters. The polymeric products were soluble in water, acetone, chloroform and toluene, and were characterized by elemental analysis, IR and NMR spectroscopy. In addition, the carboxyl functionalities were determined by titration and the hydrolytic stability studied as a function of pH. The complexing capacity of the functional polyesters was determined in dependence of pH for copper in aqueous solution using the Liquid-Phase Polymer-Based Retention (LPR) technique and found to be 257mgg(-1) for the EDTA-based copolymer at pH5 and 230mgg(-1) for the DTPA-based copolymer, respectively. (C) 1999 Society of Chemical Industry.