Novel water-soluble amphiphilic block copolymers with pendant carboxylic acid groups are synthesized and used for the preparation of ionically crosslinked hydrogels. (D,L)-Lactide (DLLA) and (L)-3-(2-benzyloxycarbonyl)ethyl-1,4-dioxane-2,5-dione (BED) are copolymerized at different ratios via organo-catalyzed ring-opening polymerization using a hydroxyl-terminated poly(ethylene glycol) (PEG-OH) macroinitiator. Dynamic light-scattering experiments show that, at low concentrations, aqueous solutions of these PEG-P(BED-DLLA) copolymers form micelles and aggregates. At higher concentrations, thermosensitive gels are obtained, exhibiting a reversible gel-to-sol transition upon a temperature increase. Ionic interactions between the COOH groups and metal ions (Cu2+ or Ca2+) are shown to significantly shift the gel-sol transition to higher temperatures. Thus, the introduction of COOH groups significantly enhances the water solubility of the amphiphilic PEG-polyester copolymer and allows additional crosslinking interactions to form functionalized hydrogels with improved physical properties, making this new class of hydrogels interesting for various applications. (C) 2015 Wiley Periodicals, Inc.