PEG–PLGA copolymers bearing carboxylated side chains: Novel hydrogels with enhanced crosslinking via ionic interactions

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, thermo-sensitive 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. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 1222–1227