Aliphatic polyesters are of increasing interest as replacements for petroleum based commodity polymers due to their biorenewability and biodegradability, and for use in biomedical applications because of their inherent biocompatibility. Their use has been significantly hampered by poor thermal properties; poly(lactic acid), arguably the most abundant aliphatic polyester, has a glass-transition temperature (Tg) of only 60–65 °C. The traditional synthesis of aliphatic polyesters – ring-opening polymerization of lactones and lactide derivatives – is partially responsible for the slow development of improved materials as it is challenging to make meaningful structural modifications to those monomers. The alternating copolymerization of epoxides and cyclic anhydrides offers an alternative route to polyesters, and has numerous advantages over the ring opening polymerization of lactones, including a wider range of monomers and the ability to easily make structural modifications to monomers that will greatly impact polymer properties and which allow for facile functionalization. In this work, catalyst development for the copolymerization of epoxides and anhydrides is reported, focusing on a mechanistic study, an investigation into the effects of electronic variations of the ligand on catalyst rate and selectivity, and the development of a reversible-deactivation system with superior polymerization control. Additionally, the application of these catalyst systems for the synthesis of high-Tg aliphatic functionalizable polyesters, and their use in post-polymerization modification reactions and in reprocessable crosslinked networks is reported.