Synthesis of Aliphatic Hyperbranched Polycarbonates via Organo-Catalyzed “A1+B2”-Ring-Opening Polymerization

Hyperbranched aliphatic polycarbonates (HBPCs) have attracted significant attention in the field of biomedical application owing to their abundant end groups, biocompatibility, and nontoxic degradation products. However, their practical application is hampered by tedious synthesis procedures. The present work described a novel organo-catalyzed "A1+B2"-ring-opening polymerization (ROP) using a monofunctional primary alcohol (A1) as an initiator and a bicyclic carbonate monomer (B2) for the straightforward synthesis of HBPCs under mild conditions. No gelation was observed up to 90% conversion of the cyclic carbonate ring. HBPCs with molar masses in the range from 7 to 20 kg/mol were obtained. Based on the "A1+B2"-ROP, HBPCs bearing a variety of functionalities including alkene, alkyne, aldehyde, furan, azide, and mPEG groups, which are of great significance in the field of click chemistry, have been successfully prepared by using functional alcoholic initiators. This polymerization strategy allowed for precise control over the HBPC structure: (1) the hyperbranched polymer (HBP) backbone can be adjusted by design of a bicyclic carbonate monomer with various linkages; (2) the use of an appropriate initiator leads to the introduction of functional end groups. Overall, the "A1+B2"-ROP provides an efficient method for preparing a variety of HBPs like hyperbranched polyester, polyether, polyphosphate, and poly(amino acid) with complex architectures in a single step.