(291b) Strong, Ductile and Resilient Functionalized Degradable Poly(alpha-Hydroxy Acids)

Despite the degradability and biocompatibility of poly(α-hydroxy acids), their utility remains limited because their thermal and mechanical properties are inferior to those of commodity polyolefins, which can be attributed to the lack of side-chain functionality on the polyester backbone. Attempts to synthesize high-molecular-weight functionalized poly(α-hydroxy acids) from O-carboxyanhydrides have been hampered by scalability problems arising from the need for an external energy source such as light or electricity. Herein, we develop an operationally simple, scalable method for the synthesis of stereoregular, high-molecular-weight (>200 kDa) functionalized poly(α-hydroxy acids) by means of controlled ring-opening polymerization of O-carboxyanhydrides mediated by a highly redox reactive manganese complex and a zinc-alkoxide. Mechanistic studies indicated the ring-opening process likely proceeded via the Mn-mediated decarboxylation with alkoxy radical formation. Our synthetic method is operationally simple, and this method can be used to prepare homopolymers, block copolymers, stereoblock copolymers, and gradient copolymers; and, in particular, it allowed us to prepare a gradient copolymer that is tougher, more ductile, and more resilient than the corresponding block copolymers and homopolymers, and outperforms commodity polyolefins such as LDPE in terms of shape recovery resilience. Therefore our results highlights the potential feasibility of functionalized poly(α-hydroxy acids) as ductile and resilient polymeric materials as degradable alternatives to unsustainable polyolefins.