A pinboard by
Quanyou Feng

Postdoctoral Associate, Virginia Polytechnic Institute and State University


Approach greatly improves customizability and efficiency of poly(α-hydroxy acid) synthesis

Poly( α -hydroxy acids) (PAHAs), including polylactide, are widely used in everyday applications ranging from clothing and packaging to agriculture and biomedicine. However, their utility for applications that demand physicochemical properties such as stiffness, ductility, and tensile strength is greatly limited by the lack of side-chain functionality in PAHAs and in their monomers. Attempts to synthesize them from O-carboxyanhydrides with pendant functional groups by various methods, including methods involving organocatalysts or organometallics, have been plagued by uncontrolled polymerization, including epimerization for some monomers, which hampers the preparation of stereoregular high-molecular-weight polymers. Therefore, the development of a viable catalyst that can mediate controlled polymerization to prepare stereoregular, high-MW PAHAs is crucial. Our work describes new catalytic process for the synthesis of functional PAHA, from O-carboxyanhydride (OCA) monomers, allowing for the resultant isotactic polyesters with expected molecular weights (>140 kDa) and narrow molecular weight distributions (Mw/Mn < 1.1). The use of a low temperature ( − 15 ° C) and photoredox Ni/Ir catalysis in our catalyst system synergistically accelerates ring-opening and decarboxylation of the monomer for chain propagation while avoiding the formation of the undesired Ni-carbonyl complex.