Biodegradable Polyhydroxyalkanoates by Stereoselective Copolymerization of Racemic Diolides: Stereocontrol Mechanism and Polyolefin-Like Properties.

Bacterial polyhydroxyalkanoates (PHAs) are a unique class of biodegradable polymers due to their biodegradability in ambient environments and structural diversity enabled by side-chain groups. However, the biosynthesis of PHAs is slow and expensive, limiting their broader applications as commodity plastics. To overcome such limitation, the catalyzed chemical synthesis of bacterial PHAs has been developed via the metal-catalyzed stereoselective ring-opening (co)polymerization of racemic cyclic diolides ( rac-8DL R , R = alkyl group). In this combined experimental and computational study, polymerization kinetics, stereocontrol mechanism, copolymerization characteristics, and the resulting PHAs' properties have been examined. Most notably, stereoselective copolymerizations of  rac-8DL Me with  rac-8DL R (R = Et, Bu) have yielded high-molecular-weight, crystalline isotactic PHA copolymers that are hard, ductile, and tough plastics, and exhibit polyolefin-like thermal and mechanical properties.