Leveraging Stereochemistry to Optimize the Properties of Polyhydroxyalkanoates

High Resolution Image Download MS PowerPoint Slide The recycling of low-density polyethylene (LDPE) is challenging due to difficulties with sorting and contamination, leading to environmental harm. Polyhydroxyalkanoates (PHAs) are at the forefront of high-performance biodegradable alternatives to olefinic plastics, but few offer LDPE-like properties such as low strength and crystallinity while maintaining high ductility and thermal stability. Herein, we report a series of isoenriched trans -poly(3-hydroxy-2-methylbutyrates) ( trans -PHMBs) with tunable mechanical and thermal properties. These polymers were synthesized through ring-opening polymerization of racemic trans -3,4-dimethylpropiolactone ( rac-trans -DMPL), sourced from C1 and C4 feedstocks, using a new class of “sandwich” C 2 symmetric rac -( Ar BDI*)ZnO i Pr catalysts (where BDI = β-diketiminate). Variation of aromatic groups (Ar) and polymerization temperature yielded mm %s between 45–79% and melting temperatures ( T m ) between 141–174 °C. trans -PHMB with intermediate isotacticities of 73 and 75 mm % exhibit similar stress–strain profiles to LDPE, indicating that these polymers have the potential to serve as higher melting, degradable substitutes for LDPE.