Poly-100: One-Pot Toughening of Polylactide with Soybean-Derived Reactive Elastomers

Poly(lactic acid) (PLA) is a leading biobased thermoplastic, but its brittleness limits broader use. Here, we report a one-pot Poly-100 route combining elastomer synthesis, formulation, and reactive extrusion without solvent removal, purification, or waste generation. Hyperbranched soybean-oil-derived elastomers were synthesized by RAFT polymerization directly in epoxidized soybean oil, which serves as monomer precursor, nonvolatile reaction medium, and formulation component. Poly(acrylated epoxidized high-oleic soybean oil) (PAEHOSO) and poly(methacrylated epoxidized high-oleic soybean oil) (PMAEHOSO) were incorporated into PLA, where residual epoxide groups promote in situ grafting and improve interfacial adhesion. PMAEHOSO showed better compatibility, producing finer dispersions and shifting toughening from interfacial cavitation to matrix shear yielding. At 20 wt % loading, it increased elongation at break from 3% to 30% while delivering the highest tensile toughness. This work establishes a scalable pathway for toughened PLA and demonstrates how reaction media can align polymer performance with sustainability goals.