Reactive Extrusion of Nonmigratory Antioxidant Poly(lactic Acid) Packaging

Reactive extrusion of bio-derived active packaging offers a new approach to address converging concerns over environmental contamination and food waste. Herein, metal-chelating nitrilotriacetic acid (NTA) ligands were grafted onto poly(lactic acid) (PLA) by reactive extrusion to produce metal-chelating PLA (PLA--NTA). Radical grafting was confirmed by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy with the introduction of secondary alkyl stretches (2919 and 2860 cm) and by X-ray photoelectron spectroscopy (XPS) with an increase in the atomic percentage of nitrogen. Compared to films prepared from native, granular PLA (gPLA), PLA--NTA films had lower contact angles and hysteresis values (86.35° ± 2.49 and 31.89° ± 2.27 to 79.91° ± 1.58 and 21.79° ± 1.72, respectively), supporting the surface orientation of the NTA ligands. The PLA--NTA films exhibited a significant antioxidant character with a radical scavenging capacity of 0.675 ± 0.026 nmol Trolox/cm and an iron chelation capacity of 54.09 ± 9.36 nmol/cm. PLA--NTA films delayed ascorbic acid degradation, retaining ∼45% ascorbic acid over the 9-day study compared to <20% for control PLA. This research makes significant advances in translating active packaging technologies to bio-derived materials using scalable, commercially translatable synthesis methods.