Antibacterial and Antioxidant Thermoplastic Corn Starch Film Incorporated With Maleopimaric Acid‐Grafted PEI 300 for Degradable Food Packaging

Thermoplastic starch (TPS), as a renewable and biodegradable alternative, has garnered significant attention. However, the practical application of TPS is hindered by inherent limitations such as poor mechanical strength, susceptibility to aging, and high hygroscopicity. In this study, a novel modification strategy is proposed involving the conversion of maleic rosin into maleopimaric acid, followed by its reaction with polyethyleneimine‐300 (PEI300) to synthesize a bifunctional oligomer‐maleopimaric acid grafted PEI300 (MPA‐PEI300) which integrates rigid cyclic structures with flexible segments for TPS enhancement. The successful synthesis of MPA‐PEI300 (M‐P) was confirmed by FTIR and 1 H NMR analyses, which revealed the formation of amide bonds. The incorporation of MPA‐PEI300 (M‐P) significantly improves the overall performance of TPS: with optimal loading, tensile strength increases by 134%, elongation at break reaches 214% (representing a 53% improvement over pure TPS), thermal stability is enhanced by 7.7°C, and water absorption is effectively reduced. Furthermore, the modified TPS demonstrates notable antioxidant activity, achieving a maximum DPPH radical scavenging rate of 66.7%, along with antibacterial efficacy against Escherichia coli and Staphylococcus aureus . Although the degradation rate is slightly decreased, all formulations retain good soil burial degradability. This work presents a strategy for developing high‐performance bio‐based plastics with enhanced strength, toughness, and multifunctional properties.