Effect of Dual Esterification of Starch on the Structure and Properties of Starch/ PLA Blend Films

Blending starch with poly(lactic acid) (PLA) is an effective way to reduce cost and improve sustainability, but their poor compatibility limits film performance. In this work, starch was sequentially acetylated and benzoylated to prepare a dual‐esterified starch (DES), which was then blended with PLA to form composite films. This study aimed to investigate whether the introduction of aromatic ester groups could enhance starch–PLA interactions, thereby modulating the resulting film structure and properties. 1 HNMR confirmed the successful introduction of both acetyl and benzoyl groups onto the starch chains. Compared with acetylated starch/PLA films, DES/PLA films showed more uniform morphology and better interfacial adhesion. XRD and DSC indicated that DES affected the crystallization behavior of PLA, while FT‐IR and molecular docking supported stronger intermolecular interactions between the two phases. As a result, the DES/PLA films exhibited improved flexibility, lower water vapor permeability, and faster soil degradation than neat PLA film. Films containing up to 75 wt% DES could still be prepared successfully. These results suggest that dual esterification is an effective approach for improving the compatibility of starch/PLA blends and preparing biodegradable films with high starch content.