A dual self-reinforcement strategy for enhancing the mechanical strength and hydrophobicity of biocompatible thermoplastic starch.

Enhancing the mechanical strength and hydrophobicity of thermoplastic starch (TPS) while maintaining its biocompatibility remains a key challenge for starch-based food packaging materials. In this study, a dual self-reinforcement strategy is proposed, involving the initial blending of glycerol with self-prepared carboxymethyl starch (CMS) with a high degree of substitution (1.05) to form TPCMS, followed by the incorporation of self-fabricated starch micro-particles (MP) featuring micro-nano surface structures to produce TPCMS@MP. The mechanical properties, hydrophobicity, and biocompatibility of TPCMS@MP were systematically evaluated. The results reveal that abundant ester bonds act as cross-linking sites, enhancing the Young's modulus and fracture toughness of TPCMS by 4.8 and 1.9 times, respectively, compared to unmodified TPS. Additionally, the combined effects of esterification and micro-nano surface structures significantly reduce surface energy, leading to improved hydrophobicity with a water contact angle of 126°. Furthermore, TPCMS@MP exhibits excellent biocompatibility, with HeLa cell viability reaching 90.33 % at 400 μg/L. The synergistic effect of chemical cross-linking and physically incorporated micro-nano particles effectively enhances the mechanical strength and hydrophobicity of thermoplastic starch while preserving its inherent biocompatibility. This strategy offers a promising approach for developing advanced starch-based functional materials and broadening their application in food packaging.