Biomimetic micro-nano architectures of PDMS-bridged ZnO-montmorillonite enable threshold-exceeding superhydrophobicity on CMC films toward liquid food packaging.

Abstract

Carboxymethyl cellulose (CMC) is promising for food packaging due to its biodegradability and cost-effectiveness. However, its application is limited by strong hydrophilicity from abundant hydroxyl and carboxyl groups. In this study, zinc oxide (ZnO) nanoparticles (< 50 nm) and layered montmorillonite (MMT) with a high-aspect-ratio (< 5 μm) are surface-modified with stearic acid (SA). At an SA@ZnO to SA@MMT mass ratio of 6:4, the ZnO nanoparticles and MMT platelets formed a comparatively uniform hierarchical micro/nanoscale coating. Additionally, polydimethylsiloxane (PDMS) is introduced to enhance interfacial compatibility between the coating and CMC substrate through hydrogen-bond bridging. The resulting CMC/PVA/DCMC/PDMS/SA/MMT/ZnO film exhibited a water contact angle of 157° ± 3.02°, a sliding angle of 6°, and self-cleaning behavior. This study demonstrates that the hierarchical coating effectively imparts superhydrophobicity to the CMC-based film, providing a material basis for its further evaluation in food-packaging applications.

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