‘Crown-Roots’ Structure Formed by Lignin-Containing Cellulose Nanofibers for All-Natural, Biorenewable Barrier Material

Degradable and cost-effective cellulose fiber-based materials are ideal substitutes for traditional plastics. However, organic additives used to enhance water and oil resistance often contain toxic substances that may migrate into food, posing health risks. In this study, inspired by tree structures, lignin-containing cellulose nanofibers (LCNFs) are used to form a “crown-roots” structure to enhance the water, oil, and gas resistance, as well as mechanical performance of composites. Mechanically fibrillated LCNFs (M-LCNFs), representing the tree roots, are blended with bamboo pulp and bagasse pulp to prepare cellulose fiber substrate. LCNFs films, representing the crown, are produced via a sol–gel method to improve the substrate's barrier properties. The LCNFs gel, representing the trunk, bonds the films to the substrate via hydrogen bond. The resulting material shows exceptional behaviors including 1) excellent water and oil resistance (Cobb value and WVTR decreased by 75.27% and 16.43% compared to the substrate, with a maximum kit value of 12), 2) outstanding mechanical performance (tensile index is 103.19 N·m g⁻¹), and 3) good natural degradability. This material holds significant potential for industries with high safety standards, such as food, cosmetics, and medicine.