Reducing Hydrophilicity of Cellulose Nanofibrils Through Lipase-Catalyzed Surface Engineering with Renewable Grafting Agents

Abstract

Cellulose nanofibrils are distinguished bionanomaterials known for their unique morphology, thermal stability, and ability to form networks, yet they encounter challenges in compatibility with hydrophobic matrices, limiting their application in various applications. This study introduces an innovative surface modification method to address the high hydrophilicity of CNFs. The novelty lies in the use of lipase as a biocatalyst in combination with renewable grafting agents, specifically butanoic and oleic acids. The lipase successfully esterified both acids onto the CNFs, with butanoic acid exhibiting a higher surface concentration, resulting in a more substantial reduction in hydrophilicity. Contact angle measurements demonstrated a notable shift, from 10.84° for untreated CNF to 68.4° and 55.1° for CNFs grafted with butanoic and oleic acid residues, respectively. While there were only slight alterations in crystallinity, thermal stability, and brittleness, lipase proved to be an effective catalyst for modifying the CNF surface with fatty acids. This approach offers a method to mitigate the high hydrophilicity of CNFs without compromising their key properties. Furthermore, it can be proposed as a means to tailor CNF for water-resistant applications in fields such as electronics, packaging, and Pickering emulsions.

Graphical Abstract

The structure of the lipase protein was sourced from the Protein Data Bank (PDB), first referenced by Xie et al. [38]