Surface Modification of Cellulose Nanofibers for Sustainable Applications in Hydrophobicity and Composite Blending

This dissertation investigates novel approaches for modifying cellulose nanofibers (CNFs) to develop sustainable alternatives to petroleum-based plastics. As plastic production continues to rise dramatically – from 2 million tons in 1950 to a projected 1231 million tons by 2060 – the need for renewable, biodegradable alternatives has become increasingly urgent. This work presents three interconnected studies exploring different aspects of CNF modification and application.

The first study introduces an innovative method for developing superhydrophobic (SHP) coatings using CNFs lyophilized from a 10 wt% tert-butyl alcohol slurry. Through solvent-free mechanochemical modification, we successfully produced oleic acid-modified CNFs (OL-CNFs), which exhibited exceptional SHP properties, demonstrating high contact angles, low hysteresis, and remarkable durability. Suspensions of OL-CNF were utilized in various spray coating applications, including moisture barriers and atmospheric water harvesting systems.

The second study explores the trifluoroacetylation of CNFs using trifluoroacetic anhydride (TFAA) without additional base. By employing glucopyranosides as small molecule models to guide reaction optimization, we developed a method for controlled trifluoroacetylation while preserving CNF crystallinity. Notably, we introduce a novel approach for quantifying the degree of substitution using ¹⁹F NMR spectroscopy of saponified trifluoroacetylated CNFs (TFA-CNFs) in methanol-d4, offering improved accuracy over traditional methods.

The third study examines the potential of TFA-CNFs as reinforcing materials in biodegradable polymer composites, particularly with poly(butylene adipate-co-terephthalate) (PBAT). We investigate the dispersibility of TFA-CNFs in various organic solvents and explore methods for creating PBAT/TFA-CNF blends. The research reveals promising aspects of TFA-CNFs, including their compatibility with biodegradable polymers and rapid ester hydrolysis in soil, while also identifying key challenges and opportunities for future development.

Together, these studies advance our understanding of sustainable CNF modification strategies and their applications in developing eco-friendly materials. This work contributes to ongoing efforts to address environmental challenges posed by conventional plastics while maintaining high performance standards for material applications.