CHEMICAL FUNCTIONALIZATION OF CELLULOSIC MATERIALS VIA AZETIDINIUM CHEMISTRY

Abstract

This proposed work explores the potential of azetidinium chemistry as a versatile platform for grafting functionalities including alkyl, alkyne, azide, and diallyl, as well as amino silicone — onto a wide range of cellulosic materials within different scales. The developed strategies enable either the functionalization of cellulosic materials to tailor their surface properties or the crosslinking of cellulosic materials to form three-dimensional hydrogels and aerogels. This thesis includes four main research as presented: First, a bifunctional azetidinium coupler was employed to graft functionalities onto carboxylate cellulosic materials. Carboxymethyl cellulose was utilized as a bridge between pulp fibres and functional groups by irreversible adsorption on the surface of pulp fibers and efficient reaction with azetidinium derivatives. Hydrophobicity was introduced through alkyl chains (C12 and C18), while bio-orthogonal reactivity was imparted via alkyne and azide functionalities, enabling further modification of paper sheets. Second, a versatile fluorescent labeling approach was developed using azetidinium–azide linkers, which allowed efficient conjugation with commercially available dyes such as FAM-alkyne and Cy5-alkyne. This method enabled labeling across all scales of cellulosic materials — including CNCs, CNFs, BC, and pulp fibers — without altering their morphology, providing a powerful tool for cellulose imaging and distribution studies. Third, a three-dimensional biomaterials ink was formulated by modifying CMC and CNCs with azetidinium–diallylamine. The resulting inks exhibited excellent shear-thinning and rapid thixotropic recovery, enabling high-fidelity extrusion printing. Incorporation of azetidinium–alkyne-modified CMC further enabled selective functionalization of specific regions within printed hydrogels, opening new possibilities for spatially controlled bioprinting applications. Finally, a water-soluble azetidinium-functionalized amino silicone was synthesized and applied in the fabrication of hydrophobic CNC/silicone aerogels through a water-based process. These aerogels demonstrated tunable mechanical properties, remarkable shape recovery (>90%) under repeated compression, and outstanding performance in solvent absorption, solvent–water separation, and thermal insulation.