FUNCTIONALIZATION OF CELLULOSE NANOFIBRILS AND THEIR APPLICATIONS AS NOVEL MATERIALS
Cellulose-based materials have been attracting significant attention in recent years for their potential as renewable and biodegradable materials. Cellulose nanofibrils (CNFs) in particular are readily attainable from woody biomass in high purity and without harsh chemical processes. These CNFs can undergo chemical surface modifications after a simple workup, imbuing them with new attributes that differ from their naturally paper-like structure and properties. In this research, CNFs are modified with oleic acid—another common biomass found in high concentrations in some vegetable oils—which transforms the naturally hydrophilic cellulose into a superhydrophobic material. This transformation can be carried out using solventless mechanochemistry and worked up in ethanol, supporting a green process from start to finish.
Since cellulose contains many free, exposed hydroxyl groups, carboxylic acids can be condensed onto exposed hydroxyls to form esters. In this research, we focus specifically on the oleic acid moiety because its internal alkene has potential for further reactivity. Here we explore methods to introduce crosslinks into esterified CNF (eCNF) for structural and mechanical reinforcement between fibrils. Several methods are attempted, including methods involving thiolene chemistry and epoxide ring opening.
Additionally, efforts have been made to develop a method to disperse eCNF materials in ethyl acetate for deposition by spray coating. Dispersions of eCNF in ethyl acetate are sufficiently stable to enable deposition using simple airbrushing tools. The eCNF coatings are homogenous, superhydrophobic, and have good adhesion to a wide variety of surfaces.