Interest in the incorporation of renewable, environmentally friendly materials, e.g. nanocellulose, into consumer products has progressed rapidly because these materials could lead to nanocomposites with enhanced functionality and mechanical properties. However, a key challenge that prevents nanocellulose from being widely used is that cellulose is insoluble, relatively inert, and difficult to disperse in non-aqueous solvents and polymeric matrices. Available methods for the surface modification of cellulose to make it dispersible in polar and non-polar systems are complex and difficult to implement on a large scale. To address these challenges, we report a simple one-step surface modification approach for tuning the interfacial properties of cellulosic materials. We use triazine chemistry as a modular handle to install various functionalities and chemistries onto filter paper, cellulose microfibrils, and cellulose nanocrystals (CNCs). The ability to carry out surface modification at room temperature in aqueous and organic media is demonstrated. This novel method allowed us to directly graft C18, allyl-PEG, benzyl and propargyl dichlorotriazinyl derivatives onto cellulose via aromatic nucleophilic substitution. These aliphatic, polymeric, alkyne chains and aromatic rings were successfully confirmed to be stable and covalently linked to cellulose. Thus, the modified cellulose/CNCs exhibited hydrophilic/hydrophobic properties depending on the grafted functionality which resulted into colloidal suspensions in aqueous/organic solvents with improved stability. Additionally, atomic force microscopy images of modified nanocellulose showed no observable change in the geometry and individualized character of CNCs after surface modification. X-ray diffraction analysis confirmed that the modification happened at the CNC interface whereas the bulk crystalline core remained unmodified. Finally, the propargyl moiety grafted onto cellulose fibres was used as a modular handle for further modification through an azide-alkyne cycloaddition reaction. In this way, azido-fluorescein molecules were grafted onto cellulose microfibrils, and fluorescence imaging showed labelling along the entire fibre. The developed modular chemistry provides the ability to tune the interfacial properties of cellulosic materials, improving their compatibility and dispersion in a wide range of solvents and solid matrices.

Designer molecules for one-step modification of cellulosic materials in aqueous and organic media through the triazine chemistry

253rd National Meeting (2017)

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