Graft Modification of Cellulose Nanocrystals
Collaborators: Dr. Pascale Champagne, Dr. Philip Jessop, Queen’s University; Dr. Julien Pinaud and Dr. Patrick Lacroix-Desmazes, CNRS/University of Montpellier, France
Industry Partners: Dr. Wadood Hamad, FPInnovations
Cellulose nanocrystals (CNC) are a natural and renewable material that possess unique physical and mechanical properties. However the poor dispersability of CNC in most hydrophobic polymer matrices has limited its incorporation into applications of interest, particularly as a reinforcing agent in polymer-based composites. CNC are most commonly obtained via either sulphuric acid hydrolysis. The hydroxyl groups react with H2SO4 to yield CNC functionalised with charged surface sulphate half-esters which significantly improves the CNC dispersion in water but inhibits effective incorporation and uniform dispersion of CNC into non-aqueous systems such as polymer matrices or organic solvents. These limitations have spurred interest in the development of methods to improve the dispersability of CNC in a variety of polar and nonpolar solvents. A useful methodology to achieve this involves grafting polymers on the CNC surface. Our group reported the first graft modification of CNC using nitroxide-mediated radical polymerization. This is a versatile process that enables us to graft a wide range of different polymers and functionalites onto the surface of CNC.
Current efforts are focussed on graft modifying the surface of CNC to allow it to behave as a tunable Pickering emulsifier for the stabilization of oil-in-water or water-in-oil emulsions. The scheme below illustrates CO2-switchable graft modified CNC Pickering stabilization of water-toluene mixtures.