Innovative approaches for nanocellulose functionalisation

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University

Nanocellulose (NC) composite derivatives are a class of materials with many advantageous properties that can be exploited for various industrial applications. This is especially pertinent considering the mandate to adopt bio-based technologies as alternatives to environmentally damaging materials in current commercial products. However, the utilisation of nanocellulose is currently limited by several factors including the cost of production, harmful chemicals and pollutants produced via its production process, lack of research into the capacity for nanocellulose functionalisation and the characteristics of such derivatives, poor mechanical properties of nanocellulose composites, the high hydrophilicity and high thermal conductivity. This thesis describes novel approaches to overcome the stated limitations by detailing the characteristics and mechanisms involved in the production of high performing nanocellulose based composites. The thesis outlines: (I) A unique TEMPO-free oxidation method for achieving a transformed nanocellulose and the mechanism for in-situ grafting of alien nanoparticle substrates; (II) A chlorine-free bleaching alternative for nanocellulose production and the commercial applicability of the developed nanocellulose via adoption into pulp paper packaging and films; (III) the applicability of nanocellulose as an aerogel composite across different aspects including the optimal production process (for example, shear rates) and constituent ratios with polyvinyl alcohol (PVA); (IV) The effect of the oxidation treatment on the mechanical properties of cellulose-based aerogels; (V) the properties of NC-PVA aerogel crosslinked with water-soluble coupling agents, where a nine-fold and three-fold enhancement in storage modulus and strength were achieved respectively; (VI) the properties of cellulose aerogels functionalised with graphene oxide. Overall this thesis paves the way for the commercialisation of novel functionalised nanocellulose materials.