The Design of Novel Functional Materials Based on Cellulose Nanocrystals/Nanofibrils
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As the most abundant organic biomass on the planet, cellulose provides environmental, biocompatible and sustainable benefits. When treated by acid hydrolysis, highly crystalline nano-rods, called cellulose nanocrystals (CNCs), are generated. Besides the characteristics inherited from natural raw cellulose, this defect-free residue also displays unsurpassed physical properties, such as high tensile strength and ultrahigh specific surface area. The combination of these features makes CNC an excellent candidate for composite materials and building blocks. A partially sulfate esterified surface endows CNC aqueous suspensions with further properties. Dispersions of CNC with this modification are more stable and the abundant hydroxyl groups allow for various kinds of chemical modifications and polymer grafting. Another by-product of cellulose, called cellulose nanofibrils (CNFs), is produced through mechanical disintegration. CNFs have a lower crystallinity than CNCs and they deserve attention due to their flexibility, compressibility and ductility. It is well-known that CNF based foam possesses many attractive features, such as being ultralight, low-cost and ease of preparation. This kind of 3D structure with superior mechanical performance has potential applications in a broad range of fields. Carbon based materials, like graphene and fullerene, are used in a wide variety of applications due to their outstanding properties. For example, graphene enhanced supercapacitors and fullerene supported anti-oxidant agents are both attracting increasing attention. However, the inherent π-π stacking phenomenon hinders their processability in water, making them less environmentally friendly in design and manufacturing. The emergence of nanotechnology has offered an alternative-method of processing carbon based materials in aqueous phase, supporting their inclusion in environmentally friendly materials. This study involves the combination of fullerene and CNC to design an aqueous system with a high stability and free-radical scavenging properties. Both physical and chemical interactions between fullerene and CNC will be examined for their long-term stability. The morphology and structure of the system will be investigated and the conditions of synthesis will be optimized. Another focus is to incorporate CNF for the preparation of three-dimensional foam/aerogel with outstanding mechanical properties for waste water treatment. Non-toxic and water-soluble cross-linking agent ethylenediamine, will be used to form and enhance the mechanical properties of the structure. They will also confer chemically domains or grafting anchors on the inner and outer surface of the structure. CNF based foam could have compressible and twistable morphologies, both of which make it applicable to wearable/portable electronic devices. Porous 3D foam with a highly reactive surface could be able to coordinate with metal ions or bind with metal nanoparticles. Thus, CNF aerogels could be used to treat waste water contaminated with heavy metals and as a catalyst support or matrix for various metal oxide nanoparticles.