Cellulose chirality

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There has been a renaissance in cellulose research, based on its ubiquitous structural role in the plant cell wall, its value as an abundant, renewable, carbon-neutral and non-toxic material that contributes to the strength of wood, paper, textiles and nanocomposites. We plan to focus on one neglected cellulose property, namely its chirality. The chirality is expressed over several length scales. Of course, the individual glucose units contain chiral carbon centres, but at longer length scales, this chirality also influences the crystalline structure of cellulose, and the superstructure of plant cell walls, pulp fibres, paper and wood. One aspect of the renaissance has been the world-wide interest in various forms of nanocellulose (a field where our research has garnered a lot of recognition this year). But there remain several untapped areas of research at larger length scales that we would like to address in this proposal. **Over the years, we have observed, for the first time, the chiral structure and response of several cellulosic materials. We plan to focus on two particular observations. First, we found that ordered colloidal suspensions of cellulose nanocrystals form a left-handed chiral nematic structure, implying that there is some chiral interaction between the rod-like nanocrystals. We and others have speculated about the nature of this interaction, but experimental evidence is lacking. We hope to apply AFM force measurements to address this problem directly. Choice of cellulose samples and instrument geometries will be the key variables. **Second, we've isolated for the first time a right-handed coiled cellulose-based structure from the petioles (leaf-stems) of many plants. Whether the handedness is a function of the chiral interactions of cellulose microfibrils, or is a result of biosynthetic pathways (or both) is unclear. In any case, the observed structures would seem to play a role in water transport through the plant vascular system. While the vascular system of plants has been extensively investigated, many questions on this key natural process remain. We would like to examine the significance of our preliminary observations on petiole structure and function from a physico-chemical viewpoint.