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submitted on 10.07.2020 and posted on 16.07.2020by Tom Willhammar, Kazuho Daicho, Duncan Johnstone, Kayoko Kobayashi, Yingxin Liu, Paul A. Midgley, Lennart Bergström, Tsuguyuki Saito
Cellulose is crystallized by plants and other organisms into fibrous nanocrystals. The
mechanical properties of these nanofibers and the formation of helical superstructures
with energy dissipating and adaptive optical properties depend on the ordering of
polysaccharide chains within these nanocrystals, which is typically measured in bulk
average. Direct measurement of the local polysaccharide chain arrangement has been
elusive. In this study, we use the emerging technique of scanning electron diffraction
to probe the packing of polysaccharide chains across cellulose nanofibers and to reveal
local ordering of the chains in twisting sections of the nanofibers. We then use atomic
force microscopy to shed light on the size dependence of the inherent driving force for
cellulose nanofiber twisting. The direct measurement of crystalline twisted regions in
cellulose nanofibers has important implications for understanding single cellulose fibril
properties that influence the interactions between cellulose nanocrystals in dense
assemblies. This understanding may enable cellulose extraction and separation
processes to be tailored and optimized.