Phase transformations in microcrystalline cellulose due to partial dissolution |
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Authors: | Benoît J.-C. Z. Duchemin Roger H. Newman Mark P. Staiger |
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Affiliation: | (1) Department of Mechanical Engineering, University of Canterbury, Private Bag 4800, Christchurch, New Zealand;(2) Scion, Private Bag 3020, Rotorua, New Zealand |
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Abstract: | All-cellulose composites were prepared by partly dissolving microcrystalline cellulose (MCC) in an 8.0 wt% LiCl/DMAc solution, then regenerating the dissolved portion. Wide-angle X-ray scattering (WAXS) and solid-state 13C NMR spectra were used to characterize molecular packing. The MCC was transformed to relatively slender crystallites of cellulose I in a matrix of paracrystalline and amorphous cellulose. Paracrystalline cellulose was distinguished from amorphous cellulose by a displaced and relatively narrow WAXS peak, by a 4 ppm displacement of the C-4 13C NMR peak, and by values of T2(H) closer to those for crystalline cellulose than disordered polysaccharides. Cellulose II was not formed in any of the composites studied. The ratio of cellulose to solvent was varied, with greatest consequent transformation observed for c < 15%, where c is the weight of cellulose expressed as % of the total weight of cellulose, LiCl and DMAc. The dissolution time was varied between 1 h and 48 h, with only small additional changes achieved by extension beyond 4 h. |
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Keywords: | All-cellulose composite Cellulose I Cellulose II Cellulose IV LiCl/DMAc Microcrystalline cellulose Solid-state 13C NMR X-ray diffraction |
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