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Dissolution state of cellulose in aqueous systems. 1. Alkaline solvents
Authors:Luis Alves  Bruno Medronho  Filipe E Antunes  Daniel Topgaard  Björn Lindman
Institution:1.Department of Chemistry,University of Coimbra,Coimbra,Portugal;2.Faculty of Sciences and Technology (MEDITBIO),University of Algarve,Faro,Portugal;3.Division of Physical Chemistry, Department of Chemistry, Center for Chemistry and Chemical Engineering,Lund University,Lund,Sweden;4.Materials Science and Engineering,Nanyang Technological University,Singapore,Singapore;5.FSCN,Mid Sweden University,Sundsvall,Sweden
Abstract:The understanding of the state of dissolution of cellulose in a certain solvent is a critical step forward in the development of new efficient solvent systems for cellulose. Nevertheless, obtaining such information is not trivial. Recently, polarization transfer solid-state NMR (PTssNMR) was shown to be a very promising technique regarding an efficient and robust characterization of the solution state of cellulose. In the present study, combining PTssNMR, microscopic techniques and X-ray diffraction, a set of alkaline aqueous systems are investigated. The addition of specific additives, such as urea or thiourea, to aqueous NaOH based systems as well as the use of an amphiphilic organic cation, is found to have pronounced effects on the dissolution efficiency of cellulose. Additionally, the characteristics of the regenerated material are strongly dependent on the dissolution system; typically less crystalline materials, presenting smoother morphologies, are obtained when amphiphilic solvents or additives are used.
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