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Weak interactions and their impact on cellulose dissolution in alkali/urea aqueous system

Abstract

Weak interactions, though sometimes easily ignored, are playing an important role in the macromolecule dissolution. In this work, the characterization of weak interactions between urea and cellulose in the LiOH/urea aqueous solution was accomplished and confirmed in-situ, for the first time, with the new insights from PFG-SE NMR, FT-IR and solvatochromic methods, etc. The NMR results indicated the binding of urea with cellulose in the solution, demonstrating the existence of the weak interactions between them. Subsequently, solvatochromic methods revealed that urea hardly affected the hydrogen bonding donor (HBD acidity) and hydrogen bonding acceptor (HBA basicity) properties of the solvent, but was related to its dipolarity and polarizability, indicating that the dispersion forces existed therein, but not likely the hydrogen bonding, which was also supported by the FT-IR. Furthermore, the impact of weak interactions between urea and cellulose was demonstrated to facilitate the dissolving process. The fine dispersion and good stability of cellulose in the solution were maintained by mitigating the effect of the hydrophobic portions from all the dilute, semi-dilute to the concentrated regimes, supported by the results of dynamic light scattering (DLS), rheology and NMR, etc. Therefore, the transmittance and mechanical properties of the regenerated cellulose materials prepared from the cellulose solution in alkali/urea aqueous system were enhanced, compared with that in only alkali system. This work provided significant and new experimental insights about the non-covalent weak interactions between urea and macromolecules from the view of polymer physics and physical chemistry, which could never be ignored and underestimated. The indispensable weak interactions in the system is also important for the green conversion of natural biomass into new materials via physical process.

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Publication details

The article was received on 18 Apr 2017, accepted on 07 Jun 2017 and first published on 07 Jun 2017


Article type: Paper
DOI: 10.1039/C7CP02514A
Citation: Phys. Chem. Chem. Phys., 2017, Accepted Manuscript
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    Weak interactions and their impact on cellulose dissolution in alkali/urea aqueous system

    S. Wang, P. Sun, M. Liu, A. lu and L. Zhang, Phys. Chem. Chem. Phys., 2017, Accepted Manuscript , DOI: 10.1039/C7CP02514A

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