jp6b10829_si_001.pdf (1.42 MB)
Dissolution and Metastable Solution of Cellulose in NaOH/Thiourea at 8 °C for Construction of Nanofibers
journal contribution
posted on 2017-02-07, 00:00 authored by Zhiwei Jiang, Yan Fang, Yanping Ma, Maili Liu, Ruigang Liu, Hongxia Guo, Ang Lu, Lina ZhangTo
develop a facile approach for the dissolution of cellulose,
a novel solvent (9.3 wt % NaOH/7.4 wt % thiourea aqueous solution)
was used, for the first time, to dissolve cellulose within 5 min at
8 °C. The results of NMR and Raman spectra demonstrated that
stable thiourea···OH– complexes were
formed through strong hydrogen bonds in NaOH/thiourea at room temperature.
Moreover, the strength of the hydrogen bonds in thiourea···OH– complexes was much higher than that in urea···OH– complexes, and the number of thiourea···OH– complexes increased significantly in 9.3 wt % NaOH/7.4
wt % thiourea compared to that in 9.5 wt % NaOH/4.5 wt % thiourea,
which dissolved cellulose at −5 °C, leading to the dissolution
of cellulose at a relatively high temperature (8 °C). The cellulose
that dissolved at such a high temperature was metastable. The results
of dynamic light scattering and transmission electron microscope experiments
confirmed that the extended cellulose chains and their aggregates
coexisted in the dilute cellulose solution. Interestingly, stiff cellulose
chains could be self-assembled in parallel to form nanofibers in the
metastable cellulose solution, from which cellulose microspheres consisting
of nanofibers could be easily produced by inducing heating. This work
not only proposed a novel method for the dissolution of cellulose
in aqueous system at temperatures over 0 °C but also opened up
a new pathway for the construction of nanofibrous cellulose materials.