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Hydrogen-bond-induced inclusion complex in aqueous cellulose/LiOH/urea solution at low temperature
Jie Cai1, Lina Zhang, Chunyu Chang
1Department of Chemistry, Wuhan University, Wuhan 430072, China.
Summary
Cellulose dissolves in a cooled lithium hydroxide (LiOH)/urea solution due to a stable hydrogen-bonded network. Low temperatures facilitate LiOH hydrates cleaving cellulose packing, forming a stable complex and enabling dissolution.
Area of Science:
- Polymer Chemistry
- Materials Science
- Physical Chemistry
Background:
- Cellulose dissolution in aqueous solutions is crucial for its processing.
- The mechanism of cellulose dissolution in LiOH/urea solutions, particularly the role of temperature, remains unclear.
Purpose of the Study:
- To elucidate the phenomenon of rapid cellulose dissolution in a precooled LiOH/urea aqueous solution.
- To investigate the structural and physical properties of the solvent and cellulose at varying temperatures.
Main Methods:
- Laser light scattering
- 13C NMR spectroscopy
- Differential scanning calorimetry
- Fourier transform infrared spectroscopy
- Wide-angle X-ray diffraction
- Transmission electron microscopy (TEM)
Main Results:
- A stable hydrogen-bonded network forms between LiOH, urea, and water, strengthening at lower temperatures.
- LiOH hydrates break cellulose chain packing via new hydrogen bonds at low temperatures, forming a cellulose-LiOH-water complex.
- Urea forms a channel inclusion complex (IC) that encages cellulose, leading to good dispersion. TEM visualized this IC in dry form.
Conclusions:
- Low-temperature pre-cooling is essential for cellulose dissolution in LiOH/urea solutions.
- The formation of a stable hydrogen-bonded network and a urea-hosted channel inclusion complex explains cellulose dissolution and dispersion.
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