Effect of solvent exchange on the solid structure and dissolution behavior of cellulose

Area of Science:

• Materials Science
• Polymer Chemistry
• Solid-State Chemistry

Background:

• Cellulose dissolution is crucial for its processing and applications.
• Understanding the relationship between cellulose's solid structure and its solubility is key.
• Solvent systems like LiCl/DMAc are explored for cellulose dissolution.

Purpose of the Study:

• To investigate how solvent exchange and milling affect cellulose's solid structure.
• To determine the influence of cellulose crystalline structure on its dissolution in LiCl/DMAc.
• To elucidate the mechanisms behind cellulose dissolution and aggregation.

Main Methods:

• Small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS).
• Solid-state Nuclear Magnetic Resonance (NMR) spectroscopy, including (1)H spin relaxation time measurements.
• Solvent exchange and milling techniques applied to cellulose.

Main Results:

• Solvent exchange facilitated cellulose dissolution in LiCl/DMAc with no change in crystalline structure.
• Milling destroyed cellulose crystalline structure but did not enhance dissolution.
• SAXS indicated increased fractal dimensions after solvent exchange, affecting microfibril aggregation.
• NMR suggested enhanced molecular mobility and reduced characteristic length along microfibrils post-solvent exchange.

Conclusions:

• Cellulose crystalline structure has minimal impact on its dissolution in LiCl/DMAc.
• Solvent exchange modifies cellulose aggregation and enhances molecular mobility for better solvent access.
• Milling is ineffective for dissolving cellulose due to structural degradation.