Establishing the constitutive relationship between deep eutectic solvents pre-treatment extent, cellulose structure...

Area of Science:

• Materials Science
• Polymer Chemistry
• Green Chemistry

Background:

• Conventional cellulose dissolution in N-methylmorpholine-N-oxide (NMMO) requires high temperatures and long times, leading to poor product quality.
• Harsh conditions in NMMO dissolution limit cellulose processing efficiency and material properties.

Purpose of the Study:

• To develop a facile pre-treatment strategy to enhance cellulose dissolution efficiency in NMMO.
• To establish the relationship between deep eutectic solvent (DES) pre-treatment, cellulose structure, and dissolution rate.
• To investigate the mechanism behind improved dissolution and cellulose structural changes.

Main Methods:

• Utilized multiple concentration gradients of Zinc Chloride/Phosphoric Acid (ZnCl₂/H₃PO₄) as deep eutectic solvents (DES) for cellulose pre-treatment.
• Employed polarized light microscopy to observe cellulose fiber morphology during NMMO dissolution.
• Quantitatively analyzed the relationship between DES concentration gradients and cellulose fiber structural parameters.

Main Results:

• DES pre-treatment effectively disrupted the amorphous regions of cellulose, exposing hydrogen bonds and accelerating NMMO dissolution.
• Observed a novel hollow fiber phenomenon during NMMO dissolution post-DES treatment, indicating simultaneous internal and external dissolution.
• Optimized pre-treatment reduced cellulose dissolution time in NMMO from 40 minutes to 13 minutes.

Conclusions:

• A DES pre-treatment strategy offers a highly efficient method for cellulose dissolution, overcoming limitations of conventional NMMO processing.
• The study reveals a quantitative mechanism linking cellulose structural modification by DES to enhanced dissolution kinetics.
• This approach provides a pathway for improved cellulose processing with reduced energy consumption and time.