Zwitterionic Cellulose Nanofibrils with High Salt Sensitivity and Tolerance

Area of Science:

• Materials Science
• Nanotechnology
• Polymer Chemistry

Background:

• Cellulose nanofibrils (CNFs) are versatile nanomaterials with potential applications in various industries.
• Improving the salt tolerance and sensitivity of CNFs is crucial for their broader industrial adoption.
• Existing CNFs often exhibit limited stability and performance in high-salt environments.

Purpose of the Study:

• To synthesize zwitterionic cellulose nanofibrils (ZCNFs) with enhanced salt tolerance and sensitivity.
• To investigate the effect of cation group content on the properties of ZCNFs.
• To explore the potential applications of ZCNFs in challenging environments.

Main Methods:

• Sequential modification of cellulose fibers: TEMPO-mediated oxidation (anionic), followed by cationization with EPTMAC.
• High-pressure homogenization to produce ZCNFs.
• Characterization using FT-IR, XPS, TGA, TEM, and rheological measurements.
• Evaluation of salt tolerance by adding mixed salts to ZCNF dispersions.

Main Results:

• Successfully produced ZCNFs with both anionic and cationic charges.
• ZCNFs demonstrated excellent "salt-thickening" behavior across a wide salt concentration range (2-24% w/w).
• Increased cation group content correlated with enhanced salt tolerance and sensitivity in ZCNFs.
• ZCNFs showed superior salt performance compared to TEMPO-oxidized cellulose nanofibrils (TOCNFs).

Conclusions:

• Introducing cationic charges onto anionic TOCNFs effectively creates ZCNFs with remarkable salt sensitivity and tolerance.
• The developed ZCNFs offer a promising solution for applications requiring stability in saline conditions.
• Potential applications include enhanced oil recovery and efficient wastewater treatment processes.