Salt-Responsive Pickering Emulsions Stabilized by Functionalized Cellulose Nanofibrils.

Area of Science:

• Materials Science
• Colloid and Surface Chemistry

Background:

• Cellulose nanofibrils (CNF) are emerging as sustainable stabilizers for Pickering emulsions.
• Functionalization of CNF can tune their surface charge and interfacial properties, impacting emulsion stability and behavior.

Purpose of the Study:

• To investigate the stabilization of oil-in-water emulsions using negatively charged oxidized cellulose nanofibrils (OCNF) and positively charged cationic cellulose nanofibrils (CCNF).
• To characterize the shell structure and salt responsiveness of CNF-stabilized Pickering emulsions.

Main Methods:

• Laser diffraction for droplet size analysis.
• Small-angle neutron scattering (SANS), confocal laser scanning microscopy (CLSM), and scanning electron microscopy (SEM) for shell structure investigation.
• Rheology measurements to assess emulsion gel properties.

Main Results:

• Both OCNF and CCNF formed stable emulsions with thick shells (>100 nm) composed of densely packed CNF.
• OCNF-stabilized emulsions exhibited salt responsiveness, influencing droplet aggregation and gel properties.
• CCNF-stabilized emulsions showed minimal salt-dependent behavior.

Conclusions:

• Surface charge of cellulose nanofibrils significantly influences the salt responsiveness of Pickering emulsions.
• OCNF are promising for developing tunable emulsion gels, while CCNF offer robust stability independent of salt concentration.