Critical-Like Gelation Dynamics in Cellulose Nanocrystal Suspensions

Area of Science:

• Materials Science
• Colloid and Surface Chemistry
• Rheology

Background:

• Cellulose nanocrystals (CNCs) are charged, rodlike colloidal particles.
• They self-assemble into physical gels, valuable as precursors for bio-based composites.
• Understanding CNC gelation dynamics is crucial for materials design.

Purpose of the Study:

• To investigate the gelation dynamics of cellulose nanocrystal (CNC) suspensions after shear cessation.
• To characterize the viscoelastic behavior across the sol-gel transition.
• To explore the influence of salt concentration on gelation principles.

Main Methods:

• Time-resolved mechanical spectroscopy was employed.
• Linear viscoelastic spectra were acquired during the sol-gel transition.
• Data were rescaled onto master curves representing liquid and solid states.

Main Results:

• Two distinct viscoelastic states (liquid and solid) were identified, separated by a critical gel point.
• Rescaling parameters diverged asymmetrically at the critical gel point, following hyperscaling relations.
• Time-connectivity and time-concentration superposition principles were observed, influenced by salt content.

Conclusions:

• The study provides a detailed picture of CNC gelation dynamics.
• Critical-like behavior at the gel point suggests universal scaling laws for colloidal gels.
• Salt concentration plays a key role in governing the time-dependent assembly and properties of CNC gels.