Cellulose nanocrystals (CNCs) have emerged as highly effective stabilizers for emulsions under extreme conditions, making them promising candidates for CO₂ sequestration applications. This study explores the stability, morphology, and interfacial characteristics of CNC-stabilized emulsions under both ambient and high-pressure conditions. To assess CNC colloidal stability, floc size was measured across different ionic strengths using laser diffraction and dynamic light scattering (DLS). Atomic force microscopy (AFM) was employed to determine CNC particle morphology and size, while surface charge and sulfate group density were quantified through zeta potential analysis and conductometric titration. The morphology of emulsion droplets was analyzed using optical microscopy, and their stability over time was evaluated through droplet size distribution measurements. To further examine interfacial structures, scanning electron microscopy (SEM) combined with critical point drying revealed the formation of dense CNC shells at droplet interfaces. Interfacial properties were investigated through interfacial rheology and interfacial tension measurements, covering CNC concentrations from 0.1 to 1.0 wt% and salinities ranging from deionized (DI) water to 1.9 M NaCl brine. Interfacial shear and dilatational rheology measurements were done at ambient conditions with heptane as the oil phase, while select interfacial dilatational measurements were done at elevated pressures (2,000 psi) with liquid CO₂. These findings provide valuable insights into the stabilization mechanisms of CNC-stabilized emulsions, emphasizing their structural robustness and interfacial resilience under extreme conditions. The study reinforces the role of CNCs as efficient stabilizers for CO₂-in-water emulsions, supporting the development of stable systems for high-pressure CO₂ sequestration.
