Experimental Investigation of Random Jamming Transition in Polydisperse Repulsive Nanoemulsions

Area of Science:

• Colloid and Surface Science
• Materials Science
• Food Science

Background:

• Repulsive emulsions form elastic materials via random jamming of oil droplets at a critical volume fraction.
• The random jamming volume fraction (ϕ_MRJ) is established for monodisperse emulsions but less understood for polydisperse systems.
• Ionic emulsifiers create interfacial charge clouds, contributing to droplet repulsion and jamming behavior.

Purpose of the Study:

• To experimentally determine the relationship between droplet size polydispersity and the random jamming volume fraction (ϕ_MRJ) in oil-in-water nanoemulsions.
• To investigate how polydispersity influences the elasticity and rheological properties of jammed nanoemulsions.
• To validate and adapt existing models for predicting jamming transitions in polydisperse emulsions.

Main Methods:

• Utilized citric acid esters of monoglyceride (CITREM)-stabilized canola oil-in-water nanoemulsions.
• Employed ultracentrifugation for size-fractionation, yielding nanoemulsions with controlled average droplet sizes and polydispersity.
• Measured the elasticity (plateau storage modulus, $G_p^{\text{'}}$) of diluted cream layers across various oil volume fractions (ϕ) and polydispersities.
• Applied a modified entropic, electrostatic, and interfacial (EEI) model to predict ϕ_MRJ.

Main Results:

• Elasticity ($G_p^{\text{'}}$) increased with decreasing oil droplet size and increasing oil volume fraction (ϕ).
• The modified EEI model successfully predicted the repulsive jamming transition and ϕ_MRJ for the size-fractionated nanoemulsions.
• Established a quantitative relationship between relative polydispersity and ϕ_MRJ.

Conclusions:

• The study successfully determined the impact of polydispersity on the random jamming volume fraction in repulsive nanoemulsions.
• The findings enable prediction of elasticity in polydisperse nanoemulsions, facilitating rational design.
• This research supports the development of emulsion-based products with optimized oil content, stability, and rheological characteristics.