Random sequential adsorption of Pickering particles onto spherical emulsion droplet surfaces

Area of Science:

• Colloid and Surface Science
• Materials Science
• Computational Chemistry

Background:

• Pickering emulsions are increasingly used in pharmaceuticals and food for their stability and low toxicity.
• Particle adsorption at the emulsion interface is key to emulsion properties but complex for non-spherical particles.
• Existing models often simplify particle shape and surface interactions, limiting predictive accuracy.

Purpose of the Study:

• To develop and validate a new model for random sequential adsorption (RSA) of particles onto emulsion droplet surfaces.
• To investigate the influence of particle shape (spherical vs. elongated), size, and interfacial properties on adsorption.
• To propose an improved available surface function (ASF) and generalized coverage evolution models.

Main Methods:

• Monte Carlo (MC) simulations were employed to model the RSA process for both spherical and elongated particles.
• Investigated parameters included particle polydispersity, droplet-to-particle size ratio, contact angle, and particle concentration.
• Response surface methodology was used to establish generalized coverage evolution models based on simulation data.

Main Results:

• A novel coverage-dependent exponent for the available surface function (ASF) was proposed, outperforming fixed-exponent models.
• For capsule-shaped particles (aspect ratio ε=2), higher coverage and faster adsorption rates were observed.
• Generalized models showed high accuracy, with mean absolute percentage errors below 2.63% for spherical and 6.58% for elongated particles.

Conclusions:

• The developed RSA model and proposed ASF expression accurately predict particle adsorption on curved emulsion droplet surfaces, considering particle shape.
• The findings provide a more robust theoretical framework for designing stable Pickering emulsions with specific functionalities.
• This work enhances the understanding of interfacial phenomena in complex colloidal systems relevant to various industrial applications.