Pickering Emulsion Transitions in 2,6-Lutidine Plus Water Critical Liquid Mixtures

Area of Science:

• Physical Chemistry
• Colloid Science
• Materials Science

Background:

• Pickering emulsions are stabilized by solid particles at oil-water interfaces.
• Critical phenomena in liquid mixtures, like 2,6-lutidine and water, exhibit unique interfacial properties.
• Particle-stabilized emulsions near critical points are sensitive to temperature and particle size.

Purpose of the Study:

• To investigate the de-emulsification behavior of silica particle-stabilized Pickering emulsions in a critical liquid mixture.
• To determine the influence of particle radius on the emulsion's stability and transition temperature.
• To analyze the interplay between gravitational forces and critical interfacial tension in emulsion stability.

Main Methods:

• Preparation and observation of silica particle-stabilized oil-in-water Pickering emulsions.
• Utilizing the critical liquid mixture of 2,6-lutidine and water.
• Measuring de-emulsification temperatures and relating them to particle radius and critical temperature.

Main Results:

• Pickering emulsions were observed in the two-phase region of the 2,6-lutidine-water mixture.
• De-emulsification occurred below a particle wetting transition temperature (T_w(R)).
• T_w(R) decreased with decreasing particle radius (R), approaching the critical temperature (T_c).

Conclusions:

• Emulsion stability is governed by a balance between destabilizing gravity and stabilizing critical interfacial tension.
• The observed Pickering emulsion transition and its particle radius dependence are explained by this force competition.
• Line tension at the three-phase contact line was determined as a function of temperature.