Amphiphilic Nanogels as Versatile Stabilizers for Pickering Emulsions

Area of Science:

• Colloid and Surface Science
• Materials Science
• Polymer Chemistry

Background:

• Pickering emulsions (PEs) offer superior stability over molecular surfactants.
• Nano/microgels are effective colloidal stabilizers, enabling stimuli-responsive emulsions.
• A predictive model for nano/microgel-driven phase inversion in PEs is lacking.

Purpose of the Study:

• To develop amphiphilic nanogels (ANGs) with tunable hydrophobicity.
• To systematically investigate the impact of network hydrophobicity on emulsion stabilization.
• To establish a quantitative method for predicting phase inversion in PEs.

Main Methods:

• Synthesis of amphiphilic nanogels (ANGs) with controlled hydrophobicity.
• Systematic investigation of emulsion formation with varying ANG hydrophobicity, oil polarity, and temperature.
• Characterization of ANG adsorption kinetics, deformation, and swelling using atomic force microscopy.
• Development of a predictive model based on Flory-Huggins parameters.

Main Results:

• Water-in-oil (W/O) emulsions are favored with increased ANG hydrophobicity, oil polarity, and oil/water ratio.
• Metastable W/O PEs can be formed at elevated temperatures for nonpolar oils.
• Interfacial adsorption kinetics and ANG deformation/swelling correlate with emulsion type.
• A quantitative prediction of phase inversion is achieved using the difference in Flory-Huggins parameters (χwater - χoil).

Conclusions:

• This study provides essential structure-property relationships for designing nano/microgels for advanced PEs.
• The developed model enables accurate prediction of phase inversion, facilitating targeted material design.
• Findings advance the understanding and application of stimuli-responsive Pickering emulsions.