Exploiting multiple phase separation to stabilize water in water emulsions and form stable microcapsules

Area of Science:

• Colloid and interface science
• Polymer science
• Materials science

Background:

• Water-in-water (W/W) emulsions consist of aqueous solutions of incompatible polymers.
• Stabilizing W/W emulsions and forming microcapsules is challenging due to droplet coalescence and dilution sensitivity.

Purpose of the Study:

• To stabilize W/W emulsions by gelling a third polymer phase.
• To create stable microcapsules from W/W emulsions that resist dilution.

Main Methods:

• W/W emulsions were prepared using poly(ethylene oxide) (PEO) and dextran.
• Gelatin was introduced as a third phase, and its gelation was induced by cooling.
• Microscopy and rheology were used to characterize morphology and properties.

Main Results:

• Gelatin's compatibility with PEO was tuned by pH, forming a continuous layer around dextran droplets.
• The gelatin layer gelled upon cooling, preventing coalescence and stabilizing the W/W emulsion.
• The resulting gelatin microcapsules demonstrated stability against dilution.

Conclusions:

• Gelling a third polymer phase is an effective strategy for stabilizing W/W emulsions.
• This method allows for the formation of robust microcapsules with tunable properties.
• The technique is versatile, demonstrated with both PEO/dextran and food-grade amylopectin/xyloglucan systems.