Formation of Carbon Dioxide in Water Miniemulsions Using the Phase Inversion Temperature Method

The curvature of an emulsion of CO 2 and brine stabilized with a triblock copolymer of poly(dimethylsiloxane) (PDMS) and poly(ethylene oxide) (PEO), PEO- b -PDMS- b -PEO, was inverted from H 2 O-in-CO 2 to CO 2 -in-H 2 O (C/W) by reducing the temperature. A “v-shaped” trough was observed in the interfacial tension between the aqueous and CO 2 phases versus temperature at constant CO 2 density. The minimum in the interfacial tension coincided with the phase inversion temperature (PIT) where the curvature of the emulsion inverts. Novel C/W miniemulsions consisting of 200 nm droplets, measured by multiwavelength turbidimetry, were formed by low-shear stirring in the low interfacial tension PIT region and then cooling to 25 °C. These droplets were 3 times smaller than those produced isothermally by high shear at a temperature below the PIT region.