Formation of carbon dioxide in water miniemulsions using the phase inversion temperature method

The curvature of an emulsion Of CO2 and brine stabilized with a triblock copolymer of poly(dimethylsiloxane) (PDMS) and poly(ethylene oxide) (PEO), PEO-b-PDMS-b-PEO, was inverted from H2O-in-CO2 to CO2-in-H2O (C/W) by reducing the temperature. A "v-shaped" trough was observed in the interfacial tension between the aqueous and CO2 phases versus temperature at constant CO2 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 degreesC. These droplets were 3 times smaller than those produced isothermally by high shear at a temperature below the PIT region.