The successful incorporation of dyes into sterically stabilized aqueous polystyrene colloids has recently been reported using a new microencapsulation technique in which liquid carbon dioxide is used to facilitate mass transport into the polymer particles. The sterically stabilized particles retain their original size and shape after impregnation with dye. However, electrostatically stabilized polystyrene latexes made by surfactant-free emulsion polymerization lose stability when exposed to liquid carbon dioxide due to pH and ionic strength changes caused by carbonic acid formation in the aqueous phase. When colloidal stability is lost, particles coalesce due to the plasticization induced by carbon dioxide. To solve this problem, a series of surfactants that simultaneously provide colloidal stability and enhance mass transport during microencapsulation have been identified. These "dual function" surfactants are active at both the CO2/water and polymer/water interfaces. By adsorption onto the particle surface, colloidal stability is enhanced, and by adsorption at the carbon dioxide/water interface, emulsion formation is enhanced so that there is improved mass transport into the polymer particles. Light scattering, zeta potential measurements, and scanning electron microscopy are used to identify a series of amphiphiles that act as dual function surfactants during microencapsulation. All of the identified surfactants are commercially available hydrocarbon-based materials, some of which are currently used in food and drug formulations. The dual function concept demonstrates that the addition of a single low-cost additive can greatly enhance the utility of the CO2-based microencapsulation technique by extending it to electrostatically stabilized polymer colloids.