Low Fluorine Content CO2-philic Surfactants

The article addresses an important, and still unresolved question in the field of CO2 science and technology: what is the minimum fluorine content necessary to obtain a CO2-philic surfactant? A previous publication (Langmuir2002, 18, 3014) suggested there should be an ideal fluorination level: for optimization of possible process applications in CO2, it is important to establish just how little F is needed to render a surfactant CO2-philic. Here, optimum chemical structures for water-in-CO2 (w/c) microemulsion stabilization are identified through a systematic study of CO2-philic surfactant design based on dichain sulfosuccinates. High pressure small-angle neutron scattering (HP-SANS) measurements of reversed micelle formation in CO2 show a clear relationship between F content and CO2 compatibility of any given surfactant. Interestingly, high F content surfactants, having lower limiting aqueous surface tensions, gamma(cmc), also have better performance in CO2, as indicated by lower cloud point pressures, P-trans. The results have important implications for the rational design of CO2-philic surfactants helping to identify the most economic and efficient compounds for emerging CO2 based fluid technologies.