Low fluorine content CO2-philic surfactants.

The article addresses an important, and still unresolved question in the field of CO(2) science and technology: what is the minimum fluorine content necessary to obtain a CO(2)-philic surfactant? A previous publication (Langmuir 2002, 18, 3014) suggested there should be an ideal fluorination level: for optimization of possible process applications in CO(2), it is important to establish just how little F is needed to render a surfactant CO(2)-philic. Here, optimum chemical structures for water-in-CO(2) (w/c) microemulsion stabilization are identified through a systematic study of CO(2)-philic surfactant design based on dichain sulfosuccinates. High pressure small-angle neutron scattering (HP-SANS) measurements of reversed micelle formation in CO(2) show a clear relationship between F content and CO(2) compatibility of any given surfactant. Interestingly, high F content surfactants, having lower limiting aqueous surface tensions, γ(cmc), also have better performance in CO(2), as indicated by lower cloud point pressures, P(trans). The results have important implications for the rational design of CO(2)-philic surfactants helping to identify the most economic and efficient compounds for emerging CO(2) based fluid technologies.