Carbon dioxide is an abundant and inexpensive material, widely available from both natural reservoirs and as a byproduct from industry. Because it is also nontoxic, nonflammable and recyclable, CO₂ can serve as a useful solvent. However, several important classes of substances such as water, hydrophilic molecules and most polymers exhibit very low solubility in it. This has led to an extensive search for surfactants with the ability to solubilize or stabilize such substances within a solution of CO₂.
These surfactants, characterized by a CO₂-phobic head and a CO₂-philic tail (generally a fluorine- or silicon-containing chain), self-assemble in carbon dioxide solution and form reverse micelles. The micelles are then employed to enhance the solubility of normally insoluble hydrophilic substances by incorporating them into their core, a process known as micellar solubilization. The core of the micelles is called differently depending on the applications it is used for. It is considered as "water pool" in non polar solvent for inorganic, organic and enzymatic reactions, as "universal" solvent medium for the extraction of pharmaceuticals, natural products, chemicals and waste streams or used as "nanoreactor" in the synthesis of nanomaterials. Because of the wide variety of applications, fundamental understanding of surfactant behaviors in carbon dioxide and carbon dioxide/water systems is of particular interest.

       Formulation variables such as the hydrophilic/CO₂-philic balance (HCB) of surfactant and the CO₂ density play an important role in the partitioning of surfactants between the CO₂-rich and H₂O-rich phases in scC/S/W systems. By increasing the HCB, the surfactant becomes more hydrophilic and partitions into the H₂O-rich phase while increasing the CO₂ pressure makes CO₂ a better solvent for the surfactant, causing it to partition into the CO₂-rich phase. The Bancroft rule, which was originally defined for water/surfactant/oil systems, uses this partitioning to predict the type of aggregate (micelle or reverse micelle) and the type of emulsion (CO₂-in-water or water-in-CO₂) formed in such systems.

     We have developed Lattice Monte Carlo simulation protocol to study the influence of formulation variables on the aggregation behavior and phase equilibria of supercritical CO₂/surfactant/water systems (scC/S/W).

     Our model allow us to reproduce the experimental trends of the effect of the surfactant HCB and the CO₂ density on micellization in scC/S/W systems at a water concentration equal to zero. Increasing the CO₂ density, we observe a decrease in the reverse micelle size and an increase in the critical micelle concentration. Increasing the HCB gives the opposite behavior. We are now increasing the water concentration in the system.

All these simulations are aimed at explaining the trends and characteristics displayed experimentally by scC/S micelles and scC/S/W emulsions and microemulsions.

     All researchs related with surfactants particularly surfactants in solution, surfactant/polymer systems, ternary systems (Water/Oil/Surfactant and scC/S/W ), emulsions and liquid membranes (multiple emulsions) are of my interest, both in a simulation and experimental point of view. My actual goal is studying the molecular level behavior of these systems in order to understand and predict their macroscopic behavior.