Surfactant properties and their influence on micellar solubilization of hydrocarbons.

摘要

To better understand the solubilization properties of surfactant for different classes of hydrocarbons, the critical micelle concentration must be obtained for each surfactant against certain hydrocarbon and this information can be measured from interfacial tension tests. The area per surfactant molecule on the interface can also be obtained from interfacial tension. Aggregation numbers for each system can be obtained by pyrene fluorescence quenching experiments, combining the micellar solubilization rate which is measured by G.C measurements, the composition of one micelle can be clearly clarified.; The dodecane/dodecylbenenesulfonate (DBS) and benzene/(DBS) micelles are examined here to explore the differences in the micelle structure and solubilization of dodecane and benzene in DBS micelles. The coordinate of each atom for a micellar system is rendered in a spherical control volume with their hydrophilic group facing water molecules that surround the micelle and hydrophobic tail stays within the interior of the micelle, the amount of molecules that form one micelle is based on the experimental results, energy minimization is performed to remove bad contacts within molecules. Molecular dynamic simulation with the CHARMM force field is conducted at constant NPT for one nano second and no additional constraint during the simulation. The equilibrated system results in a micelle structure in which water molecules do not penetrate into the interior of the micelle. Dodecane molecules stay in the core of the micelle due the movement of dodecane molecules are highly confined and hindered by the tail of the surfactant while the benzene molecules position themselves evenly among the whole micelle without any restriction. The radial distribution functions extracted from the output of the simulation show a highly ordered structure is preferred for a stable micelle. Experimental and Simulation details, micelle structures, and the atomic radial, probability and density functions will be presented.