Molecular dynamics (MD) simulation has been performed to investigate structural, thermodynamic properties of the AOT reverse micelles in nonpolar medium. The modeling is carried out for the aggregates at the temperature from 300 to 160 K. Water molecules are simulated with SPC/E model. Surfactant and oil are treated in a coarse-grained approach.
It was found out the temperature of water freezing is lower than that in bulk water. There are three different types of water molecules in reverse micelle: bulk-like water in the center of the polar core, intermediate state water and molecules in ionic shells. For the first water type the temperature of freezing is close to 270 K. Counterions are moved to the aggregate surface. The second one becomes crystal-like structure at 170 K. The water molecules in ionic shells and oil molecules demonstrate liquid state during the simulation.
Two type of water are considered in pure water clusters in oil. Water molecules are more structured without surfactant. There are more hydrogen bonds at 300 K. The water drop is compressed at this temperature and several molecules are located at the center of the cluster. Water molecules at the surface construct a layer structure with temperature decreasing. Oil molecules without surfactant demonstrate layers as well.
There is sufficient different behavior between water-in-oil system without and at the presence of surfactant. Surfactant aggregates are stable aggregates. Ionic surfactants make a main contribution into the whole energy of the system.
The work is supported by the grant “Leading Scientific School” (NSh-2744.2014.3)
galinam.chem@gmail.com
