Implicit Solvent Model Simulations of Surfactant Self-Assembly in Aqueous Solutions

The behaviors of the cationic surfactants of n-decyltrimethylammonium chloride (C10TAC) in water have been studied by the molecular dynamics (MD) simulations using the implicit solvent model proposed in our previous report (J. Chem. Theory Comput. 2007, 3, 1163). The MD simulations of 343 C10TAC surfactants in water at the surfactant concentrations of 5−100 mM have been performed for 25 ns, where the surfactant monomers at the initial configurations are uniformly dispersed. As a result, it was found that the C10TAC surfactants exist as monomers or oligomers at 5−15 mM, whereas they self-assemble to form surfactant aggregates at 30−100 mM. The growth and the breakup of these surfactant aggregates were repeatedly observed during the 25 ns simulations. The size distributions and the free monomer concentrations indicate that the critical micelle concentration of C10TAC surfactant in water represented by the ISM-3 lies between 15 and 30 mM, which fairly agrees with the experimental values of 50−65 mM.