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The morphologies and dynamics of aggregates formed by surfactant molecules are known to influence strongly performance properties spanning biology, household cleaning, and soil cleanup. Molecular dynamics simulations were used to investigate the morphology and dynamics of a class of surfactants, the gemini or dimeric surfactants, that are of potential importance in several industrial applications. Simulation results show that these surfactants form structures and have dynamic properties that are drastically different from those of single-chain surfactants. At the same weight fraction, single-chain surfactants form spherical micelles whereas gemini surfactants, whose two head groups are coupled by a short hydrophobic spacer, form thread-like micelles. Simulations at different surfactant concentrations indicate the formation of various structures, suggesting an alternative explanation for the unexpected viscosity behavior of gemini surfactants.

AbstracLIn this anicle we present a method for alculating the chemical potential of arbitrary chain molecules in a mmpuier simulation. The method is based on a generalization of Siepmann's method tor mlculaling the chemical potential of chain molecules with a finite number of conformations. Next. we show that i t is also possible 10 atend the configurational-bias Monte Carlo scheme developed recenty by Siepmann and

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Molecular dynamics simulations have been performed on a simple water/oil/surfactant model to mimic the solubilization of nonpolar molecules into aqueous surfactant solutions. Three mechanisms have been identified through which oil molecules are transferred from the oil phase to the micelles: (1) dissolution of oil molecules in the solvent phase before being captured by micelles; (2) exchange of oil molecules between the oil droplet and the micelles during a soft collision; (3) collective desorption of surfactants and oil molecules from the oil droplet surface.