Molecular-dynamics simulation of the surface layer of a nonionic micelle

A spherical micelle structure has been studied for cationic (n-dodecyltrimethylammonium chloride) and nonionic (hexaethylene glycol mono-n-hexyl ether) surfactants in pure water and a sodium chloride solution. The molecular-dynamics has been used to simulate the self-assembly of aggregates from an initially homogeneous mixture of water and surfactant molecules and to gain insight into the structure of micelles and their surface layers. The radial distribution functions obtained for charged components have been employed to calculate the local electric potentials of the micelles and the contributions from the charges of water atoms, ions, and a surfactant to it. It has been shown that, similarly to previously studied ionic micelles, in nonionic surfactant micelles, the contributions from water molecules and polar groups (and ions in the case of the salt solution) to the electric potential are mutually compensated in the region of the electrical double layer. Therefore, the resultant electric potential of the surface layer rapidly tends to zero.