A molecular dynamics study of structure, stability and fragmentation patterns of sodium bis(2-ethylhexyl)sulfosuccinate positively charged aggregates in vacuo

摘要

Positively charged supramolecular aggregates formed in vacuo by n AOTNa\ud(sodium bis(2-ethylhexyl)sulfosuccinate) molecules and nc additional sodium ions, i.e.\ud[AOTnNan+nc\ud]nc, have been investigated by molecular dynamics (MD) simulations for\udn = 1–20 and nc = 0–5. Statistical analysis of physical quantities like gyration radii, atomic\udB-factors and moment of inertia tensors provides detailed information on their structural and\uddynamical properties. Even for nc = 5, all stable aggregates show a reverse micelle-like structure\udwith an internal solid-like core including sodium counterions and surfactant polar heads\udsurrounded by an external layer consisting of the surfactant alkyl chains. Moreover, the aggregate\udshapes may be approximated by rather flat and elongated ellipsoids whose longer axis increases\udwith n and nc. The fragmentation patterns of a number of these aggregates have also been\udexamined and have been found to markedly depend on the aggregate charge state. In one\udparticular case, for which experimental findings are available in the literature, a good\udagreement is found with the present fragmentation data.