Coarse-Grained Molecular Dynamics Simulation of Ammonium Surfactant Self-Assemblies: Micelles and Vesicles

Abstract

Large-scale coarse-grained molecular dynamics simulations have been performed to investigate the self-assemblies of dodecyltrimethylammonium bromide (DTAB) and gemini surfactants 12-S-12 (S = 6, 14, and 20). At the concentrations investigated, the surfactants experience fast aggregation of monomers into oligomers until the cluster numbers reach maxima. For DTAB, larger aggregates grow at the expense of monomers, but for gemini surfactants, the growth of clusters is accomplished via the merging of oligomers. In the final stage, spherical and worm-like micelles coexist in the systems of DTAB and 12-6-12, and in gemini systems with longer spacers, namely, 12-14-12 and 12-20-12, well-defined vesicles are formed through expansion and curving of bilayer-like structures. Through detailed analysis of the vesicle structures, many of the 12-20-12 surfactants are found to have their headgroups at different surfaces, with the spacers bridging the inner and outer surface of the vesicle.

Specific ion effects on the micellization of aqueous mixed cationic/anionic surfactant systems with various counterions

“…It has been argued that for quaternary ammonium gemini surfactants, one counterion is associated with one ionic headgroup [52,56], thus the value n = 2 should be used in calculating max . For the simple alkyl spacers, the prefactor 2 agrees well with the direct result from neutron reflection [57] and the result based on the coarse-grained molecular dynamics simulation [58]. Therefore, the value of n in this study is taken as 2 for 12-3-12 2+ ·2X − .…”

Coarse-grained molecular dynamics simulation of self-assembly of polyacrylamide and sodium dodecylsulfate in aqueous solution

“…Mapping of several heavy atoms into a single interaction bead reduces the number of degrees of freedom in the simulation, so the computational time is faster by 3-4 orders of magnitude over atomistic simulation, and the simulation scales reach to nanometers. The CG MARTINI model has already been used to study the structure of polymers [22][23][24] and the selfassembly of surfactants [25,26], and the obtained results are shown to closely reproduce that obtained by atomistic simulations and experiments. Here, we simulate the self-assembly process of PAM and SDS using the CG MARTINI model to study the microscopic properties of polymer and surfactant mixtures.…”

Molecular dynamics simulation of some cyclic compounds solubilization into the nanometric core of Cetyltrimethylammonium Bromide micelle

“…All systems were described by the potential parameters of the MARTINI coarse-grained (CG) force field. The MARTINI coarse-grained force field has shown accurate agreements with atomistic simulations and experimental data [28][29][30]. The mapping that MRATINI force field utilizes to represent molecules is a four-to-one mapping, i.e.…”