Structural Properties of Ionic Detergent Aggregates:  A Large-Scale Molecular Dynamics Study of Sodium Dodecyl Sulfate

Abstract

The properties of sodium dodecyl sulfate (SDS) aggregates were studied through extensive molecular dynamics simulations with explicit solvent. First, we provide a parametrization of the model within Gromacs. Then, we probe the kinetics of aggregation by starting from a random solution of SDS molecules and letting the system explore its kinetic pathway during the aggregation of multiple units. We observe a structural transition for the surfactant aggregates brought upon by a change in temperature. Specifically, at low temperatures, the surfactants form crystalline aggregates, whereas at elevated temperatures, they form micelles. We also investigate the dependence of aggregation kinetics on surfactant concentration and report on the molecular level structural changes involved in the transition.

Ionic Surfactant Aggregates in Saline Solutions: Sodium Dodecyl Sulfate (SDS) in the Presence of Excess Sodium Chloride (NaCl) or Calcium Chloride (CaCl2)

“…Furthermore, the form of the Cl -curves indicates the weak presence of an electric double layer, although the micellar surfaces are not well-defined. The small peak observed between 0.35 and 0.4 nm in the sodium curves in the salt-free or excess NaCl systems is associated with the first binding shell of the SDS model, as discussed in ref 37. The main Na + ion condensation peak is centered approximately at 0.58 nm and provides the dominant headgroup screening due to Na + ions, see ref 37.…”

“…65 Since the micelle-forming systems studied here have typically multiple micelles, and micelle properties are computed for a given micelle, the data analysis relies on identifying to which micelle each SDS molecule belongs. The micelle classification scheme is based on geometrical distance constraints and has been described in detail in ref 37. Where applicable, the error has been estimated as the standard deviation of the data sample.…”

“…[20][21][22][23][24][25][26][27][28] More recently, atomistic studies with and without solvent have emerged. [29][30][31][32][33][34][35][36][37][38][39] Since characteristic equilibration times for micelle formation are on the order of microseconds or longer, most of these simulations start from a spherical or rodlike micelle with a predetermined number of detergent molecules. 26,30,33,35,36,40 Such an approach provides valuable insight into detergent dynamics and micelle structure within that particular initial setup, but the results implicitly contain the assumption that the global minimum energy configuration, that is, micellar shape and aggregation number, is close to the initial configuration.…”

Surfactant and Hydrocarbon Aggregates on Defective Graphite Surface: Structure and Dynamics

“…The SDS parametrization employed in the work is described in detail in ref 54 and is available online at http://www.apmaths. uwo.ca/∼mkarttu/downloads.shtml.…”

Modelling the interfacial behaviour of dilute light-switching surfactant solutions

“…The challenge remains in tackling the computationally demanding calculations in the pre-cmc region. Coarse-grained (CG) methodologies have been used to approach these systems, reducing the number of nonrelevant degrees of freedom and allowing for more tractable simulations, [22][23][24][25][26][27][28][29] . However, even with commonly used CG approaches, pre-cmc calculations are strongly dependent on (i) the capability of the model to preserve the molecular character of surfactant-solvent interactions and, (ii) the adopted methodology.…”