Molecular dynamics simulation study of sodium dodecyl sulfate micelle: Water penetration and sodium dodecyl sulfate dissociation

Abstract

h i g h l i g h t s• SDS micelle was simulated for 20 ns using all-atom MD simulation.• SDS conformations are mostly bent in micelle.• Free volume in SDS micelle is ∼0.35% of the micelle volume.• Free energy change for water penetration through SDS micelle is ∼10 kcal/mol.• Dissociation of a single SDS molecule from the micelle requires ∼13 kcal/mol. g r a p h i c a l a b s t r a c t a b s t r a c tWe investigate a micelle consisting of 60 sodium dodecyl sulfate (SDS) molecules in water phase using molecular dynamics simulation method. The dimension of the micelle is evaluated as ∼16Å and ∼21Å for the radius of gyration and geometric radius, respectively, which are well agreed with the previous studies. By calculating the formation energy, it is found that the stability of micelle is driven by the interaction of the micelle with water phase. Via Connolly surface analysis, it was found that ∼58% of the micelle surface is occupied by the hydrophobic alkyl tails. The conformation analysis shows that the individual SDS molecules are bent within the micelle and are not aligned radially from the center-of-mass of the micelle. However, it turns out that the micelle is well packed with a small free volume (0.35% of the micelle volume) which does not allow the diffusion-in of water molecules. The PMF required to drag a water molecule from water phase to the center-of-mass of micelle is calculated as ∼10 kcal/mol while the PMF for a SDS molecule to be dissociated from the micelle is ∼13 kcal/mol, both of which demonstrate that the micellization is driven by minimizing unfavorable interaction of hydrophobic alkyl tail of SDS molecule with water phase.

Prediction of EPR Spectra of Lyotropic Liquid Crystals using a Combination of Molecular Dynamics Simulations and the Model‐Free Approach

“…In contrast, in the slightly smaller DTAC micelle, even though a similar bent conformation is observed, the tails tend to remain directed towards the micelle centre. The SDS micelle was found to be stable over the entire MD trajectory at three selected temperatures, in agreement with the previous MD study by Jang and co‐workers which reported that external energy of ≈13 kcal mol −1 was required for the dissociation of the SDS molecules . Conversely, our results show that in the DTAC micelle individual molecules temporarily dissociate spontaneously, albeit infrequently.…”

“…An eccentricity of 0 indicates a perfect sphere. The averaged over time eccentricity of the SDS micelle was 0.118±0.035, which falls within the range of previously reported values obtained from MD simulations (0.057–0.154). Experimentally, the shape of the SDS micelle is still a topic of debate, with scattering data consistent with both slightly prolate and oblate spheroids .…”

“…detergents, lubricants, colloidal agents, drugd elivery vectors) in av ast range of processes, and have been the subject of intense study for many years. Sodium dodecyl sulphate (SDS) and dodecyltrimethylammonium chloride( DTAC) (Figure1), representingc lassical exampleso fa nionic and cationic surfactants, respectively,h ave been the target of awide range of experimental techniques including nuclear magnetic resonance (NMR), [1,2] electron paramagnetic resonance (EPR), [3][4][5][6] fluorescence, [7] X-ray [8] and neutron scattering, [9] as well as theoretical studies [10][11][12][13][14] in order to shed light on their structure and dynamics. Both systems are industrially ubiquitous, have well definede xperimentalp hase diagrams exhibitingm ultiple lyotropic phases including micellar,r od/hexagonal and lamellar phases,a sw ell as intermediate mixed structures.…”

The role of the asymmetric bolaamphiphilic character of VECAR on the kinetic and structural aspects of its self-assembly: A molecular dynamics simulation study

“…Most of the commonly used surfactants form micelles with radii of curvature close to the length of their hydrocarbon chains [10]. The structure, thermodynamics, and dynamic properties of aggregates or films of amphiphilic molecules are of prime importance in a great variety of systems [11–16]. …”

Influence of Surfactants and Fluoride against Enamel Erosion

“…Even though the micelles from SLS tend to expose the hydrocarbon chains (hydrophobic) on its external surface, due to the lower amount of the sulfate radical, it has been shown that they allow the entrance of water into its interior [Chun et al, 2015].…”