Molecular Dynamics Simulation of Interactions between a Sodium Dodecyl Sulfate Micelle and a Poly(Ethylene Oxide) Polymer

Abstract

We have performed atomistic molecular dynamics simulations of an anionic sodium dodecyl sulfate (SDS) micelle and a nonionic poly(ethylene oxide) (PEO) polymer in aqueous solution. The micelle consisted of 60 surfactant molecules, and the polymer chain lengths varied from 20 to 40 monomers. The force field parameters for PEO were adjusted by using 1,2-dimethoxymethane (DME) as a model compound and matching its hydration enthalpy and conformational behavior to experiment. Excellent agreement with previous experimental and simulation work was obtained through these modifications. The simulated scaling behavior of the PEO radius of gyration was also in close agreement with experimental results. The SDS-PEO simulations show that the polymer resides on the micelle surface and at the hydrocarbon-water interface, leading to a selective reduction in the hydrophobic contribution to the solvent-accessible surface area of the micelle. The association is mainly driven by hydrophobic interactions between the polymer and surfactant tails, while the interaction between the polymer and sulfate headgroups on the micelle surface is weak. The 40-monomer chain is mostly wrapped around the micelle, and nearly 90% of the monomers are adsorbed at low PEO concentration. Simulations were also performed with multiple 20-monomer chains, and gradual addition of polymer indicates that about 120 monomers are required to saturate the micelle surface. The stoichiometry of the resulting complex is in close agreement with experimental results, and the commonly accepted "beaded necklace" structure of the SDS-PEO complex is recovered by our simulations.

Investigating the Drag Reduction Performance of Rigid Polymer–Carbon Nanotubes Complexes

“…There are synergistic interactions which changed the solution characteristics in this regards expected to have taken place as a result of many factors such as the type of head or polar group of the surfactant embedded in the polymer backbone, polymer hydrophobicity, flexibility (Parathakkatt et al 2009) According to Shang et al (2008), in such type of complex formations, the surfactants micelles behave as emulsifiers which enhance surface tension control. However, the polymer additives changes solution rheological behavior and aided micelle stability.…”

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

“…Please note that SDS micelle has been selected as a model system because it is the most intensively-characterized micelle through experimental analysis [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] and simulation methods [34][35][36][37][38][39][40][41][42][43][44][45]. In experimental approaches, various techniques such as light scattering [18][19][20][21], fluorescence [24,25], SAXS [17,31] and SANS [23,26,27] have been used to characterize the size, shape, aggregation and charge of the SDS micelle at various conditions for concentration and temperature.…”

“…In this context, the molecular dynamics (MD) simulation methods have been extensively used to provide such detailed structural information on the micelle in general as well as the SDS micelle [34][35][36][37][38][39][40][41][42][43][44][45]. In 1990, Shelley and coworkers [34] reported the first large scale 182-picosecond MD simulation study on 42 monomer SDS micelle, in which they found that ∼12% of the sodium ions form contact ion pairs with the micelle.…”

A 1D‐ and 2D‐NMR Study of an Anionic Surfactant/Neutral Polymer Complex

“…An example of a system containing a neutral polymer and an anionic surfactant is the system poly(ethylene oxide) mixed with sodium dodecylsulfate (PEO/SDS). A significant amount of work has been reported in the literature on the interaction between PEO and SDS, including NMR investigations [16][17][18][19][20][21], calorimetry [22][23][24][25][26][27], and other techniques [28][29][30][31][32][33]. Given the extensive investigations on these systems, it is surprising that the manner in which the surfactant and polymer interact to form aggregates is still controversial.…”