Computational studies on the behaviour of anionic and nonionic surfactants at the SiO$_{2}$ (silicon dioxide)/water interface

TL;DR

This study uses molecular dynamics simulations to analyze how anionic and nonionic surfactants interact with silicon dioxide surfaces, revealing differences in micelle formation and water behavior near the interface.

Contribution

It provides detailed insights into the structural and dynamical behavior of SDS and SPAN80 surfactants at the SiO2/water interface, highlighting differences in micelle shapes and water penetration.

Findings

SDS forms semi-spherical micelles on SiO2 surface.

SPAN80 forms cylindrical micelles on SiO2 surface.

Water molecules penetrate and localize at specific sites on the surface.

Abstract

Molecular dynamics simulations to study the behaviour of anionic (Sodium Dodecylsulfate, SDS) and nonionic (Monooleate of Sorbitan, SPAN80) surfactants close to a SiO$_{2}$ (silicon dioxide) surface were carried out. Simulations showed that a water layer was first adsorbed on the surface and then the surfactants were attached on that layer. Moreover, it was observed that water behaviour close to the surface influenced the surfactant adsorption since a semi-spherical micelle was formed on the SiO$_{2}$ surface with SDS molecules whereas a cylindrical micelle was formed with SPAN80 molecules. Adsorption of the micelles was conducted in terms of structural properties (density profiles and angular distributions) and dynamical behaviour (diffusion coefficients) of the systems. Finally, it was also shown that some water molecules moved inside the solid surface and located at specific sites of the solid surface.