Hansen solubility parameters obtained via molecular dynamics simulations as a route to predict siloxane surfactant adsorption

Hypothesis: The Hansen Solubility Parameters (HSP) derived from Molecular Dynamics (MD) simulations can be used as a fast approach to predict surfactants adsorption on a solid surface.

Experiments and simulations: We focused on the specific case of siloxane-based surfactants adsorption on silicon oxide surface (SiO₂), encountered in inkjet printing processes. A simplified atomistic model of the SiO₂ surface was designed to enable the computation of its solubility parameter using MD, and to subsequently determine the interactions of the SiO₂ surface with the siloxane-based surfactant and the various solvents employed. Surfactant adsorption was characterized experimentally using contact angle goniometry, ellipsometry, XPS and AFM.

Findings: Comparison of the numerical results with experiments showed that the HSP theory allows to identify the range of solvents that are likely to prevent surfactant adsorption on the SiO₂ surface. The proposed approach indicates that polar solvents, such as acetone and triacetin, which are strongly attracted to the silicon oxide surface might form a shield that prevents siloxane-based surfactants adsorption. This simple approach, can guide the selection of adequate solvents for surfaces and surfactants with specific chemical structures, providing opportunities for controlling interfacial adsorption.