Modeling the Adsorption of Rheology Modifiers onto Latex Particles Using Coarse-Grained Molecular Dynamics (CG-MD) and Self-Consistent Field Theory (SCFT)

Abstract

We model the adsorption of hydrophobically ethoxylated urethane (HEUR) thickeners onto two hydrophobic surfaces separated by a 50 nm gallery using coarse-grained molecular dynamics (CG-MD) with implicit solvent and three-dimensional self-consistent field theory (SCFT) with explicit solvent. The CG-MD simulations can be readily extended to encompass very long HEUR chains (up to 540 EO groups) but cannot with current computer speed simulate adsorption of HEURs with hydrophobes longer than 12 carbons (C12). The SCFT method can readily simulate HEURs with longer, C16, hydrophobes but has a greater challenge simulating very long EO chains. For HEURs with 180 EO units and C8 and C12 hydrophobes, both methods can be applied, allowing a combination of the two methods to span much of the parameter space of interest to experimentalists. It is demonstrated that depending on the hydrophobe strength and the HEUR concentration, HEUR chains can adsorb to the surfaces directly or indirectly (as adsorbed micelles or admic...