For more than 40 years, hydrophobically modified ethylene oxide urethane associative thickeners (HEURs) have been widely used to control the rheology of waterborne paints. HEURs are known to form transient networks of flower micelles in water; in paints, however, they interact strongly with latex particles. Recent experimental studies using Pulse-Field Gradient NMR (PFGNMR) and small-angle neutron scattering (SANS) demonstrated that the majority of HEUR chains are adsorbed on the latex surfaces, either directly or as adsorbed micelles (“admicelles”). Here, we use multi-scale simulations to model structure and rheology of the water/latex/HEUR mixtures. First, atomistic molecular dynamics was used to study the structure of individual HEUR chains near the acrylic latex surfaces. Next, we used Iterative Boltzmann Inversion (ITI) procedure to parameterize an implicit-solvent coarse-grained model and performed a coarse-grained molecular dynamics (CG-MD) calculation of HEUR micelle formation as a function of the HEUR concentration and structure. We also used CG-MD, as well as Self-Consistent Field Theory (SCFT), to compute adsorption isotherms. Finally, we performed a further coarse-graining procedure to develop a Brownian Dynamics model describing the rheology of model paint (aqueous dispersion of latex particles with adsorbed HEURs) under applied shear. The results are qualitatively consistent with experimental trends, although further validation and calibration is still needed.

Modeling structure and rheology of waterborne paints thickened by hydrophobically-ethoxylated urethane (HEUR) rheology modifiers: From molecular to coarse-grained description

251st National Meeting (2016)

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