A Multiscale Approach to Modeling Polymer-Colloid Dynamics in Waterborne Coatings

Formulations containing rheology-modifying polymers and nanometer-sized colloids have widespread use in pharmaceuticals, personal care products, and water-borne coatings. When combined in solution, the polymers temporarily “stick” to the colloids and act as bridges, forming a dynamic network with characteristic timescales spanning many orders of magnitude. Because it is computationally infeasible to capture the full range of relaxation times while maintaining atomistic resolution, our group has developed a hybrid population balance-Brownian dynamics model (Pop-BD). The Pop-BD model reduces the system to pairwise colloidal interactions with attractive contributions from bridging and repulsive contributions from the layer of loops on the colloid’s surface. So far Pop-BD has been used to qualitatively model the stress relaxation behavior of waterborne coatings but has not been compared quantitatively to experimental rheology.

In this work, we use two degrees of coarse-grained simulations to quantify the bridge formation dynamics and translate the results to physical systems. We also study the flow properties and microscopic conformations of coarse-grained polymer colloid mixtures under shear flow as a benchmark for PopBD simulations. The advancements from these multiscale simulations are then integrated into the PopBD model to efficiently simulate experimental system sizes to study previous inaccessible long timescale behavior.