Associative thickeners for waterborne paints: Structure, characterization, rheology, and modeling

Architectural coatings/paints play a very important role in our world, making our houses and workplaces beautiful, comfortable, and energy-efficient. Polymeric components of coating formulations include latex or binder, dispersants, and thickeners or rheology modifiers [RM]). This review is devoted to the RMs, primarily associative thickeners [AT], specifically highlighting the relationship between the thickener molecular structure, paint formulation, rheology, and application. We briefly describe the chemistries of various associative thickeners (“hydrophobic alkali-swellable emulsion” [HASE], hydrophobically modified hydroxyethylcellulose [HMHEC], and “hydrophobically modified ethoxylated urethane” [HEUR]) polymers. Concentrating on the HEUR thickeners, we then review the structure and rheology of their aqueous solutions and of model paints containing HEURs and latex particles in water. For model paints, we review experimental studies (rheology, NMR, and SANS) and theoretical models from molecular-level classical Molecular Dynamics [MD] to mesoscale coarse-grained MD to large-scale rheology calculations. Lastly, influence of rheological metrics on specific paint application features (flow and leveling, sag resistance, and brush drug) is discussed. We conclude by highlighting opportunities and challenges for future research.