Mapping Structure\nand Rheology of pH-Responsive Resins\nfor Low-VOC Coatings

In recent years, the paint and coatings industry has\nshifted away\nfrom traditional resin formulations that require high concentrations\nof volatile organic compounds (VOCs) to achieve the desired rheological\nperformance and sustainability targets. One approach to eliminate\nor reduce VOCs in paint and coating formulations while maintaining\nthe final performance is to disperse stimuli-responsive polymer latex\nparticles in water. The chemistry and architecture of these particles\nhave been engineered such that the suspension rheology changes in\nresponse to the pH changes. The particles can also be swollen with\norganic solvents to illicit similar rheological changes. To understand\nhow the particle microstructure influences the observed macroscopic\nproperties, we use small-angle neutron scattering and dynamic light\nscattering to determine that these particles consist of a cross-linked\ncore with long polymer tails that extend into the dispersing medium.\nCarboxylic acid groups present on the tails deprotonate with increasing\npH, and the extension of the polymer chain due to charge repulsion\nincreases the hydrodynamic drag on the particle. We find that adjusting\nthe pH alone has a much more significant effect on the shear dependence\nof the viscosity of the studied resin than adding organic solvent\nalone. We also find that this resin architecture is more responsive\nper mole of pH-responsive group than other architectures of pH-responsive\nlatex particles in the literature.