Gradient and Core–Shell Waterborne Polymer Nanoparticles: Effects of Particle Morphology on Coating Performance

Current coating technologies often rely on solvent-borne formulations (using Volatile Organic Compounds (VOCs)), which typically result in high level coating performance. However, there is a strong incentive to move toward waterborne coatings due to the legislative and environmental restrictions to reduce VOC emissions. It remains challenging however to design waterborne coatings resulting in coating performance matching that of the solvent-borne counterparts. We have prepared various composite latex particles with homogeneous, core–shell, and gradient morphologies using seeded starve-feed semibatch emulsion polymerization of styrene (St) and n-butyl acrylate (BuA). The particle morphology was assessed using a combination of X-ray Photoelectron Spectroscopy (XPS-particle: surface composition) and 1H NMR (overall particle composition) analyses. The coating performances of the obtained latexes were evaluated based on the minimal film forming temperature, hardness, and flexibility at room temperature. The results demonstrate that careful tuning of particle morphology offers potential to close the performance gap between traditional solvent-borne coatings and the next generation environmentally friendly waterborne coatings.