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Latex Films: Film Formation of Smart Polymer Nanoparticles

An important challenge in waterborne coatings technology is to reduce the emissions of volatile solvents without sacrificing performance and properties. Important performance criteria include reasonable polymer diffusion rate and sufficient open time. To approach a solution for these problems, we designed two component latex nanoparticles composed of a high-molecular-weight acrylate polymer and a carboxylated-oligomer. These components were miscible at acidic pH, but in base they phase separated into a core-shell morphology. We show that in latex films formed at high pH, the oligomeric shell retarded the onset of polymer diffusion for ca. 30 min. When ammonia was used as base, the retardation stage was followed by a significant promotion of the polymer diffusion rate. We speculate that the ammonium salt of the oligomer decomposed upon drying and regenerated the acid form of the oligomer which was miscible with the high molecular weight polymer and acted as a non-volatile plasticizer.