Fundamental studies on morphology control for latex systems with application to waterborne coatings: The effect of polymer radical mobility in latex particles during polymerization

This work reports on the development of composite latex particle morphology in seeded, semicontinuous emulsion polymerization. Previous work has explained particle morphology development in terms of the ability of second stage polymer radicals to diffuse into, or "penetrate," the seed particles. This article investigates two separate effects that essentially alter the mobility of the second stage polymer radicals. The first is the initiator type, specifically nonionic versus ionic initiators, and the second is the use of chain transfer agent (CTA). It is shown that ionic initiators make it more likely to obtain core shell morphologies by decreasing the penetration of radicals, but only under a narrow set of conditions. Chain transfer agents, on the other hand, allow for more deviation from core shell morphologies by increasing the penetration of radicals, but significant changes were only observed at the highest concentration of CTA studied. Therefore, both factors are fairly subtle and effects are only observed under specific conditions.