Abstract
Most structured latex particles are formed in the nonequilibrium state as a result of the reaction kinetics proceeding faster than the phase separation kinetics. Of the many factors controlling such morphologies, the polarity and glass transition temperature (T~g~) of the seed polymer are important. In order to study the direct effect of the seed polymer T~g~ on morphology, we produced a series of poly(methyl methacrylate)/poly(methyl acrylate) seed copolymers having glass points between 52 and 98ยฐC, and particle sizes between 320 and 390 nm. We then used styrene as a secondโstage monomer reacting in both the batch and semibatch process modes, and utilized reaction temperatures (T~r~) between 50 and 70ยฐC. Monomer feed rates were varied between flooded and starveโfed conditions. The equilibrium morphology for these composite particles is an inverted coreโshell structure, but all morphologies obtained in our experiments were nonequilibrium. Under monomer starved conditions only coreโshell structures were formed when (T~r~โT~g~) < 0, but significant penetration of the polystyrene into the acrylic core occurs when (T~r~โT~g~) > 15ยฐC. These results are reasonably well predicted using the โfractional penetrationโ model developed earlier. ยฉ 2003 Wiley Periodicals, Inc. J Appl Polym Sci 90: 905โ915, 2003