Nitroxide-mediated living free radical miniemulsion polymerization of styrene

The miniemulsion technique was applied to the controlled/living free radica l polymerization of styrene utilizing TEMPO-terminated oligomers of polysty rene (TTOPS) as a macroinitiator species to initiate the polymerization at 125 degreesC. Miniemulsion polymerizations of styrene using different amoun ts of TTOPS were studied. It was found that the polymerization rate of a mi niemulsion containing no TTOPS was significantly faster than those containi ng TTOPS. In the latter reactions, the molecular weight of the polymer incr eased almost linearly with conversion up to 75% conversion. The slope of th e molecular weight vs conversion curve increased with decreasing TTOPS conc entration as expected. Particle size distributions were measured by both TE M and CHDF and were found to be broad. Using the kinetics and particle size data, the average number of active free radicals per particle ((n) over ba r in classical emulsion polymerization systems) was estimated and found to be low (less than or equal to0.005).