Compartmentalization in TEMPO-mediated radical polymerization in dispersed systems: Effects of macroinitiator concentration

The influence of the initial macroinitiator concentration ([PT](0)) on compartmentalization effects (segregation effects and confined space effects) in 2,2,6,6-tetramethylpiperidinyl-l-oxy (TEMPO)mediated radical polymerization of styrene in a dispersed system at 125 C has been investigated by simulations employing modified Smith-Ewart equations. The modeling approach accounts for compartmentalization of both propagating radicals and nitroxide, as well as the generation of radicals by thermal initiation of styrene. The manifestation of compartmentalization effects occurs at significantly greater particle diameters (d) for low [PT](0); at [PT](0) = 0.002 M, the polymerization rate, control and livingness are affected by compartmentalization for d < 120 nm, whereas the system behaves as in the corresponding bulk system for d > 45 nm at [PT](0) = 0.2 M. The results are discussed with regards to the specific effects of compartmentalization on deactivation and bimolecular termination.