Low temperature TEMPO-mediated styrene polymerization in miniemulsion

The 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO)-mediated stable free radical polymerization of styrene in miniemulsion at 100 degrees C is demonstrated. Although this temperature is 20-35 degrees C lower than typical temperatures used for TEMPO-mediated polymerizations, reasonable reaction rates were achieved by the addition of ascorbic acid or a free radical initiator. More importantly, the living character of the chains was preserved; the degree of polymer "livingness" was comparable to polymerizations conducted at 135 degrees C. Polydispersities were broader than that observed in well-controlled systems, ranging from similar to 1.4-1.6, and consistent with expectations for systems having a low activation rate. The results are significant for two reasons. They will facilitate TEMPO-mediated minemulsion polymerizations in nonpressurized. (or minimally pressurized) reactors, and they reveal the potential to expand the traditional temperature range of TEMPO and possibly other nitroxides in bulk, solution, and miniemulsion. (c) 2005 Wiley Periodicals, Inc.