Accurate structural control and block formation in the living polymerization of 1,3-dienes by nitroxide-mediated procedures

The living free radical polymerization of 1,3-dienes, such as isoprene and 1,3-butadiene, has been shown to be a facile process in the presence of alkoxyamine initiators based on a 2,2,5-trimethyl, 4-phenyl-3-azathexane-3-oxy, 2, skeleton. These alpha-hydride nitroxide derivatives were able to control the homopolymerization to high conversion and molecular weights from 1000 to 100 000 amu with polydispersities of 1.06-1.15 readily obtained. Block and random copolymers based on combinations of 1,3-dienes with a variety of functionalized vinyl monomers, such as styrene, acrylate, or methacrylate derivatives, could also be prepared with similar control. In comparison with 2,2,6,6-tetramethylpiperidinoxy (TEMPO), these new systems represent a dramatic improvement in the ability to control the polymerization of 1,3-dienes and further demonstrate the versatility of nitroxide-mediated living free radical procedures.