The role of thermal initiation in nitroxide mediated living free radical polymerizations

The BPO initiated ''living'' polymerization of styrene in the presence of nitroxide is not consistent with the recently proposed steady-state mechanism, which requires constant nitroxide and polymer radical concentrations, and equal initiation and termination rates. It is shown that none of these conditions are met. The data is consistent with a polymerization rate that is dominated by nitroxide, not by the rates of thermal initiation and termination. Further, the use of agents that reduce thermal initiation shows that thermal initiation is not necessary to ensure that the polymerization proceeds, nor to ensure fast rates.