Improved control in nitroxide-mediated radical polymerization using supercritical carbon dioxide

A demonstration of the control capability of the precipitation nitroxide-mediated radical polymerization (NMP) of styrene in scCO₂ over the molecular weight distribution than the corresponding solution polymerization. This constitutes the first example of a heterogeneous Controlled/living radical polymerization (CLRP) providing superior control over its homogenous counterpart and illustrates how benign scCO² provides new avenues for improved control of radical polymerization. CLRP is based on a dynamic equilibrium between dormant and active chains, which results in a decrease in the probability of termination events per chain and uniform growth of chains. Superior control indicated by narrower MWD in precipitation NMP of styrene in scCO² is obtained relative to the analogous homogenous solution polymerization.