Optimization of living polymerization through distributed control of a nitroxide radical

An optimal control methodology is applied to the goal of lowering the reaction time while maintaining low polydispersity in living free-radical polymerization. An illustration using a nitroxide radical profile for living free-radical polymerization of styrene in a plug flow reactor is provided. The reactor designs show that a distributed nitroxide radical flux along the length of the reactor can reduce the reaction time significantly for a given conversion. The reduction in residence time comes at the expense of a modest increase in polydispersity. A reference simulation with no optimization shows a conversion of 85% after 70 h and a final polydispersity of 1.31. Optimization of a 2,2,6,6-tetramethyl-1-piperidinyloxy flux results in a conversion of 90% after only 46 h while the polydispersity rises slightly to 1.42. The majority of the conversion takes place in the first 35 h. The theoretical designs, although not proven to be globally optimal, are of high quality.