Mechanism of free-radical copolymerization of styrene with acrylonitrile and methacrylonitrile mediated by 2,2,6,6-tetramethyl-1-piperidinyloxy

By the examples of chemically similar styrene-acrylonitrile and styrene-methacrylonitrile systems, substantially different mechanisms of TEMPO-mediated copolymerization have been theoretically predicted and experimentally verified. Living copolymer-TEMPO adducts capable of thermal decomposition and polymerization reinitiation via the pseudoliving mechanism predominantly form in the first system. The reaction proceeds under the steady-state regime and is characterized by the living growth of M _n of the copolymer with conversion. In the second system, the probabilities of formation of living and dead macromolecules are equal. Therefore, the living growth of M _n of the copolymer ceases and the reaction passes to the conventional copolymerization regime.