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 Mn 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 Mn of the copolymer ceases and the reaction passes to the conventional copolymerization regime.