Dynamic formation of graft polymers via radical crossover reaction of alkoxyamines

A novel dynamic polymer reaction system using radical exchange of alkoxyamine units has been demonstrated. Poly(methacrylic ester) having 2,2,6,6-tetramethylpiperidine-l-oxy (TEMPO)based alkoxyamine units in the side chain and TEMPO-based alkoxyamine-terminated polystyrene were prepared by atom transfer radical polymerization (ATRP) and nitroxide-mediated free radical polymerization (NMP), respectively. By the use of living radical polymerization techniques, the molecular weights of each polymer were accurately controlled. Radical crossover reaction of alkoxyamine units between the side chain and chain end of each polymer afforded the graft polymer which polystyrene chains are connected to the poly(methacrylic ester) backbone. Equilibrium M-n apparently depends on the feed ratio of polymers. The structure of the graft polymers is supported by size exclusion chromatography (SEC) and spectral data. The obtained graft polymer could be transformed reversibly to the starting materials by heating with excess amount of alkoxyamine derivative.