A New Strategy for Preparation of Graft Copolymers via “Graft onto” by Atom Transfer Nitroxide Radical Coupling Chemistry: Preparation of Poly(4-glycidyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl-co-ethylene oxide)-graft-polystyrene and Poly(tert-butyl acrylate)

A series of graft copolymers poly(4-glycidyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl- co -ethylene oxide)- graft -polystyrene or poly( tert -butyl acrylate) [poly(GTEMPO- co -EO)- g -PS/P t BA] were synthesized by atom transfer nitroxide radical coupling (ATNRC) chemistry. Linear precursor copolymers with multipending 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) groups [poly(GTEMPO- co -EO)] were prepared first by anionic ring-opening copolymerization of 4-glycidyloxy-2,2,6,6-tetramethylpiperidine-1-oxyl (GTEMPO) and ethylene oxide (EO), and then polystyrene (PS) and poly( tert -butyl acrylate) (P t BA) with bromide end group were obtained by atom transfer radical polymerization (ATRP) using ethyl 2-bromoisobutyrate (EBiB) as the initiator and CuBr/ N,N,N′, N′, N ′′-pentamethyldiethylenetriamine (PMDETA) as catalyst. When the linear precursor copolymer poly(GTEMPO- co -EO) was mixed with PS or P t BA chains and heated to 90 °C in the presence of CuBr/PMDETA, the formed secondary carbon radicals at the PS or P t BA chain ends were quickly trapped by the nitroxide radicals on poly(GTEMPO- co -EO) main chain to form graft copolymer in which the alkoxyamines were at the conjunction points. The efficiency of coupling reaction was in the range of 90.2−95.9% for PS and 82.3−88.4% for P t BA when their number average of molecular weight M n was in the range of 1500−7800 g/mol and ratio of GTEMPO/EO in copolymer was 1:21.