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-<i>co</i>-ethylene oxide)-<i>graft</i>-polystyrene and Poly(<i>tert</i>-butyl acrylate)

Abstract

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/PtBA] 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) (PtBA) 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 PtBA chains and heated to 90 °C in the presence of CuBr/PMDETA, the formed secondary carbon radicals at the PS or PtBA 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 PtBA when their number average of molecular weight Mn was in the range of 1500−7800 g/mol and ratio of GTEMPO/EO in copolymer was 1:21.