V-shaped graft copolymers via triple click reactions: Diels-alder, copper-catalyzed azide-alkyne cycloaddition, and nitroxide radical coupling

We report here a simple and universal synthetic pathway covering triple click reactions, Diels-Alder, copper-catalyzed azide-alkyne cycloaddition (CuAAC), and nitroxide radical coupling (NRC), to prepare well-defined graft copolymers with V-shaped side chains. The Diels-Alder click reaction between the furan protected-maleimide-terminated poly(ethylene glycol) (PEG) and a trifunctional core (1) carrying an anthracene, alkyne, and bromide was carried out to yield the corresponding α-alkyne- and α-bromide-terminated PEG (PEG-alkyne/Br) in toluene at 110 °C. Subsequently, the polystyrene or polyoxanorbornene with pendant azide functionality as a main backbone is reacted with the PEG-alkyne/Br and 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO)-terminated poly(ε-caprolactone) using the CuAAC and NRC reactions in a one-pot fashion in N,N′-dimethylformamide at room temperature to result in the target V-shaped graft copolymers.