3-miktoarm star terpolymers using triple click reactions: Diels-Alder, copper-catalyzed azide-alkyne cycloaddition, and nitroxide radical coupling reactions

Well-defined linear furan-protected maleimide-terminated poly(ethylene glycol) (PEG-MI), tetramethylpiperidine-1-oxyl-terminated poly(ε- caprolactone) (PCL-TEMPO), and azide-terminated polystyrene (PS-N ₃) or -poly(N-butyl oxanorbornene imide) (PONB-N ₃) were ligated to an orthogonally functionalized core (1) in a two-step reaction mode through triple click reactions. In a first step, Diels-Alder click reaction of PEG-MI with 1 was performed in toluene at 110 °C for 24 h to afford α-alkyne- α-bromide-terminated PEG (PEG-alkyne/Br). As a second step, this precursor was subsequently ligated with the PCL-TEMPO and PS-N ₃ or PONB-N ₃ in N,N-dimethylformamide at room temperature for 12 h catalyzed by Cu(0)/Cu(I) through copper-catalyzed azide-alkyne cycloaddition and nitroxide radical coupling click reactions, yield resulting ABC miktoarm star polymers in a one-pot mode.