Preparation of ABC miktoarm star terpolymer containing poly(ethylene glycol), polystyrene, and poly(tert-butylacrylate) arms by combining diels-alder reaction, atom transfer radical, and stable free radical polymerization routes

The ABC type miktoarm star terpolymer was prepared utilizing "core-in" and "core-out" methods via combination of Diels-Alder reaction (DA), stable free radical polymerization (SFRP), and atom transfer radical polymerization (ATRP). First, in DA reaction, poly(ethylene glycol)-maleimide (PEG-maleimide) precursor was reacted with succinic acid anthracen-9-ylmethyl ester 3-(2-bromo-2-methyl-propionyloxy)-2-methyl-2-[2-phenyl-2-(2,2,6, 6-tetramethyl-piperidin-1-yloxy)-ethoxy-carbonyl]-propyl ester, 8, to give DA adduct, 9, which has appropriate functional groups for SFRP and ATRP. Second, a previously obtained 9 was used as a macroinitiator for SFRP of styrene at 125°C. As a third step, this PEG-polystyrene (PEG-PSt) precursor with a bromine functionality in the core was employed as a macroinitiator for ATRP of tert-butylacrylate (tBA) in the presence of Cu(I)Br and pentamethyldiethylenetriamine at 80°C to give ABC type miktoarm star terpolymer (PEG-PSt-PtBA) with controlled molecular weight and low polydispersity (M_w/M_n < 1.27). The obtained polymers were characterized by gel permeation chromatography and ¹H NMR.