Novel miktofunctional initiator for the preparation of an ABC-Type miktoarm star polymer via a combination of controlled polymerization techniques

An ABC-type miktoarm star polymer was prepared with a core-out method via a combination of ring-opening polymerization (ROP), stable free-radical polymerization (SFRP), and atom transfer radical polymerization (ATRP). First, ROP of ε-caprolactone was carried out with a miktofunctional initiator, 2-(2-bromo-2-methyl-pro-pionyloxymethyl)-3-hydroxy-2-methyl-propionic acid 2-phenyl-2-(2,2,6,6-tetramethyl-piperidin-1-yl oxy)-ethyl ester, at 110°C. Second, previously obtained poly(ε-caprolactone) (PCL) was used as a macroinitiator for SFRP of styrene at 125°C. As a third step, this PCL-polystyrene (PSt) precursor with a bromine functionality in the core was used as a macroinitiator for ATRP of tert-butyl acrylate in the presence of Cu(I)Br and pentamethyldiethylenetriamine at 100°C. This produced an ABC-type miktoarm star polymer [PCL-PSt-poly(tert-butyl acrylate)] with a controlled molecular weight and a moderate polydispersity (weight-average molecular weight/number-average molecular weight < 1.37). The obtained polymers were characterized with gel permeation chromatography and ¹H NMR.