Synthesis of A3B3-type polystyrene-poly(methyl methacrylate) miktoarm star polymers via combination of stable free radical and atom transfer radical polymerization routes

An A(3)B(3)-type miktoarm star polymer was prepared utilizing a "core-out" method via combination of stable free radical polymerization (SFRP) and atom transfer radical polymerization (ATRP). First, SFRP of styrene was carried out by using a miktofunctional initiator, benzene- 1,3,5-tricarboxylic acid tris{3-(2-bromo-2-methyl-propionyloxy)-2-methyl-2-[2-phenyl2-(2,2,6,6-tetramethylpiperidin- 1-yloxy)ethoxy-carbonyl]propyl) ester, at 125 degrees C. Second, previously obtained polystyrene (A(3)-type PSt) precursor with three bromine functionallities in the core was used as a macroinitiator for ATRP of methyl methacrylate (MMA) in the presence of Cu(I)CI and pentamethyldiethylenetriamine at 90 degrees C in order to give an A(3)B(3)-type miktoarm star polymer, (PSt)3(PMMA)3, with controlled molecular weight and moderate polydispersity (M-w/M-n < 1.41), The obtained polymers were characterized by gel-permeation chromatography and H-1-NMR.