Synthesis of Polar Block Grafted Syndiotactic Polystyrenes via a Combination of Iridium-Catalyzed Activation of Aromatic C-H Bonds and Atom Transfer Radical Polymerization

A combination of iridium-catalyzed C-H activation/borylation and atom transfer radical polymerization (ATRP) was used to generate polar graft copolymers of syndiotactic polystyrene (sPS). The borylation at aromatic C-H bonds of sPS and subsequent oxidation of boronate ester proceeded without negatively affecting the molecular weight properties and the tacticity of sPS. A macroinitiator suitable for ATRP could be synthesized by the esterification of 2-bromo-2-methylpropionyl bromide and hydroxy-functionalized sPS. The graft polymerizations of methyl methacrylate and tert-butyl acrylate from the macroinitiator using ATRP afforded polar block grafted sPS materials, syndiotactic polystyrene-graft-poly(methyl methacrylate) (sPS-g-PMMA) and syndiotactic polystyrene-graft-poly(tert-butyl acrylate) (sPS-g-PtBA). The latter was hydrolyzed to yield an amphiphilic graft copolymer, syndiotactic poly-styrene-graft-poly(acrylic acid) (sPS-g-PAA). The structures of the copolymers were characterized by NMR and FTIR spectroscopies. Size exclusion chromatography and H-1 NMR spectroscopy were used to study any changes in the molecular weight properties from the parent polymer. A decrease in the hydrophobicity of the graft copolymers was confirmed by water contact angle measurements. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 6655-6667, 2009