Perfectly alternating amphiphilic poly(p-phenylene) graft copolymers by combination of controlled radical polymerization and Suzuki coupling processes

Abstract

The preparation of amphiphilic poly(p-phenylene) (PP) possessing completely and perfectly alternating hydrophilic poly(ethylene oxide) (PEO) and hydrophobic polystyrene (PS) side chains is described. First, PS macromonomer with suitable functionality for polyphenylation was prepared by atom transfer radical polymerization (ATRP). The antagonist rnacromonomer, PEO, was synthesized by etherification reaction. Both macromonomers were reacted in the final stage via Suzuki cross coupling in the presence of Pd(PPh3)(4) as catalyst to form the desired amphiphilic graft copolymer (M-n : 32400 g/mol and M-w/M-n : 2.28). The intermediates obtained in various stages and graft copolymers were characterized by H-1 NMR and IR analysis. The optical absorption properties of the polymer were monitored with UV, and an additional absorption at around 280-320 nm evidenced the formation of PP chain. Thermal properties of PP were investigated by DSC. The thermogram displayed two transitions at 51.98 and 89.60 degrees C, indicating the presence of both PEO and PS structures in the copolymer. The perfectly alternating hydrophilic PEO and hydrophobic PS side chains were observed by AFM measurements to nanophase-separate in thin films.