Synthesis of a novel liquid crystal rod-coil star block copolymer consisting of poly(methyl methacrylate) and poly{2,5-bis[(4-methoxy-phenyl)oxycarbonyl] styrene} via atom transfer radical polymerization

A bromine capped star-shaped poly(methyl methacrylate) (S-PMMA-Br) was synthesized with CuBr/sparteine/PT-Br as a catalyst and initiator to polymerize methyl methacrylate (MMA) according to atom transfer radical polymerization (ATRP). Then, with S-PMMA-Br as a macroinitiator, a series of new liquid crystal rod-coil Star block copolymers with different molecular weights and low polydispersity were obtained by this method. The block architecture {coil-conformation of the MMA segment and rigid-rod conformation of 2,5-bis[(4-methoxyphenyl)oxycarbonyl] styrene segment} of the four-armed rod-coil star block copolymers were characterized by H-1 NMR. The liquid-crystalline behaviour of these copolymers was studied by differential Scanning calorimetry and polarized optical microscopy. We found that the liquid-crystalline. behavior depends on the molecular weight of the rigid segment; only the four-armed rod-coil star block copolymers with each arm's M-n,(GPC) of the rigid block beyond 0.91 X 10(4) g/mol could form liquid-crystalline phases above the glass-transition temperature of the rigid block. (C) 2005 Wiley Periodicals, lnc.