Amphiphilic diblock copolymers PEO-b-PMA(4OPB) comprising hydrophilic poly(ethylene oxide) (PEO) and hydrophobic nematic liquid crystalline polymethacrylate [PMA(4OPB)] subunits were synthesized by atom transfer radical polymerization. The liquid crystalline property and microphaseseparated structure were investigated by differential scanning calorimetry, polarized optical microscopy, atomic force microscopy, and X-ray diffraction analysis. Unimodal PEO-b-PMA(4OPB) with 114 ethylene oxide repeating units and phenylbenzoate moieties as methacrylate side chain mesogens showed a nematic phase when the methacrylate repeating unit was around 57. Hexagonal cylinders of the PEO subunits were formed in nematic phase and supercooling states. The thin film on a rubbed polyimide alignment layer showed a microphase-separated structure independent of the rubbing direction, while horizontally aligned cylinders were observed in the presence of small nematic liquid crystalline molecules of 4-cyano-4$-pentyloxybiphenyl (5OCB). The assistance of nematic liquid crystalline molecules was necessary for directed self-assembly of the nematic liquid crystalline diblock copolymer in accordance with the rubbing direction of the polyimide alignment layer.
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