Directed self-assembly of nematic liquid crystalline polymers on a rubbed polyimide alignment layer

• Published in: Japanese Journal of Applied Physics Vol. 53; no. 6S; pp. 6 - 1-06JC04-5
• Main Authors: Kubo, Shoichi, Kobayashi, Sho, Hadano, Shingo, Komura, Motonori, Iyoda, Tomokazu, Nakagawa, Masaru
• Format: Journal Article
• Language: English
• Published: The Japan Society of Applied Physics 01.06.2014
• Subjects: Alignment; Copolymers; Cylinders; Liquid crystals; Nematic; Polyimide resins; Polymerization; Rubbing; Self assembly
• ISSN: 0021-4922; 1347-4065
• DOI: 10.7567/JJAP.53.06JC04

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 microphase-separated 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.