title: Unusual side-chain effects on charge-carrier lifetime in discotic liquid crystals.
abstract: When hexa-peri-hexabenzocoronene (HBC) carries paraffinic side chains with ester-ether termini (1a-1c), a hexagonal columnar liquid-crystalline (LC) mesophase forms, which is characterized by a very wide temperature range (ca. 0-300 degrees C). The LC materials from these HBC derivatives show characteristic electronic properties with an extremely long photocarrier lifetime. For example, by means of a flash-photolysis time-resolved microwave conductivity technique, the photocarrier lifetime, observed for liquid-crystalline 1a, is as long as 14 ms, which is four-orders of magnitude longer than that of fully paraffinic HBC 4 (0.0011 ms). The maximum transient photoconductivities of liquid-crystalline 1a-1c are comparable to one another and also to those of HBCs without ester-ether terminals. Liquid-crystalline 1a exhibits an obvious photocurrent generation in response to light illumination.
authors.affiliation: ERATO-SORST Nanospace Project, Japan Science and Technology Agency (JST), National Museum of Emerging Science and Innovation, 2-41 Aomi, Koto-ku, Tokyo 135-0064 (Japan), Fax: (+81) 3-5841-7310 http://macro.chem.t.u-tokyo.ac.jp/Home.html.
authors.forename: Jin
authors.initials: J
authors.lastname: Motoyanagi
authors.affiliation: ERATO-SORST Nanospace Project, Japan Science and Technology Agency (JST), National Museum of Emerging Science and Innovation, 2-41 Aomi, Koto-ku, Tokyo 135-0064 (Japan), Fax: (+81) 3-5841-7310 http://macro.chem.t.u-tokyo.ac.jp/Home.html.
authors.forename: Yohei
authors.initials: Y
authors.lastname: Yamamoto
authors.affiliation: Institute of Scientific and Industrial Research, and Graduate School of Engineering, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan).
authors.forename: Akinori
authors.initials: A
authors.lastname: Saeki
authors.affiliation: ERATO-SORST Nanospace Project, Japan Science and Technology Agency (JST), National Museum of Emerging Science and Innovation, 2-41 Aomi, Koto-ku, Tokyo 135-0064 (Japan), Fax: (+81) 3-5841-7310 http://macro.chem.t.u-tokyo.ac.jp/Home.html.
authors.forename: Md Akhtarul
authors.initials: MA
authors.lastname: Alam
authors.affiliation: ERATO-SORST Nanospace Project, Japan Science and Technology Agency (JST), National Museum of Emerging Science and Innovation, 2-41 Aomi, Koto-ku, Tokyo 135-0064 (Japan), Fax: (+81) 3-5841-7310 http://macro.chem.t.u-tokyo.ac.jp/Home.html.
authors.forename: Atsushi
authors.initials: A
authors.lastname: Kimoto
authors.affiliation: ERATO-SORST Nanospace Project, Japan Science and Technology Agency (JST), National Museum of Emerging Science and Innovation, 2-41 Aomi, Koto-ku, Tokyo 135-0064 (Japan), Fax: (+81) 3-5841-7310 http://macro.chem.t.u-tokyo.ac.jp/Home.html.
authors.forename: Atsuko
authors.initials: A
authors.lastname: Kosaka
authors.affiliation: RIKEN Advanced Science Institute, 2-1 Hirosawa, Wako, Saitama 351-0198 (Japan), Fax: (+81) 48-467-8104.
authors.forename: Takanori
authors.initials: T
authors.lastname: Fukushima
authors.affiliation: Institute of Scientific and Industrial Research, and Graduate School of Engineering, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan).
authors.forename: Shu
authors.initials: S
authors.lastname: Seki
authors.affiliation: Institute of Scientific and Industrial Research, and Graduate School of Engineering, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047 (Japan).
authors.forename: Seiichi
authors.initials: S
authors.lastname: Tagawa
authors.affiliation: ERATO-SORST Nanospace Project, Japan Science and Technology Agency (JST), National Museum of Emerging Science and Innovation, 2-41 Aomi, Koto-ku, Tokyo 135-0064 (Japan), Fax: (+81) 3-5841-7310 http://macro.chem.t.u-tokyo.ac.jp/Home.html.
authors.forename: Takuzo
authors.initials: T
authors.lastname: Aida