Chapter 18
Electrochemical Functions
of Nanostructured Liquid Crystals
with Electronic and Ionic Conductivity
Masahiro Funahashi
Abstract Nanosegregated liquid crystals are effective to construct nanostructures
in which an electronic function couples with an ionic transport. Polarization of ionic
species can form local electric fields interacting with electronic charges. In electrochromism, an electrical double layer promotes charge injection from an anode
or cathode to an active layer in which the injected charges are transported efficiently, due to the nanostructures of the liquid crystal phase. In chemical doping,
dopant ions are accumulated in ion-conductive subdomains and separated from the
electron transport channels. This type of the doping is interstitial doping which is
different from substitutional doping observed in organic molecular crystals. Sidechain engineering is effective for construction of the nanosegregated liquid crystal
phases. Imidazolium units connected to the terminal of alkyl chains of liquid crystalline oligothiophene derivatives promote formation of the nanosegregated structure in which ion-conductive and hole-transporting layers are integrated alternately.
Oligosiloxane moieties have a liquid-like property although they induce nanosegregation in liquid crystal phases. Perylene bisimide derivatives bearing oligosiloxane
moieties exhibit high solubilities in organic solvents and columnar phases at room
temperature. Perylene bisimide derivative bearing two cyclotetrasiloxane rings and
one triethylene oxide chain works as a mixed conductor. Polymerized thin films
display electrochromism in organic electrolyte solutions and anisotropic electrical
conductivity in the doped states.
Keywords Liquid crystalline semiconductor · Nanosegregation · Oligosiloxane ·
Electrochromism · Interstitial doping · Perylene bisimide · Oligothiophene
M. Funahashi (B)
Department of Advanced Materials Science, Faculty of Engineering and Design, Kagawa
University, 2217-20 Hayashi-cho, Takamatsu, Kagawa 761-0396, Japan
e-mail: m-funa@eng.kagawa-u.ac.jp
Health Research Institute, National Institute of Advanced Industrial Science and Technology,
2217-14 Hayashi-cho, Takamatsu, Kagawa 761-0395, Japan
© Springer Nature Singapore Pte Ltd. 2020
M. Sakamoto and H. Uekusa (eds.), Advances in Organic Crystal Chemistry,
https://doi.org/10.1007/978-981-15-5085-0_18
359
Electrochemical Functions
of Nanostructured Liquid Crystals
with Electronic and Ionic Conductivity
Masahiro Funahashi
Abstract Nanosegregated liquid crystals are effective to construct nanostructures
in which an electronic function couples with an ionic transport. Polarization of ionic
species can form local electric fields interacting with electronic charges. In electrochromism, an electrical double layer promotes charge injection from an anode
or cathode to an active layer in which the injected charges are transported efficiently, due to the nanostructures of the liquid crystal phase. In chemical doping,
dopant ions are accumulated in ion-conductive subdomains and separated from the
electron transport channels. This type of the doping is interstitial doping which is
different from substitutional doping observed in organic molecular crystals. Sidechain engineering is effective for construction of the nanosegregated liquid crystal
phases. Imidazolium units connected to the terminal of alkyl chains of liquid crystalline oligothiophene derivatives promote formation of the nanosegregated structure in which ion-conductive and hole-transporting layers are integrated alternately.
Oligosiloxane moieties have a liquid-like property although they induce nanosegregation in liquid crystal phases. Perylene bisimide derivatives bearing oligosiloxane
moieties exhibit high solubilities in organic solvents and columnar phases at room
temperature. Perylene bisimide derivative bearing two cyclotetrasiloxane rings and
one triethylene oxide chain works as a mixed conductor. Polymerized thin films
display electrochromism in organic electrolyte solutions and anisotropic electrical
conductivity in the doped states.
Keywords Liquid crystalline semiconductor · Nanosegregation · Oligosiloxane ·
Electrochromism · Interstitial doping · Perylene bisimide · Oligothiophene
M. Funahashi (B)
Department of Advanced Materials Science, Faculty of Engineering and Design, Kagawa
University, 2217-20 Hayashi-cho, Takamatsu, Kagawa 761-0396, Japan
e-mail: m-funa@eng.kagawa-u.ac.jp
Health Research Institute, National Institute of Advanced Industrial Science and Technology,
2217-14 Hayashi-cho, Takamatsu, Kagawa 761-0395, Japan
© Springer Nature Singapore Pte Ltd. 2020
M. Sakamoto and H. Uekusa (eds.), Advances in Organic Crystal Chemistry,
https://doi.org/10.1007/978-981-15-5085-0_18
359