18 Electrochemical Functions of Nanostructured Liquid Crystals …
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along the columnar axis should be observed, while conductivity perpendicular to the
columnar axis was low since the conducive π-stacks were surrounded by insulative
mantles consisting of oligosiloxane moieties. During the polymerization process,
structural disorder should be induced to decrease the anisotropy in the absorption
and conductivity. However, the one-dimensionality of the electronic conduction was
retained in the polymerization process [34].
18.5 Conclusion
Nanosegregated LC structures are effective to form electrical polarization from which
electrochemical functions are derived. For the construction of nanosegregated structures, the side chain engineering is indispensable rather than design π-conjugated
units. In particular, oligosiloxane side chains promote segregation between functional
units and side chains to form soft nanostructures in the LC phases.
LC oligithiophene derivatives bearing an imidazolium unit at the terminal of
the alkyl side chain exhibit nanosegregated smectic phases in which ion-conductive
and hole-conductive sublayers are integrated separately. In the SmA phase, these
compounds display electrochromism in the bulk state.
Perylene bisimide derivatives bearing oligosiloxane chains exhibit columnar
phases at room temperature. In the columnar phases, one-dimensional electrontransporting π-stacks are surrounded by electrically insulative mantle consisting
of oligosiloxane chains. The mantle is liquid-like and the bulk states of the columnar
phases are waxy solid. However, they exhibit high electron mobilities, due to the
crystal-like π-stacks of perylene bisimide units.
The cyclotetrasiloxane moiety is not only polymerizable but also promotes
nanosegregation. Perylene bisimide derivatives bearing the cyclotetrasiloxane
moieties can be insolubilized in the thin film state via ring-opening polymerization
induced by the exposure on vapors of trifluoromethanesulfonic acid.
Perylene bisimide derivative bearing a triethylene oxide chain and two disiloxane
chains exhibits a lamellar LC phase which can be hybridized with lithium salts.
Perylene bisimide derivative bearing two cyclotetrasiloxane rings and one triethylene oxide chain exhibits a nanostructured columnar phase in which ion-conductive
sublayers and electro- and redox-active π-stacks are integrated on a nanometer scale.
This nanostructure is retained during the acid-induced polymerization process. The
polymerized thin films display electrochromism between red and blue, due to the
penetration of the ionic species and the rapid formation of electrical double layer.
In the doping of nanostructured π-conjugated liquid crystals, ionic reductants
diffuse through the ion-conductive sublayers within the columnar aggregates and
reduce the electron deficient π-conjugated cores to increase the electron density.
Dopant ions are separated from the electron-transporting π-stacks and this polarized
structure is categorized as an interstitial doping. Doped thin films which exhibit
anisotropic conductivity could be produced.
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along the columnar axis should be observed, while conductivity perpendicular to the
columnar axis was low since the conducive π-stacks were surrounded by insulative
mantles consisting of oligosiloxane moieties. During the polymerization process,
structural disorder should be induced to decrease the anisotropy in the absorption
and conductivity. However, the one-dimensionality of the electronic conduction was
retained in the polymerization process [34].
18.5 Conclusion
Nanosegregated LC structures are effective to form electrical polarization from which
electrochemical functions are derived. For the construction of nanosegregated structures, the side chain engineering is indispensable rather than design π-conjugated
units. In particular, oligosiloxane side chains promote segregation between functional
units and side chains to form soft nanostructures in the LC phases.
LC oligithiophene derivatives bearing an imidazolium unit at the terminal of
the alkyl side chain exhibit nanosegregated smectic phases in which ion-conductive
and hole-conductive sublayers are integrated separately. In the SmA phase, these
compounds display electrochromism in the bulk state.
Perylene bisimide derivatives bearing oligosiloxane chains exhibit columnar
phases at room temperature. In the columnar phases, one-dimensional electrontransporting π-stacks are surrounded by electrically insulative mantle consisting
of oligosiloxane chains. The mantle is liquid-like and the bulk states of the columnar
phases are waxy solid. However, they exhibit high electron mobilities, due to the
crystal-like π-stacks of perylene bisimide units.
The cyclotetrasiloxane moiety is not only polymerizable but also promotes
nanosegregation. Perylene bisimide derivatives bearing the cyclotetrasiloxane
moieties can be insolubilized in the thin film state via ring-opening polymerization
induced by the exposure on vapors of trifluoromethanesulfonic acid.
Perylene bisimide derivative bearing a triethylene oxide chain and two disiloxane
chains exhibits a lamellar LC phase which can be hybridized with lithium salts.
Perylene bisimide derivative bearing two cyclotetrasiloxane rings and one triethylene oxide chain exhibits a nanostructured columnar phase in which ion-conductive
sublayers and electro- and redox-active π-stacks are integrated on a nanometer scale.
This nanostructure is retained during the acid-induced polymerization process. The
polymerized thin films display electrochromism between red and blue, due to the
penetration of the ionic species and the rapid formation of electrical double layer.
In the doping of nanostructured π-conjugated liquid crystals, ionic reductants
diffuse through the ion-conductive sublayers within the columnar aggregates and
reduce the electron deficient π-conjugated cores to increase the electron density.
Dopant ions are separated from the electron-transporting π-stacks and this polarized
structure is categorized as an interstitial doping. Doped thin films which exhibit
anisotropic conductivity could be produced.