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M. Funahashi
prepared. These compounds exhibit columnar phases at room temperature. However,
the structures of the supramolecular aggregation were quite different; compound 10
formed columnar rectangular phase with a dimeric structure. In the columnar aggregates, ion-conductive sublayers consisting of triethylene oxide chains and electrontransporting π-stacks were formed separately. In contrast, conventional monomeric
columnar aggregates were formed for compound 11.
The triethylene oxide chains of compound 10 form hydrophilic sublayers within
the columnar aggregates. This sublayer works as an ion-conductive layer. For electrochromism, ionic species penetrate into active film for the formation of an electrical
double layer at the anode.
In electrochromism of organic thin films, the films are dipped in organic electrolyte solutions and the insolubilized thin films in the organic solvents are requisite.
Compound 10 is soluble in various organic solutions and thin films can be produced
by the spin-coating method. The as-deposited thin films are soluble in various organic
solvents, and therefore, they could not retain in the electrolyte solution. The solubility of thin films of compound 10 in acetonitrile is relatively low and can retain the
thin film state in acetonitrile solution of tetrabutylammonium perchlorate. However,
the thin film was dissolved when a negative DC bias was applied to the thin film
because anion radicals which have higher solubility in acetonitrile.
After insolubilization of the thin film by the acid vapor-induced ring-opening
polymerization method, the thin film of compound 10 can retain not only in the
neutral state but also even when they are reduced to anion radical and dianion states.
Insolubilized films of compound 10 by the ring-opening polymerization indicated electrochromism in an organic electrolyte solution, i.e., acetonitrile solution
of tetrabutylammonium perchlorate. Figure 18.12a displays the color change of the
polymerized thin film of compound 10 in the electrochromic process. As shown in
Fig. 18.12b, two-step reversible reduction waves were observed for solution and film
states. As shown in Fig. 18.12c, the reduction wave at −0.8 V and −1.2 V versus
an Ag
+ /Ag electrode were assigned to the generation of anion radicals and dianions of the perylene bisimide core, respectively. In this efficient electrochromism,
the presence of the ion-conductive sublayers is significant. The absorption spectrum
of the polymerized film of compound 10 during the electrochromism indicated that
efficient generation of dianions of the perylene bisimide units by a two-electron
reduction [34].
In contrast, for compound 11 which has no ion-conductive sublayers, electrochromism was not observed under the application of −1.5 V versus Ag
+ /Ag
electrode. Formation of electrical double layers by polarization of ionic species is
requisite for electrochemical function. This nanosegregated structure in which redoxactive π-stacks and ion-conductive sublayers are separated on a nanometer scale is
effective for efficient electrochromic response.
M. Funahashi
prepared. These compounds exhibit columnar phases at room temperature. However,
the structures of the supramolecular aggregation were quite different; compound 10
formed columnar rectangular phase with a dimeric structure. In the columnar aggregates, ion-conductive sublayers consisting of triethylene oxide chains and electrontransporting π-stacks were formed separately. In contrast, conventional monomeric
columnar aggregates were formed for compound 11.
The triethylene oxide chains of compound 10 form hydrophilic sublayers within
the columnar aggregates. This sublayer works as an ion-conductive layer. For electrochromism, ionic species penetrate into active film for the formation of an electrical
double layer at the anode.
In electrochromism of organic thin films, the films are dipped in organic electrolyte solutions and the insolubilized thin films in the organic solvents are requisite.
Compound 10 is soluble in various organic solutions and thin films can be produced
by the spin-coating method. The as-deposited thin films are soluble in various organic
solvents, and therefore, they could not retain in the electrolyte solution. The solubility of thin films of compound 10 in acetonitrile is relatively low and can retain the
thin film state in acetonitrile solution of tetrabutylammonium perchlorate. However,
the thin film was dissolved when a negative DC bias was applied to the thin film
because anion radicals which have higher solubility in acetonitrile.
After insolubilization of the thin film by the acid vapor-induced ring-opening
polymerization method, the thin film of compound 10 can retain not only in the
neutral state but also even when they are reduced to anion radical and dianion states.
Insolubilized films of compound 10 by the ring-opening polymerization indicated electrochromism in an organic electrolyte solution, i.e., acetonitrile solution
of tetrabutylammonium perchlorate. Figure 18.12a displays the color change of the
polymerized thin film of compound 10 in the electrochromic process. As shown in
Fig. 18.12b, two-step reversible reduction waves were observed for solution and film
states. As shown in Fig. 18.12c, the reduction wave at −0.8 V and −1.2 V versus
an Ag
+ /Ag electrode were assigned to the generation of anion radicals and dianions of the perylene bisimide core, respectively. In this efficient electrochromism,
the presence of the ion-conductive sublayers is significant. The absorption spectrum
of the polymerized film of compound 10 during the electrochromism indicated that
efficient generation of dianions of the perylene bisimide units by a two-electron
reduction [34].
In contrast, for compound 11 which has no ion-conductive sublayers, electrochromism was not observed under the application of −1.5 V versus Ag
+ /Ag
electrode. Formation of electrical double layers by polarization of ionic species is
requisite for electrochemical function. This nanosegregated structure in which redoxactive π-stacks and ion-conductive sublayers are separated on a nanometer scale is
effective for efficient electrochromic response.