€
130, 732; (d) M. C. Scharber, D. Muhlbacher, M. Koppe, P. Denk,
C. Waldauf, A. J. Heeger and C. J. Brabec, Adv. Mater., 2006, 18,
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curves of TPD-PFCB thin films obtained during chro-
noamperometric measurement applied between 0.7 V and 1.2 V.
We calculated the charge density (Qd) by integration of the
current density and time obtained from the graph of Fig. 5(a) to
investigate the amount of charge incorporated during the redox
reactions. The amount of Qd is 0.299 mC/cm2 and 0.308 mC/cm2
for oxidation and reduction process, respectively. The ratio of
the charge density is 0.97, indicating that charge injection/
extraction is highly reversible during the electrochemical reac-
tions. Fig. 5(b) shows the corresponding percentage transmittance
of TPD-PFCB film monitored at a wavelength of 700 nm.
Transmittance difference (DT%) is 33.2%. The relatively low DT%
is thought to be due to a very thin film thickness of about 30 nm.
However, the coloration efficiency (CE), which is calculated by
following equation: log(Tbleaching/Tcoloring)/Qd, is about 602 cm2/C.
This value is much higher compared to electrochromic compounds
based on arylamine.5,7,8 Also, response time, which is defined as
time needed to reach 90% of DT%, was 0.71 s and 0.12 s for the
coloring and bleaching processes, respectively. Considering that
electrochromic polymers typically have a response rate less than
1 s, our results are comparable or better than other reports.17
€
3 (a) C. Muller, S. Goffri, D. W. Breiby, J. W. Andreasen,
H. D. Chanzy, R. A. J. Janssen, M. M. Nielsen, C. P. Radano,
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Mater., 2007, 17, 2674; (b) Y. Li, Y. Wu, P. Liu, M. Birau, H. Pan
and B. S. Ong, Adv. Mater., 2006, 18, 3029.
4 (a) B. D. Reeves, E. Unur, N. Ananthakrishnan and J. R. Reynolds,
Macromolecules, 2007, 40, 5344; (b) C.-G. Wu, M.-I. Lu, S.-J. Chang
and C.-S. Wei, Adv. Funct. Mater., 2007, 17, 1063; (c) Y.-C. Nah, S.-
S. Kim, J.-H. Park, H.-J. Park, J. Jo and D.-Y. Kim, Electrochemistry
Communications, 2007, 9, 1542; (d) Y.-C. Nah, S.-S. Kim, J.-H. Park
and D.-Y. Kim, Electrochem. Solid-State Lett., 2007, 10, j12; (e) Y.-
C. Nah, W. S. Choi and D.-Y. Kim, Sol. Energy Mater. Sol. Cells,
2008, 92, 1547.
5 K. Choi, S. J. Yoo, Y.-E. Sung and R. Zentel, Chem. Mater., 2006, 18,
5823.
6 (a) B. Lim, J.-T. Hwang, J. Y. Kim, J. Ghim, D. Vak, Y.-Y. Noh, S.-
H. Lee, K. Lee, A. J. Heeger and D.-Y. Kim, Org. Lett., 2006, 8, 4703;
(b) H. Yan, P. Lee, N. R. Armstrong, A. Graham, G. A. Evmenenko,
P. Dutta and T. J. Marks, J. Am. Chem. Soc., 2005, 127, 3172.
7 (a) S. J. Yeh, C. Y. Tsai, C.-Y. Huang, G.-S. Liou and S.-H. Cheng,
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Conclusions
8 (a) H. Tanaka, S. Tokito, Y. Taga and A. Okada, Chem. Commun.,
1996, 2175; (b) Y. Shirota, J. Mater. Chem., 2000, 10, 1.
In summary, we synthesized PFCB containing an arylamine
polymer via a 2 + 2 cyclodimerization and investigated its elec-
trochromic properties. The new electrochromic polymer, TPD-
9 (a) C.-W. Chang, G.-S. Liou and S.-H. Hsiao, J. Mater. Chem., 2007,
17, 1007; (b) E. T. Seo, R. F. Nelson, J. M. Fritsch, L. S. Marcoux,
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11 (a) D. W. Smith, Jr. and D. A. Babb, Macromolecules, 1996, 29, 852;
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ꢀ
PFCB, showed high thermal stability (Td ¼ 435 C) due to the
incorporation of stable PFCB. During the electrochemical
reactions, the color of the TPD-PFCB thin films changed from
transparent to greenish blue through yellow intermediate colors,
and vice versa. Also, highly reversible charge injection/extraction
reactions took place during the redox reaction. Compared to
other arylamine-based compounds, TPD-PFCB exhibited
a higher electrochromic coloration efficiency and comparable
response time. We believe that this new polymer can find appli-
cations in electrochromic devices. Further investigation into
fabrication of multilayer electrochromic films using a PFCB-
based cross-linking agent is currently underway.6a
12 (a) A. P. Kennedy, D. A. Babb, J. N. Bremmer and A. J. Pasztor, Jr.,
J. Polym. Sci., Part A: Polym. Chem., 1995, 33, 1859; (b) D. W. Smith,
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Acknowledgements
This work was financially supported by the Ministry of Educa-
tion of Korea through the Brain Korea 21 (BK21) program, the
National Research Laboratory (NRL) Program of the Korea
Science and Engineering Foundation (KOSEF) grant funded by
the Korean government (MEST) (M10500000077-06J0000-
07710), the Bio Imaging Research Center at GIST, and the
Program for Integrated Molecular Systems (PIMS) at GIST.
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