EFFECT OF TEMPERATURE ON THE PHOTOALIGNMENT
681
perpendicular orientation of the probe radiation rela- perature determined the values of the induced DRs of
thin films after their exposure to polarized light.
tive to the irradiating light and its reduction when the
directions of the radiation coincided (Figs. 5a, 5b).
REFERENCES
The realignment of molecules, apparent in the
increased absorption of the polarized probe radiation
when its direction perpendicular to that of the polar-
ization of the irradiating light and the reduced absorp-
tion for the coincident direction, was observed after
irradiation with UV light (Figs. 5a, 5b). The presence
of realigned FtF-2 and FbF-2 molecules in the thin
film after irradiation with polarized UV (Figs. 5a, 5b)
and visible (Figs. 3a, 3b) light suggests that these dyes
can be classified as belonging to the aminoazobenzene
and pseudo-stilbene groups, respectively.
1. N. Kawatsuki, K. Matsuyoshi, M. Hayashi, et al.,
Chem. Mater. 12, 1549 (2000).
2. M. Ibn-Elhaj, S. Chappellet, and F. Lincker, Solid
State Phenom. 181, 3 (2012).
3. S. Furumi and K. Ichimura, Thin Solid Films 499, 135
(2006).
4. T. G. Pedersen, P. M. Johansen, N. Ch. Rømer Holme,
et al., J. Opt. Soc. Am. B 15, 1120 (1998).
5. T. Seki, Polym. J., 1 (2014).
6. V. Chigrinov, E. Prudnikova, V. Kozenkov, et al.,
J. Soc. Info Display 11, 579 (2003).
The temperature dependences of the induced DRs
of different series of azo dyes varied (Figs. 3a, 3b). For
example, an increase in the induced DRs as the tem-
perature rose to 60°C was typical of the thin films of
FbF-2 and GbG-2 dyes. This could have been due to
an accelerated rate of the transition of the cis-isomer
to the trans-form [43]. A reduction of the photoin-
duced DRs in the thin films of FtF-1 and FtF-2 azo
dyes and those of FbF-2 and GbG-2 (at temperatures
above 60°C with the latter pair) could have been due to
the stabilization of the trans-forms of the dyes.
7. A. Muravsky, V. Agabekov, An. Murauski, et al., SID
Symp. Digest 41, 1724 (2010).
8. A. A. Muravsky, V. E. Agabekov, P. M. Malashko, et al.,
Probl. Fiz., Mat. Tekh., No. 2, 68 (2010).
9. V. Chigrinov, An. Muravski, H. S. Kwok, et al., Phys.
Rev. E 68, 061702 (2003).
10. V. Mikulich, An. Murauski, Al. Muravsky, et al., J. Soc.
Info Display 22, 199 (2014).
11. Al. A. Muravsky, An. A. Muravskii, V. S. Mikulich,
et al., Vestn. Mosk. Obshchestv. Univ., No. 1, 48
(2013).
There were thus two processes determining the rate
of realignment of molecules of the studied azo dyes in
films after their irradiation: the cis → trans isomeriza-
tion of azo dyes upon irradiation with light,
12. T. Fukuda, H. Matsuda, T. Shiraga, et al., Macromol-
ecules 33, 4220 (2000).
13. I. V. Tomov, T. E. Dutton, B. van Wonterghem, et al.,
J. Appl. Phys. 70, 36 (1991).
14. V. S. Mikulich, Al. A. Muravsky, An. A. Murauski,
hV
trans ⎯⎯⎯→cis
et al., J. Soc. Info Display 22, 29 (2014).
15. T. Kaneda, S. Ishikawa, H. Daimon, et al., Makromol.
and the dark relaxation of cis-isomers to trans-forms
Chem. 183, 433 (1982).
under heating [44, 45],
16. V. Chigrinov, S. Pikin, A. Verevochnikov, et al., Phys.
Rev. E 69, 061713 (2004).
T
.
cis ⎯⎯⎯→trans
17. A. Muravsky, U. Mahilny, V. Agabekov, et al., SID
Symp. Digest 40, 1623 (2009).
18. S. K. Prasad, G. G. Nair, and D. S. S. Rao, Liq. Cryst.
CONCLUSIONS
36, 705 (2009).
19. P. L. Rochon, Opt. Spectrosc. 103, 858 (2007).
It was shown that heating samples of thin films of
azo dyes above 100°C during their exposure at a con-
stant dose reduces the induced DRs (the DR values of
FbF-2 and GbG-2 were 1.6, while those of FtF-1 and
FtF-2 were 1.2), due to the stabilization of trans-iso-
mers at a temperature of 103°C. With dyes FbF-2 and
GbG-2, the induced DR grew from 3.5 to 4.5 and
from 4.6 to 5.8, respectively, as the temperature rose
from 20 to 60°C, due to the accelerated rate of the
reversible cis–trans isomerization. Raising the sample
temperature from 20 to 103°C reduced the values of
the induced DRs of thin films of FtF-1 and FtF-2 azo
dyes from 5.8 to 1.2 and from 5.3 to 1.2, respectively.
The rate of the reversible trans–cis–trans isomeriza-
tion and the changes in this rate depending on tem-
20. M. V. Kozlovsky and V. V. Lazarev, Macromol. Chem.
Phys. 204, 1226 (2003).
21. Z. Sekkat, A. Knoesen, V. Y. Lee, et al., J. Phys. Chem.
B 101, 4733 (1997).
22. V. Chigrinov, H. S. Kwok, H. Takada, et al., Liq. Cryst.
Today 14 (4), 1 (2005).
23. A. di Matteo, A. Ferrarini, and G. J. Moro, J. Phys.
Chem. B 104, 7764 (2000).
24. A. Natansohn and P. Rochon, Chem. Rev. 102, 4139
(2002).
25. S. H. Lee, S. Balasubramanian, D. Y. Kim, et al., Mac-
romolecules 33, 6534 (2000).
26. K. G. Yager and C. J. Barrett, Macromolecules 39,
9320 (2006).
RUSSIAN JOURNAL OF PHYSICAL CHEMISTRY A Vol. 90 No. 3 2016