Synthesis and photoinduced surface relief grating formation of novel photo-responsive amorphous molecular materials, 4-[bis(9,9-dimethylfluoren-2-yl)amino]-4′-cyanoazobenzene and 4-[bis(9,9-dimethylfluoren-2-yl)-amino]-4′-nitroazobenzene

Article abstract of DOI:10.1016/j.dyepig.2009.07.002

Novel azobenzene-based photo-responsive amorphous molecular materials, 4-[bis(9,9-dimethylfluoren-2-yl)amino]-4′-cyanoazobenzene and 4-[bis(9,9-dimethylfluoren-2-yl)amino]-4′-nitroazobenzene, have been synthesized and the formation of surface relief grating on their amorphous films has been investigated. It was found that a relatively large surface relief grating could be inscribed on both amorphous films upon interference exposure to the writing laser beams. The modulation depth of the surface relief grating inscribed on the amorphous film of the cyano-substituted material was found to be larger than that inscribed on the film of the nitro-substituted one and seemed to be comparable to that inscribed on the amorphous film of the parent material, 4-[bis(9,9-dimethylfluoren-2-yl)amino]azobenzene. These results were discussed from the viewpoint of their trans-cis photoisomerizations as amorphous films and glass-transition temperatures.

Full text of DOI:10.1016/j.dyepig.2009.07.002

Dyes and Pigments 84 (2010) 102–107
Contents lists available at ScienceDirect
Dyes and Pigments
journal homepage: www.elsevier.com/locate/dyepig
Synthesis and photoinduced surface relief grating formation of novel
photo-responsive amorphous molecular materials, 4-[bis(9,9-dimethylfluoren-
2-yl)amino]-40-cyanoazobenzene and 4-[bis(9,9-dimethylfluoren-2-yl)-amino]
-40-nitroazobenzene
,
a
a
a,b
Hideyuki Nakano a , Toru Takahashi , Takahiro Tanino , Yasuhiko Shirota
*
a Department of Applied Chemistry, Faculty of Engineering, Osaka University, Yamadaoka, Suita, Osaka 565-0871, Japan
b Department of Environmental and Biotechnological Frontier Engineering, Fukui University of Technology, 3-6-1, Gakuen, Fukui City, Fukui 910-8505, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
Novel azobenzene-based photo-responsive amorphous molecular materials, 4-[bis(9,9-dimethylfluoren-
2-yl)amino]-40-cyanoazobenzene and 4-[bis(9,9-dimethylfluoren-2-yl)amino]-40-nitroazobenzene, have
been synthesized and the formation of surface relief grating on their amorphous films has been inves-
tigated. It was found that a relatively large surface relief grating could be inscribed on both amorphous
films upon interference exposure to the writing laser beams. The modulation depth of the surface relief
grating inscribed on the amorphous film of the cyano-substituted material was found to be larger than
that inscribed on the film of the nitro-substituted one and seemed to be comparable to that inscribed on
the amorphous film of the parent material, 4-[bis(9,9-dimethylfluoren-2-yl)amino]azobenzene. These
results were discussed from the viewpoint of their trans–cis photoisomerizations as amorphous films
and glass-transition temperatures.
Received 18 April 2009
Received in revised form
1 July 2009
Accepted 1 July 2009
Available online 8 July 2009
Keywords:
Photo-responsive amorphous molecular
material
Photoinduced surface relief grating
formation
Ó 2009 Elsevier Ltd. All rights reserved.
Azobenzene
trans–cis Photoisomerization
Glass-transition temperature
1. Introduction
photocrosslinkable polymer liquid crystals [20,21]. With regard to
photoinduced SRG formation using azobenzene-based materials, it
Recently, mechanical motions of materials induced by photo-
irradiation, so-called ‘‘photomechanical effects’’, have attracted
a great deal of attention. Several examples of the photomechanical
effects observed for photochromic materials, such as bending of
liquid–crystalline azo-polymer network films [1] and reversible
shape changes of molecular crystals of diarylethene derivatives [2],
have been reported. Photoinduced surface relief grating (SRG)
formation observed for films of azobenzene-based materials, which
is induced by mass transport upon interference exposure to
coherent laser beams, is also an attractive subject as one of the
photomechanical effects. A number of studies of photoinduced SRG
formation have been made using a variety of systems including
azobenzene-based amorphous polymers [3–11], azobenzene-based
liquid–crystalline films [12–17], poly(methyl methacrylate) films
doped with spiropyran [18] and diarylethene derivatives [19], and
is believed that the mass transport is induced by trans–cis and
cis–trans isomerizations of the azobenzene chromophore to
produce the SRG. Several models for the mechanism of the
photoinduced SRG formation have been proposed [5–9,17,22];
however, the precise details are not yet clear.
In contrast to the foregoing polymeric systems, we have studied
the photoinduced SRG formation using azobenzene-based photo-
responsive amorphous molecular materials, namely, low molec-
ular-weight photo-responsive molecules that form amorphous
glasses by themselves [23–27]. In addition, we have demonstrated
very recently that photoinduced SRG formation can take place even
on the single crystals of azobenzene-based materials [28–30]. With
regard to photo-responsive amorphous molecular materials, rela-
tively large SRG with a modulation depth of more than 400 nm
could be inscribed on an amorphous film of 4-[bis(9,9-dimethyl-
fluoren-2-yl)amino]azobenzene (BFlAB) [27]. In addition, the
increase of glass-transition temperature (Tg) of the material was
found to be favorable for photoinduced SRG formation [27].
Photoinduced SRG formation using amorphous molecular materials
* Corresponding author. Tel.: þ81 6 6879 7365; fax: þ81 6 6879 7367.
E-mail address: nakano@chem.eng.osaka-u.ac.jp (H. Nakano).
0143-7208/$ – see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.dyepig.2009.07.002

H. Nakano et al. / Dyes and Pigments 84 (2010) 102–107
103
has also been reported by other groups [31–35]. However, the
phenomena using photo-responsive amorphous molecular mate-
rials remain to be fully elucidated and therefore it is of importance
to elucidate SRG-forming properties of a variety of azobenzene-
based photo-responsive amorphous molecular materials in relation
to their molecular structures, Tgs, reactivity, and other properties.
In the present study, we have designed and synthesized novel
azobenzene-based photo-responsive amorphous molecular mate-
rials possessing either a cyano- or a nitro-substituent at the
40-position of the azobenzene moiety of BFlAB, i.e. 4-[bis(9,9-
dimethylfluoren-2-yl)amino]-40-cyanoazobenzene (CN-BFlAB) and
4-[bis(9,9-dimethylfluoren-2-yl)amino]-40-nitroazobenzene (NO2-
BFlAB) [36], and investigated photoinduced SRG formation on their
amorphous films.
m/z 606 (Mþ). 1H NMR (750 MHz, THF):
d
7.96 (d, 8.3 Hz, 2H), 7.87
(d, 8.8 Hz, 2H), 7.86 (d, 8.3 Hz, 2H), 7.73 (d, 8.1 Hz, 2H), 7.71 (d,
7.4 Hz, 2H), 7.43 (d, 7.4 Hz, 2H), 7.38 (s, 2H), 7.29 (dd, 7.4, 7.4 Hz, 2H),
7.25 (dd, 7.4, 7.4 Hz, 2H), 7.22 (d, 8.8 Hz, 2H), 7.19 (dd, 8.1 Hz, 2H),
1.42 (s, 12H) ppm. 13C NMR (188 MHz, THF):
d 156.4, 155.9, 154.6,
153.0, 147.8, 147.1, 139.6, 137.0, 134.1, 127.9, 127.8, 125.8, 125.6, 123.8,
123.3, 122.0, 121.8, 121.0, 120.5, 118.9, 114.3, 47.7, 27.2 ppm. EA:
Calcd for C43H34N4: C, 85.12; H, 5.65; N, 9.23%. Found: C, 84.98; H,
5.82; N, 9.01%.
2.4. 4-[Bis(9,9-dimethylfluoren-2-yl)amino]-40-nitroazobenzene
(NO2-BFlAB)
4-Amino-40-nitroazobenzene (3.7 g, 0.015 mol) and 2-iodo-9,9-
dimethylfluorene (12 g, 0.037 mol) were heated under reflux in the
presence of copper powder (2.4 g, 0.037 mol), K2CO3 (6.5 g,
0.047 mol) and 18-crown-6 (0.7 g, 0.026 mol) in mesitylene (50 ml)
for 4 h under nitrogen atmosphere. After the solvent was removed
under reduced pressure, the residue was extracted with toluene and
washed with water. The product was purified by silica-gel column
chromatography using a mixed solvent of toluene and hexane as an
eluent, followed by recrystallization from cyclohexane. Yield: 3.5 g
(37%), m.p.: 228 ꢀC. MS: m/z 626 (Mþ). 1H NMR (750 MHz, THF):
N
N
N
X
BFlAB
: X = H
CN-BFlAB : X = CN
d
8.37 (d, 9.0 Hz, 2H), 8.01 (d, 9.0 Hz, 2H), 7.89 (d, 8.9 Hz, 2H), 7.74 (d,
NO -BFlAB : X = NO
2
2
8.1 Hz, 2H), 7.72 (d, 7.4 Hz, 2H), 7.43 (d, 7.4 Hz, 2H), 7.39 (d, 1.9 Hz,
2H), 7.29 (dd, 7.4, 7.5 Hz, 2H), 7.26 (dd, 7.4, 7.5 Hz, 2H), 7.23 (d, 8.9 Hz,
2H), 7.20 (dd, 1.9, 8.1 Hz, 2H), 1.43 (s, 12H) ppm. 13C NMR (188 MHz,
2. Experimental
THF):
d
¼ 157.2, 156.4, 154.6, 153.2, 149.3, 147.9, 147.0, 139.6, 137.1,
127.9, 127.8, 126.0, 125.6, 125.5, 123.7,123.3,121.9,121.8,121.1, 120.5,
47.4, 27.2 ppm. EA: Calcd for C42H34N4O2: C, 80.49; H, 5.47; N, 8.94%.
Found: C, 80.31; H, 5.58; N, 8.71%.
2.1. Materials
4-Nitroaniline, 4-cyanoaniline, and 4-amino-40-nitroazoben-
zene were purchased (Tokyo Chemical Industry Co., Ltd.) and used
without further purification. 2-Iodo-9,9-dimethylfluorene was
synthesized according to the previously described procedure [37].
2.5. Measurements and apparatus
Differential scanning calorimetry (DSC) was carried out by
means of a Seiko DSC220C. Photoisomerization was carried out by
irradiation of the amorphous films with 500 nm light with
a bandwidth of 10 nm from a 500 W Xenon lamp (UXL-500D,
USHIO) through an interference filter (IF-S 500, Vacuum Optics Co.)
using an optical fiber. The reactions were monitored by the change
in the electronic absorption spectra by means of a Hitachi U-3200
spectrophotometer.
2.2. N,N0-Bis(9,9-dimethylfluoren-2-yl)-4-nitroaniline (1)
2-Iodo-9,9-dimethylfluorene (136 g, 430 mmol) and 4-nitro-
aniline (24.1 g, 170 mmol) were heated under reflux in the presence
of copper powder (27.0 g, 430 mmol), K2CO3 (110.5 g, 800 mmol)
and 18-crown-6 (8.5 g, 50 mmol) in mesitylene (300 ml) for 8 h
under nitrogen atmosphere. After the solvent was removed under
reduced pressure, the residue was extracted with toluene and
washed with water. The product was purified by silica-gel column
chromatography using a mixed solvent of toluene and hexane as an
eluent. Yield: 56.3 g (63%), m.p.: 147 ꢀC. MS: m/z 522 (Mþ). 1H NMR
Photoinduced SRG formation was carried out by using an Arþ
laser (488 nm: BeamLok 2060, Spectra Physics) as writing beams
and a semiconductor laser (830 nm: LDP-8340, NEOARK) as a probe
beam at ambient temperature (ca. 30 ꢀC). Sample thickness of CN-
BFlAB and NO2-BFlAB films for SRG formation was ca. 200
mm.
(750 MHz, THF): d 8.06 (dd, 2.1, 7.2 Hz, 2H), 7.76 (d, 8.0 Hz, 2H), 7.72
Atomic force microscopy (AFM) was performed by means of JSTM-
(d, 7.4 Hz, 2H), 7.44 (d, 7.4 Hz, 2H), 7.39 (d, 2.0 Hz, 2H), 7.30 (ddd,1.1,
7.4, 7.4 Hz, 2H), 7.26 (ddd, 1.1, 7.4, 7.4 Hz, 2H), 7.19 (dd, 2.0, 8.0 Hz,
2H), 7.10 (dd, 2.1, 7.2 Hz, 2H), 1.42 (s, 12H) ppm. 13C NMR (188 MHz,
4200D (JEOL) with
OLYMPUS).
a micro cantilever (OMCL-AC160 T-C2,
THF):
d
156.5, 154.7, 154.6, 146.4, 141.5, 139.4, 137.7, 128.0, 127.9,
3. Results and discussion
126.0, 126.0, 123.4, 122.0, 121.5, 120.6, 119.9, 47.7, 27.2 ppm.
3.1. Synthesis and glass-forming properties of CN-BFlAB
and NO2-BFlAB
2.3. 4-[Bis(9,9-dimethylfluoren-2-yl)amino]-40-cyanoazobenzene
(CN-BFlAB)
A
novel photo-responsive amorphous molecular material,
4-Aminobenzonitrile (0.47 g, 4 mmol) and 1 (1.56 g, 3 mmol)
were heated under reflux in the presence of NaOH (0.85 g,
21 mmol) in mesitylene (10 ml) for 1 h under nitrogen atmosphere.
After the solvent was removed under reduced pressure, the residue
was extracted with toluene and washed with water. The product
was purified by silica-gel column chromatography using a mixed
solvent of toluene and hexane as an eluent, followed by recrystal-
lization from cyclohexane. Yield: 600 mg (33%), m.p.: 236 ꢀC. MS:
CN-BFlAB, was synthesized by the condensation reaction of
N,N0-bis(9,9-dimethylfluoren-2-yl)-4-nitroaniline (1) and 4-ami-
nobenzonitrile (Scheme 1a). The Ullmann reaction between
4-amino-40-nitroazobenzene and 2-iodo-9,9-dimethylfluorene
afforded another novel photo-responsive amorphous molecular
material, NO2-BFlAB (Scheme 1b). Both new compounds were
identified by various spectroscopy, mass spectrometry, and
elemental analysis.

104
H. Nakano et al. / Dyes and Pigments 84 (2010) 102–107
Scheme 1. Synthesis of a) CN-BFlAB and b) NO2-BFlAB.
Both CN-BFlAB and NO2-BFlAB were found to readily form
gradually increased due to the reverse cis–trans thermal
isomerization.
The fraction of the photogenerated cis-isomer at the photosta-
tionary state (Ypss) can be estimated experimentally from the
following equation;
amorphous glasses by cooling their molten samples on standing in
air. Fig. 1 shows DSC curves of CN-BFlAB and NO2-BFlAB. When
crystalline samples of CN-BFlAB and NO2-BFlAB obtained by
recrystallization from solution were heated, endothermic peaks
due to melting were observed at 236 ꢀC and 228 ꢀC, respectively.
When the molten samples were cooled on standing in air, amor-
phous glasses were readily obtained. When the glasses were again
heated, baseline shifts due to a glass-transition were observed at
116 ꢀC and 117 ꢀC, respectively, being higher than the Tg of the
parent material, BFlAB (97 ꢀC). On further heating, no crystalliza-
tion phenomena were observed, suggesting that the amorphous
glasses were fairly stable [38].
h
ꢀ
ꢁi.h
ꢀ
ꢁi
Ypss
¼
1 ꢁ Alpss=Altrans
1 ꢁ 3lcis
=
3ltrans
(1)
where 3transl and 3cisl represent the molar extinction coefficients of
the trans- and cis-isomers at a measured wavelength l
, Atransl and
Apssl the absorbance of the sample at the same wavelength before
photoirradiation and at the photostationary state, respectively.
Since the cis-isomers could not be isolated because of their insta-
l
bility in solution, the value of 3cis was estimated by the spectral
changes of the solution upon irradiation with two different wave-
lengths (400 nm and 450 nm) as described in our previous paper
[39]. Table 1 summarizes optical and reaction parameters including
wavelength of absorption maximum before photoirradiation (lmax),
3.2. Photo and thermal isomerizations of CN-BFlAB and NO2-BFlAB
Both CN-BFlAB and NO2-BFlAB were found to exhibit trans–cis
photoisomerizations and reverse cis–trans thermal isomerizations
as amorphous films as well as in solution. Fig. 2 shows electronic
absorption spectral changes of CN-BFlAB and NO2-BFlAB as amor-
phous films. When the films were irradiated with 500 nm light, the
absorbance around 510 nm gradually decreased due to trans–cis
photoisomerization. When the irradiation was stopped after the
reaction system reached to photostationary state, the absorbance
molar extinction coefficients of trans- and cis-form at lmax
(
3trans
-
l
l
max and 3cis max, respectively), cis-fraction at photostationary state
(Ypss) upon irradiation with 500 nm light, and first-order rate
constant of reverse cis–trans thermal isomerization at 30 ꢀC (k) in
toluene solution and as amorphous films for CN-BFlAB and NO2-
BFlAB. The values for BFlAB are also indicated in Table 1 for
comparison.
Fig. 1. DSC curves of a) CN-BFlAB and b) NO2-BFlAB. i) Crystalline sample obtained by recrystallization from solution. ii) Amorphous glass obtained by cooling the molten sample.
Heating rate: 5 ꢀC minꢁ1
.

H. Nakano et al. / Dyes and Pigments 84 (2010) 102–107
105
Fig. 2. Electronic absorption spectral changes of a) CN-BFlAB and b) NO2-BFlAB amorphous films. i) Before photoirradiation. ii) Photostationary state upon irradiation with 500 nm light.
Both lmax values in solution and as amorphous films for CN-
BFlAB and NO2-BFlAB were found to be red-shifted relative to those
for BFlAB. The result was due to the effect of introduction of elec-
tron-withdrawing cyano- and nitro-groups into the 40-position of
the azobenzene moiety in the parent BFlAB. The lmax values as
amorphous films for CN-BFlAB and NO2-BFlAB were slightly red-
shifted from those in toluene solution as well as that for the parent
BFlAB due to intermolecular interaction. The magnitude of the lmax
shifts for CN-BFlAB and NO2-BFlAB was not too different from that
for BFlAB, suggesting that the degree of the intermolecular inter-
action as amorphous films for CN-BFlAB and NO2-BFlAB was not so
much different from that for BFlAB.
It was found that the Ypss values for all the present materials
were smaller for the amorphous films than in solutions, similar to
the result observed for other azobenzene-based photo-responsive
amorphous molecular materials we have previously reported [39].
The reactions as amorphous films were suggested to be suppressed
relative to that in solution due to small local free volume as
amorphous films. The ratio of Ypss for amorphous film to that for
toluene solution (R), which was assumed to give an indication of
the extent of suppression of the photoisomerizations as amorphous
films relative to those in solution, was also summarized in Table 1. It
was found that the R value decreased in the order, BFlAB > CN-
BFlAB > NO2-BFlAB, suggesting that the extent of the suppression
of the reaction increased in the order, BFlAB < CN-BFlAB < NO2-
BFlAB. It is conceivable that the volume required to facilitate the
isomerization becomes larger in this order and hence the reaction
in the small local free volume in the amorphous film was sup-
pressed to a greater extent, i.e. quantum yield of trans–cis photo-
isomerization was reduced, for the material with more bulky
substituent at the 40-position of azobenzene moiety.
Like a variety of azobenzene derivatives, the reverse cis–trans
thermal isomerization reactions of CN-BFlAB and NO2-BFlAB in
toluene solution followed the first-order kinetics with the first-
order rate constants (k) of 2.2 ꢂ10ꢁ2 and 1.1 ꢂ10ꢁ1 minꢁ1 at 30 ꢀC,
respectively (Table 1). On the other hand, the cis–trans thermal
isomerization reactions of CN-BFlAB and NO2-BFlAB as amorphous
films after the reaction system has reached the photostationary
state by irradiation with 500 nm light did not follow the expected
first-order kinetics and their apparent rate constant at initial stage
(k0) was larger than those in solution. This phenomenon was similar
to that observed for BFlAB [39] and suggested that there exists cis-
isomers trapped in constrained conformations in the amorphous
film which go back faster into the trans-isomer than the structurally
relaxed cis-isomer molecules.
3.3. Photoinduced SRG formation of CN-BFlAB and NO2-BFlAB
Using the novel photo-responsive amorphous molecular mate-
rials, CN-BFlAB and NO2-BFlAB, photoinduced SRG formation has
been investigated. The schematic experimental setup was illus-
trated in Fig. 3. The amorphous film with a thickness of ca. 200 mm
was irradiated with two writing beams (Arþ laser: 488 nm) with
polarization angles of þ45ꢀ and ꢁ45ꢀ with respect to the p-polar-
ization at 10 mW (ca. 80 mWcmꢁ2) each. SRG formation was
monitored by diffraction efficiency, which was defined here as the
intensity ratio of the first diffraction beam to the incident beam of
the probe (laser diode: 830 nm).
As Fig. 4 shows, the diffraction efficiencies gradually increased
with exposure time and were finally saturated at ca.19% and 14% for
CN-BFlAB and NO2-BFlAB, respectively. SRG formation was
confirmed by AFM. For CN-BFlAB, SRG with a modulation depth of
Table 1
Optical and reaction parameters in toluene solution and as amorphous film.
Material
Toluene solution
Amorphous film
Rd
lmax
l
a
b
a
c
lmax (nm)
3trans
(Mꢁ1cmꢁ1
)
3cis max (Mꢁ1cmꢁ1
)
Ypss
k (minꢁ1
)
lmax (nm)
Ypss
k0 (minꢁ1
)
CN-BFlAB
NO2-BFlAB
BFlABg
494
513
451
3.1 ꢂ 104
3.0 ꢂ 104
2.7 ꢂ 104
8.0 ꢂ 103
7.9 ꢂ 103
7.0 ꢂ 103
0.67e
0.54e
0.74f
2.2 ꢂ 10ꢁ2
1.1 ꢂ 10ꢁ1
4.7 ꢂ 10ꢁ3
508
522
461
0.33e
0.14e
0.48f
1.4 ꢂ 10ꢁ1
2.8 ꢂ 10ꢁ1
1.5 ꢂ 10ꢁ2
0.49
0.26
0.65
a
Ypss: cis-fraction at photostationary state.
b
c
d
e
f
k: first-order rate constant of cis–trans thermal isomerization at 30 ꢀC.
k0: apparent first-order rate constant of cis–trans thermal isomerization at 30 ꢀC at initial stage (10 s).
R ¼ [Ypss as amorphous film]/[Ypss in toluene solution].
Upon irradiation with 500 nm light.
Upon irradiation with 450 nm light.
g
Reference [39].

106
H. Nakano et al. / Dyes and Pigments 84 (2010) 102–107
Fig. 3. Experimental setup of photoinduced SRG formation.
400–430 nm was clearly observed as shown in Fig. 5. SRG with
a modulation depth of 310–350 nm was also observed for NO2-
BFlAB by AFM. Thus, relatively large SRG could be inscribed on the
amorphous films of CN-BFlAB and NO2-BFlAB.
The modulation depth of SRG inscribed on the CN-BFlAB
amorphous film was larger than that inscribed on the NO2-BFlAB
film. As discussed in our previous paper [27], it is thought that
photoinduced SRG formation using photo-responsive amorphous
molecular materials is influenced by both the photoinduced reac-
tion as amorphous film and Tg of the material, that is, the increasing
frequency of trans–cis and cis–trans isomerization cycles facilitates
the mass transport to grow SRG and increasing Tg of the material
prevents the collapse of the SRG due to surface tension to make the
surface smooth. Since Tg of NO2-BFlAB was almost the same as that
of CN-BFlAB, the smaller modulation depth for NO2-BFlAB than that
for CN-BFlAB was suggested to be mainly due to the fact that the
quantum yield of trans–cis photoisomerization was lower for NO2-
BFlAB than for CN-BFlAB as described above. Thus, introduction of
bulky substituent at 40-position of azobenzene moiety in BFlAB
makes unfavorable for photoinduced SRG formation.
However, the modulation depth of SRG inscribed on CN-BFlAB
amorphous film seemed to be comparable to that inscribed on the
amorphous film of BFlAB under the similar conditions (450–
490 nm) [27] even though the photoisomerization was more sup-
pressed as amorphous film than that for BFlAB. The result indicated
that the SRG-forming property of CN-BFlAB was not significantly
reduced by introduction of the cyano-substituent into BFlAB. It is
conceivable that the higher Tg of CN-BFlAB resulted in the effective
enhancement of SRG-forming property, compensating the effect of
the suppression of the reaction.
Fig. 5. AFM image of SRG inscribed on CN-BFlAB amorphous film.
4. Conclusion
Novel azobenzene-based photo-responsive amorphous molec-
ular materials, CN-BFlAB and NO2-BFlAB, were designed and
synthesized. They were found to readily form amorphous glasses
with relatively high Tgs and to exhibit trans–cis photo-
isomerizations and reverse cis–trans thermal isomerizations as
amorphous films as well as in solution. In addition, relatively large
SRGs could be inscribed on both amorphous films of CN-BFlAB and
NO2-BFlAB upon interference exposure to writing laser beams. The
modulation depth of the SRG inscribed on the CN-BFlAB amor-
phous film was found to be larger than that inscribed on the NO2-
BFlAB film, which was attributable to the fact that the photo-
isomerization for the amorphous film was more suppressed for
NO2-BFlAB than for CN-BFlAB. In addition, SRG-forming property of
CN-BFlAB was not significantly reduced relative to that of BFlAB
even though the photoisomerization was more suppressed as
amorphous film than that for BFlAB. The fact confirmed that
increasing Tg of the material enhances the SRG-forming property.
References
[1] Yu Y, Nakano M, Ikeda T. Nature 2003;425:145.
[2] Kobatake S, Takami S, Muto H, Ishikawa T, Irie M. Nature 2007;446:778–81.
[3] Rochon P, Batalla E, Natansohn A. Appl Phys Lett 1995;66:136–8.
[4] Kim DY, Tripathy SK, Li L, Kumar J. Appl Phys Lett 1995;66:1166–8.
[5] Barret C, Natansohn A, Rochon P. J Phys Chem 1996;100:8836–42.
[6] Kumar J, Li L, Jiang XL, Kim DY, Lee TS, Tripathy SK. Appl Phys Lett
1998;72:2096–8.
[7] Lefin P, Fiorini C, Nunzi J- M. Pure Appl Opt 1998;7:71–82.
[8] Viswanathan NK, Kim DY, Bian S, Williams J, Liu W, Li L, et al. J Mater Chem
1999;9:1941–55.
[9] Fiorini C, Prudhomme N, de Veyrac G, Maurin I, Raimond P, Nunzi J-M. Synth
Met 2000;115:121–5.
[10] Natansohn A, Rochon P. Chem Rev 2002;102:4139–75.
[11] Ando H, Tanino T, Nakano H, Shirota Y. Mater Chem Phys 2009;113:376–81.
[12] Ramanujam PS, Holme NCR, Hvilsted S. Appl Phys Lett 1996;68:1329–31.
[13] Pedersen TG, Johansen PM, Holme NCR, Ramanujam PS. Phys Rev Lett
1998;80:89–92.
[14] Stracke A, Wendorff JH. Adv Mater 2000;12:282–5.
[15] Ubukata T, Seki T, Ichimura K. Adv Mater 2000;12:1675–8.
[16] Yamamoto T, Hasegawa M, Kanazawa A, Shiono T, Ikeda T. J Mater Chem
2000;10:337–42.
[17] Gadidei YB, Christiansen PL, Ramanujam PS. Appl Phys B 2002;74:139–46.
[18] Ubukata T, Takahashi K, Yokoyama YJ. Phys Org Chem 2007;20:981–4.
[19] Ubukata T, Yamaguchi S, Yokoyama Y. Chem Lett 2007;36:1224–5.
[20] Ono H, Emoto A, Kawatsuki N, Hasegawa T. Appl Phys Lett 2003;82:1359–61.
[21] Kawatsuki N, Hasegawa T, Ono H, Tamoto T. Adv Mater 2003;15:991–4.
[22] Yang K, Yang S, Kumar J. Phys Rev B 2006;73:165204/1–14.
[23] Nakano H, Takahashi T, Kadota T, Shirota Y. Adv Mater 2002;14:1157–60.
[24] Shirota Y, Utsumi H, Ujike T, Yoshikawa S, Moriwaki K, Nagahama D, et al. Opt
Mater 2003;21:249–54.
Fig. 4. Growth of diffraction efficiencies for amorphous films upon interference
exposure to the writing beams. a) CN-BFlAB. b) NO2-BFlAB.

H. Nakano et al. / Dyes and Pigments 84 (2010) 102–107
107
[25] Ueda H, Tanino T, Ando H, Nakano H, Shirota Y. Chem Lett 2004;33:1152–3.
[26] Takahashi T, Tanino T, Ando H, Nakano H, Shirota Y. Mol Cryst Liq Cryst
2005;430:9–14.
[33] Kim M-J, Seo E-M, Vak D, Kim D- Y. Chem Mater 2003;15:4021–7.
[34] Ishow E, Lebon B, He Y, Wang X, Bouteiller L, Galmiche L, et al. Chem Mater
2006;18:1261–7.
[27] Nakano H, Tanino T, Takahashi T, Ando H, Shirota Y.
2008;18:242–6.
J
Mater Chem
[35] Ishow E, Camacho-Aguilera R, Guerin J, Brosseau A, Nakatani K. Adv Funct
Mater 2009;19:796–804.
[28] Nakano H, Tanino T, Shirota Y. Appl Phys Lett 2005;87:061910/1–3.
[29] Nakano H. ChemPhysChem 2008;9:2174–6.
[30] Nakano H. J Phys Chem C 2008;112:16042–5.
[31] Fuhrmann T, Tsutsui T. Chem Mater 1999;11:2226–32.
[32] Chun C, Kim M-J, Vak D, Kim DY. J Mater Chem 2003;13:2904–9.
[36] Nakano H, Takahashi T, TaninoT, Shirota Y. J Photopolym Sci Tech 2007;20:87–9.
[37] Okumoto K, Shirota Y. Chem Mater 2003;15:699–707.
[38] Kageyama H, Itano K, Ishikawa W, Shirota Y. J Mater Chem 1996;6:675–6.
[39] Tanino T, Yoshikawa S, Ujike T, Nagahama D, Moriwaki K, Takahashi T, et al.
J Mater Chem 2007;17:4953–63.