Sol-gel synthesis of organic-inorganic hybrid materials comprising boehmite, silica, and thiazole dye

Article abstract of DOI:10.1016/j.dyepig.2012.01.020

A hybrid material was prepared from a boehmite sol and a thiazole derived azo dye. The thiazole azo dyes were subjected to hydrolytic polycondensation with vinyltriethoxysilane, tetraethoxysilane, and aluminium isopropoxide in different ratios to afford a

Full text of DOI:10.1016/j.dyepig.2012.01.020

Dyes and Pigments 94 (2012) 349e354
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Dyes and Pigments
journal homepage: www.elsevier.com/locate/dyepig
Solegel synthesis of organiceinorganic hybrid materials comprising boehmite,
silica, and thiazole dye
*
Ming-Shien Yen , Mu-Cheng Kuo
Department of Materials Engineering, Kun Shan University, Tainan 71003, Taiwan, ROC
a r t i c l e i n f o
a b s t r a c t
Article history:
A hybrid material was prepared from a boehmite sol and a thiazole derived azo dye. The thiazole azo
dyes were subjected to hydrolytic polycondensation with vinyltriethoxysilane, tetraethoxysilane, and
aluminium isopropoxide in different ratios to afford a hybrid of boehmite, silica, and the thiazole
heterocycle azo dye. The structures of these hybrid materials were characterized using X-ray diffraction,
Fourier-transform infrared analysis, 29Si- and 27Al-nuclear magnetic resonance, ultravioletevisible
absorption spectrophotometry, and an energy-dispersive X-ray spectroscopy.
Received 8 November 2011
Received in revised form
19 January 2012
Accepted 20 January 2012
Available online 8 February 2012
Ó 2012 Elsevier Ltd. All rights reserved.
Keywords:
Tetraethoxysilane
Vinyltriethoxysilane
Boehmite
Azo dye
Solegel
Hybrid materials
1. Introduction
An inorganic sol is blended with an organic polymer solution
and then gelatinized. The organic monomer and the inorganic sol
Most new products are designed to have multiple functions and
a form of intelligence. Thus, hybrid materials have recently become
one of the main trends in materials science research. Compared
with traditional materials, the most important feature of a hybrid
material is its designability. The mechanical, physical, and chemical
properties of a hybrid material can be designed and controlled by
changing its composition or by using interface control, com-
pounding technology, or moulding technology in order to meet the
requirements of maximum usability and environmental compati-
bility. In particular, organiceinorganic hybrid materials have
attracted significant interest [1e3] because they offer the advan-
tages of both: the plasticity of organic materials and the functional
properties of inorganic materials. In order to exploit the versatility
of hybrid materials, the processing methods used for their prepa-
ration include a combination of organiceinorganic hybrids and the
solegel process [4,5]. They encompass inorganic oxides that func-
tion as fillers in organic polymers and solids consisting of polymers
or organic molecules in inorganic oxide networks. Functional
materials can be prepared using organiceinorganic hybrid tech-
nology and the solegel method [6e9].
are polymerized simultaneously using a hybridization method to
form an interpenetrating network. The major structural feature of
this composite material is that the microzones are in the order of
nanometres and can be interpenetrating [10,11]. The
g-AlOOH
coating is a thin layer material that adheres to a parent material to
play a special role and provides a certain anchoring strength to the
parent material. It can overcome some types of defects in the parent
material and improve the material’s surface characteristics, such as
optical characteristics, electrical characteristics, erosion and
corrosion resistance, wearability, and mechanical strength. It is
a film with support. There are many preparation methods for the
coating material, which can be classified into two major types:
physical processes, such as the vapour deposition method and the
sputtering method, and chemical processes, such as chemical
vapour deposition, spray pyrolysis, and solegel methods. The
solegel method for coating preparation has the following charac-
teristics when compared with other coating preparation methods:
(1) simple process equipment: expensive vacuum equipment or
vacuum conditions are not required; (2) low-temperature techno-
logical process: this characteristic is very important for the prep-
aration of versatile systems containing light-volatile components
or likely to undergo phase separation at high temperature; (3) the
film can be prepared on substrates made of different materials,
with different shapes and a large area [12e15]. At present, it is
* Corresponding author. Tel./fax: þ886 62050349.
E-mail address: yms0410@mail.ksu.edu.tw (M.-S. Yen).
0143-7208/$ e see front matter Ó 2012 Elsevier Ltd. All rights reserved.
doi:10.1016/j.dyepig.2012.01.020

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M.-S. Yen, M.-C. Kuo / Dyes and Pigments 94 (2012) 349e354
known that
g
-AlOOH can induce improved hardness and other
20 min. Sodium nitrite (0.72 g, 0.0105 mol) was added in portions to
concentrated sulphuric acid (5 mL) at 10 ꢂC and stirred for 1 h at
60ꢂe65 ꢂC. The solutionwas cooled to below 5 ꢂC, and then the finely
ground derivatives were slowlyadded; the mixturewas stirred foran
additional 1 h at 5e10 ꢂC until it was clear. The resulting diazonium
solution was used immediately in the coupling reaction. A clear
mixed solution of the coupling component 4-phenyl-2-
aminothiazole 1 (2.0 g, 0.01 mol) and 10% sodium carbonate was
stirred.Thediazoniummixturewasaddedat0e5ꢂC, andthesolution
was stirred for at least 2 h; it was diluted to raise its pH to 5e6 (by
adding aqueous sodium hydroxide or sodium acetate). The resulting
product was filtered, washed with water, and re-crystallized from
ethanol to give a deep red solid 5-[2-(4-nitrophenyl)-diazen-1-yl]-4-
phenyl-1,3-thiazol-2-amine (3a) (2.3 g, 70%). m.p. 245e247 ꢂC; FT-IR
properties, and although it is mostly applied to ceramics as
a substrate, it has recently been applied to other materials [16e20].
Furthermore, silica is a natural material derived from common
materials such as quartz, sand, and flint. Silica has a high chemical
stability, a low thermal expansion coefficient, and high heat resis-
tance. The relatively high chemical stability of the silica phase can
be advantageous in some cases [21e24]. If the g-AlOOH and silica
gel condensation polymerization method are sufficiently inter-
mixed in the surface layer, a short travelling distance between the
surface-modified silica thermal stability sites and the mechanical
strength sites on the boehmite phase may result in a high chemical
stability performance.
The molecules of heteroaryl azo dyes contain unshared electron
pairs of nitrogen and sulfur, which can easily trigger resonance and
(KBr)/cmꢁ1: 3433 (NH2), 3057 (CeH); 1H-NMR( DMSO-d6.)
d ppm:
cause the
p
electrons of the compound to leap from the ground
7.04(1H, s, eNH2), 7.51e7.55(5H, m, ArH), 7.71, (2H, d, 2,6 e Ph-H),
8.19 (2H, d, 3,5 e Ph-H).
state to the excited state. The synthesis and spectroscopic proper-
ties of azo dyes are well-established [25e29]. The use of hetero-
cyclic aromatic amines for improving higher tinctorial strength has
been well-established. 2-Aminothiazole compounds which possess
different substituents in the 4-position of analogous derivatives as
diazo components tend to bathochromic shifts as compared to
analogous dyes derived from benzenoid compounds [30e32].
In this study, we aim to synthesize a series of thiazole hetero-
cyclic dyes. The solegel method is utilized herein to process an
organiceinorganic hybrid material and produce hybrid materials
C15H17N2O2S (325.1) Calcd.: C, 55.38; H, 3.41; N, 21.53; O, 9.84; S,
9.85
Found: C, 55.32; H, 3.44; N, 21.58; O, 9.78; S, 9.87
2.3.2. Preparation of dyes 5-[2-(4-methoxyphenyl)-diazen-1-yl]-4-
phenyl-1,3-thiazol-2-amine (3b)
As shown in Scheme 1, Dye 5-[2-(4-methoxyphenyl)-diazen-1-
yl]-4-phenyl-1,3-thiazol-2-amine (3b) was synthesized by using
the same method as that used for synthesizing 3a, which was coor-
dinated with diazo components p-nitroaniline 2a. The resulting
product was filtered, washed with water, and re-crystallized from
ethanol to give an orange solid 5-[2-(4-methoxyphenyl)-diazen-1-
yl]-4-phenyl-1,3-thiazol-2-amine (3b) (1.65 g, 50%). m.p.
253e255 ꢂC; FT-IR (KBr)/cmꢁ1: 3430 (NH2), 3105 (CeH), 1179
from SiO2/g-AlOOH and a thiazole azo dye in a blending reaction
with various proportions of vinyltriethoxysilane, tetraethoxysilane,
and aluminium isopropoxide (AIP) via an addition hydrolysis
reaction to generate a blended dye having a network structure.
2. Experimental
(OeCH3); 1H-NMR(DMSO-d6)
d ppm: 3.80 (3H, s, eOCH3), 7.04(1H, s,
eNH2), 7.40e7.50(5H, m, ArH), 7.61 (2H, d, 3,5 e Ph-H), 7.82 (2H, d,
2,6 e Ph-H).
2.1. Analytical instruments
Fourier-transform infrared (FT-IR) spectra were recorded on
a Bio-Rad Digilab FTS-40 spectrometer (KBr); 1H nuclear magnetic
resonance (NMR) spectra were obtained on a BRUKER AVANCE
C16H14N4OS (310.3) Calcd.: C, 61.92; H, 4.55; N, 18.05; O, 5.15; S,
10.33
Found: C, 61.88; H, 4.57; N, 18.11; O, 5.11; S, 10.28
400MHz NMR spectrometer. Chemical shifts (d) are expressed in
parts per million using tetramethylsilane (TMS) as an internal
standard. The 29Si-NMR and 27Al-NMR spectra were collected using
a BRUKER AVANCE 400 MHz NMR spectrometer at 78.49 MHz, with
a recycle time of 60 s, and the number of scans was 914. The
elemental analysis was carried out using a Philips XL40 FEG-Energy
Dispersive X-ray Spectrometer. Electronic spectra were recorded
using a SHIMADZU UV-1201 from dyes solutions in DMF and THF at
a concentration of 1 ꢀ 10ꢁ5 mol Lꢁ1. X-ray diffraction (XRD)
measurements were performed on a Rigaka D/MAX 2500V X-ray
powder diffractometer in steps of 0.01ꢂ using Cu Ka radiation as the
X-ray source.
2.4. Preparation of precursors 4ae4b
2.4.1. 5-[2-(4-nitrophenyl)-diazen-1-yl]-4-phenyl-N-[2-
(triethoxysilyl)ethyl]-1,3-thiazol-2-amine (4a)
Precursor 4a was prepared by the reaction of dyes 3a (3.25 g,
0.01 mol) followed by the addition of vinyltriethoxysilane (9.5 g,
0.05 mol) in THF (80 mL) with stirring at 65 ꢂC for 4 h at an adjusted
pH of 4e5. The resulting product was filtered, washed with water,
and re-crystallized from ethanol to give a dark red solid 5-[2-(4-
2.2. Materials
Vinyltriethoxysilane, tetraethoxysilane, aluminium isoprop-
oxide (Al(OC3H7)3), acetophenone, and p-methoxyaniline were
purchased from Acros Co., Ltd., Belgium. Thiourea, sulfuric acid, p-
nitroaniline, and iodide were purchased from Hayashi Pure
Chemical Co., Ltd.
2.3. Preparation of dyes 3ae3b
2.3.1. Preparation of dyes 5-[2-(4-nitrophenyl)-diazen-1-yl]-4-
phenyl-1,3-thiazol-2-amine (3a)
A finely ground powder of p-nitroaniline 2a (1.38 g, 0.01 mol) was
added to a mixture of hydrochloric acid (12 mL) and stirred for
Scheme 1. Synthesis of hybrid material 6ae6b.

M.-S. Yen, M.-C. Kuo / Dyes and Pigments 94 (2012) 349e354
351
Fig. 1. The X-Ray diffraction pattern of
g-AlOOH sol.
Fig. 3. FT-IR spectra of hybrid materials ATN1eATN4.
nitrophenyl)-diazen-1-yl]-4-phenyl-N-[2-(triethoxysilyl)ethyl]-
1,3-thiazol-2-amine (4a) (2.76 g, 59%). m.p. 304e306 ꢂC; FT-IR
(KBr)/cmꢁ1: 3395 (NH), 3073 (CeH), 1096 (OeSi).
2.5. Preparation of boehmite sol
The boehmite sol was prepared by the Yoldas process using AIP as
the precursor [33]. The AIP was hydrolyzed in excess of deionized
water (nH2O:nAIP ¼ 100:1) for 1 h under vigorous stirring at 80 ꢂC.
Peptizationwas then initializedbyadding HNO3 (nAIP:nHNO3 ¼1:0.1).
Subsequently, the resulting colloidal suspension was heated under
reflux for 2 h with vigorous stirring at 80 ꢂC. At the end of this process,
a stable transparent boehmite sol was obtained.
C23H29N5O5SSi (515.4) Calcd.: C, 53.57; H, 5.67; N, 13.58; O,
15.51; S, 6.22; Si, 5.45
Found: C, 53.63; H, 5.62; N, 13.56; O, 15.55; S, 6.28; Si, 5.41
2.4.2. 5-[2-(4-methoxyphenyl)-diazen-1-yl]-4-phenyl-N-[2-
(triethoxysilyl)ethyl]-1,3-thiazol-2-amine (4b)
Precursor 5-[2-(4-methoxyphenyl)-diazen-1-yl]-4-phenyl-N-
[2-(triethoxysilyl)ethyl]-1,3-thiazol-2-amine (4b) was synthesized
by the same method as that used for synthesizing 4a. The resulting
product was filtered, washed with water, and re-crystallized from
ethanol to give a deep orange solid 5-[2-(4-methoxyphenyl)-dia-
zen-1-yl]-4-phenyl-N-[2-(triethoxysilyl)ethyl]-1,3-thiazol-2-
amine (4b) (2.04 g, 45%). m.p. 313e315 ꢂC; FT-IR (KBr)/cmꢁ1: 3280
(NH), 3103 (CeH), 1134 (OeCH3), 1032 (OeSi).
2.6. Preparation of hybrid materials AN1eAN4, AM4, ATN1eATN4,
and ATM4
The hybrid material AN1 was prepared by the condensation of
precursor 4a (5.01 g, 0.01 mol) and boehmite sol (0.001 mol) in
ethanol (80 mL) by stirring at 65 ꢂC for 2 h, by adding hydro-
chloric acid (0.365 g, 0.01 mol) and water (5 mL). The hybrid
materials AN2eAN4 were synthesized using the same method as
that used for synthesizing AN1. The hybrid materials AN1eAN4
were prepared using different molar ratios of precursor 4a to
the boehmite sol in the hydrolysis polycondensation; the molar
C26H32N4O4SSi (500.2) Calcd.: C, 57.57; H, 6.44; N, 11.19; O,
12.78; S, 6.40; Si, 5.61
Found: C, 57.65; H, 6.49; N, 11.23; O, 12.75; S, 6.45; Si, 5.54
Fig. 2. FT-IR spectra of hybrid materials AN1eAN4.
Fig. 4. 29Si-NMR spectra of hybrid materials AN1eAN4.

352
M.-S. Yen, M.-C. Kuo / Dyes and Pigments 94 (2012) 349e354
Fig. 7. 27Al-NMR spectra of hybrid materials ATN1eATN4.
reported that the network structure could make this peak broad-
ening, suggesting that a given mixed phase is present in the
boehmite. Accordingly, in the present study we postulated that the
broadening peak at 2q
around 37ꢂ may result from the structure of
Fig. 5. 29Si-NMR spectra of hybrid materials ATN1eATN4.
SieOeAl networks in the gel. Meanwhile, the other diffraction
peaks at 46ꢂ and 67ꢂ are the (200) and (002) planes of hexahedron
ratios were 1:0.1, 1:0.2, 1:0.4, and 1:0.6. The hybrid material AM4
was prepared by the condensation of precursor 4b with boehmite
sol at a molar ratio of 1:0.6. The hybrid material ATN1 was
prepared by the condensation of precursor 4a (5.01 g, 0.01 mol),
TEOS (4.16 g, 0.02 mol), and boehmite sol (0.001 mol) in ethanol
(80 mL) by stirring at 65 ꢂC for 2 h, by adding hydrochloric acid
(0.365 g, 0.01 mol) and water (5 mL). The hybrid materials
ATN2eATN4 were synthesized using the same method as that
used for synthesizing ATN1. The hybrid materials ATN1eATN4
were prepared using different molar ratios of precursor 4a to
TEOS and the boehmite sol in the hydrolysis polycondensation;
the molar ratios were 1:2:0.1, 1:2:0.2, 1:2:0.4, and 1:2:0.6. The
hybrid material ATM4 was prepared by the condensation of
precursor 4b with TEOS and the boehmite sol at the molar ratio of
1:2:0.6.
g
-AlOOH, respectively [34,35].
3.2. FT-IR analysis
According to Fig. 2, precursors 4ae4b had absorption peaks of
the NeH group and the CeH group, respectively, near 3440 cmꢁ1
and 3113 cmꢁ1; an additional SieO absorption peak was observed
near 1100 cmꢁ1 and an additional SieC absorption peak near
1247 cmꢁ1. The precursor 4b had an additional methoxy group
absorption peak near 1320 cmꢁ1. According to Fig. 3, hybrid
materials AN1eAN4 had absorption peaks of the NeH group and
the CeH group, respectively, near 3064 cmꢁ1 and 2962 cmꢁ1. The
nitric acid addition increased when the g-AlOOH addition level was
maximized; hence, the absorption peaks of the NeH group and the
CeH group in the maximum ratio shifted left. The additional SieO
absorption peak near 1098 cmꢁ1 was also the characteristic peak of
AleO. The additional SieC absorption peak was observed near
1249 cmꢁ1, and the SieOeAl absorption peak was seen near
1518 cmꢁ1. According to Fig. 3, the hybrid materials ATN1eATN4
had absorption peaks of the NeH group and the CeH group,
respectively, near 3079 cmꢁ1 and 2934 cmꢁ1. The additional SieO
absorption peak observed near 1076 cmꢁ1 was also the character-
istic peak of AleO; there was an additional SieC absorption peak
observed near 1243 cmꢁ1. However, the absorption peak was
3. Results and discussion
3.1. X-ray diffraction analysis
The XRD pattern of the gel film is shown in Fig. 1. The XRD
pattern indicates that the gel film has a boehmite (
g-AlOOH)
structure.
g
-AlOOH was calcined at 550 ꢂC for 10 h and measured by
an X-ray diffraction analyzer. As shown in Fig. 1, the diffraction peak
at 2
q
around 37ꢂ is the (031) plane of boehmite [34,35]. It was
relatively weak when the amount of
minimum ratio; the SieOeAl absorption peak rose as the amount of
-AlOOH increased.
g-AlOOH was small in the
g
Table 1
EDS analysis of hybrid materials AN1eAN4, ATN1eATN4.
Samples
Elemental composition (%)
C
O
S
Si
9.92
9.85
8.27
8.63
8.19
18.26
17.84
17.08
16.96
17.40
Al
AN1
AN2
AN3
AN4
70.21
70.07
68.92
58.33
66.08
53.78
53.63
53.33
52.09
50.16
16.08
16.26
18.59
25.09
20.42
26.45
26.07
26.74
27.31
27.07
2.68
2.32
2.39
2.17
2.09
1.29
1.70
1.07
1.41
2.90
1.11
1.50
1.83
5.78
3.21
0.22
0.76
1.78
2.23
2.47
AM4
ATN1
ATN2
ATN3
ATN4
ATM4
Fig. 6. 27Al-NMR spectra of hybrid materials AN1eAN4.

M.-S. Yen, M.-C. Kuo / Dyes and Pigments 94 (2012) 349e354
353
Table 2
UV spectra of dyes, precursor, hybrid materials.
Compound
lmax(nm)
Compound
lmax(nm)
Ethanol
DMF
Ethanol
DMF
6a
6b
7a
7b
8a
8b
AN1
AN2
494
450
494
450
495
444
495
495
509
456
509
463
510
466
510
510
AN3
AN4
495
495
440
492
492
495
496
448
510
509
463
509
508
509
510
466
AM4
ATN1
ATN2
ATN3
ATN4
ATM4
According to 27Al-NMR inspection, the coordinate bonds that
resulted from the Al hydrolysis were usually 6-coordinate bonds at
d
: ꢁ10 to 10 ppm, 5-coordinate bonds at
coordinate bonds at : >50 ppm. According to Fig. 6, the hybrid
material AN1 used a 6-coordinate bond as the main peak at the
minimum -AlOOH ratio. The absorption peak of the 4-coordinate
bond was around : 51.2 ppm and disappeared gradually with an
increase in the -AlOOH addition. It was obvious that the hybrid
material AN4 was predominated by the 6-coordinate bond that had
an absorption peak around : 6.4 ppm at the maximum ratio.
d: 30e50 ppm, and 4-
Fig. 8. The EDS diagram of hybrid materials AN4.
d
3.3. 29Si-NMR and 27Al-NMR spectra analyses
g
d
According to the 29Si-NMR inspection, there were Q1, Q2, Q3, and
g
Q4 absorption peaks; Q1 and Q2 were at
d
: ꢁ80 to ꢁ90 ppm, Q3 was
at
d
: ꢁ101 ppm, and Q4 was at
: ꢁ110 ppm. However, the structure
d
d
of Q1 and Q2 was such that some Si quadruple bonds had two
unreacted SieOH functional groups, such as (HeO)Si(eOSi^)2. The
structure of Q3 was such that some Si quadruple bonds had one
unreacted SieOH functional group such as (HeO)Si(eOSi^)3. The
structure of Q4 was such that all the Si quadruple bonds were
completely reacted SieO functional groups such as Si(eOSi^)4.
Fig. 4 shows the minimum proportion of the hybrid material
AN1. The condensation polymerization of vinyltriethoxysilane
(VTES) reduced the purity of the net structure, and there were
many noise peaks. This situation could be improved by increasing
the AlOOH addition. Hence, it was inferred that the AleOeAl
bonding became the main structure. VTES revealed signals for Q1
According to Fig. 7, the hybrid materials ATN1eATN4 had 4-
coordinate and 6-coordinate bonds at the minimum ratio. The
absorption peak of the 4-coordinate bond of
52.2 ppm decreased with decrease in the -AlOOH addition. It was
obvious that the hybrid material ATN4 was predominated by the
6-coordinate bond at the absorption peak around : 6.7 ppm at the
g-AlOOH around d:
g
d
maximum ratio. The 6-coordinate bond was the main peak at the
maximum ratio.
3.4. EDS element analysis of hybrid material
According to Table 1, the EDS analysis of the hybrid materials
showed that the aluminium content increased with increasing g-
and Q2 at
d
: ꢁ71.2 ppm and
d: 79.2 ppm because VTES was the
bridging bond that caused the final absorption peak to take Q1 and
AlOOH addition to hybrid materials AN1eAN4, but each increment
was small. Hence, the difference was slight. The element carbon
decreased at the maximum ratio of the hybrid material, whereas the
element oxygen increased. This was because the high ratio formed
more alumina film bonding AleOeAl, and as shown in the Fig. 8
illustrates the aluminium content in the hybrid material AN4
increased suddenly. In addition, according to Table 1, the relatively
large mole number of aluminium in the hybrid materials
ATN1eATN4 indicated a relatively high aluminium content accord-
ing to the EDS analysis. However, the increase in the mole number
Q2 as the main peaks.
According to Fig. 5, the hybrid material ATN1 did not have
a noise peak in the minimum ratio when there was silica gel. When
the g
-AlOOH addition was at its minimum, there were Q1, Q2, Q3,
and Q4 absorption peaks. Q3 was predominant, and Q4 increased
suddenly in the hybrid material ATN2. AleO substituted SieO of
tetraethoxysilane (TEOS) to form SieOeAl TEOS with signals for Q1
and Q2 at
d
: ꢁ79.2 ppm, Q3 at
d
: ꢁ101.5 ppm, and Q4 at
d:
ꢁ109 ppm. The
g-AlOOH addition increased proportionally, and the
Q3 absorption peak was predominant at the maximum addition
level.
Fig. 9. The EDS diagram of hybrid materials ATN4.
Fig. 10. UV spectra of dyes, precursor, hybrid materials in ethanol solvent.

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Table 2 and Fig. 10 present the results of the ultravioletevisible
absorption spectral analysis of each compound. The lmax values
associated with the mono-substituent follow the order 3a
(494 nm) > 3b (450 nm). Based on this result, if the mono-
substituent is a donor group, then its lmax is assumed to increase.
Meanwhile, the effect of the dye-bonding precursor and the hybrid
material on lmax is insignificant. The hybrid materials AN4 and ATN4
with various diazonium components are compared, and lmax is
found to vary with the substituent. A benzene ring structure to
which a nitro group diazonium component is bonded as an
acceptor group will prompt lmax to move toward a relatively long
wavelength. Bonding a methoxy group substituent diazonium
component to a benzene ring reduces its lmax. According to the
spectra shown in Table 2, which indicate the effect of different
solvents on the compound, dissolution in DMF increases lmax. Since
the dipole moment of ethanol is smaller than that of DMF and
a relatively large dipole moment induces resonance among mole-
cules more easily, less energy is required for dissolution in DMF
than in ethanol, and consequently, the absorption wavelength is
relatively high, leading to the bathochromic effect.
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g-alumina granules.
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[20] Chen D, Jordan EH. Solegel synthesis and characterization of Al2O3eTiO2
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4. Conclusions
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In this study, a series of 4-substitution thiazole heterocyclic azo
polymer by the solegel, in situ generation of
phase. J Appl Polym Sci 2001;79:2326e30.
a rubbery silicaesiloxane
dyes were synthesised, and then added VTES/g-AlOOH and VTES/
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Morphology and natural wettability properties of solegel derived TiO2-SiO2
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TEOS/ -AlOOH in different ratios to prepare a series of hybrid
g
materials using the solegel method. The broadening diffraction peak
of the XRD pattern indicated the structure of SieOeAl networks of
boehmite in the hybrid gel. The SieOeAl absorption peaks were
observed from the FT-IR characterizations, and the intensities of
these absorption peaks increased with increasing g-AlOOH amount.
On 29Si-NMR and 27Al-NMR determinations the hybrid gels,
including AN4 and ATN1eATN4, showed the main peak due to a 6-
coordinate bond at the maximum ratio, suggesting the occurrence
of SieOeAl and AleOeAl networks. The ultraviolet spectra analysis
showed that lmax is greater for the more polar DMF than for ethanol.
According to the experimental FT-IR, NMR, and energy-dispersive X-
ray spectroscopy results, the boehmite or boehmite/silica in the
hybrid material could bond thiazole dyes to form the AleOeAl or
AleOeSi network structures with a thiazole moiety.
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for nonlinear-optical application. Dyes Pigm 2006;71:207e11.
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from coupler 4-aryl-3-cyano-2-aminothiophenes. Dyes Pigm 2004;61:
243e50.
[27] Yen MS, Wang IJ. A facile syntheses and absorption characteristics of some
monoazo dyes in bis-heterocyclic aromatic systems part II: syntheses of 4-(p-
substituted) phenyl-2-(2-pyrido-5-yl and 5-pyrazolo-4-yl) azo-thiazole
derivatives. Dyes Pigm 2004;63:1e9.
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diazo components. Dyes Pigm 1999;42:3e28.
[29] Hallas G, Towns AD.
A comparison of the properties of some 2-amino
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Acknowledgment
[31] Peters AT, Yang SS. Monoazo disperse dyes derived from mononitro-dichloro-
2-aminobenzothiazoles. Dyes Pigm 1996;30:291e9.
[32] Hallas G, Choi JH. Synthesis and spectral properties of azo dyes derived from
2-aminothiophenes and 2-aminothiazoles. Dyes Pigm 1999;42:249e65.
[33] Yoldas BE. Alumina sol preparation from alkoxides. Ceram Bull 1975;54:
289e90.
The authors would like to thank the National Science Council of
the Republic of China, Taiwan, for financially supporting this
research under Contract No. NSC-99-2622-E- 168- 001-CC3.
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