Synthesis of photosensitive organic-inorganic polymer hybrids by utilizing caged photoactivatable alkoxysilane

Article abstract of DOI:10.1021/ma0400057

Photosensitive polymer hybrids with poly(acrylic acid) (PAA) could be obtained by using caged (photosensitive protecting group modified) alkoxysilane (NVOC-U-PTEOS). Transparent polymer hybrids were prepared with UV irradiation, while the obtained materia

Full text of DOI:10.1021/ma0400057

5916
Macromolecules 2004, 37, 5916-5922
Synthesis of Photosensitive Organic-Inorganic Polymer Hybrids by
Utilizing Caged Photoactivatable Alkoxysilane
Tom ok i Ogosh i a n d Yosh ik i Ch u jo*
Department of Polymer Chemistry, Graduate School of Engineering, Kyoto University, Katsura,
Nishikyo-ku, Kyoto 615-8510, J apan
Received J anuary 8, 2004; Revised Manuscript Received May 13, 2004
ABSTRACT: Photosensitive polymer hybrids with poly(acrylic acid) (PAA) could be obtained by using
caged (photosensitive protecting group modified) alkoxysilane (NVOC-U-PTEOS). Transparent polymer
hybrids were prepared with UV irradiation, while the obtained materials were turbid without UV
irradiation. This can be attributed to the strong ionic interaction between carboxylic acid groups of PAA
and amino groups generated from NVOC-U-PTEOS by photoirradiation. The ionic interaction in polymer
hybrids was confirmed utilizing FT-IR and 1H NMR, and the transparency of the polymer hybrids was
evaluated by SEM.
Sch em e 1
In tr od u ction
A combination of different type of materials (organic,
inorganic, and metallic) is an important and evolution-
ary way to achieve the desired properties which cannot
be accomplished with single materials. Especially,
nanosize level composite materials show unique chemi-
cal and physical properties which are different from
microsize level composites.1-6 Organic-inorganic poly-
mer hybrids, in which organic polymers are dispersed
in inorganic matrix at a nanometer or molecular level,
have attracted tremendous attention and been widely
investigated because of unique properties of the polymer
hybrids resulting from nanometer level composite such
as high gas-barrier property,7 excellent solvent resis-
tance,8 flame resistance, and high transparency.9 The
transparency of the nanocomposite materials is the most
characteristic property due to the dispersion of compo-
nents on the order of nanometers, which is far less than
the wavelength of visible light and even near-ultraviolet
light, and as a result, the scattering loss is avoided.
The most popular, practical approach for preparing
organic-inorganic polymer hybrids is utilizing sol-gel
reaction.10 The advantage of sol-gel reaction is its mild
processing characteristics. The process involves the
hydrolysis of metal alkoxide, followed by a condensation
reaction with solvent evaporation to produce metal
oxides. A silicon alkoxide such as tetramethoxysilane
(TMOS) or tetraethoxysilane (TEOS) was widely used
to obtain silica gel by far.
(Scheme 1). For example, the hydrogen bond interaction
between residual silanol groups from sol-gel reaction
and organic polymer having strong hydrogen-accepting
groups such as poly(2-methyl-2-oxazoline) (POZO), poly-
(N-vinylpyrrolidone) (PVP), and poly(dimethylacryla-
mide) (PDMAAm) results in the molecular dispersion
in silica gel matrix.
In this research, we pay attention to the transparency
changes of the polymer hybrids depending on the
interactions between organic polymer and silica gel. The
controlling of the transparency of the polymer hybrids
can be achieved by creating the interaction between
organic polymer and silica utilizing stimuli (photo,
thermal, oxidation-reduction, and so on), while the
appearance of the polymer hybrids is phase separated
without stimuli. The concept of caged compounds is
introduced during the preparation of polymer hybrids
to obtain photosensitive polymer hybrids in this article.
Caged compounds are biologically active molecules or
ions, which are modified chemically with photosensitive
protecting groups. In other words, caged compounds are
nonactive usually and can be activated upon photoir-
radiation. Therefore, caged compounds are mainly ap-
plied in the field of biochemistry and drug delivery
system.20-22 Nitrobenzyl groups were widely used as a
photocaged compound. In the present study, photosensi-
tive polymer hybrids could be prepared by utilizing
caged (photosensitive protecting groups modified) al-
koxysilane. The idea is shown in Scheme 2.
Organic-inorganic polymer hybrids are easily pre-
pared by the sol-gel reaction of alkoxysilanes in the
presence of organic polymer. However, the appearance
of the obtained polymer hybrid is usually turbid by only
mixing organic polymer and alkoxysilane in the solvent
because the aggregation of organic polymer in silica gel
matrix would take place during the preparation of
polymer hybrids. To obtain transparent polymer hy-
brids, it is necessary to introduce covalent bond11-13 or
physical interaction between organic polymer and silica
gel.
In path I, the polymer hybrids with caged alkoxysi-
lane were prepared without photoirradiation. In this
case, the obtained polymer hybrid was phase separated
due to weak interaction between organic polymer and
silica gel resulting from “nonactive” caged alkoxysilane.
In our group, novel organic-inorganic polymer hy-
brids could be created by utilizing physical interactions
such as hydrogen bond,14-16 aromatic,17,18 and ionic
interactions19 between organic polymer and silica gel
10.1021/ma0400057 CCC: $27.50 © 2004 American Chemical Society
Published on Web 07/09/2004

Macromolecules, Vol. 37, No. 16, 2004
Photosensitive Organic-Inorganic Polymer Hybrids 5917
Sch em e 2
Sch em e 3
The organic polymer aggregated in the silica gel matrix.
On the other hand, transparent polymer hybrids could
be obtained with photoirradiation during preparing
polymer hybrids (path II). It is because “nonactive”
caged alkoxysilane was changed to nonprotected “active”
alkoxysilane with photoirradiation by removing cage
groups and the strong interaction formed between
organic polymer and silica gel from nonprotected alkoxy-
silane. That is the reason why organic polymer can be
dispersed in a silica gel matrix at the nanometer level,
and the obtained polymer hybrid is transparent with
photoirradiation. In this study, ionic interaction between
carboxylic acid groups of poly(acrylic acid) (PAA) and
amine groups of 3-(aminopropyl)triethoxysilane (AP-
TEOS) and the caged compound of 6-nitroveratryloxy-
carbonyl (NVOC) group were used. It is interesting to
note that the control of the transparency of the polymer
hybrids can be easily achieved by utilizing the concept
of the caged compounds. As shown in Scheme 3, photo-
resist like polymer hybrids could be prepared using this
preparation method.
The photoirradiated parts are activated and bring
about transparent, while the other parts without photo-
irradiation (utilizing photomask) are nonactivated and
become phase separation as a result. To our best
knowledge, it is little known that the transparency of
the polymer hybrids can be controlled by utilizing
photoirradiation. The properties of the obtained polymer

5918 Ogoshi and Chujo
Sch em e 4
Macromolecules, Vol. 37, No. 16, 2004
Sch em e 5
Sch em e 6
hybrids dramatically depended on the miscibility be-
tween organic polymer and silica phase. The dispersion
of organic polymer in silica gel matrix could be easily
controlled by the time of the UV irradiation in this
approach. Therefore, the polymer hybrid having desired
properties resulting from the miscibility between or-
ganic polymer and silica gel could be obtained using this
photosensitivity. Therefore,the transparent parts pre-
paring with photoirradiation should show the high
mechanical and thermal properties compared to phase
separation parts due to nanometer level miscibility
between organic polymer and silica gel. It is the first
report that the biochemical idea of caged compounds is
utilized in the field of nanocomposite materials science.
This photosensitive polymer hybrid can be accomplished
by not using covalent bond but using physical interac-
tion because it is easy to create physical interaction
between organic polymer and silica by photoirradiation
compared with the formation of covalent bonds.
hexane. The compound NVOC-U-PTEOS was obtained as a
light pink solid in a quantitative yield. 1H NMR (CDCl3): δ
7.68 (s, 1H), 7.00 (s, 1H), 5.51 (m, 2H), 5.16 (br, 1H), 4.02-
3.90 (m, 6H), 3.85-3.76 (m, 6H), 3.25 (t, 2H), 1.67 (m, 2H),
1.23 (m, 9H), 0.67 (t, 2H).
Syn th esis of NVOC P r op a n e via Ur eth a n e F u n ction a l
Gr ou p (NVOC-U-P ) (Mod el Com p ou n d ) (Scheme 4). Under
a nitrogen atmosphere, NVOC-OH (1.00 g, 4.69 mmol), propyl
isocyanate (1.00 mL, 9.67 mmol), and 0.03 mL of di-n-butyltin
dilaulate (catalyst) were dissolved in 15 mL of THF, and the
mixture was refluxed overnight. After evaporation of THF, the
crude product was purified by recrystallization in hexane three
times. The light pink solid (NVOC-U-P) was obtained (1.29 g,
4.09 mmol, yield 87.2%). 1H NMR (CDCl3): δ 7.72 (s, 1H), 7.00
(s, 1H), 5.55 (s, 2H), 4, 86 (br, 1H), 4.02-3.93 (m, 6H), 3.19
(t, 2H), 1.57 (m, 2H), 0.94 (m, 3H).
Syn th esis of NVOC Gr ou p Mod ified Alk oxysila n e via
Alk yl Gr ou p (NVOC-P TEOS) (Scheme 5). The compound of
allyl-NVOC was prepared according to the detailed experi-
mental procedure described in a previous literature.25 The
compound of NVOC-PTEOS was prepared by the hydrosi-
lylation of allyl-NVOC with triethoxysilane using a platinum
catalyst. Under a nitrogen atmosphere, 0.70 g (3.12 mmol) of
allyl-NVOC, 1.50 mL (8.13 mmol) of triethoxysilane, and 0.03
mL of the platinum-divinyltetramethyldisiloxane complex (in
xylene solution) were dissolved in 2 mL of THF solution, and
the mixture was refluxed for 72 h. After evaporation of THF,
the oily product was washed using hexane three times under
nitrogen. The slightly black oily product was obtained (yield
12.6%). 1H NMR (CDCl3): 7.59 (s, 1H), 6.73 (s, 1H), 4.02-
3.90 (m, 6H), 3.85-3.80 (m, 6H), 2.96 (t, 2H), 1.78 (m, 2H),
0.74 (t, 2H).
P r ep a r a tion of P olym er Hybr id s w ith P h otoir r a d ia -
tion . The organic-inorganic polymer hybrids were prepared
from PAA by utilizing the sol-gel reaction of various kinds of
alkoxysilanes (Scheme 6). PAA and alkoxysilanes were dis-
solved in methanol, and a prescribed amount of aqueous
hydrochloric acid was added as a catalyst for the sol-gel
reaction. The mixture was stirred at 2 h in a sealed bottle with
photoirradiation. As an ultraviolet source, a 450 W high-
pressure mercury lump was used. Then, the mixture was
placed in an open container with a paper towel and left in an
oven at 60 °C to evaporate the solvent. The resulting samples
were dried in a vacuum oven at 80 °C to remove the solvent
completely.
Exp er im en ta l Section
Ma ter ia ls. Poly(acrylic acid) (PAA) of average molecular
weight 25 000 was obtained from Wako Pure Chemical Indus-
tries, Ltd. Tetraethoxysilane (TEOS) was distilled and stored
under nitrogen. Tetrahydrofuran (THF) was dried and distilled
over sodium under nitrogen. Methanol was dried with mag-
nesium methoxide and distilled under a nitrogen atmosphere.
Hexane was dried and distilled over MgSO4 under nitrogen.
The other solvents and reagents were used as supplied.
1
Mea su r em en ts. The H NMR spectra were recorded on a
270 MHz J EOL-J NM-GX270 NMR spectrometer. Thermo-
gravimetric analysis (TGA) was performed using a TG/
DTA6200, Seiko Instruments, Inc., with heating rate of 10 °C
min-1 in air. Scanning electron microscopy (SEM) measure-
ments were conducted using a J EOL J NM-5310/LV system.
Absorption spectra were obtained on a J asco V-530 spectrom-
eter. The FT-IR spectra were obtained using a Perkin-Elmer
1600 infrared spectrometer.
Syn th esis of 6-Nitr over a tr yloxyca r bon yl (NVOC)
Gr ou p Mod ified Alk oxysila n e via Ur eth a n e F u n ction a l
Gr ou p (NVOC-U-P TEOS) (Scheme 4). To 20 mL of THF were
added 1.00 g (4.68 mmol) of 6-nitroveratryloxycarbonyl alcohol
(NVOC-OH), 2.00 mL (2.00 g, 8.07 mmol; about 2 equiv to
NVOC-OH) of isocyanatopropyltriethoxysilane (NCO-PTEOS),
and 0.03 mL of di-n-butyltin dilaulate (used as a catalyst to
proceed urethane formation23,24 between alcohol and isocyanate
group), and the mixture was refluxed overnight under a
nitrogen atmosphere. After evaporation of THF, the crude
product was washed using hexane three times under nitrogen.
The solubility of NVOC-OH was very poor in hexane compared
with that of NCO-PTEOS. Therefore, excess molar amounts
of NCO-PTEOS could be easily removed by washing with
Resu lts a n d Discu ssion
Effect of AP TEOS on Hom ogen eity of P AA/Silica
P olym er Hybr id s. The effect of APTEOS on the
homogeneity of PAA/silica hybrids was investigated
(Table 1). As illustrated in Figure 1, APTEOS, MeTEOS,

Macromolecules, Vol. 37, No. 16, 2004
Photosensitive Organic-Inorganic Polymer Hybrids 5919
Ta ble 1. Effect of AP TEOS on Hom ogen eity of P AA/Silica
Hybr id sa
run
alkoxysilane
PAA/alkoxysilane (w/w)
appearance
1
2
3
4
APTEOS
MeTEOS
PhTEOS
TEOS
4
4
4
4
transparent
translucent
turbid
turbid
a
Methanol 5 mL, HClaq (0.1 M) 0.2 mL, stirring time 2 h,
evaporating methanol at 60 °C.
F igu r e 2. FT-IR spectra of the PAA/silica hybrid (a) using
APTEOS (Table 1, run 1), (b) using MeTEOS (Table 1, run 2),
and (c) PAA.
F igu r e 1. Alkoxysilanes for preparation of polymer hybrids
and model compound.
Sch em e 7
F igu r e 3. 1H NMR spectra of (a) APTEOS, (b) APTEOS with
the same molar ratio of PAA, and (c) PAA in CD3OD.
PhTEOS, and TEOS were used for the synthesis of PAA/
silica hybrids.
As shown in Table 1, the obtained polymer hybrid
using APTEOS was homogeneous and transparent (run
1). On the other hand, when MeTEOS was used as an
alkoxysilane, the polymer hybrid brought about turbid
(run 2). The same results were also observed with
PhTEOS (run 3) and TEOS (run 4). These observations
resulted from strong ionic interaction between carbox-
ylic acid groups of PAA and amine groups of APTEOS.
As described in Scheme 7, the proton transfer should
be performed from carboxylic acid groups to amino
groups at the moment of addition of APTEOS to the
solution of PAA. Then the ionic interaction between the
caboxylate ion and the ammonium ion would be formed
and link PAA and APTEOS by the ionic pairs. There-
fore, the obtained polymer hybrid with APTEOS was
transparent as a result.
Evid en ce of Ion ic In ter a ction betw een P AA a n d
AP TEOS. The ionic interaction between PAA and
APTEOS was confirmed by FT-IR spectra. It was
recognized that the new CdO stretching band of car-
boxylate ion was observed due to the proton transfer
from carboxylic acid groups to amine groups. The FT-
IR spectra are shown in Figure 2.
peak appeared around 1550 cm-1 in the case of the
transparent samples using APTEOS (Figure 2a) com-
pared to the other phase-separated samples using
MeTEOS (Figure 2b) and PAA (Figure 2c). This peak
was assignable to the CdO stretching vibration of the
carboxylate ion.26 This result indicates the proton
transfer from the carboxylic acid groups to amino groups
and the formation of ionic bonds.
1H NMR was also utilized to check the ionic interac-
tions between carboxylic acid groups of PAA and amino
groups of APTEOS. As shown in Figure 3a, alkyl peaks
of APTEOS were observed at 2.58 and 1.54 ppm in CD3-
OD. But these peaks were shifted to 2.92 and 1.76 ppm
with the same molar ratio of PAA in CD3OD (Figure
3b). It suggests that anime groups are changed to
ammonium ion moieties because of the proton transfer
from carboxylic acid groups to amine groups.27
P h otoclea va ge Rea ction of NVOC Ca ged Com -
p ou n d . The photocleavage reaction of the model com-
pound (NVOC-U-P) in methanol was checked (Scheme
8). The change of UV absorption spectra during the
photoirradiation is shown in Figure 4.
In all samples were found the CdO stretching bands
The UV absorbance of around 340 nm was decreased
by photoirradiation, and the reaction was saturated
of carboxylic acid at 1700 cm-1. In addition, the new

5920 Ogoshi and Chujo
Ta ble 2. Syn th esis of UV-Sen sitive Or ga n ic-In or ga n ic P olym er Hybr id s Usin g Ca ged Alk oxysila n ea
ceramic yield (wt %)
calcd
obsdc
6.03 4.57
Macromolecules, Vol. 37, No. 16, 2004
run
PAA (mg)
alkoxysilane (mg)
APTEOS 25
NVOC-U-PTEOS 25
NVOC-U-PTEOS 25
NVOC-PTEOS 25
NVOC-PTEOS 25
NVOC-U-P 10 + TEOS 25
NVOC-U-P 10 + TEOS 25
UVb
appearance
1
5
6
7
8
100
100
100
100
100
100
100
-
+
-
+
-
+
-
transparent
transparent
translucent
phase separated
phase separated
phase separated
phase separated
3.03 2.08
9
10
a
b
Methanol 5 mL, HClaq (0.1 M) 0.2 mL, stirring time 2 h. Irradiating time of UV (λ ) 365 nm) 2 h. c Calculated from TGA.
Ta ble 3. Syn th esis of P h otosen sitive P AA/Silica Hybr id s Usin g Ca ged Alk oxysila n ea
ceramic yield (wt %)
run
PAA (mg)
NVOC-U-PTEOS (mg)
0.1 M HClaq (mL)
UVb
appearance
calcd
3.24
obsdc
5
6
11
12
13
100
100
100
100
100
25
25
50
50
50
0.2
0.2
0.2
+
-
+
+
-
transparent
turbid
translucent
transparent
phase separated
2.08
5.46
3.26
a
b
Methanol 5 mL, stirring time 2 h, evaporating methanol at 60 °C. Irradiating time of UV (λ ) 365 nm) 2 h. c Calculated from TGA.
Sch em e 8
Sch em e 9
The transparent polymer hybrid utilizing NVOC-U-
PTEOS could be obtained with UV (run 5). In contrast,
the polymer hybrid without UV was translucent (run
6). The interaction between “nonactive” NVOC-U-
PTEOS and PAA was so weak that the obtained polymer
hybrids were phase-separated. But, by photoirradiation,
“nonactive” NVOC-U-PTEOS was converted to “active”
APTEOS. Then the strong ionic interaction between
ammonium ion resulted from APTEOS and carboxylate
ion of PAA formed. Therefore, transparent polymer
hybrids could be obtained in the case of the sample with
photoirradiation. Furthermore, in the case of the sample
using NVOC-PTEOS without UV, the obtained polymer
hybrid was phase-separated (run 8). The obtained
polymer hybrid using NVOC-PTEOS with photoirra-
diation also brought about phase separation (run 7).
NVOC-PTEOS was inert and nonactivated by photoir-
radiation; thus, the obtained polymer hybrids were
phase-separated even if the sample was photoirradiated.
Both samples using NVOC-U-P and TEOS with UV (run
9) and without UV (run 10) were phase-separated.
NVOC-U-P was changed to propylamine by photoirra-
diation and formed ionic interaction with carboxylic acid
of PAA. But there is no interaction between PAA and
silica because ionic interaction groups of ammonium ion
could not connected with silica gel from TEOS.
F igu r e 4. Change of UV absorption during irradiation of
NVOC-U-P in methanol.
within 2 h. The photocleavage reaction of the model
compound (NVOC-U-P) occurred readily in methanol.
This result is consistent with the previous observations
of the spectral changes during photoirradiation of ac-
companying NVOC-modified compounds.24,25
Syn th esis of P h otosen sitive P olym er Hybr id s
Utilizin g NVOC-Mod ified Alk oxysila n e. Organic-
inorganic polymer hybrids of PAA utilizing NVOC-
modified alkoxysilane were prepared. NVOC-U-PTEOS,
NVOC-PTEOS, and the mixture of TEOS and NVOC-
U-P (model compound) were used for preparation of
PAA/silica hybrids (Figure 1). The results are sum-
marized in Table 2.
PAA/silica hybrids using NVOC-U-PTEOS was pre-
pared in different PAA/silica ratios (Table 3). When the
PAA/NVOC-U-PTEOS ratio was 4/1, transparent PAA/
silica hybrids were obtained by photoirradiation (run
5). The appearance of the polymer hybrid was phase-

Macromolecules, Vol. 37, No. 16, 2004
Photosensitive Organic-Inorganic Polymer Hybrids 5921
F igu r e 5. 1H NMR spectra of NVOC-U-PTEOS with PAA (a) before photoirradiation and (b) after photoirradiation in CD3OD.
F igu r e 6. SEM images of polymer hybrids of PAA (a) using TEOS (Table 1, run 4), (b) using NVOC-U-PTEOS without
photoirradiation (Table 2, run 6), (c) using APTEOS (Table 1, run 1), and (d) using NVOC-U-PTEOS with photoirradiation
(Table 2, run 5).
separated with photoirradiation when the PAA/NVOC-
U-PTEOS ratio was 2/1 (run 11). On the other hand,
the sample without aqueous HCl (run 12), transparent
and homogeneous polymer hybrid could be obtained
with photoirradiation. It is thought that the ionic
interaction was so weak in aqueous solution compared
to methanol that transparent polymer hybrids could not
be obtained by using aqueous hydrochloric acid. The
strength of the ionic interaction could be attributed to
the different dielectric constant of the solvent. Water
has a much higher dielectric constant than methanol;
thus, water can solvate ionic pairs via strong electronic

5922 Ogoshi and Chujo
Macromolecules, Vol. 37, No. 16, 2004
interaction and should hinder the formation of the ionic
interaction between PAA and APTEOS. The same trend
was observed in the polymer hybrid using sulfonic acid
groups of poly(styrenesulfonic acid) (PSSA) and amine
moieties of APTEOS.19
sample using NVOC-U-PTEOS with photoirradiation
(Table 2, run 5), some particles or aggregation at 10 000
magnifications were also not found (Figure 6d). These
results suggest that silica is dispersed at the nanometer
level in the hybrid materials.
As shown in Scheme 3, photoresist like polymer
hybrids could be prepared using this preparation method.
In the case of the sol state (liquid phase) of the polymer
hybrids, the patterning using this approach is difficult
because of the strong migration tendency. But, the sol
state of the hybrid became the gel state according to
the proceeding of the sol-gel reaction of alkoxysilane.
In the gel stage, the migration tendency should be
inhibited and the photoresist like polymer hybrids
should be obtained. It is considered that the controlling
of the UV irradiation timing and time can accomplish
the preparation of the photoresist hybrid in this ap-
proach. This work is now under investigation.
Evid en ce of Ion ic In ter a ction betw een P AA a n d
NVOC-U-P TEOS a fter P h otoir r a d ia tion . The ionic
interaction between carboxylic acid groups of PAA and
amine groups resulted from nonprotected NVOC-U-
PTEOS by photoirradiation could be checked by FT-IR
and 1H NMR measurements as well as previously
described ionic interaction between PAA and APTEOS.
Unfortunately, it was difficult to observe the shift of Cd
O groups due to overlap with the band from phenyl
groups around 1590 cm-1. Therefore, 1H NMR was
utilized to examine the ionic interaction between car-
boxylic acid groups of PAA and amine groups of NVOC-
U-PTEOS after photoirradiation.
Con clu sion s
The transparency of polymer hybrids utilizing caged
alkoxysilane (NVOC-U-PTEOS) could be controlled by
photoirradiation because caged alkoxysilane was changed
to nonprotected alkoxysilane by utilizing photoirradia-
tion and the ionic interaction formed between carboxylic
acid groups of PAA and amine groups of nonprotected
alkoxysilane. This strong ionic interaction could be
confirmed by FT-IR and 1H NMR spectra. The resist-
like polymer hybrids could be obtained utilizing this
idea. This novel photosensitive polymer hybrid using the
biochemical concept of the caged compound is the first
example and gives beneficial clues in the field of
materials science.
Refer en ces a n d Notes
(1) Wen, J .; Wilkes, G. L. Chem. Mater. 1996, 8, 1667.
(2) Loym, D. A.; Shea, K. J . Chem. Rev. 1995, 95, 1431.
(3) Novak, B. M. Adv. Mater. 1993, 5, 422.
(4) Giannelis, E. P. Adv. Mater. 1996, 8, 29.
(5) Chujo, Y.; Tamaki, R. MRS Bull. 2001, 26, 389.
(6) Special issue for organic-inorganic nanocomposite materials.
Chem. Mater. 2001, 13.
(7) Tamaki, R.; Chujo, Y.; Kuraoka, K.; Yazawa, T. J . Mater.
Chem. 1999, 8, 1741.
(8) Ogoshi, T.; Itoh, H.; Kim, K. M.; Chujo, Y. Macromolecules
2002, 35, 1741.
As shown in Figure 5b, the proton peak of the
methoxy groups of NVOC moieties, which were observed
around 3.8-4.0 ppm, was shifted to about 3.6 ppm after
UV irradiation. The shift resulted from the photocleav-
age. This observation was similar to the case of previ-
ously reported.30 Furthermore, the new peak around
2.92 ppm was observed after photoirradiation in the
sample of PAA/NVOC-U-PTEOS (1/1) in CD3OD com-
pared to Figure 5a (the same sample before photoirra-
diation). This peak consisted of the alkyl peak of the
sample of the PAA/APTEOS in CD3OD (Figure 3b). This
result indicates the ionic interaction between amine
groups generated from NVOC-U-PTEOS with photo-
irradiation and carboxylic acid groups of PAA. The
efficiency of the formation of the ionic interaction was
about 15%, which was calculated by the integration of
the peak at 2.92 ppm. The percentage was slightly
small, but it should be enough to obtain the transparent
polymer hybrid because ionic interaction was stronger
than the other kinds of physical interaction such as
hydrogen bond and aromatic interaction.
(9) Bohren, C. F.; Huffman, D. R. Absorption and Scattering of
Light by Small Particles; Wiley: New York, 1983.
(10) Brinker, C. J .; Scherer, G. W. Sol-Gel Science, The Physics
and Chemistry of Sol-Gel Processing; Academic Press: San
Diego, 1990.
(11) Wei, Y.; J in, D.; Brennan, D. J .; Rivera, D. N.; Zhuang, Q.;
DiNardo, N. J .; Qiu, K. Chem. Mater. 1998, 10, 769.
(12) Sun, C.-C.; Mark, J . E. Polymer 1989, 30, 104.
(13) Wei, Y.; Yeh, J .-M.; J in, D.; J ia, X.; Wang, J . Chem. Mater.
1995, 7, 969.
(14) Chujo, Y.; Ihara, E.; Kure, S.; Saegusa, T. Macromolecules
1993, 26, 5681.
(15) Chujo, Y.; Matsuki, H.; Kure, S.; Saegusa, T.; Yazawa, T. J .
Chem. Soc., Chem. Commun. 1994, 635.
(16) Chujo, Y.; Saegusa, T. Adv. Polym. Sci. 1992, 100, 11.
(17) Tamaki, R.; Samura, K.; Chujo, Y. Chem. Commun. 1998,
1131.
(18) Tamaki, R.; Han, S. Y.; Chujo, Y. Polym. Prepr. J pn. 1998,
47, 1016.
(19) Tamaki, R.; Chujo, Y. Chem. Mater. 1999, 7, 1719.
(20) Hess, G. P. Biochemistry 1993, 32, 989.
(21) Cameron, J . F.; Fre´chet, J . M. J . J . Am. Chem. Soc. 1991,
113, 4303.
(22) Muralidharan, S.; Nerbonne, J . M. J . Photochem. Photobiol.
B 1995, 27, 123.
SEM Im a ges of P olym er Hybr id s. The miscibility
of organic and inorganic phase was confirmed by SEM
(Figure 6). As shown in Figure 6a, the sample with
TEOS (Table 1, run 4) showed phase separation between
organic polymer and silica gel at about 3000 magnifica-
tions. The white parts indicate silica particles. The
white particles about 1 µm could be clearly observed.
The turbid polymer hybrids using NVOC-U-PTEOS
without photoirradiation (Table 2, run 6) also showed
honeycomb-like phase separation at 1000 magnifications
(Figure 6b). However, in the case of the transparent
PAA/silica hybrid using APTEOS (Table 1, run 1),
aggregations of silica were not observed even at about
10 000 magnifications (Figure 6c). In the transparent
(23) Calvet, D.; Collet, A.; Viguier, M.; Berrer, J .-F.; Se´re´ro, Y.
Macromolecules 2003, 36, 449.
(24) Wang, D.-A.; J i, J .; Feng, L.-X. Macromolecules 2000, 33,
8472.
(25) Chamorro, G.; Gardun˜o, L.; Sa´nchez, A.; Labarrios, F.;
Salazar, M.; Mart´ınez, E.; D´ıaz, F.; Tamariz, J . Drug Dev.
Res. 1998, 43, 105.
(26) Mori, H.; Lanzendo¨rfer, M. G.; Mu¨ller, A. H. E. Langmuir
2004, 20, 1934.
(27) Feher, F. J .; Wyndham, K. D.; Soulivong, D.; Nguyen, F. J .
Chem. Soc., Dalton Trans. 1999, 1491.
(28) Zhang, Z. Y.; Smith, B. D. Bioconjugate Chem. 1999, 10, 1150.
(29) Ottl, J .; Gabriel, D.; Mariott, G. Bioconjugate Chem. 1998,
9, 143.
(30) Kevwitch, R. M.; McGrath, D. V. Synthesis 2002, 9, 1171.
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