Synthesis and optical properties of σ-π Conjugated organic-inorganic hybrid gels

Article abstract of DOI:10.1002/pola.27571

Organic-inorganic hybrid gels containing Si-vinylene units have been synthesized by a hydrosilylation reaction of tri- or tetra-ethynyl aryl compounds, 1,3,5-triethynylbenzene (TEB), 3,3,5,5-tetraethynylbiphenyl (TEBP), or tetrakis(4-ethynylphenyl)methane

Full text of DOI:10.1002/pola.27571

JOURNAL OF
POLYMER SCIENCE
ARTICLE
WWW.POLYMERCHEMISTRY.ORG
Synthesis and Optical Properties of r–p Conjugated
Organic–Inorganic Hybrid Gels
Naofumi Naga,1 Hitomi Nagino,1 Midori Iwashita,1 Tomoharu Miyanaga,1 Hidemitsu Furukawa2
1Department of Applied Chemistry, College of Engineering, Shibaura Institute of Technology, 3-7-5 Toyosu, Koto-ku, Tokyo
135-8548, Japan
2Life-3D Printing Innovation Center, Soft & Wet Matter Engineering Laboratory, Yamagata University, 4-3-16 Jonan, Yonezawa,
Yamagata 992–8510, Japan
Correspondence to: N. Naga (E-mail: nnaga@sic.shibaura-it.ac.jp) or H. Furukawa (E-mail: furukawa@yz.yamagata-u.ac.jp)
Received 20 August 2014; accepted 28 January 2015; published online 4 March 2015
DOI: 10.1002/pola.27571
ABSTRACT: Organic–inorganic hybrid gels containing Si-vinylene
units have been synthesized by a hydrosilylation reaction of tri-
or tetra-ethynyl aryl compounds, 1,3,5-triethynylbenzene (TEB),
3,30,5,50-tetraethynylbiphenyl (TEBP), or tetrakis(4-ethynylphenyl)-
methane (TEPM), and bisdimethylsilyl compounds, 1,1,3,3-tetra-
methyldisiloxane (TMDS) or 1,4-bisdimetylsilylbenzene (BDMSB),
in toluene. Network structure of the resulting gels was quantita-
tively characterized by a scanning microscopic light scattering.
The reactions yielded the gels having homogeneous network
structure of 1.5–2.9 nm mesh size under the monomer concen-
trations that were relatively higher than the critical gelation con-
centration. The gels obtained from TEB showed broad
absorption in the range from 340 to 370 nm, and emission in the
range from 440 to 490 nm. The TEB–BDMSB gels showed
remarkable red shift of the emission in comparison with that of
the corresponding reaction solutions derived from the network
formed by r–p conjugation. The TEPM–TMDS, BDMSB gels
exited by 280 nm showed not only the emission peak at around
360 nm derived from TEPM, but the broad peak at around
420 nm, which should be derived from interaction between phe-
C
V
nyl groups of TEPM in the gels. 2015 Wiley Periodicals, Inc. J.
Polym. Sci., Part A: Polym. Chem. 2015, 53, 1360–1368
KEYWORDS: r–p conjugation; gels; hydrosilylation; lumines-
cence; organic–inorganic hybrid gels; pi interaction; photophys-
ical property; scanning microscopic light scattering
compounds using a Pd catalyst produced the copolymers in
good yield.15 These copolymers showed good solubility in
conventional organic solvents and high photo luminescence
(PL) quantum yield. We thought about to synthesize the gels
composed by the network having Si-vinylene units. Two syn-
thetic paths would be applicable to synthesize the gels. One is
Mizoroki–Heck reaction of multiple brominated aryl com-
pounds and divinyl disilane compounds with Pd catalysts. The
residues of the Pd catalyst, however, dark-colored the gels,
and made it difficult to investigate optical properties of the
resulting gels. The other method is hydrosilylation reaction of
multiple-ethynyl aryl compounds and disilane compounds
with Pt catalysts. The Pt catalysts for the hydrosilylation reac-
tion are almost colorless. Highly active catalysts for the reac-
tion would yield the transparent clear gels, which should be
suitable for investigation of the optical properties.
INTRODUCTION A number of p conjugated polymers have
been developed due to their applicability to organic light-
emitting diodes (LED). One of the advantageous properties of
the conjugated polymers is solubility in organic solvents. This
feature makes it possible to form thin layer of polymers for the
LED devices via wet process. Molecular design of the conjugated
polymers, such as incorporation of some kinds of side groups,
is effective not only to improve the solubility in the organic sol-
vents but to control the photophysical properties, quantum
yield, and emission wavelength, of the polymers. Solutions of
the fluorescent polymers are applicable for electrogenerated
chemiluminescent cell of the light-emitting devices.1–11 There is
concern for the leakage of liquid luminescent layers from the
device cell. Physical gels and chemical gels, which are composed
of organic solvent and conjugated polymer or crosslinked poly-
mer with fluorescent molecule, for light-emitting devices have
been developed to solve the issue.12–14
In this paper, we report the synthesis of organic–inorganic
hybrid gels containing r–p conjugated Si-vinylene units by
hydrosilylation reactions of 1,3,5-triethynylbenzene (TEB),
3,30,5,50-tetraethynylbiphenyl (TEBP), or tetrakis(4-ethynyl-
phenyl)methane (TEPM), and 1,1,3,3-tetramethyldisiloxane
Some organic–inorganic hybrid copolymers containing r–p
conjugated Si-vinylene units in the main chain have been
developed in our laboratory. Mizoroki–Heck reaction of 9,9-
dihexyl-2,7-dibromofluorene with disubstituted divinyl silane
Additional Supporting Information may be found in the online version of this article.
C
V
2015 Wiley Periodicals, Inc.
1360
JOURNAL OF POLYMER SCIENCE, PART A: POLYMER CHEMISTRY 2015, 53, 1360–1368

JOURNAL OF
POLYMER SCIENCE
WWW.POLYMERCHEMISTRY.ORG
ARTICLE
SCHEME 1 Synthesis of r-p conjugated organic-inorganic hybrid gels from TEB and TMDS or BDMSB using a hydrosilylation reac-
tion with Karstedt’s catalyst.
(TMDS) or 1,4-bisdimetylsilylbenzene (BDMSB) using a Pt
catalyst, Karstedt’s catalyst, as shown in Scheme 1. There
should be some merits in the developed gels. The network
of the designed gels is formed by the highly emissive parts
of Si-vinylene units without small PL molecules, and there
should be no leaking of the PL molecules from the gels. The
gels are formed by a hydrosilylation reaction of the multi-
functional aryl compounds as joint molecules and dimethylsi-
lane compounds as linker molecules. This synthetic method
yielded the gels with homogeneous network structure, as
previously reported.16 The geometry or mesh size of the gels
is controllable by the structure of the joint molecules or
molecular size of the linker molecules, respectively. The net-
work structure in the gel is quantitatively studied by a scan-
ning microscopic light scattering (SMILS). The absorption
and emission properties of the reaction systems before and
after gelation are investigated with UV–vis and PL spectros-
copy, and interrelation between network structure and the
optical properties of the resulting gels is studied.
ane solution) of platinum–divinyltetramethyldisiloxane com-
plex (Karstedt’s catalyst, 1) was purchased from Chisso, and
used without purification. Toluene was dried over calcium
hydride by refluxing for 6 h and distilled before use under
nitrogen atmosphere. TEBP or TEPM was synthesized by
aryl-ethynyl coupling reaction of 3,30,5,50-tetrabromobiphenyl
or tetrakis(4-iodophenyl)methane and trimethylsilylethyne
using bis(triphenylphosphine)palladium(II) dichloride, cop-
per(I) iodide, and triphenylphosphine catalyst system follow-
ing desilylation of methylsilylethynyl derivatives, according
to the literature.17
Synthesis of r–p Conjugated Organic–Inorganic Hybrid
Gels
The mole ratio of ethynyl group in TEB, TEBP, or TEPM to
Si–H group in TMDS or BDMSB was adjusted to 1.0. The sol-
vent was filtered by a disk filter for getting rid of dusts. The
resulting gels were measured in as-prepared state without
ꢀ
further treatment at 25 C.
Synthesis of TEB–TMDS Gel (Sample 1)
EXPERIMENTAL
In a sample tube of 4 mm diameter (60 mm length),
12.0 mg (0.08 mmol) of TEB and 16.1 mg (21.3 mL, 0.12
mmol) of TMDS were dissolved in a 179 lL of toluene. Then
a 60 lL of toluene solution (0.6 mmol/mL) of the catalyst 1
(36 mmol) was added to the sample tube, and mixed in the
Materials
TEB (Wako Pure Chemical Industries), diethynylbenzene
(DEB) (Wako Pure Chemical Industries), TMDS (Chisso), and
BDMSB (Chisso) were used as received. A poly(dimethylsilox-
WWW.MATERIALSVIEWS.COM
JOURNAL OF POLYMER SCIENCE, PART A: POLYMER CHEMISTRY 2015, 53, 1360–1368
1361

JOURNAL OF
POLYMER SCIENCE
ARTICLE
WWW.POLYMERCHEMISTRY.ORG
in the reaction system. After the sample tube was sealed by
ꢀ
burning off, it was heated at 100 C for 2 h without stirring.
The reaction solution turned a slightly brawny cleared gel.
The gels with different monomer concentrations and/or
monomers were also conducted with the same procedure.
ANALYTICAL PROCEDURES
1H NMR spectra of sol samples were recorded on a JEOL-
JNM-LA300 spectrometer in pulse Fourier transform mode
to determine the reaction conversion. The pulse angle of 45ꢀ
was applied, and 32 scans were accumulated in 7 s of the
pulse repetition. The spectra were recorded at room temper-
ature with about 10 vol % of CDCl3.
Quantitative determination of minute mesh size of the gels
was performed with the SMILS system, as previously
reported.18,19 The radius of mesh n (mesh size) was calcu-
lated from the relaxation time in SMILS analysis with Ein-
stein–Stokes formula (1):
FIGURE 1 Ensemble-averaged relaxation time distributions as
a function of the relaxation time of TEB–TMDS gels with the
monomer concentration of 12.0 wt % (a), 14.0 wt % (b), and
16.0 wt % (c).
16pn2sRKBsin 2 h
2
n5
(1)
3gk2
where n, sR, KB, h, g, and k are refractive index of toluene,
ensemble-averaged relaxation time (s), Boltzmann constant
(1.38 3 10223 JK21), scattering angle (90ꢀ), viscosity coeffi-
cient of toluene at 298 K (5.6 3 1024 Nm2 s21), and wave
length of incident ray (4.42 3 1027 m), respectively.
reaction system. After the sample tube was sealed by burn-
ing off, it was heated at 100 C for 2 h without stirring. The
reaction solution turned a slightly brawny cleared gel. The
gels with different monomer concentrations and /or mono-
mers were also conducted with the same procedure.
ꢀ
UV–vis spectroscopy was conducted with Shimadzu UV-
1600PC. PL spectroscopy was investigated with a Shimadzu
RF-1500. Molecular weight and molecular weight distribu-
Synthesis of TEB–BDMSB Gel (Sample 5)
In a sample tube of 4 mm diameter (60 mm length),
12.0 mg (0.08 mmol) of TEB, and 23.3 mg (26.7 mL, 0.12
mmol) of BDMSB were dissolved in a 225 lL of toluene.
Then, a 75 lL of toluene solution (0.6 mmol/mL) of the cata-
lyst 1 (45 mmol) was added to the sample tube, and mixed
ꢀ
tion of a liner polymer were measured at 40 C by means of
a gel-permeation chromatography (Shimadzu Prominence
GPC System) using chloroform as a solvent and calibrated
with standard polystyrene samples.
TABLE 1 Network Structure of TEB–TMDS, BDMSB Gels
a
Run
Monomer
wt %
sR 3 1026
s
Mesh Size (nm)
rb
Reaction Rate (%)
70.9
1
2
TEB–TMDS
TEB–TMDS
10.0
12.0
–
–
–
4.73
150
1530
4.50
950
4.87
–
1.3
40
0.049
0.085
0.089
0.038
0.085
0.039
–
4000
1.2
2500
1.3
–
3
TEB–TMDS
14.0
4
5
6
TEB–TMDS
TEB–BDMSB
TEB–BDMSB
16.0
6.0
56.0
8.0
4.91
59.5
7.18
113
5.73
1.0
23
0.27
0.31
0.075
0.14
0.036
7
TEB–BDMSB
TEB–BDMSB
12.0
16.0
1.9
30
8
1.5
a
b
Relaxation time.
Standard deviation of a peak of the ensemble-averaged relaxation
time distribution.
1362
JOURNAL OF POLYMER SCIENCE, PART A: POLYMER CHEMISTRY 2015, 53, 1360–1368

JOURNAL OF
POLYMER SCIENCE
WWW.POLYMERCHEMISTRY.ORG
ARTICLE
the absence of fluidity of the reaction system. The reaction
of TEB and TMDS more than 12.0 wt % (wt % of summation
of TEB and TMDS in the reaction system) of the monomer
concentration formed the gels. On the other hand, the reac-
tion of the monomer concentration of 10.0 wt % yielded a
viscous liquid. We will use the term of “critical gelation con-
centration” to refer the lowest monomer concentration that
can form a gel. The reaction of TEB and BDMSB of 6.0 wt %
did not form gel. The reaction of TEB and BDMSB more than
8 wt % of the monomer concentration formed the gels.
Reaction conversion of ethynyl group in the sol samples
were determined by 1H NMR spectroscopy. The conversions
in the TEB–TMDS system (10.0 wt % Run 1) or TEB–BDMSB
system (6.0 wt % Run 5) were 70.9 or 56.0%, respectively.
Higher reaction conversion of the TEB–TMDS system can be
explained by flexibility of the TMDS.
Figure 1 shows the ensemble-averaged relaxation time distri-
butions as a function of the relaxation time of the TEB–
TMDS gels. The network structure of the TEB–TMDS gels is
summarized in Table 1. The ensemble-averaged relaxation
time distributions of the gel with 12.0 wt % monomer con-
centration, which was the critical gel concentration of TEB–
TMDS system, showed multiple relaxation peaks. The peaks
at short relaxation time, less than 1025 s, correspond to
mesh sizes of about 1.2–1.3 nm. The mesh size gave roughly
agreement with that of the expected mesh size derived from
TEB and TMDS about 0.4–0.9 nm, calculated by a molecular
mechanics method. On the other hand, the peak at long
FIGURE 2 Ensemble-averaged relaxation time distributions as
a function of the relaxation time of TEB–BDMSB gels with the
monomer concentration of 8.0 wt % (a), 12.0 wt % (b), and 16.0
wt % (c).
RESULTS AND DISCUSSION
Network Structure of Gels
The hydrosilylation reaction of TEB and TMDS or BDMSB
was investigated with the catalyst 1 under the various mono-
mer concentrations. Formation of the gel was confirmed by
TABLE 2 Network Structure of TEBP–TMDS, BDMSB Gels
Reaction
Run
Monomer
wt %
sR 3 1026
a
s
Mesh Size (nm)
rb
Rate (%)
9
TEBP–TMDS
TEBP–TMDS
6.3
6.9
–
–
–
49.5
10
6.61
154
1.8
0.03
0.07
0.10
0.03
0.12
0.15
0.04
0.11
0.03
–
40.8
4770
1.8
1800
6.62
406
11
12
TEBP–TMDS
TEBP–TMDS
7.2
8.1
108
1990
1.8
7500
6.73
21000
6.33
–
5560
1.7
13
14
15
TEBP–TMDS
TEBP–BDMSB
TEBP–BDMSB
9.0
6.1
6.7
–
45.4
7.28
205
1.9
0.04
0.11
0.32
0.03
0.22
0.04
0.03
54.3
841
1.8
3170
6.80
3505
5.73
6.30
16
TEBP–BDMSB
7.0
9300
1.5
17
18
TEBP–BDMSB
TEBP–BDMSB
8.8
13.3
1.7
a
b
Relaxation time.
Standard deviation of a peak of the ensemble-averaged relaxation
time distribution.
WWW.MATERIALSVIEWS.COM
JOURNAL OF POLYMER SCIENCE, PART A: POLYMER CHEMISTRY 2015, 53, 1360–1368
1363

JOURNAL OF
POLYMER SCIENCE
ARTICLE
WWW.POLYMERCHEMISTRY.ORG
TABLE 3 Network Structure of TEPM–TMDS, BDMSB Gels
Reaction
Rate (%)
Run
Monomer
wt %
sR 3 1026
s
a
Mesh Size (nm)
rb
19
20
TEBP–TMDS
TEPM–TMDS
10.0
12.0
–
–
–
48.2
7.38
2420
7.00
2.0
642
1.9
0.04
0.15
0.04
21
22
23
24
TEPM–TMDS
TEPM–BDMSB
TEPM–BDMSB
TEPM–BDMSB
14.0
10.0
12.0
14.0
44.9
6.81
6.74
1.8
1.8
0.03
0.03
a
b
Relaxation time.
Standard deviation of a peak of the ensemble-averaged relaxation
time distribution.
relaxation time at around 1.5 3 1024 s corresponded to the
mesh size about 40 nm, which was much larger than that of
the mesh size derived from TEB and TMDS. The structure
should be derived from microgels. The relaxation peaks at
around 1023 s, which were derived from the large size of
2500–4000 nm, were detected in the gels with the monomer
concentrations of 12.0 and 14.0 wt %. The large structure
would be the fragments of the network due to the defect in
the network. The gels generated at 16.0 wt % of monomer
concentrations showed unimodal distribution of the
ensemble-averaged relaxation time. The network structure in
the gel should occupy all the space in the gel, as previously
reported.16
homogeneous network structure as observed in the TEB–TMDS
gels, described above. The monomer concentrations, which
form the sufficient network to occupy the space in the gels,
should be necessary to form the gels with homogeneous net-
work structure.
The hydrosilylation reaction of TEBP or TEPM and TMDS or
BDMSB was also investigated with the catalyst 1 under vari-
ous monomer concentrations. The reactions of TEBP–TMDS
system of 6.3 wt % (Run 9) and TEBP–BDMSB system of 6.1
wt % (Run 14) did not form gel. The critical gelation concen-
trations of TEBP–TMDS or TEBP–BDMSB systems were about
7 wt %. The reaction conversions of ethynyl group in the
TEBP–TMDS system (6.3 wt % Run 9) or TEBP–BDMSB sys-
tem (6.1 wt % Run 5) determined by 1H NMR spectroscopy
were 49.5 or 45.4%, respectively.
Figure 2 shows the ensemble-averaged relaxation time distribu-
tions as a function of the relaxation time of TEB–BDMSB gels.
The network structure of the TEB–BDMSB gels is summarized
in Table 1. The gels obtained from the low monomer concen-
trations, 8.0 and 12.0 wt %, showed multimodality in the
ensemble-averaged relaxation time distributions. The gels with
16.0 wt % monomer concentration showed a unimodal distri-
bution of the ensemble-averaged relaxation time. Although
the reaction conversion of the TEB–BDMSB system was lower
than that of the TEB–TMDS system, the TEB–BDMSB gels with
relatively high monomer concentration formed the gels with
The mesh size and mesh size distribution of the TEBP–TMDS
and TEBP–BDMSB gels determined by SMILS are summar-
ized in Table 2. The TEBP–TMDS or -BDMSB gels with rela-
tively low monomer concentrations (less than about 8 wt %)
showed a multimodal distribution of the ensemble-averaged
relaxation time, due to the formation of imperfect network
structure. The gels with relatively high monomer concentra-
tions, more than 9 wt %, formed the homogeneous network
FIGURE 4 PL spectra of TEB–TMDS system,
kex 5 304 nm,
monomer concentration; 12.0 wt % before (i) and after (ii) gela-
tion, 16.0 wt % before (iii) and after (iv) gelation.
FIGURE 3 UV–Vis spectra of TEB–TMDS system before gelation
(i) and after gelation (ii), monomer concentration5 12.0 wt %.
1364
JOURNAL OF POLYMER SCIENCE, PART A: POLYMER CHEMISTRY 2015, 53, 1360–1368

JOURNAL OF
POLYMER SCIENCE
WWW.POLYMERCHEMISTRY.ORG
ARTICLE
spectroscopy were 48.2 or 44.9%, respectively. Although
these values were almost same with the TEBP system, the
critical gelation concentrations of the TEPM systems were
higher than those of the TEBP systems. The difference
should be derived from differences in the geometry and/or
the mobility of the tetra-ethynyl aryl compounds. Rigid struc-
ture of the crosslinking monomer is effective to decrease the
critical gelation concentration, as previously reported.16 It is
likely that the flexible structure of TEPM would prevent
form forming an infinite network structure and increase the
critical gelation concentrations in the reaction systems. The
mesh size and mesh size distribution of the TEPM–TMDS
and TEPM–BDMSB gels determined by SMILS are summar-
ized in Table 3. The resulting gels showed a unimodal distri-
bution of the ensemble-averaged relaxation time derived
from the homogeneous mesh, about 2 nm, due to the rela-
tively high monomer concentrations.
FIGURE 5 PL spectra of TEB–TMDS system,
kex 5 370 nm,
monomer concentration; 12.0 wt % before (i) and after (ii) gela-
tion, 16.0 wt % before (iii) and after (iv) gelation.
Optical Properties of the Gels
with the mesh of 1.5–1.7 nm, as observed in the TEB
systems.
Absorption spectra of TEB–TMDS system before gelation and
after gelation were collected by UV–vis spectroscopy. Figure
3 shows the UV–vis spectra of the TEB–TMDS system with
12.0 wt % of monomer concentration. The UV–vis spectra of
the reaction system before gelation showed broad absorption
ranged from 280 to 500 nm with shoulder peaks at around
304 and 370 nm derived from p–p* transition of the mono-
mers.20 After the gelation, the peaks slightly red shifted due
to the extension of conjugation length via formed Si-vinylene
units. The TEB–BDMSB system showed similar spectra
Although the TEPM–TMDS or TEPM–BDMSB systems with
10.0 wt % of monomer concentration yielded a portion of
gels, a small amount of fluid solvent was detected in the
reaction systems (Run 19 or Run 22). These reaction sys-
tems containing 12.0 or 14.0 wt % of monomers produced
the clear gels. The reaction conversions of ethynyl group in
the TEPM–TMDS system (10.0 wt % Run 19) or TEPM–
1
BDMSB system (10.0 wt % Run 22) determined by H NMR
TABLE 4 Emission Wavelength of r–p Conjugated Organic–Inorganic Hybrid Gels
kaem Before
kaem After
Run
Monomer
wt %
Excitation(nm)
Reaction (nm)
Reaction(nm)
Dkbem (nm)
P1
2
DEB–BDMSB
TEB–TMDS
12.0
12.0
376
304
370
370
304
370
304
370
370
304
370
280
280
280
280
280
280
280
280
472
475
3
362, 411
439
373, 413
442
3
8
3
4
TEB–TMDS
TEB–TMDS
14.0
16.0
442
450
363, 413
445
373, 414
454
9
6
TEB–BDMSB
8.0
349, 443
440
357, 482
458
18
22
7
8
TEB–BDMSB
TEB–BDMSB
12.0
16.0
439
461
351, 442
439
356, 486
487
48
10
12
15
18
20
21
23
24
TEBP–TMDS
TEBP–TMDS
TEBP–BDMSB
TEBP–BDMSB
TEPM–TMDS
TEPM–TMDS
TEPM–BDMSB
TEPM–BDMSB
6.9
354
356, 410
356, 407
358, 409
359, 407
358, 418
359, 424
356, 414
361, 421
8.1
6.7
356
13.3
12.0
14.0
12.0
14.0
357
353
a
b
Emission wavelength.
Red shift of emission wavelength TEB–TMDS, BDMSB gels after the
reaction exited by 370 nm.
WWW.MATERIALSVIEWS.COM
JOURNAL OF POLYMER SCIENCE, PART A: POLYMER CHEMISTRY 2015, 53, 1360–1368
1365

JOURNAL OF
POLYMER SCIENCE
ARTICLE
WWW.POLYMERCHEMISTRY.ORG
SCHEME 2 Structure of linear polymer DEB-BDMSB (P1) for
reference; Mn54000, Mw/Mn53.4.
by 304 nm showed strong emission at around 480 nm,
which was newly appeared after the gelation, as shown in
Figure 6. The emission peak could not be detected in the
TEB–TMDS gels. The emission should be derived from inter-
action between the phenyl groups of BDMSB in the network.
Chujo et al. developed through-space conjugated polymers
containing p stack structure of paracycophane units in the
polymer chain.22 These polymers showed high photo lumi-
nescence. One explanation for the emission appeared in the
TEB–BDMSB gels may be that the phenyl groups of BDMSB
form a kind of p stack structure in the high dense network
structure of the gels. The excitation of the TEB–BDMSB gels
by 370 nm generated the emission at around 458–487 nm.
The emission wavelengths remarkably red shifted
(Dkem 5 18–48 nm) in comparison with those of the reaction
systems before gelation, as shown in Figure 7.
FIGURE 6 PL spectra of TEB–BDMSB system, kex 5 304 nm,
monomer concentration; 8.0 wt % before (i) and after (ii) gela-
tion, 16.0 wt % before (iii) and after (iv) gelation.
patterns those of the TEB–TMDS system. Emission property
of the reaction systems before and after gelation was also
investigated by PL spectroscopy. Figures 4 and 5 show PL
spectra of the TEB–TMDS systems exited by 304 and
370 nm wavelengths, which were the shoulder peaks
detected in the UV–vis spectroscopy (Figure 3), respectively.
The emission wavelengths in the spectra are summarized in
Table 4. The excitation of the TEB–TMDS systems before
gelation by 304 nm wavelength generated the broad emis-
sion ranged from 320 to 600 nm with peaks at around 360
and 410 nm derived from the monomers, as shown in Figure
4. The former peak slightly red shifted (Dkem 5 3–9 nm)
after the gelation, whereas the latter peak did not change.
The excitation of the TEB–TMDS systems before gelation by
370 nm wavelength generated the emission at around
440 nm, as shown in Figure 5.21 These emission peaks in
the TEB–TMDS gels slightly red shifted (Dkem 5 2–11 nm) in
comparison with those of before gelation. Figures 6 and 7
show PL spectra of the TEB–BDMSB systems exited by
304 or 307 nm wavelengths, respectively. The TEB–BDMSB
systems before gelation, which were excited by 304 nm
wavelength, showed similar emission spectra to that of the
TEB–TMDS systems. The excitation of the TEB–BDMSB gels
The red shift of the emission wavelengths observed in the
gels should be due to the extension of conjugation length
with the r–p conjugation formed by Si-vinylene units. The
TEB–BDMSB gel showed remarkable red shift of the emis-
sion wavelength in comparison with that of the TEB–TMDS
gel. Furthermore, the red shift value (Dkem) exited by
370 nm drastically increased from 18 to 48 nm with increas-
ing of the monomer concentration from 8.0 to 16.0 wt %.
We synthesized a corresponding linear polymer by the
hydrosilylation reaction of DEB–BDMSB (P1) for a reference
(Scheme 2). The linear polymer P1 showed only a slight red
shift of the emission, Dkem 5 3 nm, in comparison with that
of the reaction system before polymerization.23 The results
indicate that the remarkable red shift in the emission spectra
FIGURE 8 Emission spectra of TEBP–TMDS system; before (i)
or after (ii) gelation: monomer concentration: 6.9 wt %, TEBP–
BDMSB system; before (iii) or after (iv) gelation: monomer con-
centration: 6.7 wt %, exited at 280 nm.
FIGURE 7 PL spectra of TEB–BDMSB system, kex 5 370 nm,
monomer concentration; 8.0 wt % before (i) and after (ii) gela-
tion, 16.0 wt % before (iii) and after (iv) gelation.
1366
JOURNAL OF POLYMER SCIENCE, PART A: POLYMER CHEMISTRY 2015, 53, 1360–1368

JOURNAL OF
POLYMER SCIENCE
WWW.POLYMERCHEMISTRY.ORG
ARTICLE
CONCLUSIONS
Synthesized from A hydrosilylation reaction of TEB, TEBP, or
TEPM with TMDS or BDSMB with Karstedt’s catalyst produced
the organic–inorganic hybrid gels composed by r–p conjuga-
tion network. The SMILS analysis of the gels cleared that the
obtained gels containing high monomer concentration formed
homogeneous network structure with 1–2 nm of mesh size.
The TEB–BDMSB gels exited by 304 nm wavelength showed
an emission at around 480 nm, which would be derived from
interaction like a p stacking between phenyl groups of BDMSB
in the gels. The TEB–TMDS, BDSMB gels which were exited by
370 nm wavelength showed blue emission ranged from 440–
490 nm due to the r–p conjugation in the network. The TEB–
BDMSB gel showed wide red shift in the emission in compari-
son with that of the reaction solution before gelation. The red
shift of the emission of the gels should due to the formation of
the two- or three-dimensional r–p conjugation network. The
TEBP–TMDS and TEBP–BDMSB gels showed similar spectra
patterns with those of the reaction solutions before gelation.
The TEPM–TMDS, BDMSB gels exited by 280 nm wavelength
showed the broad peak at around 420 nm, which should be
derived from interaction like a p stacking between phenyl
groups of TEPM in the gels. The present organic–inorganic
hybrid gels having r–p conjugation network should be useful
for the light-emitting devices, because the device can be easily
prepared by the synthesis of the gels between sandwiched
two electrodes with narrow gap. Application of the gels for a
light-emitting device is now proceeding, and the results will
be reported elsewhere.
FIGURE 9 Emission spectra of TEPM–TMDS system; before (i)
or after (ii) gelation: monomer concentration: 14.0 wt %,
TEPM–BDMSB system; before (iii) or after (iv) gelation: mono-
mer concentration: 14.0 wt %, exited at 280 nm.
of the TEB–BDMSB gels should be derived from the forma-
tion of network structure, two or three dimensional expan-
sion, by the r–p conjugation. The similar phenomenon was
previously reported in a dendrimer having a r–p conjugation
moiety.24 Increase of the monomer concentration in the
TEB–BDMSB gels would form the high dense network
structure with the small mesh size by the r–p conjugation
network, which should enhance the red shift of the emission
wavelength in the gels.
The emission property of the TEBP, TEPM, and TMDS, BDMSB
systems before and after gelation is also investigated by the
PL spectroscopy. Figure 8 shows the PL spectra of the TEBP–
TMDS and TEBP–BDMSB systems exited by 280 nm wave-
length, which is a shoulder peak detected in the UV–vis spec-
troscopy of these systems. The emission wavelengths in the
spectra are summarized in Table 4. The PL spectra of the
TEBP systems before reaction showed an emission peak at
around 356–359 nm derived from the TEBP monomer. The
TEBP–TMDS and TEBP–BDMSB gels showed similar spectra
patterns with those of the reaction solutions before gelation.
Figure 2 shows the PL spectra of the TEPM–TMDS and
TEPM–BDMSB systems exited by 280 nm wavelength, which
is a shoulder peak detected in the UV–vis spectroscopy of
these systems. The emission wavelengths in the spectra are
summarized in Table 4. Both the TEPM–TMDS and TEPM–
BDMSB gels showed the emission at around 360 nm derived
from the TEPM monomer. Broad emission peaks newly
appeared at around 420 nm after the gelation. The peaks
were not observed in the TEPM monomer [Fig. 2(i,iii)] and
TEBP systems gels (Fig. 8). The broad peaks appeared in the
TEPM gels would be derived from a kind of p stacking inter-
action between the phenyl groups of TEPM in the gels, as
observed in the TEB–BDMSB gels described above. TEPM has
four phenyl groups per one molecule in three-dimensional
structure with flexibility. The chemical structure and/or steric
structure of TEPM should induce effective interaction between
the phenyl groups in the network structure of the gels.
REFERENCES AND NOTES
1 K. S. Santhanam, A. J. Bard, J. Am. Chem. Soc. 1965, 87,
139–140.
2 H. A. Brilmyer, J. Bard, J. Electroanal. Chem. Soc. 1980, 127,
104–110.
3 J. Kim, L. R. Faulkner, J. Am. Chem. Soc. 1988, 110, 112–119.
4 J. Kim, L. R. Faulkner, J. Electroanal. Chem. 1988, 242, 107–121.
5 A. Kapturkiewicz, J. Electroanal. Chem. 1991, 302, 131–144.
6 H. Schaper, H. Kostlin, E. Schnedler, J. Electrochem. Soc.
1982, 129, 1289–1294.
7 D. M. Hercules, R. C. Lansbury, D. K. Roe, J. Am. Chem. Soc.
1966, 88, 4578–4583.
8 K. Nishimura, Y. Hamada, T. Tsujioka, S. Matsuta, K. Shibata,
T. Fuyuki, Jpn J. Appl. Phys. 2001, 40, L1323–L1326.
9 S. C. Chang, Y. Yang, Q. Pei, Appl. Phys. Lett. 1999, 74, 2081–2083.
10 S. C. Chang, Y. Li, Y. Yang, J. Phys. Chem. B 2000, 104,
11650–11655.
11 S. C. Chang, Y. Yang, F. Wudl, G. He, Y. Li, J. Phys. Chem.
B 2001, 105, 11419–11423.
12 S. C. Chang, Y. Yang, Appl. Phys. Lett. 1999, 75, 2713–2715.
13 Y. Hamada, T. Tsujioka, K. Nishimura (SANYO Electric Co.,
Ltd.,
Japan),
Electrochemiluminescent
material,
WO
2002066885-A1.
14 M. Yukawa (Semiconductor Energy Laboratory Co., Ltd.),
Light-emitting device, light-emitting apparatus, electronic
device and production of light-emitting device, JP2006-11403A
20 UV-vis and PL spectra of the monomers are available in the
Supporting Information (Figures S1–S3).
WWW.MATERIALSVIEWS.COM
JOURNAL OF POLYMER SCIENCE, PART A: POLYMER CHEMISTRY 2015, 53, 1360–1368
1367

JOURNAL OF
POLYMER SCIENCE
ARTICLE
WWW.POLYMERCHEMISTRY.ORG
15 N. Naga, N. Tagaya, H. Noda, T. Imai, H. Tomoda, J. Polym.
Sci., Part A Polym. Chem. 2008, 46, 4513–4521.
20 UV–vis and PL spectra of the monomers are available in the
Supporting Information.
16 N. Naga, E. Oda, A. Toyota, K. Horie, H. Furukawa, Macro-
mol. Chem. Phys. 2006, 207, 627–635.
21 Photos of TEB-TMDS gel are available in the Supporting
Information (Figure S4).
17 U. M. Wiesler, A. J. Berresheim, F. Morgenroth, G. Lieser, K.
22 Y. Morisaki, Y. Chujo, Angew. Chem. Int. Ed. 2006, 45, 6430–6437.
€
Mullen, Macromolecules 2001, 34, 187–199.
23 PL spectra of DEB-BDMSB system before and after polymer-
18 H. Furukawa, K. Horie, R. Nozaki, M. Okada, Phys. Rev. E
2003, 68, 031406–1.
ization are available in Supporting Information (Figure S5).
€
24 J. Kiu, R. Zheng, T. Matthias, Y. Tang, M. Haussler, J. W. Y.
19 H. Furukawa, M. Kobayashi, Y. Miyashita, K. Horie, High
Perform. Polym. 2006, 18, 837–847.
Lam, A. Qin, M. Ye, Y. Hong, P. Gao, B. Z. Tang, Macromole-
cules 2007, 40, 7473–7486.
1368
JOURNAL OF POLYMER SCIENCE, PART A: POLYMER CHEMISTRY 2015, 53, 1360–1368