close

Вход

Забыли?

вход по аккаунту

?

Preparation and properties of polyhedral oligomeric silsesquioxane polymers.

код для вставкиСкачать
Full Paper
Received: 29 April 2011
Revised: 2 June 2011
Accepted: 3 June 2011
Published online in Wiley Online Library: 10 August 2011
(wileyonlinelibrary.com) DOI 10.1002/aoc.1820
Preparation and properties of polyhedral
oligomeric silsesquioxane polymers
Takahiro Shiodaa , Takahiro Gunjia∗ , Noritaka Abea and Yoshimoto Abeb
Polyhedral oligomeric silsesquioxane (POSS) polymers were synthesized by the dehydrogenative condensation of (HSiO3/2 )8
with water in the presence of diethylhydroxylamine followed by trimethylsilylation. Coating films were prepared by spin-coating
of the coating solution prepared by the dehydrogenative condensation of POSS. The hardness of the coating films was evaluated
using a pencil-hardness test and was found to increase up to 8H with increases in the curing temperature. Free-standing film
and silica gel powder were prepared by aging the coating solution at room temperature. The silica gel powder was subjected
to heat treatment under air atmosphere to show a specific surface area of 440 m2 g−1 at 100 ◦ C, which showed a maximum at
c 2011 John Wiley & Sons, Ltd.
400 ◦ C as 550 m2 g−1 . Copyright Keywords: polyhedral oligomeric silsesquioxane; diethylhydroxylamine; dehydrogenative condensation; silica gel; free-standing film
Introduction
Appl. Organometal. Chem. 2011, 25, 661–664
Experimental
Reagents and Substrate
(HSiO3/2 )8 was synthesized by a previously described method.[20]
Other chemicals were of reagent grade or higher and purified
according to standard protocols.
Synthesis of W-POSS
In a 200 ml two-necked flask with a reflux condenser were
placed (HSiO3/2 )8 (300 mg, 710 µmol), water (0.026 g, 1.4 mmol),
tetrahydrofuran (THF; 30 ml) and benzene (40 ml) under a nitrogen
atmosphere. To this solution was added N,N-diethylhydroxylamine
(1.0 µl, 9.7 µmol), and the mixture was stirred at 0 ◦ C for 90 min.
Chloro(trimethyl)silane (0.92 g, 8.5 mmol) was added, and the
mixture was stirred at room temperature for 30 min followed by the
∗
Correspondence to: Takahiro Gunji, Department of Pure and Applied Chemistry,
Faculty of Science and Technology, Tokyo University of Science, Tokyo, Japan.
E-mail: gunji@rs.noda.tus.ac.jp
a Department of Pure and Applied Chemistry, Faculty of Science and Technology,
Tokyo University of Science, Tokyo, Japan
b Department of Food Science, Faculty of Health and Nutrition, Tokyo Seiei
College, Tokyo, Japan
c 2011 John Wiley & Sons, Ltd.
Copyright 661
Polysilsesquioxanes are polysiloxanes consisting of the structure
unit (RSiO3/2 )n . They are classified into three groups: amorphous,
cage-type and ladder-structured polysilsesquioxanes. Among
these polymers, cage-type polysilsesquioxanes have attracted
considerable attention from the perspective of synthesis and
application owing to their nano-sized three-dimensional structure
consisting of a silica backbone, an angstrom-sized cavity and high
thermal stability.[1 – 13]
Polyhedral oligomeric silsesquioxanes (POSS) are the bestknown and most useful polysiloxanes and have the formula
(RSiO3/2 )8 . Since POSS have a pore at the center of the molecule and
are composed of 12 Si–O–Si bonds to form a rigid structure, POSS
are potential candidates for providing functional nano-building
blocks that can be used to form micro- or mesoporous silica.
The organic/inorganic hybrids are prepared by introducing POSS
moiety into organic polymers. Hydrosilylation of (HSiO3/2 )8 with
the corresponding olefins is the simplest and most widely used
technique to connect POSS moieties with organic polymer chains
by chemical bonding. Such organic/inorganic hybrids are also prepared by the reaction of carbo-functional groups on silicon atoms,
for example the polymerization of methacryloyloxy groups for the
compound octakis(methacryloyloxypropyl)octasilsesquioxane.
On the other hand, the preparation of siloxane-based hybrids has
been insufficiently investigated owing to the difficulty of synthesizing sila-functionalized POSS derivatives through conventional
means: mesoporous silica materials have been prepared by the
hydrolytic polycondensation of {[(EtO)3−n Men SiO]SiO3/2 }8 in the
presence of polymer surfactants.[14] Films with heat-resistivity
and easily modulated films with high heat resistance have been
prepared by the reaction of (PhSiO3/2 )8 [(HO)PhSiO]2 with chloroterminated polydimethylsiloxane.[15] Preparation of porous silica
or Si–C–O ceramic material was reported by simple pyrolysis of
POSS without a precise investigation of its precursor polymer.[16]
We have reported the dehydrogenative reaction of alcohol
with (HSiO3/2 )8 in the presence of diethylhydroxylamine to
produce octaalkoxylated octasilsesquioxanes.[17] This reaction
was applied to the synthesis of siloxane-based POSS hybrids
by the dehydrogenative reaction of (HSiO3/2 )8 with silanols
such as diphenylsilanol, tetraphenyldisiloxanediol and α, ωdihydroxypolydimethylsiloxanes[18] to show a relatively high heat
resistivity and high surface area on heating. In the same way, POSS
polymer (W-POSS) was synthesized by the reaction of (HSiO3/2 )8
with water in the presence of diethylhydroxylamine, which was
briefly reported as a short communication.[19]
In this paper, therefore, the synthesis of W-POSS according to
Scheme 1 and its thermal and mechanical properties are reported.
In particular, the preparation and properties of W-POSS coating
films and silica gels are presented in detail.
T. Shioda et al.
Scheme 1. Schematic figure for the synthesis of W-POSS.
addition of triethylamine (0.86 g, 8.5 mmol). After the mixture was
refluxed for 2 h, the solvents were removed on a rotary evaporator.
The residue was extracted with THF (20 ml), filtered and poured
into methanol to give a white powder (111 mg, 34%) of W-POSS.
Preparation of Coating Films
In a 200 ml two-necked flask with a reflux condenser were placed
(HSiO3/2 )8 (300 mg, 710 µmol), water (0.026 g, 1.4 mmol), THF
(30 ml) and benzene (30 ml) under a nitrogen atmosphere. To this
solution was added N,N-diethylhydroxylamine (1.0 µl, 9.7 µmol),
and the mixture was stirred at 0 ◦ C for 90 min. The solvents were
removed on a rotary evaporator and the residue was diluted
with THF to 10 wt%. To this solution, water (10 µg) and N,Ndiethylhydroxylamine (10 µl) were added and this solution was
stirred at 0 ◦ C for 30 min.
Coating films were prepared by spin-coating on a silicon wafer
(30 s, 2000 rpm) followed by heating in an electrical furnace for
1 h under air atmosphere at 100–800 ◦ C.
Preparation of Free-standing Films
In a 200 ml two-necked flask with a reflux condenser were placed
(HSiO3/2 )8 (300 mg, 710 µmol), water (0.026 g, 1.4 mmol), THF
(30 ml) and benzene (30 ml) under a nitrogen atmosphere. To this
solution was added N,N-diethylhydroxylamine (1.0 µl, 9.7 µmol),
and the mixture was stirred at 0 ◦ C for 90 min. The solvents were
removed on a rotary evaporator and the residue was diluted
with THF to 10 wt%. To this solution, water (10 µg) and N,Ndiethylhydroxylamine (10 µl) were added and this solution was
stirred at 0 ◦ C for 30 min.
The process above was repeated 10 times and the solution
was collected. This solution was poured into a sharle made from
polymethylpentane and subjected to aging at room temperature
for several days to evaporate solvent.
Measurements
662
Gel permeation chromatography was carried out by Shimadzu
LD-10AD with two Polymer Laboratory Mixed-D 250 × 20 mm
columns and a refractive index detector. THF was used as an
eluent. Molecular weights were calculated based on standard
polystyrene.
The 29 Si NMR spectra were recorded using a Jeol ECP-500 (29 Si
at 99 MHz) spectrometer. Chemical shifts were reported as δ units
(ppm) relative to SiMe4 .
The Fourier transform infrared (FTIR) spectra were measured
using a Jasco FT/IR-6100 IR spectrophotometer using the KBr disk
wileyonlinelibrary.com/journal/aoc
method or CCl4 solution method. Differential thermogravimetric
analysis (TG-DTA) was performed using MAC Science TG-DTA2020S
under an air atmosphere.
BET surface area was measured using a Shimadzu Gemini 2360.
Samples were degassed by heating under an nitrogen atmosphere
to 100 ◦ C for 1 h and then cooling to room temperature before
measurement.
The pencil-hardness was tested using a Yasuda Seiki Seisakusho
electric system pencil hardness tester no. 533-M1 according to
Japanese Industrial Standard JIS-K5400. The hardness was evaluated in the increasing order of 6B, 5B, 4B, 3B, 2B, B, HB, F, H, 2H, 3H,
4H, 5H, 6H, 7H, 8H and 9H using the Mitsubishi Pencil Uni series.
Results and Discussion
Results of the Synthesis of W-POSS
The results of the synthesis of W-POSS are summarized in
Table 1. W-POSS was synthesized by the same procedure by
changing the molar ratio of water to (HSiO3/2 )8 to 1, 2 or 4
followed by the end-capping of the terminal hydroxy groups
with chloro(trimethyl)silane. The progress of the dehydrogenative
reaction was monitored by the evolution of hydrogen gas when
diethylhydroxylamine was added to the system. W-POSS was
isolated as a white gel or solid by reprecipitation from methanol.
White gel was recovered when the molar ratio of water to
(HSiO3/2 )8 was 1. When the molar ratio of water to (HSiO3/2 )8
was 2, the yield of W-POSS was 34% and the weight-averaged
Table 1. Results of the preparation of W-POSSa)
Molecular weight by GPCb)
Molar ratio of
water/POSS
1
2
4
Yield/%
Mw
Mw /Mn
Td5 c)
– d)
34
42
–
29,000
15,000
–
2.0
1.9
–
512
539
a)
Scale in operation: POSS 0.30 g (0.71 mmol), THF 30 mL, benzene
40 mL, diethylhydroxylamine (8 µL, 80 µmol). Time: 2 h. Temp.: r.t.
Silylation: chloro(trimethyl)silane (7.1 mmol, 14 mmol), triethylamine
(7.1 mmol, 14 mmol). Time: 1 h. Temp: r.t.
b) Calculated based on standard polystyrene.
c) Temperature of the 5% weight loss. Measured by thermogravimetry;
10 ◦ C/min, under air atmosphere.
d) State: gel.
c 2011 John Wiley & Sons, Ltd.
Copyright Appl. Organometal. Chem. 2011, 25, 661–664
Polyhedral oligomeric silsesquioxane polymers
Figure 1. FTIR spectrum of W-POSS.
Figure 2. 29 Si NMR spectrum of W-POSS.
Figure 3. FTIR spectra of W-POSS silica gels on heat treatment.
molecular weight (Mw ) was 29 000. The yield was 42% and Mw was
15 000 when the molar ratio was 4. W-POSS solids were soluble
in THF, diethyl ether, chloroform, carbon tetrachloride, benzene,
acetone and hexane, and insoluble in methanol.
The 5% mass loss temperatures (Td5 ) and ceramic yield were
determined by thermogravimetric analysis. When the molar ratio
of water to (HSiO3/2 )8 was 2, Td5 was 512 ◦ C and the ceramic yield
at 1000 ◦ C was 90%; they were 539 ◦ C and 90%, respectively, when
the molar ratio of water to (HSiO3/2 )8 was 4. The relatively high Td5
shows the high thermal stability of W-POSS. The weight loss mainly
stems from the combustion of the trimethylsilyl group in W-POSS.
The FTIR spectrum of W-POSS is shown in Fig. 1. Signals from
νC – H (ca. 3000 cm−1 ), νSi – H (2300 cm−1 ), νSi – O – Si (ca. 1100 cm−1 )
and νO – Si – O (ca. 450 cm−1 ) were observed, while the absorption
peak owing to the hydroxy group was not observed. The
appearance of νC – H supports the formation of hydroxy group and
the following trimethylsilylation. The remaining νSi – H suggests
that all of the hydrosilyl groups are not reacted with water.
The 29 Si NMR spectrum of W-POSS is shown in Fig. 2. The signals
at around 12, −83 and −109 ppm were assigned to the Me3 SiO
(M), HSiO3 (T) and SiO4 (Q) units, respectively. The appearance
of the signal owing to the Q unit supports the progress of the
dehydrogenative reaction to form a siloxane network, while the
signal owing to the T unit suggests the presence of a remaining
hydrosilyl group in W-POSS. The peak areas of M, T and Q signals
were calculated to be 22, 33 and 45%, respectively, when the
molar ratio of water to (HSiO3/2 )8 was 2. The composition of
(HSiO3/2 )8 and water in W-POSS was calculated to be 1 : 1.18,
which suggests that (HSiO3/2 )8 reacts as difunctional monomer
to form a pseudo-linear polymer of W-POSS. The composition of
(HSiO3/2 )8 and water was increased to 1 : 1.53 when the molar
ratio of water to (HSiO3/2 )8 was increased to 4. Although we
expected there to be complete consumption of the hydrosilyl
groups in (HSiO3/2 )8 by water, the Mw decreased with increasing
the molar ratio of water. The reaction between the hydrosilyl
groups and water probably became less favorable in response
to increasing steric hindrance owing to the (HSiO3/2 )8 moiety. In
addition, the reaction between two silanols is not favored in the
presence of diethylhydroxylamine to decrease Mw .
Coating films were prepared using the reaction mixture of
(HSiO3/2 )8 with water. Therefore, unreacted or remaining water
would contribute to the formation of the films. Starting from
the (HSiO3/2 )8 –water systems, transparent coating films were
prepared with a sub-micrometer thickness.
The pencil-hardness of coating films was evaluated by pencilhardness tests. The pencil-hardness changed in the order of <6B,
<6B, 4B, HB, 5H, 7H, and 8H by heating at 100, 200, 300, 400,
500, 600 and 700 ◦ C, respectively. The FTIR spectra of coating film
are shown in Fig. 3. After heating at 100 ◦ C, some characteristic
absorption bands were observed owing to νCH , νSiH and νSi – O – Si .
The absorption band owing to νSiOH disappeared, and the intensity
of the absorption band owing to νSiH was decreased after heating
at 300 ◦ C. The absorption bands from νCH and νSiH disappeared,
and a weak absorption band from δSi – O – Si appeared at 500 ◦ C.
The absorption band from νSiOH appeared again, and the intensity
of the absorption band owing to δSiOSi was increased at 600 ◦ C.
These spectral changes correspond to the pencil-hardness of the
coating films, which is based on the thermal behavior of functional
groups: the increase in the pencil hardness can be ascribed to the
oxidation and condensation of hydrosilyl groups to form siloxane
networks, consistent with the formation of silanol groups and
siloxane bondings between 400 and 500 ◦ C.
c 2011 John Wiley & Sons, Ltd.
Copyright wileyonlinelibrary.com/journal/aoc
663
Appl. Organometal. Chem. 2011, 25, 661–664
Results of the Preparation of Films and Silica Gels,
and Free-standing Film
T. Shioda et al.
The isotherm was type I. The pore size was mainly distributed less
than 2 nm, indicating that W-POSS is a microporous material.
Free-standing films of W-POSS were prepared successfully as
shown in Fig. 6. The films were highly transparent and rigid. The
film had a large BET surface area of 480 m2 g−1 , comparable to
those of calcined powder of W-POSS.
Conclusions
Figure 4. Nitrogen adsorption–desorption isotherm of W-POSS, calcined
at 400 ◦ C.
POSS polymer, W-POSS, was synthesized by the dehydrogenative
condensation reaction of (HSiO3/2 )8 with water in the presence
of diethylhydroxylamine followed by trimethylsilylation. The
progress of the dehydrogenative reaction was confirmed by
infrared spectroscopy and 29 Si nuclear magnetic resonance of the
polymers.
Coating films were prepared by spin-coating of the polymer
solutions, which were prepared by the dehydrogenative condensation of (HSiO3/2 )8 with water. The hardness of the coating films
was evaluated by a scratch test, with the hardness increasing to 8H
with increased sintering temperature. In addition, silica gels were
prepared by sintering the products prepared by concentrating the
coating solution. These silica gels showed a relatively high surface
area even at 100 ◦ C, then a maximum surface area at 400 ◦ C. The
surface area trend upon sintering showed good agreement with
the formation of siloxane networks in response to oxidation of
hydrosilyl groups and the formation of a dense silica network on
heating.
References
Figure 5. Pore size distribution of W-POSS, calcined at 400 ◦ C.
Figure 6. Photograph of the free-standing film of W-POSS.
664
Silica gels were prepared by drying and heating the coating
solutions. The BET surface areas were 470 m2 g−1 at 100 ◦ C,
470 m2 g−1 at 200 ◦ C, 550 m2 g−1 at 400 ◦ C, 510 m2 g−1 at 650 ◦ C,
and 280 m2 g−1 sintered at 800 ◦ C. The maximum was observed at
400 ◦ C. On heating at 400 ◦ C, a stiff silica network was formed by the
oxidative condensation of hydrosilyl group, which resulted in the
formation of porous silica gels. When the silica gels were sintered at
800 ◦ C, this probably allowed the newly formed siloxane bridges
to be densified and form a dense silica network. The nitrogen
adsorption–desorption isotherm and pore size distribution of WPOSS, calcined at 400 ◦ C, are shown in Figs 4 and 5, respectively.
wileyonlinelibrary.com/journal/aoc
[1] J. D. Lichtenhan, Comm. Inorg. Chem. 1995, 17, 115.
[2] J. J. Schwab, J. D. Lichtenhan, Appl. Organometal. Chem. 1998, 12,
707.
[3] C. Marcolli, G. Calzaferri, Appl. Organometal. Chem. 1999, 13, 213.
[4] F. J. Feher, R. Terroba, R. -Z. Jin, K. D. Wyndham, S. Lucke, R. Brutchey,
F. Nguyen, Polym. Mat. Sci. Eng. 2000, 82, 301.
[5] F. J. Feher, R. Terroba, R. -Z. Jin, S. Lucker, F. Nguyen, R. Brutchey, K. D.
Wyndham, Organic/Inorganic Hybrid Materials. Materials Research
Society Symposium Proceedings Vol. 628 (Ed.: R. M. Laine), MRS:
Warrendale, PA, 2001, p. CC2.1.1.
[6] G. Li, L. Wang, H. Ni, C. U. Pittman Jr. J. Inorg. Organometal. Polym.
2002, 11, 123.
[7] J. Pyun, J. Xia, K. Matyjaszewski, Synthesis and Properties of Silicones
and Silicone-Modified Materials. ACS Symposium Series Vol. 838 (Eds.:
S. J. Clarson, J. J. Fitzgerald, M. J. Owen, S. D. Smith, M. E. Van Dyke),
ACS: Washington, DC, 2003, 273.
[8] K. Kobata, Konbatekku 2003, 31, 52.
[9] R. M. Laine, J. Mat. Chem. 2005, 15, 3725.
[10] G. Li, C. U. Pittman Jr, Group IVA Polymers. Macromolecules Containing Metal and Metal-Like Elements, Vol. 4 (Eds.: A. S. Abd-El-Aziz,
C. E. Carraher Jr, C. U. Pittman Jr, M. Zeldin), John and Wiley Sons:
Chichester, 2005, 79.
[11] K. Pielichowski, J. Njuguna, B. Janowski, J. Pielichowski, Supramolecular Polymers, Polymeric Betains, Oligomers. Advances in Polymer
Science, Vol. 201, Springer: Berlin, 2006, 225.
[12] Y. Abe, T. Gunji, Shikizai Kyokaishi 2007, 80, 458.
[13] Y. Abe, T. Gunji, Prog. Polym. Chem. 2004, 29, 149.
[14] Y. Hagiwara, A. Shimojima, K. Kuroda, Chem. Mater. 2008, 20, 1147.
[15] S. Chinen, Y. Murakami, M. Sakata, K. Sakai, T. Ooba, K. Watanabe,
M. Kunitake, Polym. Prepr Jpn. 2006, 55, 2597.
[16] N. Ueda, T. Gunji, Y. Abe, Mater. Technol. 2008, 26, 162.
[17] P. A. Agaskar, J. Chem. Soc., Chem. Commun., 1992, 1024.
[18] T. Gunji, T. Shioda, K. Tsuchihira, H. Seki, T. Kajiwara, Y. Abe, Appl.
Organometal. Chem., 2010, 24, 545.
[19] T. Kajiwara, T. Shioda, Y. Abe, T. Gunji, World J. Eng., 2009, 6, 451.
[20] C. L. Frye, W. T. Collins, J. Am. Chem. Soc., 1970, 92, 5586.
c 2011 John Wiley & Sons, Ltd.
Copyright Appl. Organometal. Chem. 2011, 25, 661–664
Документ
Категория
Без категории
Просмотров
5
Размер файла
199 Кб
Теги
polymer, preparation, polyhedra, silsesquioxane, properties, oligomer
1/--страниц
Пожаловаться на содержимое документа