Novel fluorene-based biphenolic monomer: 9,9-Bis(4-hydroxyphenyl)-9- silafluorene

Article abstract of DOI:10.1246/cl.2007.1138

A 9-silafluorene-containing biphenolic monomer, 9,9-bis(4hydroxyphenyl)-9- silafluorene, was prepared from 9,9-dichloro9-silafluorene and employed for the synthesis of polyesters using a fluorene-based homoditopic acid chloride. Some properties of the pol

Full text of DOI:10.1246/cl.2007.1138

1138
Chemistry Letters Vol.36, No.9 (2007)
Novel Fluorene-based Biphenolic Monomer: 9,9-Bis(4-hydroxyphenyl)-9-silafluorene
Surasak Seesukphronrarak and Toshikazu Takataꢀ
Department of Organic and Polymeric Materials, Tokyo Institute of Technology,
Ookayama, Meguro-ku, Tokyo 152-8552
(Received June 4, 2007; CL-070601; E-mail: takata.t.ab@m.titech.ac.jp)
A 9-silafluorene-containing biphenolic monomer, 9,9-bis(4-
hydroxyphenyl)-9-silafluorene, was prepared from 9,9-dichloro-
9-silafluorene and employed for the synthesis of polyesters using
a fluorene-based homoditopic acid chloride. Some properties of
the polyesters were examined.
a
HO
d
OH
b
b
a
Si
c
f
d
e
c
e
f
3
HO
OH
Fluorene-containing polymers, especially 9,9-diarylfluorene
group-containing polymers, have recently collect much atten-
tion1 because of their attractive properties coming from the so-
called cardo structure which consists of rectangular two aromat-
ic groups including the fluorene plane. The cardo structure
often contributes to a variety of excellent properties such as high
solubility, high refractive index, low birefringence, and high
affinity toward carbon fillers enabling the fine dispersion into
composite materials.2 We reported the synthesis and unique
properties of 9,9-diarylfluorene-containing polythioethers and
polyethers accumpanied with excellent optical, physical, and/
or chemical properties.3 Recently, we have designed a silicon-
modified 9,9-diarylfluorene monomer, 9,9-bis(4-hydroxyphen-
yl)-9-silafluorene (3), in order to endow some characteristic
properties of silicon-containing polymers to fluorene-based
polymers, such as high thermal stability, oxidation stability,
low glass-transition temperature, and flame retardant.4 This pa-
per describes the synthesis of a novel fluorene-based biphenolic
monomer 3 possessing a silicon atom attached to four aromatic
nuclei, which was used for the preparation of fluorene-rich poly-
esters (FPEs).
C
4
8
7.8
7.6
7.4
7.2
7
6.8
6.6
6.4
Figure 1. Partial 1H NMR spectra of 3 (top) and its carbon
analog 4 (bottom) for comparison (400 MHz, CD3OD, 298 K).
(5) by the interfacial polycondensation in dichloromethane–
water in the presence of benzyltriethylammonium chloride
(BTEAC) as a phase-transfer catalyst and sodium hydroxide as
a base (Scheme 2). Non-silicon-containing polymer FPE5 was
similarly obtained from 4 and 5. The results are summarized
in Table 1.
Although Mw of FPE1, a homopolymer, was less than
10,000, Mw of the copolyesters FPEs2–4 was sufficiently high
(47,600–60,300) with polydispersity ranging from 2.1 to 2.7,
depending slightly on the monomer feed ratio of 3 and 4. The
compositions of copolymers FPE2–4 determined from 1H NMR
integral ratio revealed that 3 was less reactive than the corre-
sponding carbon analogue 4.
The structures of FPEs were confirmed by 1H NMR and IR
spectra. The IR spectra of FPEs showed the characteristic ab-
sorptions around 1730 and 1220 cmꢁ1 which corresponded to
the vibrational stretchings of the ester bond, while the absorption
of the aromatic rings appeared around 1600 cmꢁ1 1H NMR
.
spectra of FPEs also supported the polymer structures: all aro-
2,20-Dibromobiphenyl 1 was treated with n-BuLi and
successively with an ethereal solution of SiCl4 at ꢁ100 ꢂC to
give 9,9-dichloro-9-silafluorene (2) in 44% yield. Biphenlic
monomer 3 was prepared by the reaction of 2 with lithium 4-
lithiophenolate at ꢁ78 ꢂC (Scheme 1).5 By the purification by
column chromatography, 3 was isolated as pale yellow solid
in 60% yield.
The chemical structure of 3 was fully confirmed by FT-IR,
1H, 13C, 29Si NMR, and mass spectra, in addition to elemental
1
analysis.6 Figure 1 shows the partial H NMR spectrum which
HO
OH
HO
OH
is well consistent with the structure of 3. Namely, each aromatic
signal was assignable as indicated in the spectrum where typical
down field shift was confirmed in protons b and c of 3 in
comparison with those of its carbon analog 4.
O
O
Cl
Si
Cl
5
4
3
A series of silicon-containing homo (FPE1) and copolyest-
ers (FPE2–4) were synthesized from 3, 4, and fluorene-contain-
ing acid chloride 9,9-dimethyl-2,7-bis(chlorocarbonyl)fluorene
BTEAC
NaOH
CH2Cl2-H2O
O
HO
OH
O
O
O
Cl
O
O
O
O
O
LiO
Li
Cl
1. n-BuLi, -100 °C
Si
Si
2. SiCl4
Br
-78°C
Si
Br
y
x
1
2
3
Scheme 1.
Scheme 2.
Copyright Ó 2007 The Chemical Society of Japan

Chemistry Letters Vol.36, No.9 (2007)
1139
Table 1. Synthesis of homo and copolyesters FPEs
the key position of the fluorene skeleton actually induced some
specific properties such as the oxidation stability. The
potential utility of this new monomer will be clarified by
successive studies on the synthesis of polymers and evaluation
of their properties.
Intensity in
copolymera
Molecular
weightb
Feed
Yield
/%
Entry Polymer
Mw
3/4
3/4
Mw=Mn
ꢃ104
1
2
3
4
5
6
FPE1
FPE2
FPE3
FPE4
FPE5
100/0
75/25
50/50
25/75
0/100
—
65/35
40/60
18/82
—
75
85
85
82
92
78
0.84
4.79
6.03
4.76
5.10
2.84
2.3
2.6
2.7
2.2
2.1
2.8
References and Notes
1
a) X. Y. Shang, D. Shu, S. J. Wang, M. Xiao, Y. Z. Meng,
J. Membrane. Sci. 2007, 291, 140. b) R. S. Ashraf, H. Hoppe,
M. Shahid, G. Gobsch, S. Sensfuss, E. Klemm, J. Polym. Sci.,
Part A: Polym. Chem. 2006, 44, 6952. c) G. Klarner, J.-I.
¨
FPE1c 100/0
—
Lee, V. Y. Lee, E. Chan, J.-P. Chen, A. Nelson, D. Markiewicz,
R. Siemens, J. C. Scott, R. D. Miller, Chem. Mater. 1999, 11,
1800.
aDetermined by 1H NMR. bGel-permeation chromatography (GPC)
data based on polystryrene standard (eluent: chloroform). cThe poly-
condensation of 3 and 5 was carried out at 185 ꢂC in diphenyl ether
for 2 h.
2
a) S. Setayesh, A. C. Grimsdale, T. Weil, V. Enkelmann, K.
Mullen, F. Meghdadi, E. J. W. List, G. Leising, J. Am. Chem.
¨
Soc. 2001, 123, 946. b) T. Inada, H. Masunaga, S. Kawasaki,
M. Yamada, K. Kobori, K. Sakurai, Chem. Lett. 2005, 34,
524. c) K. Sakurai, M. Fuji, Polym. J. 2000, 32, 676. d) S.
Kawasaki, M. Yamada, K. Kobori, T. Kakumoto, F. Jin, A.
Tarutani, T. Takata, Polym. J. 2007, 39, 115.
a) S. Seesukphronrarak, T. Takata, J. Polym. Sci., Part A:
Polym. Chem., 2007, 37, 0000. b) S. Kawasaki, M. Yamada,
K. Kobori, F. Jin, Y. Kondo, H. Hayashi, Y. Suzuki, T. Takata,
Macromolecules, in press.
Table 2. Thermal properties of FPEs
b
a
Atmosphere: N2
/ꢂC Td5 Td10 Chard/% Td5 Td10 Char/%
Atmosphere: Airb
Tg
Polymer
3
4
FPE1
FPE2
FPE3
FPE4
FPE5
NDc 469 503
55
61
59
53
46
437 493
422 443
442 462
443 464
452 476
25
21
15
14
ND
ND
ND
474 487
482 498
490 502
´
a) L. A. Mercado, M. Galia, J. A. Reina, Polym. Degrad. Stab.
2006, 91, 2588. b) C. Hamciuc, E. Hamciuc, T. Pakula, L.
Okrasa, J. Appl. Polym. Sci. 2006, 102, 3062. c) M. Bruma,
B. Schulz, J. Macromol. Sci. 2001, C41, 1.
W. Davidsohn, B. R. Laliberte, C. M. Goddard, M. C. Henry,
J. Organometal. Chem. 1972, 36, 283.
217 502 515
0.7
aDSC measurement was conducted at a heating rate 10 ꢂC/min.
bMeasured by TGA was carried out at a heating rate of 10 ꢂC/min.
5
6
c
cND: Not detected. Char yield (wt %) at 800 ꢂC.
A dry THF solution (134 mL) of p-bromophenol (9.7 g,
50 mmol) was added slowly under argon atmosphere at
ꢁ78 ꢂC to a hexane solution of n-BuLi (70.4 mL, 1.5 M,
0.100 mol). The mixture was warmed up to þ5 ꢂC and stirred
at that temperature for 1 h. To the mixture cooled to ꢁ50 ꢂC
was added a dry THF solution of 2 (0.015 mol, 15 mL). The
mixture was warmed up to þ10 ꢂC and stirred for 1 h. Then,
the mixture was hydrolyzed by adding 5% HCl until obtaining
a yellow solution. The resulting mixture was evaporated and the
residue was dissolved in diethyl ether, washed with water,
concentrated, dried, filtered, and evaporated to dryness. The
residue was triturated with dry pentane for 20 min. The crude
product obtained by decantation of pentane was chromato-
graphed on silica gel with chloroform/ethyl acetate (1:1) as
eluent to give 3 as semi-solid (3.15 g, 60%). Mp 103–105 ꢂC;
IR (KBr, cmꢁ1): 825, 1176, 1501, 1595, 3348. 29Si NMR
(CD3OD, 60 MHz) ꢀ ꢁ 11:6 ppm. 1H NMR (CD3OD, 400
MHz) ꢀ 7.81 (d, J ¼ 8 Hz, 2H), 7.59 (d, J ¼ 8 Hz, 2H), 7.34
(m, 2H), 7.30 (d, J ¼ 8:5 Hz, 4H), 7.18 (m, 2H), 6.67 (d,
J ¼ 8:5 Hz, 4H). 13C NMR (CD3OD, 100 MHz) ꢀ 115.3,
121.1, 123.7, 127.7, 130.5, 133.8, 136.5, 137.3, 148.0, 157.3.
MALDI-TOF-MS (m=z): Calcd for C24H18O2Si 366.46, Found
366.90. Anal. Calcd for C24H18O2Si: C, 78.65; H, 4.95%;
Found: C, 78.40; H, 5.01%.
matic signals appeared at similar chemical shifts to those of the
monomers, although the signals were broadened.7
Thermal property of FPEs was evaluated by means of
thermogravimetric analysis (TGA) and differential scanning
calorimetry analysis (DSC). All FPEs showed almost similar
thermal degradation behavior. As summarized in Table 2, FPEs
had good thermal stability with an onset of degradation temper-
ature consistently higher than 460 and 420 ꢂC in nitrogen and air
atmosphere, respectively. The 10% weight loss temperature was
in a range of 487–515 ꢂC (in nitrogen). On the other hand, no
glass-transition temperature (Tg) was observed for FPEs1–4.
None of them showed melting points, being consistent with
that the results of the wide angle X-ray diffraction (WAXD).
Copolymers FPEs2–4 had slightly lower thermal stability than
their carbon analog (FPE5). Char yield at 800 ꢂC for FPEs1–4
was in the range of 45–61% in nitrogen and 0.7–25% in air,
indicating their high oxidation stability characteristic of
silicon-containing polymers.4,8
FPEs1–4 exhibited good solubility similar to their carbon
analog (FPE5). They were soluble in ordinary organic solvents
such as chloroform, tetrahydrofuran, and dimethylformamide
at room temperature.9 The high solubility can be attributed not
only to the fluorene unit but also to the silicon atom introduced
in the polymer main chain which reduces the chain stiffness.4
Self-standing films of FPEs obtained by casting from chloroform
solution were transparent, flexible, and tough. Each silicon-con-
taining FPE had adhesive nature to the substrate.
7
FPE1; 1H NMR (C4D8O, 400 MHz) ꢀ 8.35 (s, 2H), 8.23 (d,
J ¼ 8 Hz, 2H), 8.04 (d, J ¼ 8 Hz, 2H), 7.98 (d, J ¼ 8 Hz,
2H), 7.88 (d, J ¼ 8 Hz, 2H), 7.78 (d, J ¼ 8 Hz, 2H), 7.51–
7.48 (m, 2H), 7.40–7.29 (m, 6H).
S. F. Thames, K. G. Malone, J. Polym. Sci., Part A: Polym.
Chem. 1993, 31, 521.
8
9
Thus, a novel biphenolic 9-silafluorene-containing mono-
mer 3 was synthesized and utilized for the synthesis of polyesters
FPEs as a typical application. The introduction of silicon atom to
Solubility of FPEs was evaluated by using 3 mg of polymer and
1 mL of solvent.
Published on the web (Advance View) August 4, 2007; doi:10.1246/cl.2007.1138