Poly(arylene ether)s with low refractive indices: Poly(biphenylene oxide)s with trifluoromethyl pendant groups via a meta-activated nitro displacement Reaction

Article abstract of DOI:10.1021/ma2028209

High-molecular-weight poly(biphenylene oxide)s (PBPO) were prepared from AB-type monomers, 4′(3′)-hydroxy-4-nitro-2,6-bis(trifluoromethyl) biphenyl, through a meta-activated nitro displacement reaction. The displacement of nitro leaving group activated by

Full text of DOI:10.1021/ma2028209

Article
pubs.acs.org/Macromolecules
Poly(arylene ether)s with Low Refractive Indices: Poly(biphenylene
oxide)s with Trifluoromethyl Pendant Groups via a Meta-Activated
Nitro Displacement Reaction
Sun Dal Kim,† Duyoun Ka,† Im Sik Chung,*,‡ and Sang Youl Kim*,†
†Department of Chemistry, KAIST, Daejeon 305-701, Korea
‡Immunotherapy Research Center, KRIBB, Daejeon 305-806, Korea
S
* Supporting Information
ABSTRACT: High-molecular-weight poly(biphenylene oxide)s
(PBPO) were prepared from AB-type monomers, 4′(3′)-
hydroxy-4-nitro-2,6-bis(trifluoromethyl)biphenyl, through a
meta-activated nitro displacement reaction. The displacement
of nitro leaving group activated by the two trifluoromethyl
groups at the meta-position produced high-molecular-weight polymers, which implies that nucleophilic aromatic substitution
reaction of the nitro leaving group proceeded very effectively with two activating groups at the meta-position. The obtained
polymers have weight-average molecular weight of 20 800−143 300 g/mol and molecular weight distribution of 1.68−2.85.
While two homopolymers of 4′- or 3′-hydroxy-4-nitro-2,6-bis(trifluoromethyl)biphenyl, p-PBPO and m-PBPO, showed a
semicrystalline morphology, copolymers of the two monomers were amorphous and dissolved in a wide range of organic
solvents. The PBPOs possessed a high glass transition temperature (Tg) in the range of 169 to 208 °C depending on their
structure and high thermal stability with 10% weight loss temperatures from 486 to 542 °C in nitrogen and from 465 to 516 °C
in air. Moreover, PBPOs containing two trifluoromethyl groups showed low refractive indices in the range of 1.4979−1.5052 as
well as low birefringence values of 0.0095−0.0148.
also useful for SNAr reactions to activate fluoro or nitro groups
for displacement by phenoxides.20−33
INTRODUCTION
■
Fluorine-containing polymers are of considerable interest for
optical and electronic applications owing to their low refractive
index, optical loss, dielectric constant, surface energy, moisture
absorption, and good thermal and chemical stability.1,2
Although many synthetic methods for fluorine-containing
polymers have been reported, a use of the trifluoromethyl
group is known as very effective and practical method to
incorporate fluorines into the polymer chains.2 Trifluoromethyl
groups provide not only several desirable properties, as above-
mentioned, but also good solubility and good optical
transparency.3−10
The activating groups in SNAr reaction stabilize the negative
charge that develops during the transition state largely through
conjugation,34−36 and the electron withdrawing group at the
meta position of the leaving group is less effective than the same
group at the ortho or para position. Therefore, activating groups
at the ortho or para position are generally required to obtain
high-molecular-weight polymers. Since we first succeeded in
making linear poly(arylene ether)s via a meta-activated SNAr
reaction,37 some examples of the meta-activated SNAr reaction
have been reported to make linear polymers38−42 as well as
hyperbranched polymers.43,44
In previous work,45 we found that trifluoromethyl groups and
ether linkages are stable in a nitro displacement reaction, even
at 190 °C, and that the displacement reaction occurs
quantitatively without side reactions that are frequently
observed during the nitro displacement reactions at high
temperatures due to the reactive nitrite ion byproduct.46−52
In this study, new poly(biphenylene oxide)s containing two
trifluoromethyl groups positioned symmetrically on one phenyl
ring were prepared from 4′-hydroxy-4-nitro-2,6-bis-
(trifluoromethyl)biphenyl and 3′-isomer through a meta-
activated nucleophilic nitro displacement reaction. The effect
Poly(arylene ether)s have been widely used as engineering
thermoplastics due to their good mechanical properties, high
thermal stability, and excellent resistance to hydrolysis and
oxidation reaction.11 The known approaches for the synthesis
of poly(arylene ether)s include electrophilic aromatic sub-
stitution, nucleophilic aromatic substitution, and metal
catalyzed coupling reactions.11−13 Among these methods, the
nucleophilic aromatic substitution (SNAr) reaction is the most
practical method for the preparation of poly(arylene ether)s
despite the fact that it requires some structural features, leaving
group activated with electron withdrawing groups.14,15 Various
heterocyclic rings16 and electron withdrawing groups such as
sulfone, ketone, and imide groups have been used as an
activating group for SNAr reactions to produce high-molecular-
weight poly(arylene ether)s.17−19 Trifluoromethyl groups are
Received: December 30, 2011
Revised: March 14, 2012
Published: March 26, 2012
© 2012 American Chemical Society
3023
dx.doi.org/10.1021/ma2028209 | Macromolecules 2012, 45, 3023−3031

Macromolecules
Article
132.48 (q, J = 31.9 Hz), 126.71 (q, J = 5.7 Hz), 125.63, 121.68
(q, J = 272.9 Hz). Anal. Calcd for C8H2BrF6NO2: C, 28.43; H,
0.60; N, 4.14. Found: C, 28.57; H, 0.76; N, 4.03.
of the two trifluoromethyl groups on the reactivity of the meta-
activated SNAr reaction and other mechanical and optical
properties of the polymers were investigated.
4′-Hydroxy-4-nitro-2,6-bis(trifluoromethyl)biphenyl (5). 4-Me-
thoxyphenylboronic acid (3.37 g, 22.2 mmol) was reacted with 2
(4.98 g, 14.7 mmol) in the presence of Pd(PPh3)4 (1.00 g). The
reaction mixture of 40 mL of toluene, 20 mL of ethanol, and 8.18 g of
K2CO3 dissolved in 40 mL of water was refluxed for 27 h. The product
was extracted with ethyl acetate and passed through a silica column
using CH2Cl2/hexane (v/v = 1/4) as an eluent to give pale yellow 4′-
methoxy-4-nitro-2,6-bis(trifluoromethyl)biphenyl (3) (4.16 g, 77.5%
yield): mp 94−95 °C. FTIR (KBr, cm−1): 2847 (−OCH3); 1610
EXPERIMENTAL SECTION
■
Materials. 4-Bromo-3,5-bis(trifluoromethyl)aniline (1, Fluoro-
chem), oxone (Aldrich), 4-methoxyphenylboronic acid (Aldrich), 3-
methoxyphenylboronic acid (TCI), tetrakis(triphenylphosphine)
palladium(0) (Pd(PPh3)4, Aldrich), boron tribromide (BBr3 1 M
solution in CH2Cl2, Aldrich) were used as received. Potassium
carbonate (K2CO3) was dried in vacuo at 150 °C for 24 h prior to use.
N-methylpyrrolidone (NMP) was stirred in the presence of CaH2
overnight and then distilled under reduced pressure. Other
commercially available reagent-grade chemicals were used without
further purification.
1
(aromatic CC); 1536, 1331 (NO2); 1124−1183 (C−F). H NMR
(DMSO-d6, 400 MHz, ppm): 8.76 (s, 2H), 7.22 (d, 2H, J = 8.52 Hz),
7.02 (d, 2H, J = 8.88 Hz), 3.81(s, 3H, −OCH3). 13C NMR (DMSO-d6,
100 MHz, ppm): 159.78, 146.82, 146.07, 131.91(q, J = 30.3 Hz),
130.59, 124.73(q, J = 5.7 Hz), 123.69, 122.16(q, J = 273.5 Hz), 112.73,
55.13. Anal. Calcd for C15H9F6NO3: C, 49.33; H, 2.48; N, 3.84.
Found: C, 51.15; H, 2.48; N, 3.72.
General Measurements. The Fourier-transform infrared (FTIR)
spectra of the compounds were obtained with a Bruker EQUINOX-55
spectrophotometer using a KBr pellet. The NMR spectra of the
synthesized compounds were recorded on a Bruker Fourier Transform
Avance 400 or Avance 300 spectrometer. The chemical shift of the
NMR was reported in parts per million (ppm) using tetramethylsilane
as an internal reference. Splitting patterns were designated as s
(singlet), d (doublet), t (triplet), q (quartet), or m (multiplet).
Elemental analyses (EA) of the synthesized compounds were carried
out with a CE Instrument EA1110-FISONS analyzer. Gel permeation
chromatography (GPC) diagrams were obtained with a Viscotek
TDA302 equipped with a triple RI detector array and a packing
column (PLgel 10 μm MIXED-B) using tetrahydrofuran (THF) as an
eluent at 35 °C. The number and weight-average molecular weight of
the polymers were calculated relative to linear polystyrene standards.
Thermogravimetric analysis (TGA) and differential scanning calorim-
etry (DSC) were performed on a TA Instruments TGA Q500 and a
DSC Q100 instrument, respectively. The TGA measurements were
conducted at a heating rate of 10 °C/min in N2 and air. The melting
points (m.p.) of the synthesized compounds and the Tg and Tm values
of the polymers were obtained with DSC instrument at a heating rate
of 10 °C/min in N2. The Tm values were taken from the first heating
scan ranging from 0 to 450 °C. Tg values were taken from the second
heating scan after cooling to 0 °C from 350 °C. The wide-angle X-ray
diffraction (WAXD) patterns were obtained with a Rigaku D/MAX III
diffractometer. The refractive indices nTE and nTM for the transverse
electric (TE) and transverse magnetic (TM) modes of the polymer
films were measured with a Sairon SPA-4000 prism coupler with a
gadolinium gallium garnet (GGG) prism at the wavelength of 1310
nm at room temperature. The birefringence values (Δn) were
A solution of 3 (3.00 g, 8.21 mmol) in 60 mL of CH2Cl2 was cooled
to −78 °C, and 18 mL of 1 M BBr3 was added slowly. The resulting
mixture was stirred at 0 °C for 7 h and quenched by cautiously pouring
it into 300 mL of cold water. The mixture was heated until CH2Cl2
evaporated completely. The product was extracted with excess CH2Cl2
and recrystallized from toluene/n-hexane to give pale yellow 4′-
hydroxy-4-nitro-2,6-bis(trifluoromethyl)biphenyl (5) (2.89 g, 100%
yield): mp 139−140 °C. FTIR (KBr, cm−1): 3418 (O−H); 1613
1
(aromatic CC); 1538, 1335 (NO2); 1142−1189 (C−F). H NMR
(DMSO-d6, 400 MHz, ppm): 9.80 (s, 1H, −OH), 8.74 (s, 2H), 7.07
(d, 2H, J = 8.33 Hz), 6.82 (d, 2H, J = 8.56 Hz). 13C NMR (DMSO-d6,
100 MHz, ppm): 158.06, 146.68, 146.58, 131.90 (q, J = 30.2 Hz),
130.45, 124.70 (q, J = 5.6 Hz), 122.17 (q, J = 273.6 Hz), 121.98,
114.12. Anal. Calcd for C14H7F6NO3: C, 47.88; H, 2.01; N, 3.99.
Found: C, 49.74; H, 1.54; N, 3.83.
3′-Hydroxy-4-nitro-2,6-bis(trifluoromethyl)biphenyl (6). 3-Me-
thoxyphenylboronic acid (3.80 g, 25.0 mmol) was reacted with 2
(6.97 g, 20.6 mmol) in the presence of Pd(PPh3)4 (1.00 g). The
reaction mixture of 40 mL of toluene, 40 mL of ethanol, and 8.61 g of
K2CO3 dissolved in 40 mL of water was refluxed for 31 h. The product
was extracted with ethyl acetate and passed through a silica column
using CH2Cl2/hexane (v/v = 1/4) as an eluent to give pale yellow 3′-
methoxy-4-nitro-2,6-bis(trifluoromethyl)biphenyl (4) (5.94 g, 78.8%
1
yield). H NMR (DMSO-d6, 400 MHz, ppm): 8.76 (s, 2H), 7.37(t,
1H, J = 7.96 Hz), 7.06 (m, 1H), 6.86 (s, 1H), 6.85 (d, 1H, J = 12.16
Hz), 3.75 (s, 3H, −OCH3). 13C NMR (DMSO-d6, 100 MHz, ppm):
158.03, 146.89, 145.50, 133.06, 131.58 (q, J = 30.8 Hz), 128.42, 124.71
(q, J = 5.7 Hz), 122.09 (q, J = 273.5 Hz), 121.65, 115.49, 114.38,
55.08.
calculated as the difference between nTE and nTM
Monomer Syntheses. 1-Bromo-4-nitro-2,6-bis-
.
(trifluoromethyl)benzene (2). In a three-neck round-bottom
flask fitted with two addition funnels and a pH electrode was
placed 50 mL of dichloromethane, 50 mL of acetone, 50 mL of
a 0.8 M aqueous solution of sodium phosphate, 170 mg of
tetrabutylammonium hydrogen sulfate, and 0.950 g (3.08
mmol) of 1. In one addition funnel was added a solution of
20.0 g (32.5 mmol) of oxone in 150 mL of water, and in the
other addition funnel was placed 100 mL of a 2 N aqueous
solution of potassium hydroxide. After cooling the mixture to 0
°C, the aqueous solution of oxone was added dropwise over 30
min while maintaining a pH of 7.5−8.5 with the addition of the
aqueous solution of potassium hydroxide. The resulting
suspension was filtered off, and the filtrate was partitioned.
The organic layer was washed with water, dried over anhydrous
magnesium sulfate, filtered, and concentrated under a reduced
pressure environment. The solid residue was passed through a
silica column using CH2Cl2/hexane (v/v = 1/4) as an eluent to
give pale yellow 1-bromo-4-nitro-2,6-bis(trifluoromethyl)-
benzene (0.860 g, 82.6% yield): mp 56−57 °C. FTIR (KBr,
cm−1): 1613, 1598 (aromatic CC); 1540, 1332 (NO2);
1125−1197 (C−F). 1H NMR (CDCl3, 400 MHz, ppm):
8.71(s, 2H). 13C NMR (DMSO-d6, 100 MHz, ppm): 146.62,
A solution of 4 (3.44 g, 9.42 mmol) in 69 mL of CH2Cl2 was cooled
to −78 °C, and 21 mL of 1 M BBr3 was slowly added. The resulting
mixture was stirred at 0 °C for 19 h and quenched by cautiously
pouring it into 300 mL of cold water. The mixture was heated until the
CH2Cl2 evaporated completely. The product was extracted with excess
CH2Cl2 and passed through a silica column using ethyl acetate/n-
hexane (v/v = 1/3) as an eluent to give pale yellow 3′-hydroxy-4-nitro-
2,6-bis(trifluoromethyl)biphenyl (6) (3.30 g, 100% yield): mp 84−86
°C. FTIR (KBr, cm−1): 3271 (O−H); 1610 (aromatic CC); 1539,
1
1333 (NO2); 1141−1187 (C−F). H NMR (DMSO-d6, 400 MHz,
ppm): 9.69 (s, 1H, −OH), 8.76 (s, 2H), 7.24 (t, 1H, J = 8.20 Hz), 6.88
(m, 1H), 6.69 (d, 1H, J = 6.98 Hz), 6.68 (s, 1H). 13C NMR (DMSO-
d6, 100 MHz, ppm): 156.10, 146.87, 145.69, 132.94, 131.30 (q, J =
30.5 Hz), 128.36, 124.89 (q, J = 5.7 Hz), 122.14 (q, J = 273.6 Hz),
120.09, 116.35, 116.15. Anal. Calcd for C14H7F6NO3: C, 47.88; H,
2.01; N, 3.99. Found: C, 50.29; H, 1.52; N, 3.90.
Model Reactions. Model Reaction of 3 with Sodium
Phenoxide at Room Temperature. A 25 mL three-necked flask
equipped with an N2 inlet was charged with 3 (500 mg, 1.37
mmol), sodium phenoxide trihydrate (300 mg, 1.77 mmol),
and 5 mL of NMP. The reaction mixture was stirred at room
3024
dx.doi.org/10.1021/ma2028209 | Macromolecules 2012, 45, 3023−3031

Macromolecules
Article
temperature (ca. 25 °C) for 4 days. The major part of the
starting compound (3) remained intact in TLC.
2p1m-PBPO. The same procedure used for 1p3m-PBPO was
repeated with 520 mg (1.48 mmol) of 5, 264 mg (0.750 mmol) of 6,
348 mg (2.52 mmol) of K2CO3, and 4 mL of NMP. (633 mg, 93.2%
yield).: FTIR (KBr, cm−1): 1605, 1584 (aromatic CC); 1294, 1261,
Model Reaction of 3 with m-Cresol. A 25 mL three-necked flask
equipped with an N2 inlet, a Dean−Stark trap, and a condenser was
charged with 3 (500 mg, 1.37 mmol), m-cresol (190 mg, 1.75 mmol),
K2CO3 (284 mg, 2.06 mmol), and 3 mL of NMP. The reaction
mixture was heated to 90 °C for 31 h. The product was extracted with
CH2Cl2 to give colorless product 7. (570 mg, 98.0% yield). The
procedure was repeated at 140 °C and at 175 °C. The reaction was
complete within 4 and 1 h at 140 and 175 °C, respectively. The
isolation yield was almost quantitative in all cases: mp 104−105 °C.
FTIR (KBr, cm−1): 1614, 1583 (aromatic CC); 1295, 1259 (C−O−
1
1232 (C−O−C); 1134−1187 (C−F). H NMR (THF-d8, 400 MHz,
ppm): 7.72 (m, 4H), 7.64 (m, 2H), 7.54 (m, 1H), 7.39 (m, 4H), 7.30
(m, 1H), 7.20 (m, 5H), 7.12 (m, 1H).
3p1m-PBPO. The same procedure used for 1p3m-PBPO was
repeated with 602 mg (1.71 mmol) of 5, 201 mg (0.750 mmol) of 6,
346 mg (2.52 mmol) of K2CO3, and 4 mL of NMP. (689 mg, 99.4%
yield). FTIR (KBr, cm−1): 1605, 1584 (aromatic CC); 1293, 1261,
1233 (C−O−C); 1136−1186 (C−F). 1H NMR (soluble part in THF,
THF-d8, 400 MHz, ppm): 7.72 (m, 4H), 7.65 (m, 2H), 7.55 (m, 1H),
7.40 (m, 5H), 7.20 (m, 6H).
1
C); 1133−1185 (C−F). H NMR (DMSO-d6, 400 MHz, ppm): 7.57
(s, 2H), 7,36 (t, 1H, J = 7.84 Hz), 7.15 (d, 2H, J = 8.42 Hz), 7.09 (d,
1H, J = 7.56 Hz), 7.04 (s, 1H), 6.99 (dd, 1H, J = 8.09 Hz, J = 2.11 Hz),
3.79 (s, 3H), 2.32 (s, 3H). 13C NMR (DMSO-d6, 100 MHz, ppm):
159.19, 156.84, 154.59, 140.52, 133.44, 131.97 (q, J = 29.2 Hz),
131.34, 130.21, 126.03, 124.83, 122.74 (q, J = 273.3 Hz), 120.42,
118.23 (q, J = 5.4 Hz), 116.87, 112.50, 55.00, 20.80. Anal. Calcd for
C22H16F6O2: C, 61.98; H, 3.78; N, 0. Found: C, 63.96; H, 3.69; N, 0.
Polymerizations. All polymerizations were conducted under a dry
nitrogen atmosphere.
RESULTS AND DISCUSSION
Monomer Syntheses. The monomers, 4′-hydroxy-4-nitro-
2,6-bis(trifluoromethyl)biphenyl (5) and 3′-isomer (6), were
■
Scheme 1
p-PBPO. A 25 mL three-necked flask equipped with a N2 inlet, a
mechanical stirrer, a Dean−Stark trap, and a condenser was charged
with 804 mg (2.29 mmol) of 5, 470 mg (3.40 mmol) of K2CO3, 4 mL
of NMP, and 2 mL of toluene. The reaction mixture was heated to 135
°C for 3 h, at which the toluene was brought to reflux. The toluene
was periodically removed from the Dean−Stark trap, and fresh dry
toluene was added to the reaction mixture to ensure dehydration of
the system. After the reaction temperature was raised to 175 °C,
precipitation occurred within 1 min. The precipitated product was
washed with hot water and methanol repeatedly and dried in vacuo at
100 °C for 24 h (654 mg, 93.8% yield).: FTIR (KBr, cm−1): 1603
(aromatic CC); 1295, 1261, 1235 (C−O−C); 1135−1186 (C−F).
m-PBPO. The same procedure used for p-PBPO was repeated with
499 mg (1.42 mmol) of 6, 216 mg (1.57 mmol) of K2CO3, and a total
of 4.5 mL of NMP. The precipitation also occurred after 1 h at 175 °C.
The product was washed with hot water and methanol repeatedly and
dried in vacuo at 100 °C for 24 h (498 mg, 99.0% yield). The soluble
part in THF was collected for characterization.: FTIR (KBr, cm−1):
1610, 1585 (aromatic CC); 1287, 1268 (C−O−C); 1133−1189
Scheme 2
1
(C−F). H NMR (soluble part in THF, THF-d8, 400 MHz, ppm):
7.62 (s, 2H), 7.51(t, 1H, J = 7.94 Hz), 7.26 (d, 1H, J = 8.17 Hz), 7.19
(d, 1H, J = 7.65 Hz), 7.09 (s, 1H).
1p3m-PBPO. A 25 mL three-necked flask equipped with a N2 inlet,
a mechanical stirrer, a Dean−Stark trap, and a condenser was charged
with 201 mg (0.570 mmol) of 5, 600 mg (1.71 mmol) of 6, 348 mg
(2.52 mmol) of K2CO3, and 4 mL of NMP. The reaction mixture was
heated to 135 °C for 3 h, at which the toluene was brought to reflux.
The toluene was periodically removed from the Dean−Stark trap, and
fresh dry toluene was added to the reaction mixture to ensure
dehydration of the system. The temperature was raised to 175 °C and
the polymerization continued for 14 h. The polymer was precipitated
into a 400 mL of vigorously stirred water and then filtered. The
precipitated polymer was washed with hot water and methanol
repeatedly and dried in vacuo at 100 °C for 24 h. Further purification
was carried out by dissolving the polymers in THF and then
precipitating it into methanol (575 mg, 83.0% yield). FTIR (KBr,
cm−1): 1607, 1583 (aromatic CC); 1293, 1262, 1227 (C−O−C);
Chart 1
1
1136−1188 (C−F). H NMR (THF-d8, 400 MHz, ppm): 7.70 (m,
prepared as shown in Scheme 1 with a good yield. 4-Bromo-
3,5-bis(trifluoromethyl)aniline (1) was oxidized with oxone.53
The resulting nitro compound (2) was reacted with p- and m-
(methoxyphenylbronic acid) through a Suzuki coupling
reaction54 to produce 4′-methoxy-4-nitro-2,6-bis-
(trifluoromethyl)biphenyl (3) and its 3′-isomer (4), respec-
tively. The methoxy compounds were converted to the
corresponding monomers by demethylation with BBr3. The
2H), 7.62 (m, 6H), 7.52 (m, 3H), 7.37 (m, 2H), 7.28 (m, 3H), 7.19
(m, 5H), 7.10 (m, 3H).
1p1m-PBPO. The same procedure used for 1p3m-PBPO was
repeated with 400 mg (1.14 mmol) of 5, 402 mg (1.14 mmol) of 6,
348 mg (2.518 mmol) of K2CO3, and 4 mL of NMP. (554 mg, 80.0%
yield).: FTIR (KBr, cm−1): 1606, 1583 (aromatic CC); 1294, 1261,
1
1230 (C−O−C); 1133−1188 (C−F). H NMR (THF-d8, 400 MHz,
ppm): 7.71(m, 2H), 7.63 (m, 2H), 7.53 (m, 1H), 7.38 (m, 2H), 7.31
(m, 1H), 7.20 (m, 3H), 7.11 (m, 1H).
3025
dx.doi.org/10.1021/ma2028209 | Macromolecules 2012, 45, 3023−3031

Macromolecules
Article
hydroxyl group and a nitro leaving group activated by two
trifluoromethyl groups at the meta position was confirmed by
spectroscopic data (Experimental Section and Supporting
Information, Figures S1 and S2).
Scheme 3
Model Reactions. To investigate the reactivity of the meta-
activated nitro displacement, model reactions were conducted
with 3 and m-cresol in NMP at several temperatures. The
model compound containing diary ether linkage (7) was
obtained as outlined in Scheme 2. The reactions were complete
without any detectable side reactions within 31, 4, and 1 h at
90, 140, and 175 °C, respectively, and the yields were
quantitative in all cases. The structure of 7 was confirmed by
spectroscopic data (Experimental Section and Supporting
Information, Figures S3 and S4). On the other hand, the
model reaction at room temperature was not effective. The
major part of 3 remained intact even after 4 days.
Table 1. Molecular Weight and Polydispersity Index of the
Polymers
a
a
b
PBPOs
feed ratio 5/6
Mn /103
Mw /103
PDI
In the previous report,42 the reactivity of 2,2′-bis-
(trifluoromethyl)-4,4′-dinitro-1,1′-biphenyl (8) was higher
than that of 4-nitro-2-trifluoromethylbiphenyl (9) due to the
electron withdrawing characteristic of the nitro leaving group
and the trifluoromethyl group attached to the other aromatic
ring of the biphenyl structure (Chart 1). The reaction of 8 with
two equivalents of 4-tert-buthylphenol was complete at 175 °C
for 4 h, whereas the reaction of 9 with 4-tert-butylphenol was
complete at 175 °C for 12 h.37 Interestingly, the reaction of 4′-
methoxy-4-nitro-2,6-bis(trifluoromethyl)biphenyl (3) with m-
cresol was complete at 175 °C for 1 h; even at a reaction
temperature of 140 °C, the reaction was complete in 4 h. It
appears that the higher reactivity of 3 compared to 8 and 9 is
caused by the very strong electron withdrawing characteristic of
the two trifluoromethyl groups at the meta position of the nitro
leaving group in the same phenyl ring. These results imply that
activation by the two activating groups at the meta position is a
very effective strategy for successful SNAr reactions.
c
p-PBPO
100/0
−
9.3
−
−
d
3p1m-PBPO
2p1m-PBPO
1p1m-PBPO
1p3m-PBPO
75/25 (3/1)
67/33 (2/1)
50/50 (1/1)
25/75 (1/3)
0/100
26.4
58.6
143.3
42.0
20.8
2.85
1.68
2.03
1.70
2.23
34.9
70.6
24.6
9.3
d
m-PBPO
a
Determined by GPC using THF as an eluent at 35 °C with
polystyrene standards. Polydispersity Index = Mw/Mn. Insoluble.
Soluble part in THF.
b
c
d
monomers were purified by chromatography and recrystalliza-
tion and were dried in vacuo for 24 h prior to polymerization.
The structure of the synthesized monomers having both a
Polymerizations. On the basis of the successful results of
the model reaction, we carried out the polymerization process
at 175 °C. The monomers were polymerized according to the
conventional poly(arylene ether) synthesis method with K2CO3
as a base in NMP, as shown in Scheme 3. The initial solid
contents were maintained at 20 w/v %, and toluene as an
azeotrope was used during the initial stage of polymerization to
remove water that formed due to phenoxide generation.
Initially, we tried to obtain the homopolymers (p-PBPO and
m-PBPO) with 5 and 6 as a single monomer. However, the
precipitation occurred in 1 h at 175 °C in both cases. It has
been known that the incorporation of trifluoromethyl groups in
polymer chains improves the solubility of polymers because
bulky trifluoromethyl groups disturb the crystal packing
between the polymer chains,55 but the resulting homopolymers,
containing numerous trifluoromethyl groups in the main chain,
showed limited solubility. It seems that the symmetric
incorporation of trifluoromethyl groups cannot effectively
hinder the chain packing of poly(arylene ethers). (The details
will be discussed later.)
To resolve the unexpected solubility problem, copolymeriza-
tion, which can hinder chain packing around the diaryl ether by
introducing irregular para- and meta- connections in the main
chain, were also conducted. The mixture of 5 and 6 were
polymerized to the corresponding copolymers (1p3m-PBPO,
1p1m-PBPO, 2p1m-PBPO, and 3p1m-PBPO). In italics, each
number indicates the feed ratio of the para- and meta-
monomers. For example, 1p3m corresponds to the 1 to 3 feed
ratio of para to meta monomers. When the polymerization
Figure 1. FTIR spectra of monomer 5, model compound 7, polymer
p-PBPO, and 1p1m-PBPO.
3026
dx.doi.org/10.1021/ma2028209 | Macromolecules 2012, 45, 3023−3031

Macromolecules
Article
1
Figure 2. H NMR spectra of PBPOs (THF-d8, 400 MHz, 25 °C).
mixtures reacted for 14 h at 175 °C, precipitation did not occur,
contrary to homopolymerization. After the polymerization
process, the brown polymers were precipitated in a water/
methanol (v/v = 1/1) mixture and washed with hot water and
methanol repeatedly, after which they were dried in vacuo.
Further purification was carried out by dissolving the polymers
in THF and then precipitating this mixture into methanol. The
molecular weight and polydispersity indices as determined by
GPC are listed in Table 1 (Supporting Information, Figure S7).
The weight-average molecular weights of the soluble PBPOs
(1p3m-PBPO, 1p1m-PBPO, and 2p1m-PBPO) and the
partially soluble PBPOs (the soluble part in THF of 3p1m-
PBPO and m-PBPO) were in the range 20800−143000 g/mol
based on the polystyrene standard, indicating high-molecular-
weight polymers were obtained.
a
Table 2. Solubility of PBPOs
p-
3p1m-
2p1m-
1p1m-
1p3m-
m-
solvents
NMP
PBPO PBPO
PBPO
PBPO
PBPO PBPO
−
−
−
−
−
−
−
−
−
−
−
−
−
−
−
−
−
+−
+−
−
+−
−
+−
+−
−
−
+−
−
−
−
++
++
+−
++
+−
++
++
++
+−
++
++
+−
++
+−
−
++
++
++
++
+−
++
++
++
++
+−
+−
++
+−
−
++
++
++
++
+−
++
++
++
++
++
++
++
+−
++
−
+−
+−
+−
+−
+−
+−
+−
+−
−
+−
+−
−
+−
−
DMF
DMAc
The structures of the synthesized polymers were confirmed
by spectroscopic data, which indicated the formation of ether
linkages without degradation of their trifluoromethyl groups.
The representative FTIR spectra are shown in Figure 1. All of
the FTIR spectra of monomer (5), model compound (7), and
p-PBPO and 1p1m-PBPO show absorption bands at 1130−
1190 cm−1 corresponding to trifluoromethyl (C−F) stretching.
While the FTIR spectrum of monomer (5) shows the
absorption bands at 3418 cm−1 and at 1538 and 1335 cm−1
corresponding to hydroxyl (O−H) and nitro (N−O)
stretching, respectively, the FTIR spectra of model compound
(7) and the polymers show a new absorption band around
1250 cm−1 corresponding to the diaryl ether (Ph−O−Ph)
stretching generated by successful meta-activated SNAr
reactions without any trace of nitro or hydroxyl stretching.
FTIR spectra of all PBPOs showed similar patterns (Supporting
DMPU
DMSO
THF
1,4-dioxane
cyclohexanone
acetone
ODCB
chloroform
ethyl acetate
anisole
toluene
−
−
−
−
n-hexane
acetonitrile
methanol
−
−
−
−
−
−
−
−
−
−
a
Solubility: ++, soluble at room temperature; +−, partially soluble; −,
insoluble. Abbreviations: THF, tetrahydrofuran; DMF, N,N-dimethyl-
formamide; DMAc, N,N-dimethylacetamide; DMPU, 1,3-dimethylte-
trahydropyrimidin-2(1H)-one; DMSO, dimethyl sulfoxide; ODCB,
1,2-dichlorobenzene.
1
Information, Figure S6). The H NMR spectra of the PBPOs
are shown in Figure 2. The lack of traces of −OH (9−10 ppm)
or −NO2 (8−9 ppm) end groups in the soluble polymers
supports the formation of high-molecular-weight polymers. The
3027
dx.doi.org/10.1021/ma2028209 | Macromolecules 2012, 45, 3023−3031

Macromolecules
Article
Figure 4. TGA curves of PBPOs in (a) nitrogen and (b) air at a
heating rate of 10 °C/min.
Figure 3. (a) WAXD patterns and (b) DSC curves (the first scan
ranging from 0 to 450 °C, Heating rate: 10 °C/min, in N2) of p-
PBPO, m-PBPO, 3p1m-PBPO, and 1p3m-PBPO.
2 to 1 integral ratio of para to meta moieties, indicating that a 2
to 1 ratio is a critical point to obtain good solubility.
Table 3. Thermal Properties of the Polymers
Solubility of the Polymer. The solubility of the PBPOs in
various solvents is summarized in Table 2. While p-PBPO and
a
a
Td5 (°C)
Td10 (°C)
b
c
PBPOs
in N2 in air in N2 in air Tg (°C)
Tm (°C)
p-PBPO
430
500
432
505
463
394
398
457
416
475
399
377
486
542
522
534
521
516
465
511
499
516
480
474
d
208
192
187
176
169
405
3p1m-PBPO
2p1m-PBPO
1p1m-PBPO
1p3m-PBPO
m-PBPO
429 (403)
d
d
d
337
a
5% and 10% weight loss temperature measured by TGA at a heating
b
rate of 10 °C/min. Glass transition temperature measured by DSC
(the second scan) in N2 at a heating rate of 10 °C/min. Crystalline
melting temperature measured by DSC (the first scan) in N2 at a
c
d
heating rate of 10 °C/min. Not detected.
peaks at 7.7 and 7.6 ppm in the spectra indicate the
representative repeating unit of para- and meta-moieties in
the PBPOs, respectively. The integral ratio of the peaks
between 7.7 and 7.6 ppm are well matched with the feed ratio
of the para- and meta-monomers, implying that the copolymers
contain consistent amounts of the monomers as regards the
feed ratio. However, the soluble part of 3p1m-PBPO showed a
Figure 5. DSC curves (the second scan ranging from 0 to 350 °C,
heating rate: 10 °C/min, in N2) of PBPOs.
3028
dx.doi.org/10.1021/ma2028209 | Macromolecules 2012, 45, 3023−3031

Macromolecules
Article
appear in crystalline polymers. The WAXD results are
consistent with the DSC results. While 1p3m-PBPO shows a
glass transition temperature (Tg) at 172 °C, p-PBPO, m-
PBPO, and 3p1m-PBPO show crystalline melting temperatures
(Tm) at 405, 337, and 429 (403) °C, respectively. These
WAXD and DSC results show that p-PBPO, m-PBPO, and
3p1m-PBPO have crystallinity, leading to its limited solubility.
Thermal Properties. The thermal properties of the
polymers were evaluated by TGA and DSC, and the results
are summarized in Table 3. They have high thermal stability, as
expected for fluoroalkyl-containing poly(arylene ether)s. The
TGA and DSC thermograms are shown in Figures 4 and 5,
respectively. The dynamic TGA result shows that a 10% weight
loss occurred for PBPOs in the range of 486−542 °C in
nitrogen and 465−516 °C in air. Although p-PBPO and m-
PBPO, precipitated during the polymerization process, showed
relatively low thermal stability due to the remaining end groups,
the main decomposition of p-PBPO and m-PBPO starts at
above 500 °C in nitrogen. As mentioned above, p-PBPO, m-
PBPO, and 3p1m-PBPO have Tm values. In the second scan of
the DSC measurement in the range of 0 and 350 °C, all of the
polymers except p-PBPO showed a high glass transition
temperature (Tg) in the range of 169−208 °C. When increasing
the quantity of the para-linkage in the main chain, the Tg value
of PBPOs increased gradually from 169 to 208 °C. The Tg
value of 3p1m-PBPO is comparable to that of PPOTM (Tg =
210 °C)56 despite the fact that 3p1m-PBPO does not have any
pendent group near the ether linkage. 3p1m-PBPO did not
show Tm in the second heating scan of DSC from 0 to 350 °C,
although they showed a melting peak in the first heating cycle
up to 450 °C while the melting peak of m-PBPO was observed
at 337 °C. The first heating, cooling, and second heating traces
of m-PBPO are shown in Figure 6. In the first cooling and the
second heating, the trace of Tc and Tm is observed with Tg,
respectively. These results imply that a thermal treatment may
change the crystalline state of the polymer to an amorphous
state in the cases of 3p1m-PBPO and m-PBPO.
Figure 6. DSC curves (the second scan ranging from 0 to 350 °C,
heating rate: 10 °C/min, in N2) of m-PBPO.
a
Table 4. Refractive Indices of the Synthesized Polymers
g
d
b
c
d
e
f
PBPOs
nTE
nTM
nav
Δn
ε
(μm)
2p1m-PBPO
1p1m-PBPO
1p3m-PBPO
1.5084
1.5028
1.5052
1.4988
1.4880
1.4957
1.5052
1.4979
1.5020
0.0096
0.0148
0.0095
2.49
2.47
2.48
4.15
6.50
4.51
a
b
Measured at a wavelength of 1310 nm at room temperature. nTE: the
c
d
in-plane refractive index. nTM: the out-of plane refractive index. nav:
e
the average refractive index (nav = (2nTE + nTM)/3). Δn: birefringence
f
(nTE − nTM). Dielectric constant estimated from the refractive index: ε
g
2
≈ 1.10nav Film thickness for the refractive index measured.
m-PBPO have limited solubility, the copolymers were soluble
in various organic solvents, including NMP, DMF, DMPU,
THF, 1,4-dioxane, and cyclohexanone. Generally, the solubility
of the polymers increases as the amount of the meta-connected
moiety in the polymer backbone increases. The solubility of
1p1m-PBPO, which was soluble in ethyl acetate and acetone,
was better than that of 2p1m-PBPO presumably due to its
higher meta-linkage content. In addition, 1p3m-PBPO was
soluble even in toluene. In contrast, 3p1m-PBPO showed poor
solubility due to its higher content of the para-moiety. All of
the polymers were insoluble in n-hexane, acetonitrile, and
methanol.
It is known that trifluoromethyl pendent groups in rigid
polymer chains improve the solubility of polymers because
bulky trifluoromethyl groups disturb the crystal packing
between the polymer chains.55 While the PBPOs having one
trifluoromethyl group on their repeating unit showed good
solubility,37 three polymers (p-PBPO, m-PBPO, and 3p1m-
PBPO) have limited solubility. p-PBPO is insoluble in any
organic solvents, and less than 10% of m-PBPO and 3p1m-
PBPO are soluble in THF. The unexpected limited solubility
behavior was caused by their crystalline characteristics, which
indicates that the increased symmetry in the polymer structure
overrides the bulkiness of trifluoromethyl groups in their crystal
packing structure. The wide-angle X-ray diffraction (WAXD)
patterns and the DSC curves of p-PBPO, m-PBPO, 3p1m-
PBPO, and 1p3m-PBPO are shown in Figure 3, parts a and b,
respectively. While the WAXD pattern of 1p3m-PBPO is broad
without any obvious peak features, the patterns of p-PBPO, m-
PBPO, and 3p1m-PBPO show relatively sharp peaks that often
The Refractive Indices of the Polymers. The refractive
indices and birefringence of the polymers were measured using
a prism coupling method with the laser beam having 1330 nm
wavelength. The results are summarized in Table 4. As
expected, all of the soluble PBPOs which have two CF3 groups
per biphenyl unit showed very low refractive indices (nav) in the
range of 1.4979 to 1.5052 due to the high fluorine content. The
refractive indices (nav) of CF3-substituted poly(arylene ether)s,
with one CF3 group per biphenyl unit of their polymer chains,
were reported in the range of 1.5992 to 1.6223.37,42,45 These
values are higher than those of the PBPOs synthesized in this
study. The low refractive indices of the PBPOs likely originated
from the low molecular polarizability and density caused by the
two CF3 groups of polymeric repeating unit of PBPOs5,57−61
Moreover, the polymers showed low birefringence (Δn) of less
than 0.015, indicating that the linear polarizability and
segmental orientation of the amorphous PBPOs are nearly
isotropic. The dielectric constant (ε) can be estimated from the
refractive index n according to Maxwell’s equation, ε ≈ n2. The
2
ε value at 1 MHz was determined to be ε ≈ 1.10 nav , including
an additional contribution of approximately 10% due to
infrared absorption.62 The ε values of the polymer films
estimated from the average refractive indices were in the range
of 2.47−2.49. The low dielectric constants may be also
attributed to the existence of trifluoromethyl groups in the
main chain.
3029
dx.doi.org/10.1021/ma2028209 | Macromolecules 2012, 45, 3023−3031

Macromolecules
Article
(12) Rogers, M. E.; Long, T. E. Synthesis of Poly(arylene ether)s. In
Synthetic Methods In Step-Growth Polymers; John Wiley & Sons, Inc.;
Hoboken, NJ, 2003.
(13) Johnson, H. N.; Farnham, A. G.; Clendinning, R. A.; Hale, W.
F.; Merriam, C. N. J. Polym. Sci., Part A: Polym. Chem. 1967, 5, 2375.
(14) Theil, F. Angew. Chem., Int. Ed. 1999, 38, 2435.
(15) Pitsinos, E. N.; Vidali, V. P.; Couladouros, E. A. Eur. J. Org.
Chem. 2011, 1207.
(16) Labadie, J. W.; Hedrick, J. L.; Ueda, M. Step growth polymers for
high-performance materials: New synthetic method; ACS Symposium
Series 624; American Chemical Society: Washington, DC, 1996; pp
210−25.
(17) Kricheldorf, H. R.; Handbook of polymer synthesis; CRC Press:
New York, 1992; pp 545−615.
(18) Mati, S.; Mandal, B. Prog. Polym. Sci. 1986, 12, 111.
(19) Chung, I. S.; Eom, H. J.; Kim, S. Y. Polym. Bull. 1998, 41, 631.
(20) Labadie, J. W.; Hedrick, J. L. Macromolecules 1990, 23, 5371.
(21) Kim, S. Y.; Labadie, J. W. Polym. Prepr. (Am. Chem. Soc., Div.
Polym. Chem.) 1991, 32 (1), 164.
(22) Banerjee, S.; Maier, G.; Burger, M. Macromolecules 1999, 32,
4279.
CONCLUSION
■
In this study, we prepared new aromatic polymers with low
refractive indices as well as high temperature resistances. The
polymers, poly(biphenylene oxide)s containing two pendent
trifluoromethyl groups, were synthesized from 4′-hydroxy-4-
nitro-2,6-bis(trifluoromethyl)biphenyl and 3′-isomer through a
meta-activated nucleophilic aromatic substitution (SNAr)
reaction. The nitro leaving group activated by the two
trifluoromethyl groups at the meta-position was effectively
displaced, resulting in high-molecular-weight polymers. This
implies that activation by two activating groups at the meta-
position is an effective strategy for successful SNAr reactions.
While both the para- and meta-connected homopolymers were
crystalline, the copolymers of the para- and meta-connected
monomers were amorphous and dissolved in a wide range of
organic solvents. The polymers were thermally stable and
showed very low refractive indices in the range of 1.488−1.508
with low birefringence.
(23) Banerjee, S.; Maier, G. Chem. Mater. 1999, 11, 2179.
(24) Maier, G. Prog. Polym. Sci. 2001, 26, 3.
(25) Lee, M. S.; Kim, S. Y. Macromol. Rapid Commun. 2005, 26, 52.
ASSOCIATED CONTENT
■
S
* Supporting Information
1H and 13C NMR spectra of the monomers and the model
compound, FTIR of polymers, and GPC curves. This material
is available free of charge via the Internet at http://pubs.acs.org.
(26) Banerjee, S.; Komber, H.; Haussler, L.; Voit, B. Macromol. Chem.
̈
Phys. 2009, 210, 1272.
(27) Ghosh, A.; Banerjee, S.; Komber, H.; Lederer, A.; Haussler, L.;
Voit, B. Macromolecules 2010, 43, 2846.
̈
(28) Carter, K. R.; Kim, S. Y.; Labadie, J. W. Polym. Prepr. (Am.
Chem. Soc., Div. Polym. Chem.) 1993, 34 (1), 415.
(29) Park, S. K.; Kim, S. Y. Macromolecules 1998, 31, 3385.
(30) Lee, H. S.; Kim, S. Y. Macromol. Rapid Commun. 2002, 23, 665.
(31) Kim, Y. J.; Chung, I. S.; Kim, S. Y. Macromolecules 2003, 36,
3809.
(32) Lee, M. S.; Kim, S. Y. Macromolecules 2005, 38, 5844.
(33) Kim, Y. J.; Kakimoto, M.; Kim, S. Y. Macromolecules 2006, 39,
7190.
(34) Bunnett, J. F.; Zahler, R. E. Chem. Rev. 1951, 49, 273.
(35) Bartoli, G.; Todesco, P. E. Acc. Chem. Res. 1977, 10, 125.
(36) Terrier, F. Nucleophilic aromatic displacement: the influence of
the nitro group; VCH Publishers: New York, 1991.
(37) Chung, I. S.; Kim, S. Y. J. Am. Chem. Soc. 2001, 123, 11071.
(38) Kaiti, S.; Himmelberg, P.; Williams, J.; Abdellatif, M.; Fossum, E.
Macromolecules 2006, 39, 7909.
(39) Beek, D. V.; Fossum, E. Macromolecules 2009, 42, 4016.
(40) Tienda, K.; Yu, Z.; Constandinidis, F.; Fortney, A.; Feld, W. A.;
Fossum, E. J. Polym. Sci., Part A: Polym. Chem. 2011, 49, 2908.
(41) Rusanov, A. L.; Komarova, L. G. High Perf. Polym. 2009, 21, 535.
(42) Chung, I. S.; Kim, K. H.; Lee, Y. S.; Kim, S. Y. Polymer 2010, 51,
4477.
(43) Hawker, C. J.; Chu, F. Macromolecules 1996, 29, 4370.
(44) Himmelberg, P.; Fossum, E. J. Polym. Sci., Part A: Polym. Chem.
2005, 43, 3178.
(45) Chung, I. S.; Kim, S. Y. Macromolecules 2000, 33, 9474.
(46) Williams, F. J.; Donahue, P. E. J. Org. Chem. 1977, 42, 3414.
(47) Markezich, R. L.; Zamek, O. S.; Donahue, P. E.; Williams, F. J. J.
Org. Chem. 1977, 42, 3435.
(48) Takekoshi, T.; Wirth, J. G.; Heath, D. R.; Kochanowski, J. E.;
Manello, J. S.; Webber, M. J. J. Polym. Sci., Part A: Poym. Chem. 1980,
18, 3069.
(49) White, D. M.; Takekoshi, T.; Williams, F. J.; Relles, H. M.;
Donahue, P. E.; Klopfer, H. J.; et al. J. Polym. Sci., Part A: Poym. Chem.
1981, 19, 1635.
AUTHOR INFORMATION
■
Corresponding Author
*E-mail: cis123@kribb.re.kr (I.S.C.); kimsy@kaist.ac.kr
(S.Y.K.).
Notes
The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
This work was supported by a grant from the National
Research Foundation of Korea (NRF) funded by the Korean
Government (Ministry of Education, Science, and Technology
(MEST)), the Basic Science Research Program (2010-07592)
and the Nano/Bio Science and Technology Program (2005-
01321). This work was also supported by a NRF grant funded
by MEST through the NRL (R0A-2008-000-20121-0) and the
ERC (R11-2007-050-00000-0) program.
REFERENCES
■
(1) Hougham, G.; Cassidy, P. E.; Johns, K.; Davidson, T.
Fluoropolymers (Part 2); Plenum Press: New York, 1999; pp 233−76.
(2) Dhara, M. G.; Banerjee, S. Prog. Polym. Sci. 2010, 35, 1022.
(3) Tsuchiya, K.; Shibasaki, Y.; Aoyagi, M.; Ueda, M. Macromolecules
2006, 39, 3964.
(4) Wan, Y.; Fei, X.; Shi, Z.; Hu, J.; Zhang, X.; Zhao, L.; Chen, C.;
Cui, Z.; Zhang, D. J. Polym. Sci., Part A: Polym. Chem. 2011, 49, 762.
(5) Hougham, G.; Tesoro, G.; Viehbeck, A.; Chapple-Sokol, J. D.
Macromolecules 1994, 27, 5964.
(6) Chung, I. S.; Kim, S. Y. Macromolecules 2000, 33, 3190.
(7) Chung, I. S.; Park, C. E.; Ree, M.; Kim, S. Y. Chem. Mater. 2001,
13, 801.
(8) Liu, B.; Hu, W.; Matsumoto, T.; Jiang, Z.; Ando, S. J. Polym. Sci.,
Part A: Polym. Chem. 2005, 43, 3018.
(50) Takekoshi, T. Polym. J. 1987, 19, 191.
(51) In, I. S.; Eom, H. J.; Kim, S. Y. Polymer (Korea) 1998, 22, 544.
(52) In, I.; Kim, S. Y. Polymer 2006, 47, 4549.
(9) Choi, H.; Chung, I. S.; Hong, K.; Park, C. E.; Kim, S. Y. Polymer
2008, 49, 2644.
(10) Kim, Y. J.; Seo, M.; Kim, S. Y. J. Polym. Sci., Part A: Polym. Chem.
(53) Zabrowski, D. L.; Moormann, A. E.; Beck, K. R. Tetrahedron
2010, 48, 1049.
(11) Cotter, R. J. Engineering Plastics: A Handbook of Polyaryl ethers;
Gordon and Breach Publishers: Amsterdam, 1995.
Lett. 1988, 29, 4501.
(54) Miyaura, N.; Suzuki, A. Chem. Rev. 1995, 95, 2457.
3030
dx.doi.org/10.1021/ma2028209 | Macromolecules 2012, 45, 3023−3031

Macromolecules
Article
(55) Qiu, Z.; Wang, J.; Zhang, Q.; Zhang, S.; Ding, M.; Gao, L.
Polymer 2006, 47, 8444.
(56) Hay, A. S. J. Polym. Sci., Part A: Polym. Chem. 1998, 36, 505.
(57) Lee, K. S.; Kim, J. P.; Lee, J. S. Polymer 2010, 51, 632.
(58) Yu, H.; Wang, L.; Wang, Z.; Han, X.; Zhao, M. Polymer 2010,
51, 3269.
(59) Ghim, J.; Shim, H. S.; Shin, B. G.; Park, J. H.; Hwang, J. T.;
Chun, C.; Oh, S. H.; Kim, J. J.; Kim, D. Y. Macromolecules 2005, 38,
8278.
(60) Song, Y.; Wang, J.; Li, G.; Sun, Q.; Jian, X.; Teng, J.; Zhang, H.
Polymer 2008, 49, 724.
(61) Kang, J. W.; Kim, J. P.; Lee, J. S.; Kim, J. J. J. Lightw. Technol.
2005, 23, 364.
(62) Matsumoto, T. Macromolecules 1999, 32, 4933.
3031
dx.doi.org/10.1021/ma2028209 | Macromolecules 2012, 45, 3023−3031