High-Tg Transparent Poly
on Phosphinated Bisphe
,
Introduction
Bisphenols, such as bisphenol A or bisphenol F, are
difunctional buildingblocksof several importantpolymers,
such as epoxy resins, cyanate esters, benzoxazines,
polyesters, polycarboantes, polyethers, and poly(ether
sulfone)s. Thus, over 106 tons per year of bisphenol A are
consumed. As a result, modifications of bisphenols should
be of interest to the bisphenol-based industry. Among the
bisphenol-based polymers, poly(ether sulfone)s are impor-
tant high-performance engineering thermoplastic and
well-known for their excellent mechanical, thermal, and
gas transport properties.[1–9] They are typically prepared by
nucleophilic displacement polymerization of bisphenols
with 4, 4’-dihaloaromatic sulfones, where the electronega-
tive sulfone group activates the halides to nucleophilic
displacement. Poly(ether sulfone)s are naturally transpar-
applications in some electronic field.
In contrast, polyimides, although exhibit high Tg, are
typically yellow to amber in color. The intermolecular
charge-transfer complex (CTC) formation is responsible for
the color of polyimides. The intermolecular CTC is derived
fromthe interactionbetweenelectron-donor (diamine) and
electron-acceptor (dianhydride) groups, so the CTC forma-
tion can be reduced by incorporating an electron-donating
group into a dianhydride or introducing an electron-
withdrawing group into a diamine.[10] The intermolecular
CTC formation can also be reduced by introducing a bulky
pendent group to prevent the polyimide chains from being
well-stacked. Reducing conjugation or introducing alipha-
tic dianhydride/diamine is another method to lighten the
color of polyimides.[11–14] However, because the aliphatic
segments are less stable, the thermal stability of aliphatic
polyimides is not high. As to aromatic polyimides, unless
diamines[15] or dianhydrides[16] with extremely bulky
their applications in flexible display.
It has been reported that incorporating asymmetric
,
Full Paper
lym
r s
d.
se
f w
pendants[17–30] into polymers can enhance the Tg of
polymers due to restricted segmental mobility. As a result
preparation of bisphenol monomers with bulky pendant
for poly(ether sulfone)s may be a route for high-Tg
poly(ether sulfone)s. Herein, three poly(ether sulfone)s
C. H. Lin, S. L. Chang, T. P. Wei
Department of Chemical Engineering, National Chung Hsing
University, Taichung, Taiwan
E-mail: linch@nchu.edu.tw
ent and exhibitmoderate to high Tg. However, compared to
polyimides, their Tgs are not high enough, limiting their
pendant are employed, polyimideswith cutoff wavelength
less than 350nm are rarely seen in the literature, limiting
Ching Hsuan Lin,* Sheng Lung Chang
The preparation of high-Tg transparent po
phosphinate pendants is described. Poly(ethe
phinate-substituted bisphenols were prepare
studied and compared with a bisphenol-A-ba
foldable, and highly transparent with a cutof
ively. They display higher glass tran-
sition temperature (258 and 274 8C) and
lower coefficient of thermal expansion
(d¼ 48ppm per 8C by TMA) than those
of P0 (208 8C and d¼ 57ppm per 8C).
HO
Macromol. Chem. Phys. 2011, 212, 455–464
� 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim wileyonlin
(ether sulfone)s Based
nols
Tsai Pei Wei
ers from poly(ether sulfone)s with bulky
ulfone)s P1–P3 based on biphenylene phos-
The thermal properties of P1 and P2 were
d poly(ether sulfone). P1 and P2 are flexible,
avelength around 327 and 328nm, respect-
P OO
pTSA
OH
O
X
H
Y
Y
P O
C OH
O
HO
X
Y
Y
X=CH3; Y=H for (1)
X=CH3; Y=CH3 for (2)
X=H; Y=H for (3)
H-OH+
elibrary.com DOI: 10.1002/macp.201000505 455
P1–P3 based on three biphenylene phosphinate-substi-
tuted bisphenols 1–3 were prepared. The reaction condi-
tions for preparing P1–P3 were discussed. The thermal
properties of poly(ether sulfone)s were evaluated and
compared with those of the bisphenol-A-based poly(ether
sulfone) (P0).
Experimental Part
Materials
Synthesis of (3)
DOPO (10.81 g, 0.05mol), 4-hydroxybenzaldehyde 6.11 g (0.05mol),
p-TSA 0.432 g (4wt.-% relative to DOPO) and phenol 23.2 g
(0.25mol) were introduced into a 250-mL round-bottom glass flask
equipped with a nitrogen inlet and a magnetic stirrer (Scheme 2).
Themixturewas stirred at 130 8C for 24h. After that, excess phenol
was removed by a rotary evaporator. The crude product was
dissolved in ethanol and poured into hot water to remove residual
phenol. 13.9 g (67% yield) 3 (Scheme 1) were obtained as a yellow
powder. After recrystallization from DMAc/methanol solution, a
23
1
2
3 4 5
6
78
9
10 11
12
13
14 15
16
1718
19
20
21
22
P OO
CH3
HO
OH
(2)
10 11 14 15
1
2 3
4 5
6
78
12
1817
19
20 21
22
23
P OO
CH3
O O S
O
O
30
2928
2726
2524
n
(P1)
Scheme 1. Structures of (2), (3), and (P1).
pTSA
OH
O
Y
P O
C OH
O
HO
X
Y
Y
X=CH3; Y=H for (1)
X=CH3; Y=CH3 for (2)
X=H; Y=H for (3)
H-OH+
456
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C. H. Lin, S. L. Chang, T. P. Wei
P OO
HO
X
H Y
9,10-Dihydro-9-oxa-10-phosphaphenanthrene 10-oxide (DOPO)
waspurchased fromTCI. 4-Hydroxyacetophenone, 4-hydroxybenz-
aldehyde, 4,4’-difluorodiphenylsulfone (DFS), 4,4’-dichlorodiphe-
nyl ulfone (DClS), cesium fluoride, and p-toluenesulfonic acid
(p-TSA) were purchased from Arcos. Phenol and potassium
carbonate were purchased from Showa. Both N,N-dimethylform-
amide (DMAc) and tetrahydrofuran (THF)were distilled over CaH2.
The other solvents used are commercial products (HPLC grade) and
used without further purification. Bisphenol (1) was prepared
according to our previous paper.[31]
Synthesis of (2)
DOPO (10.81 g, 0.05mol), 4-hydroxyacetophenone6.81 g (0.05mol),
p-TSA 0.432 g (4wt.-% relative to DOPO) and 2,6-dimethylphenol
30.54 g (0.25mol) were introduced into a 250-mL round-bottom
glass flask equipped with a nitrogen inlet and a magnetic stirrer.
The mixture was stirred at 130 8C for 24h. After that, the mixture
was poured into toluene to remove excess 2,6-dimethylphenol.
21.8 g (96% yield) 2 (Scheme 1) were obtained as a yellow powder.
After recrystallization from acetic acid, a neat and sharp melting
point at 281 8C was observed in the DSC scans.
C25H19O4P (456.149): HR-MS (FAB
þ) m/z¼ 457.1571 (Mþ 1).
Calcd. C 73.67, H 5.52, O 14.02; Found C 73.41, H 5.74, O 14.83.
1H NMR (DMSO-d6): d¼ 1.59 (3H, H6), 1.98 (6H, H22), 6.63 (2H, H2),
6.83 (2H, H20), 7.09 (1H, H17), 7.13 (1H, H15), 7.16 (2H, H3), 7.22
(1H, H11), 7.32 (1H, H16), 7.36 (1H, H10), 7.65 (1H, H9), 7.91 (1H, H14),
8.03 (1H, H8), 8.13 (1H, OH), 9.42 (1H, OH). 13C NMR (DMSO-d6):
d¼ 16.85 (C22), 24.38 (C6), 51.51 (C5), 114.59 (C2), 118.85 (C17), 120.76
(C12), 121.98 (C7), 123.16 (C8), 123.34 (C21), 123.80 (C15), 125.21 (C14),
127.81 (C10), 128.55 (C20), 130.12 (C16), 130.54 (C3), 131.87 (C11),
132.52 (C13), 133.28 (C9),136.15 (C4), 136.19 (C19), 150.90 (C18), 151.76
(C23), 156.23 (C1).
Scheme 2. Synthesis of (1–3).
Macromol. Chem. Phys. 2
� 2011 WILEY-VCH Verlag Gmb
1
2
3 4 5
6
78
9 12
13 16
1718
19
20 21
22
(3)
P OO
H
HO
OH
9
10 11
13
14 15
16
011, 212, 455–464
H & Co. KGaA, Weinheim www.MaterialsViews.com
neat and sharp melting point at 292 8C was observed in the DSC
scans.
C25H19O4P (414.1021): HR-MS(FABþ ) m/z¼415.1107 (Mþ 1).
Calcd. C 72.46, H 4.62, O 15.44; Found C 72.02, H 4.43, O 15.29.
1H NMR (DMSO-d6): d¼ 4.47 (1H, H6), 6.69 (2H, H21), 6.71 (2H, H2),
7.07 (1H, H17), 7.19 (2H, H20), 7.28 (2H, H3), 7.31 (1H, H15), 7.39
(1H, H10), 7.44 (1H, H16), 7.47 (1H, H11), 7.67 (1H, H9), 8.10 (1H, H8),
8.13 (1H, H14), 9.40 (2H, OH). 13C NMR (DMSO-d6): d¼49.08 (C5),
115.19 (C21), 115.35 (C2), 120.02 (C17), 122.12 (C7), 123.95 (C8), 124.80
(C15), 125.85 (C14), 126.07 (C12), 126.97 (C13), 128.07 (C10), 130.29
(C20), 130.74 (C16), 130.89 (C11), 131.11 (C3), 133.39 (C9), 135.09 (C4,19),
148.97 (C18), 156.40 (C1,22).
Synthesis of P1
To a 100mL three-neck round-bottom flask equipped with
a magnetic stirrer, nitrogen inlet, bisphenol (1) 3.2878g
(7.67mmol),K2CO3 2.1213g (15.34mmol), DFS 1.9511g (7.67mmol),
and DMAc 21g were added. The mixture was stirred at 130 8C for
12h. After cooling to room temperature, the solution was poured
into 300mL methanol. The fiber-like precipitate was filtered
and extracted by methanol in a Soxhlet extractor for 12h, and
thendried inavacuumovenat 150 8C. Theyield is quantitative. The
fiber-likeP1 (Scheme1)wasdissolved inDMAcinaconcentrationof
20wt.-% and cast on glass by an automatic film applicator.
The films were dried overnight at 80 8C and dried at 100 (1h) and
200 8C (2h).
1HNMR (DMSO-d6): d¼ 1.72 (3H,H6), 6.90 (2H,H2), 6.92 (1H,H17),
6.93 (1H, H11), 7.02 (2H, H29), 7.04 (2H, H24), 7.09 (2H, H21), 7.13
(1H, H15), 7.30 (2H, H20), 7.32 (1H, H16), 7.39 (2H, H3), 7.41 (1H, H10),
7.68 (1H, H9), 7.94 (2H, H28), 7.96 (2H, H25), 7.98 (1H, H14), 8.10
(1H, H8). P2 and P0were prepared in a similar procedure using (2)
and bisphenol A as the starting materials, respectively.
Characterization
DSC was carried out on a Perkin-Elmer DSC 7 in nitrogen
atmosphere at a heating rate of 20 8C �min�1. Thermal gravi-
metric analysis (TGA) was performedwith a Seiko EXSTAR 600 at
a heating rate of 20 8C �min�1 under nitrogen atmosphere.
Dynamic mechanical analysis (DMA) was performed with a
Perkin-Elmer Pyris Diamond DMA with a sample size of
5.0� 1.0�0.002 cm3. The storage modulus E0 and tan d were
determined as the samplewas subjected to the temperature scan
mode at a programmed heating rate of 5 8C �min�1 at a frequency
of 1Hz. The test was performed by tension mode with an
amplitude of 25mm. Thermal mechanical analysis (TMA) was
performed with a Perkin-Elmer Pyris Diamond TMA at a heating
rate of 5 8C �min�1. The onset of transition in dimension was
defined as Tg, and the coefficient of thermal expansion (CTE)
P
H
OO
H+P O
X
O P OO
H
tro
stit
-se
High-Tg Transparent Poly(ether sulfone)s . . .
www.mcp-journal.de
HO
O
X
P O
C
X
O
HO
HO
-H2O
nucleophilic
addition
elec
sub
(regio
P O
C
X
O
HO
resonance
the carbocationis
stabilizedby resonance
Scheme 3. Proposed mechanism for the synthesis of (1–3).
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Macromol. Chem. Phys. 2
� 2011 WILEY-VCH Verlag Gmb
P O
X
O
HO OH
OH
X
OHO
H
P O
C
X
O
HO OH
H
H2O
H3O
philic
ution
lective)
(1-3)
OH
Y
Y
Y
Y
Y
Y
X=CH3; Y=H for (1)
X=CH3; Y=CH3 for (2)
X=H; Y=H for (3)
011, 212, 455–464
H & Co. KGaA, Weinheim 457
ata from 40 to Tg –
ing a Varian Inova
was calibrated by
9. Gel permeation
tachi L2130 with a
mide (DMF) as the
�1. The data were
ra were measured
eter in KBr powder
performed by a
Finnigan/Thermo Quest MAT 95XL mass spectrometer.
shiftduetotheelectron-donatingcharacteristicofdimethyl
group. The signals of Ar-H, assigned by the assistance of
1H-1H COSY, confirm the structure of (2). In the 13C NMR
spectrum, due to the P-C 1J coupling, the signals of carbon 5
split into two peaks at d¼ 51.51 and 52.12 with a coupling
constant of 92.03Hz. Because of the same reason, the
signals of carbon 7 split into two peaks at d¼ 121.98 and
122.73with a coupling constant of 113.15Hz. The signals of
aromatic carbon, assigned by the assistance of
H-13C HETCOR NMR spectrum, also confirm the structure
of (2). Figure 2 shows the (a) 1H and (b) 13C NMR spectra of
(3), and the peak patterns are consistent with the structure
of (3).
458
www.mcp-journal.de
C. H. Lin, S. L. Chang, T. P. Wei
in preparing 3]. As a result, the electro-
philic substitution can carry out easily
with high yield.
Characterization of (2) and (3)
Figure 1 shows the (a) 1H and (b) 13CNMR
spectra of (2). In the 1H NMR spectrum,
the signals of methyl group were split
into two peaks with a coupling constant
of 17.4Hzbecauseof a 3JP-H coupling. Two
phenol peaks at d¼ 8.2 and 9.4 were
observed. The phenol adjacent to
1
Results and Discussion
Synthesis of Bisphenols
Bisphenols 2 and 3were prepared by the
reaction of DOPO, 4-hydroxyacetophe-
none (or 4-hydroxybenzaldehyde), and
excess 2,6-dimethylphenol (or phenol)
usingp-TSAas catalyst (Scheme2). Excess
2,6-dimethylphenol (or phenol) plays the
roles of both reactant and reaction
medium. Scheme 3 shows the proposed
mechanism for the synthesis. DOPO
initially attacks the carbonyl group via
a nucleophilic addition, forming a ter-
tiary (or secondary) hydroxyl group. The
hydroxyl group is then protonated by
acid. Then, spontaneous dissociation of
the protonated hydroxyl group occurs to
yield a carbocation intermediate plus
water. Finally, 2,6-dimethyl phenol (or
phenol) reacts with the resulting carbo-
cation via an electrophilic substitution,
yielding 2 or 3, respectively. In this
mechanism, the carbocation can be
stabilized by the electron-donating phe-
nolic OH, making the carbocation stable
[even the carbocation is a secondary one
before Tg was defined by calculating the TMAd
20 8C. NMRmeasurements were performed us
600NMR in DMSO-d6, and the chemical shift
setting the chemical shift of DMSO-d6 as d¼ 2.4
chromatography (GPC) was carried out on a Hi
UV detector (L2400) using N,N-dimethylforma
eluent at 60 8C with a flow rate of 1.0mL �min
calibrated with polystyrene standard. IR Spect
by a Perkin-Elmer RX1 infrared spectrophotom
form. High resolution mass spectra were
dimethyl groups has smaller chemical Figure 1. (a) H NMR
Macromol. Chem. Phys. 2
� 2011 WILEY-VCH Verlag Gmb
13
and (b) C NMR spectra of (2) (in DMSO-d6).
011, 212, 455–464
H & Co. KGaA, Weinheim www.MaterialsViews.com
This result is speculated with the config-
uration of the carbocation intermediate
in the electrophilic substitution. Gener-
ally, the configuration of carbocation
intermediate is not planar, so the electro-
philic substitutionwill occurnon-equally
from the both faces. One of the two faces
is likely, for steric reasons, tobeabitmore
accessible than the other face, leading to
diastereomers with unequal amounts of
RR and RS ratio. Scheme 4 shows the
proposed mechanism for the regioselec-
tive electrophilic substitution. According
to the minimum energy model of carbo-
cation (calculated by ChemBio 3D Ultra
High-Tg Transparent Poly(ether sulfone)s . . .
www.mcp-journal.de
As shown in Scheme 2, bisphenol (2) is an asymmetric
bisphenol. Generally, the bisphenols[32–36] could be pre-
pared by acid-catalyzed condensation of ketone or alde-
hyde-containing compoundswith excess phenol. However,
only symmetric bisphenols can be obtained by that
approach. However, asymmetric bisphenols can easily be
preparedby this strategybychoosing substitutedphenol as
reactants. Since the phosphorus and aliphatic carbon in
bisphenol (2) are both chiral centers, four stereoisomers
should be resulted. Theoretically, each stereocenter can be
either R or S configuration, and hence, the possible
combinations are RR, RS, SR, and SS configurations. The
four stereoisomers can be grouped into two pairs of
enantiomers, resulting in two diastereomers: RRþ SS and
RSþRS. The RR stereoisomer is the enantiomer of the SS
stereoisomer, and is diastereomerically related to the RS
and SR stereoisomers. However, according to the NMR
spectra of (2), only one pair of the diastereomers, not two
pairs of diastereomers, was obtained in this synthesis. That
means that this reaction is a 100% regioselective reaction.
A, (1–2) with DFS in DMAc (or DMAc/
results are listed i
weight for P0–P2
respectively. Figu
spectra of P1. The
Figure 2. (a)1H NMR and (b)13C NMR spectra of (3) (in DMSO-d6).
Scheme 4. Propo
philic substitutio
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Macromol. Chem. Phys. 2011, 212, 455–464
� 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinhe
Toluene) using potassium carbonate as
catalyst (Scheme5andTable1, Runs1–2).
The molecular weight of P0–P2 was
measured by means of GPC, and the
n Table 2. The number-averagemolecular
is 1.00� 105, 1.02� 105, and 1.24� 105,
re 3 shows the (a)1H and (b)13C NMR
assignment of each peak, assisted by the
sed mechanism for the regioselective electro-
on the right face. This explains theperfect
regioselectivity. However, detailed
experiment is still required to confirm
this speculation.
Synthesis and Characteristics of
Poly(ether sulfone)s
P0–P2 were successfully prepared by
nucleophilic substitution of bisphenol
11.0), the left face is severely blocked by
the biphenylene and the phenol groups,
so electrophilic substitution of 2,6-
dimethyl phenol occurs exclusively only
n.
im 459
K
460
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C. H. Lin, S. L. Chang, T. P. Wei
S
O
O
FF+
P O
C
O
HO OH
X
Y
Y
1H-1H COSY and 1H-13C HETERCOSY spectra, supports the
structure of P1. Figure 4 shows the 1HNMR spectrum of P2.
One can see the characteristic dimethyl peak (H22) at d¼ 1.6,
and the assignment of other peaks supports the structure of
P2. Generally, fluorine end groups have a higher reactivity
than chloride end groups toward the nucleophilic substitu-
tion, butDFS ismuchexpensive than theDClS. To reduce the
cost, DClS was applied to replace DFS to prepare P1 (Run 3).
However, after reacting at 130 8C for 12h, a small
Scheme 5. Synthesis of P1–P3.
Table 1. Polymerization conditions for P1.
Run Reactant Temperature -C
1 DFS 130
2 DFS 130
3 DClS 130
4 DClS 130
5 DClS 120
6 DClS 130
7 DClS 145
8 DClS 160
Table 2. GPC data and thermal properties of P0–P2.
Sample Mn
a) Mw
b) E(c) tan d c) Tg (DSC)
105 105 GPa -C -C
P0 1.00 1.75 3.9 208 194
P1 1.02 1.85 5.5 258 240
P2 1.24 2.05 4.9 274 253
a)Number-average molecular weight (relative to polystyrene standar
c)Measured by means of DMA at a heating rate of 5 8C �min�1, storage
at a heating rate of 20 8C �min�1; e)Measured by TMA at a heating rat
from 50 8C to Tg – 20 8C;
g)Temperature corresponding to 5wt.-% loss b
atmosphere; h)At 800 8C in nitrogen atmosphere.
Macromol. Chem. Phys. 2
� 2011 WILEY-VCH Verlag Gmb
2CO3
P O
C
O
O O
X
S
O
O
n
Y
Y
X=CH3, Y=H for P1
X=CH3; Y=CH3 for P2
X=H; Y=H for P3
ph-CH(CH3)-ph signal at d¼ 5.5 was observed in the
1H NMR spectrum (Figure 5). In addition to the CH signal,
the signals of Ar-H were reduced apparently. Obviously, a
cleavage of the P–C bond occurred during the preparation.
At thismoment, it is speculated that the lower reactivity of
chloride end groups increase the life time of phenolate,
which will attack the electron deficient phosphorus atom,
resulting in a cleavage of P–C bond. However, such
a speculation still needs investigation. The cleavage
Solvent Result
DMAc successful
DMAc/toluene successful
DMAc P–C cleavage
DMAc/toluene P–C cleavage
DMAc incomplete
NMP incomplete
NMP P–C cleavage
NMP P–C cleavage
d) Tg (TMA)e) CTEf) Td,5%g) Char yieldh)
-C 10�6 -C�1 -C wt.-%
202 57 506 41
240 48 451 43
262 48 456 40
d, using DMF as the eluent); b)Weight-average molecular weight;
modulus (E0) recorded at 50 8C; d)From the second DSC heating scan
e of 10 8C �min�1; f)Coefficients of thermal expansion are recorded
y thermogravimetry at a heating rate of 20 8C �min�1 in nitrogen
011, 212, 455–464
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High-Tg Transparent Poly(ether sulfone)s . . .
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phenomenonwasalsoobservedusingDMAc/tolueneas the
solvent (Run 4), in which water was distilled during the
reaction. When the reaction was reduced to 120 8C to avoid
the cleavage (Run 5), some residual peaks of (1) were
observed, indicating that the reaction was not complete at
the lower reaction temperature. In addition, the prepara-
tionwasnot successfulwhenthesolventwaschanged from
DMAc toN-methylpyrrolidone (NMP) (Runs 6–8). Thus, it is
not easy to prepare P1 using DClS as reactant. Various
attempts have been made to prepare P3 by nucleophilic
substitutionof (3)andDFSusingK2CO3orcesiumfluorideas
catalyst. However, after reaction, the signal of methine
[(O¼ P)C–H] of (3) at d¼ 5.0 disappears, while a sign