Synthesis and characterization of novel organosoluble methyl substituted poly(aryl ether ketone)s containing sulfone linkage

Article abstract of DOI:10.1002/jccs.200500131

Several new methyl substituted poly(aryl ether ketone)s containing sulfone linkage with inherent viscosities of 0.62-0.84 dL/g have been prepared from 4,4 -bis(2-methylphenoxy)diphenylsulfone and 4,4 -bis(3-methylphenoxy) diphenylsulfone with terephthaloyl chloride and isophthaloyl chloride by electrophilic Friedel- Crafts acylation in the presence of DMF with an hydrous AlCl₃ as a catalyst in 1,2-dichloroethane, respectively. These polymers having weight-average molecular weight in the range of 71,000-49,000 are all amorphous and show high glass transition termperatures ranging from 167°C to 191°C, excellent thermal stability at temperatures over 400°C in air or nitrogen, high char yields of 51-58% in nitrogen and good solubility in CHCl₃ and polar solvents such as DMF, DMSO and NMP at room temperature.

Full text of DOI:10.1002/jccs.200500131

Journal of the Chinese Chemical Society, 2005, 52, 943-946
943
Synthesis and Characterization of Novel Organosoluble Methyl
Substituted Poly(aryl ether ketone)s Containing Sulfone Linkage
Shou-Ri Sheng* (
Lie Chen (
Institutes of Chemistry, Jiangxi Normal University, Nanchang, 330027, P. R. China
), Xiao-Ling Liu (
), Hong-Li Wen (
), Yong-Fen Tong (
) and Cai-Sheng Song (
),
)
Several new methyl substituted poly(aryl ether ketone)s containing sulfone linkage with inherent viscosi-
ties of 0.62-0.84 dL/g have been prepared from 4,4¢-bis(2-methylphenoxy)diphenylsulfone and 4,4¢-bis(3-
methylphenoxy)diphenylsulfone with terephthaloyl chloride and isophthaloyl chloride by electrophilic
Friedel-Crafts acylation in the presence of DMF with anhydrous AlCl3 as a catalyst in 1,2-dichloroethane, re-
spectively. These polymers having weight-average molecular weight in the range of 71,000-49,000 are all
amorphous and show high glass transition temperatures ranging from 167 °C to 191 °C, excellent thermal sta-
bility at temperatures over 400 °C in air or nitrogen, high char yields of 51-58% in nitrogen and good solubil-
ity in CHCl3 and polar solvents such as DMF, DMSO and NMP at room temperature.
Keywords: Poly(aryl ether ketone)s; Sulfone linkage; Methyl-substituted; Synthesis; Characteriza-
tion.
INTRODUCTION
Aromatic poly(aryl ether ketone)s (PEKs) are classi-
improve solubility or processability of PEKs without losing
their original excellent thermal stability. Therefore, it would
be very interesting to develop novel PEKs with a combined
advantage of excellent processing properties and thermal sta-
bility. Our research group has been interested in the design
and modifications of PEKs with structure to improve their
properties.4 In this paper we describe the synthesis of several
novel soluble methyl substituted aromatic poly(ether sulfone
ether ketone ketone)s prepared by electrophilic Friedel-
Crafts acylation condensation of 4,4¢-bis(2-methylphen-
oxy)diphenylsulfone and 4,4¢-bis(3-methylphenoxy)diphen-
ylsulfone with aromatic diacid chloride such as terephthaloyl
chloride and isophthaloyl chloride, respectively, as shown in
Scheme I. These novel PEKs are all amorphous and are
fied as high performance engineering thermoplastics and are
widely used in the electronic, electric, aircraft and aerospace
industries.1 Friedel-Crafts acylation and nucleophilic dis-
placement are synthetic routes for producing PEKs.2 Al-
though PEKs show excellent thermal, mechanical and electri-
cal properties, their poor solubility in ordinary organic sol-
vents and high processing temperature limit their extensive
application. In view of this, considerable structural modifica-
tions have been carried out to improve the properties of PEK
type polymers by incorporating the various moieties in or
onto the polymer backbone.3 However, it has been difficult to
Scheme I
AlCl3 / DMF
ClCH2CH2Cl
-20 oC, 1h
CH3
O
C
O
C
O
n
n
Cl
Ar
Cl
O
S
O
+
O
CH3
then rt. 8h
2a-2b
1a-1b
CH3
O
O
O
S
C
Ar
C
O
O
+
2n HCl
n
O
CH3
3aa-3bb
1a: o-Me- 1b: m-Me-
2a: Ar =
2b: Ar =

944 J. Chin. Chem. Soc., Vol. 52, No. 5, 2005
Sheng et al.
readily soluble in common organic solvents at room tempera-
ture. They have excellent thermo-oxidative stabilities with
high glass transition temperatures.
polymer.
Measurements
Infrared spectra (FT-IR) were determined on a Perkin-
1
Elmer SP One FT-IR spectrophotometer. H NMR spectra
EXPERIMENTAL
were recorded on Bruker Avance 400 MHz spectrometer us-
ing CDCl3 as the solvent and with TMS as internal standard.
Elemental analyses were performed on a Perkin-Elmer C, H,
N 2400 elemental analyzer. Differential scanning calorimetry
(DSC) was conducted on a Perkin-Elmer Pyris 1 at a heating
rate of 10 °C/min under nitrogen atmosphere. Thermogravi-
metric analysis (TGA) was recorded with a Shimadzu TG 40
thermogravimetric analyzer at a heating rate of 10 °C/min un-
der nitrogen or air atmosphere. The wide-angle X-ray diffrac-
tion measurements were recorded at room temperature (ca.
25 °C) on power with a Rigaku Geiger Flex D-Max III X-ray
diffractometer, using Ni-filtered CuKa radiation (operating at
40 kV and 15 mA); the scanning rate was 2°/min over a range
of 2q = 2-40°). The inherent viscosity data was obtained us-
ing conc. H2SO4 solutions with a concentration of 0.50 g/dL
in an Ubbelohde viscometer at 30 °C. Molecular weights
were determined by a gel permeation chromatography (GPC)
with polystyrene calibration using a water ALC/GPC244
equipped with TSKGH9P, GMH6, Hitachi GL/A-120, A-130
columns at 25 °C using chloroform as eluent. Polymer sam-
ples were dissolved in CHCl3, filtered, precipitated in metha-
nol and dried under vacuum at room temperature before per-
forming GPC measurements.
Material
4,4¢-Dichlorodiphenylsulfone (DCPS), anhydrous alu-
minium chloride, concentrated sulfuric acid, N-methyl-2-
pyrrolidone (NMP), dimethylsulfoxide (DMSO), chloro-
form, dichloromethane, acetone, methanol, chlorobenzene,
tetrahydrofuran, toluene and calcium hydride were used as
received. N,N-Dimethylformamide (DMF) was refluxed with
calcium hydride and distilled under reduced pressure, then
dried over molecular sieves 4 Å prior to use. 1,2-Dichloro-
ethane and chloroform were refluxed with phosphorous pent-
oxide and distilled. o-Cresol and m-cresol were purified by
distillation under reduced pressure. Terephthaloyl chloride
and isophthaloyl chloride were prepared in our laboratory
and purified by distillation under reduced pressure, m.p.
82-83 °C and 42-43 °C, respectively.
Monomer Synthesis
4,4¢-Bis(3-methylphenoxy)diphenylsulfone (1b) were
prepared from DCPS with m-cresol according to the litera-
ture.5 The 1H NMR spectrum of 1b was identical to that re-
ported in the literature. 4,4¢-Bis(2-methylphenoxy)diphenyl-
sulfone (1a) was also prepared from DCPS with o-cresol us-
ing a procedure similar to that given in a paper.5 Yield 92%;
FT-IR: nmax 2912, 1595, 1288, 1295, 1110, 1151, 1205, 965,
821, 700 cm-1; 1H NMR: d 7.80 (d, J = 8.0 Hz, 4H), 6.88 (d, J
= 8.0 Hz, 4H), 7.10-7.24 (m, 4H), 7.27-7.55 (m, 4H), 2.35 (s,
6H). Anal. calcd. for C26H22O4S: C, 72.55%; H, 5.11%.
Found: C, 72.45%; H, 5.18%.
RESULTS AND DISCUSSION
As depicted in Scheme I, four new polymers (3aa-3bb)
were synthesized by reaction of compounds 1 with selected
aromatic diacid chloride 2 using Friedel-Crafts acylation
polymerization as described in our previous paper.6 When a
monomer concentration of 0.40-0.45 mol/L was adopted, the
polymers with high inherent viscosity in the range of 0.62-
0.84 dL/g and high yields (> 95% in all cases) were obtained.
The GPC curves indicated that Mw values of the polymers 3
were in the range of 71,000-49,000, relative to standard poly-
styrene, and the polydispersity index Mw/Mn ranged from 1.7
to 1.9. The molecular weights of these polymers are suffi-
ciently high to permit casting flexible and tough films. The
FT-IR of polymers showing strong characteristic absorptions
of carbonyl group at 1648 cm-1, -SO2- at 1148 cm-1, -CH3 at
2925, 1375 cm-1 and C-O-C at 1250 cm-1 demonstrated the
performance of Friedel-Crafts acylation. In a typical 1H NMR
Polymer Synthesis
The general procedure in this study was performed as
follow. Under a N2 atmosphere, DMF (5.0 mL, 47.6 g, 0.065
mol) was added with stirring and cooling to a mixture of alu-
minum chloride (18.0 g, 0.135 mol) in 1,2-dichloroethane (40
mL). The mixture was cooled to -20 °C and aromatic ether
monomer 1 (0.02 mol) and aromatic diacid chloride mono-
mer 2 (0.02 mol) were then added with stirring for 1 h. The
mixture was allowed to warm to room temperature and stirred
for about 8 h, then worked up by blending it with methanol in
a Waring blender, filtering, washing with methanol, and dry-
ing at 140 °C for 4 h in vacuum to furnish a white powder

Methyl Substituted Poly(aryl ether ketone)s
J. Chin. Chem. Soc., Vol. 52, No. 5, 2005 945
Table 1. Preparation of polymer 3
Residuec
(wt %)
a
b
b
hinh
Tg
Td
Td
Polymer 3
d ´ 10 -4
/
Mw Mn
Mw
(dL/g)
(°C)
N2 (°C) air (°C)
3aa
3ab
3ba
3bb
0.84
0.68
0.65
0.62
191.0
181.5
181.3
167.0
475
465
439
428
470
458
430
421
58
56
54
51
7.1
5.8
5.3
4.9
1.9
1.7
1.8
1.7
a Measured at a concentration of 0.5 g/dL in conc. H2SO4 at 30 °C.
b 5% Weight loss temperature measured at 10 °C/min by TGA.
c Char residual at 700 °C in N2.
d Determined by GPC, using CHCl3 as the eluent and the polystyrene as the standard.
Table 2. The solubility of polymer 3 in various organic solvents at room temperature
Polymer 3 DMF DMSO NMP CHCl3 CH2Cl2 ClC6H5 CH3OH Acetone THF Toluene
3aa
3ab
3ba
3bb
++
++
++
++
++
++
++
++
++
++
++
++
++
++
++
++
++
++
++
++
+
+
+
+
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
-
++: soluble; +: soluble under heat; -: insoluble.
spectrum of polymer 3aa in CDCl3, the peak that appeared at
2.36 ppm was assigned to six methyl pendent protons, and the
remaining aromatic protons were detected as multiplets at
7.12-7.86 ppm.
the polymers 3aa, 3ab and 3ba showed a high Tg over 180 °C.
The WAXD analysis showed that all polymers were amor-
phous, which was consistent with the results of DSC analysis
with no melting temperatures.
Polymers 3aa-3bb have excellent thermal stability ac-
cording to dynamic TGA results (Table 1). Thermal stability
as indicated by the temperature (Td) at which 5% weight loss
observed were over 420 °C both in nitrogen and air. Polymers
3aa and 3ab exhibited better thermal stability than polymers
3ba and 3bb. Furthermore, the Td of polymers containing all
para-phenylene linkages was higher than those of corre-
sponding polymers containing meta-phenylene linkages. It
should be noted that the relatively low Td of the polymers are
lower than those of most known wholly aromatic PEKs such
as ICI’ PEEK and Dupont’ PEKK, which possibly arises
from the presence of less stable methyl groups. The represen-
tative TG diagrams of polymer 3aa in air and nitrogen are
shown in Fig. 1. The initial decomposition temperature of the
polymer 3aa in air is lower than in nitrogen. In air, the rate of
the weight loss was relatively rapid above 490 °C, and there
was about 35% residue remaining at 700 °C. All other poly-
mers showed similar thermal behavior. Char yields at 700 °C
in nitrogen atmosphere exceed 50% for all polymers, compa-
rable to those of wholly aromatic PEKs. All polymers exhib-
ited higher glass transition temperatures than did PEEK (Tg =
143 °C) and PEKK (Tg = 156 °C), which might mainly result
from the methyl side group of monomers inhibiting the poly-
mer backones’ free rotation. Especially, it is noteworthy that
The solubility of the polymers in various solvents was
examined and the results are shown in Table 2. These poly-
mers could not dissolve in methanol, acetone, toluene or
THF, but were well soluble in many kinds of organic solvents
such as DMF, DMSO, NMP, CHCl3, CH2Cl2 and chloroben-
zene. Therefore, introducing polar bulky sulfone group and
methyl pendant into PEKs would improve their solubility,
which is necessary in industrial processing for the polymer.
Strong, transparent, creasable films of the polymers are read-
Fig. 1. TGA curves of the polymer 3aa in N2 (a) and in
air (b).

946 J. Chin. Chem. Soc., Vol. 52, No. 5, 2005
Sheng et al.
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In conclusion, four novel methyl substituted poly(aryl
ether ketone)s containing sulfone linkage with high molecu-
lar weight, high glass transition temperatures and good ther-
mal stability have been prepared. These polymers were well
soluble in CHCl3 and polar solvents such as DMF and DMSO,
etc., and afforded transparent, flexible and amorphous films
by solution-casting.
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ACKNOWLEDGEMENTS
We are grateful for the National Natural Science Foun-
dation of China (No. 20264001), the National 863 High Tech-
nology Program (No. 2002AA333120) and the NSF of Jiang-
xi Province for their financial support.
Received February 9, 2004.
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