Synthesis and characterization of novel organosoluble polychloro substituted aromatic poly(ether ketone)s

Article abstract of DOI:10.1002/jccs.200800028

A novel monomer of tetrachloroterephthaloyl chloride (TCTPC) was prepared by the chlorination of terephthaloyl chloride catalyzed by ferric chloride at 175-180°C for 10 h, and confirmed by FTIR, MS and elemental analysis. Aseries of new polychloro substituted poly(aryl ether ketone)s with inherent viscosities of 0.58-0.65 dL/g have been prepared from TCTPC with aromatic ether monomers by electrophilic Friedel-Crafts acylation in the presence of DMF with anhydrous AlCl₃ as a catalyst in 1,2-dichloroethane. Glass-transition temperatures of these polychlorinated polymers ranged from 267 to 28°C by DSC. The degradation temperature at 5% weight loss by TGAin nitrogen for these polymers ranged from 486 to 534°C, and the char yields at 700°C were 54-65%. The polymers having a weight-average molecular weight in the range of 65,900-79,300 are all amorphous and readily soluble in polar solvents such as DMF, DMSO and NMP at room temperature. All the polymers formed transparent, strong, and flexible films, with tensile strengths of 86.1-99.7MPa, Young'smoduli of 2.32-3.35 GPa, and elongations at break of 10-15%.

Full text of DOI:10.1002/jccs.200800028

Journal of the Chinese Chemical Society, 2008, 55, 189-195
189
Synthesis and Characterization of Novel Organosoluble Polychloro
Substituted Aromatic Poly(ether ketone)s
Shou-Ri Sheng* (
), Xue-Chun Mao (
), Xue-Liang Pei (
),
Xiao-Ling Liu (
) and Cai-Sheng Song (
College of Chemistry and Chemical Engineering, Jiangxi Normal University (YaoHu Campus),
)
Nanchang, 330022, P. R. China
A novel monomer of tetrachloroterephthaloyl chloride (TCTPC) was prepared by the chlorination of
terephthaloyl chloride catalyzed by ferric chloride at 175-180 °C for 10 h, and confirmed by FTIR, MS
and elemental analysis. A series of new polychloro substituted poly(aryl ether ketone)s with inherent vis-
cosities of 0.58-0.65 dL/g have been prepared from TCTPC with aromatic ether monomers by electro-
philic Friedel-Crafts acylation in the presence of DMF with anhydrous AlCl3 as a catalyst in 1,2-dichloro-
ethane. Glass-transition temperatures of these polychlorinated polymers ranged from 267 to 280 °C by
DSC. The degradation temperature at 5% weight loss by TGA in nitrogen for these polymers ranged from
486 to 534 °C, and the char yields at 700 °C were 54-65%. The polymers having a weight-average molecu-
lar weight in the range of 65,900-79,300 are all amorphous and readily soluble in polar solvents such as
DMF, DMSO and NMP at room temperature. All the polymers formed transparent, strong, and flexible
films, with tensile strengths of 86.1-99.7 MPa, Young’s moduli of 2.32-3.35 GPa, and elongations at break
of 10-15%.
Keywords: Poly(aryl ether ketone)s; Polychloro-substituted; Soluble; Synthesis; Characteriza-
tion.
INTRODUCTION
Aromatic poly(ether ketone)s (PEKs), including poly
cessing temperature limit their extensive application. In
view of this, a great deal of research on PEKs has been con-
centrated on the introduction of pendant groups to improve
the solubility and processability, and to provide other de-
sired properties. To meet various demands without thermal
stability being sacrificed, PEKs with phenyl, methyl, butyl,
halogen trifluoromethyl, ditrifluoromethylphenyl, bromo-
methyl and sulfonate side groups have been successfully
prepared.7–15 However, to our knowledge, PEKs containing
polychloro substituents have not been reported. As part of
an ongoing research program we focused on the design and
modification of PEKs with structure to improve their prop-
erties.16 Herein, we wish to report the synthesis and charac-
terization of a novel aromatic diacid chloride monomer,
tetrachloroterephthaloyl dichloride (TCTPC) (Scheme I),
and a series of the corresponding PEKs with pendent poly-
chloro groups (Scheme II) via the electrophilic aromatic
(ether ether ketone) (PEEK), poly(ether ketone ketone)
(PEKK), and poly(ether ether ketone ketone) (PEEKK),
are a family of high-performance engineering thermoplas-
tics, and are currently receiving considerable attention for
potential applications in aerospace, automobile produc-
tion, electronics, and other high technology fields.1–5 PEKs
are commonly prepared by two general methods: (1) a syn-
thesis involving an aromatic electrophilic substitution that
yields an aryl ketone linkage and (2) a route involving an
aromatic nucleophilic substitution in which an aryl ether
linkage is obtained.6 Although PEKs show good solvent re-
sistance, excellent thermal, mechanical and electrical prop-
erties, their poor solubility in almost all known ordinary
solvents except for concentrated sulfuric acid and high pro-
Scheme I

190 J. Chin. Chem. Soc., Vol. 55, No. 1, 2008
Sheng et al.
Scheme II
substitution polymerization. In this communication, the
solubility, thermal and mechanical properties of these new
polymers are investigated.
fitted with TPC (20.3 g, 0.10 mol), iron powder (0.28 g,
0.005 mol) and anhydrous FeCl3. The reaction mixture was
placed in an oil bath preheated to 120 °C, charged with
dried Cl2 maintained at 120 °C for 2 h, and the temperature
was then raised to175-180 °C until the Cl2 uptake ceased
(generally 9-10 h). The hot reaction mixture was rapidly
filtered, and the white precipitate which formed was col-
lected and recrystallized from carbon tetrachloride twice to
afford 27.25 g (80% yield) of white crystals, m.p. 144-145
°C; 13C NMR (CDCl3): d 162.9, 139.8, 128.3; EI-MS (70
eV): m/z = 340 (M+, 15.26), 342 (M++2, 12.46), 305
(100.00), 277 (59.47), 249 (22.36), 214 (23.64), 177
(23.31), 142 (47.66), 107 (36.28), 95 (8.48), 71 (21.04), 47
(15.61); FT-IR: nmax 1776, 1377, 1354, 1242, 1164, 945,
893, 743, 697, 589, 482 cm-1.
EXPERIMENTAL
Materials
Terephthaloyl chloride (TPC), N-methyl-2-pyrroli-
done (NMP), dimethylsulfoxide (DMSO), tetrahydrofuran
(THF), chloroform, carbon tetrachloride, dichloromethane,
methanol, toluene, anhydrous aluminium chloride, anhy-
drous ferric chloride, iron powder, concentrated sulfuric
acid and calcium hydride were used as received. N,N-
Dimethylformamide (DMF) was refluxed with calcium hy-
dride and distilled under reduced pressure, then dried over
molecular sieves 4 Å prior to use. 1,2-Dichloroethane were
refluxed with phosphorous pentoxide and distilled. Di-
phenyl ether (2a) was purified by vacuum distillation be-
fore use. 2-Methyldiphenylether (2b), 3-methyldiphenyl-
ether (2c), 4,4¢-diphenoxybenzophenone (2d), 1,4-bis(4-
phenoxybenzoyl)benzene (2e) and 4,4¢-bis(4-phenoxyben-
zoyl)biphenyl (2f) were prepared in our lab according to
the standard procedure.
Polymer Synthesis
The general procedure in this study was performed as
follows. Under a N2 atmosphere, DMF (5.0 mL, 47.6 g,
0.065 mol) was added with stirring and cooling to a mixture
of aluminum chloride (18.0 g, 0.135 mol) in 1,2-dichloro-
ethane (40 mL). The mixture was cooled to -20 °C and
TCTPC 1 (6.8156 g, 0.02 mol) and aromatic ether 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 several times, extracting with boiling methanol
Synthesis of Tetrachloroterephthaloyl Dichloride
(TCTPC)
A 100-mL three necked flask equipped with a reflux
condenser, magnetic stirrer, thermometer, and Cl2 inlet was

Polychloro Substituted Poly(aryl ether ketone)s
J. Chin. Chem. Soc., Vol. 55, No. 1, 2008 191
for 20 h in a Soxhlet instrument, and drying at 120 °C over-
night in vacuo to furnish pale yellow powder polymer in
95-97% yield.
was prepared by the chlorination of commercially available
terephthaloyl chloride (TPC) at 175-180 °C for 10 h in the
presence of ferric chloride outlined in Scheme I. To opti-
mize crystallizing agents, several different solvents includ-
ing n-hexane, petroleum ether, dichloromethane, benzene
as well as carbon tetrachloride for purification of TCTPC
were used. After a series of experiments, we found that car-
bon tetrachloride gave the best results. The structure of
TCTPC was confirmed by mass spectrometry, FTIR, 13C
NMR spectroscopy, and elemental analysis. In the IR spec-
troscopy (Fig. 1), TCTPC showed strong characteristic car-
bonyl absorption at 1776 cm-1. Fig. 2 shows the 13C NMR
spectrum of TCTPC, in which all the carbons were as-
signed as expected.
Measurements
Infrared spectra (FT-IR) were determined on a Perkin-
Elmer SP One FT-IR spectrophotometer. 1H NMR spectra
were recorded on a Bruker Avance 400 MHz spectrometer
using CDCl3 as the solvent and with TMS as internal stan-
dard. Elemental analyses were performed on a Perkin-
Elmer C, H, N 2400 elemental analyzer. Mass spectra (EI,
70 eV) were recorded on an HP 5989B mass spectrometer.
Differential scanning calorimetry (DSC) and thermogravi-
metric analysis (TGA) were performed with Perkin Elmer
DSC 7 and TGA 7 analyzers, respectively. All of the sam-
ples were tested under nitrogen, at 10 °C/min for TGA and
at 20 °C/min for DSC. Mechanical properties of the thin
films (about 0.2 mm, cast from NMP solutions onto the
glass plates, and followed by heating at 100-250 °C in
vacuo) were evaluated at room temperature on an Instron
1121 instrument at a strain rate of 10 mm/min. The wide-
angle x-ray diffraction measurements were recorded at
room temperature (approx. 25 °C) on power with a Rigaku
Geiger Flex D-Max III x-ray diffractometer, using Ni-fil-
tered CuKa radiation (operating at 40 kV and 15 mA); the
scanning rate was 2°/min over a range of 2q = 2-40°). In-
herent viscosities were measured with an automated
Ubbelohde viscometer, with concentrated H2SO4 as a sol-
vent for all polymers at a 0.5 g/dL concentration at 25.0 ±
0.1 °C. Gel permeation chromatography experiments were
carried out on a device consisting of a Waters 510 pump, a
set of three PL columns of the nominal pore sizes 500, 103,
and 104 Å, and a Phillips Pye Unicam PU 4025 ultraviolet
detector. Chloroform was used as a solvent, and the analy-
ses were carried out at room temperature at a flow rate of
1.0 mL/min. The molecular weights of the polymers were
calculated with the aid of polystyrene standards. Polymer
samples were dissolved in CHCl3, filtered, precipitated in
methanol and dried under vacuum at room temperature be-
fore performing GPC measurements. The solubility of the
polymers was determined with 2 mg of a polymer in 3 mL
of a solvent.
Polymer Synthesis
As depicted in Scheme II, a series of new polymers 3
were synthesized by reaction of TCTPC with selected aro-
matic ethers 2 using Friedel-Crafts acylation polymeriza-
tion under mild conditions as described in one of our previ-
ous papers.16a This technique was used in this work, with an
initial reaction temperature between -20 and 0 °C, which
was found to be the most effective. In the course of the re-
Fig. 1. FTIR spectrum of TCTPC.
RESULTS AND DISCUSSION
Synthesis of TCTPC
Fig. 2. 13C NMR spectrum of TCTPC.
The main aromatic diacid chloride monomer, TCTPC

192 J. Chin. Chem. Soc., Vol. 55, No. 1, 2008
Sheng et al.
Table 1. Preparation and characterization of polymers 3
Elemental analysis a
C (%) H (%)
hinh
Mn
Mw
(dL/g)b (g/mol)c (g/mol)c
Polymer Yield (%)
Mw/Mn
3a
3b
3c
3d
3e
3f
96
95
97
96
95
97
53.78 (54.83) 1.89 (1.84)
54.88 (55.79) 2.29 (2.23)
54.91 (55.79) 2.27 (2.23)
62.34 (62.49) 2.62 (2.54)
64.84 (65.06) 2.81 (2.73)
66.78 (67.83) 3.15 (2.97)
0.65
0.60
0.58
0.64
0.63
0.62
41,500 79,300
36,500 69,400
34,200 65,900
37,100 72,600
39,300 72,700
1.91
1.90
1.93
1.96
1.85
d
d
d
–
–
–
a Theoretical percentages are in parentheses.
b Measured at a concentration of 0.5 g/dL in concentrated H2SO4 at 25 °C.
c Determined by GPC, using CHCl3 as the eluent and the polystyrene as the standard.
d Not obtained.
action, a polymer/catalyst complex precipitated from the
packing of the polymer chains.
Thermal Properties of Polymers
reaction media in the form of swollen, isolated particles.
After completion of the reaction, the polymer particles
formed were isolated from the reaction media in high yields
(Table 1).
As anticipated, all of the polymers with pendent poly-
Gel permeation chromatography and solution viscos-
ity results are given in Table 1. When a monomer concen-
tration of 0.40-0.45 mol/L was adopted, the polymers with
high inherent viscosity in the range of 0.58-0.65 dL/g were
obtained. The GPC curves indicated that weight-average
molecular weight (Mw’s) values of these new polymers ex-
cept for polymer 3f were in the range of 65,900-79,300, rel-
ative to standard polystyrene, and the polydispersity index
[weight-average molecular weight/number-average molec-
ular weight (Mw/Mn)] ranged from 1.85 to 1.96. There is
no GPC data available because the obtained polymer 3f
was insoluble in chloroform presumably because of its
rigid biphenyl structure.
Fig. 3. FTIR spectrum of polymer 3a.
Structural features of all the polymers were con-
formed by FTIR and NMR spectroscopy. All the polymers
exhibit the characteristic absorption bands around 1220
cm-1 due to aryl ether linkages and around 1660 cm-1 corre-
sponding to aryl carbonyl groups. As an example, the FTIR
spectrum of polymer 3a has been reproduced in Fig. 3. Fig.
4 shows a typical set of 1H NMR and 13C NMR spectra for
polymer 3a. As can be seen, the spectra are in good agree-
ment with the proposed structures.
The wide-angle X-ray diffraction (WAXD) patterns
of some chlorinated PEKs are shown in Fig. 5. The results
indicate that the polymers are amorphous in nature. The
amorphous behavior of the polymers was mainly due to the
presence of polychloro pendant groups, which disrupted
the regularity of molecular chains and inhibited the close
Fig. 4. 1H NMR (a) and 13C NMR (b) spectra of poly-
mer 3a.

Polychloro Substituted Poly(aryl ether ketone)s
J. Chin. Chem. Soc., Vol. 55, No. 1, 2008 193
chloro groups showed high glass transition temperatures
(Tg’s) as listed in Table 2, as measured by a differential
scanning calorimeter, and their corresponding DSC curves
are shown in Fig. 6. The high Tg’s for these polymers might
mainly result from the pendent polychloro substituents of
monomers inhibiting the polymer backones’ free rotation.
The incorporated, single, undersized methyl groups might
act as self-lubricant groups, which lead to polymers 3b and
3c showing slightly lower Tg’s than non substituted poly-
mer 3a. As depicted in Table 2, the Tg values of the polymer
3f are higher than those of the other corresponding poly-
mers. This is explained by the introduction of carbonyl and
biphenyl groups that lead to an increase in the rigidity of
the polymer chains, which would increase the Tg’s of the
polymer. No melting endotherms were observed in the
DSC traces, which further confirmed the amorphous nature
Table 2. The thermal properties of polymers 3
Polymer
Tg (°C) a
DT5 (°C) b DT10 (°C) c Yc (%) d
3a
3b
3c
3d
3e
3f
270
268
267
272
274
280
525
488
486
526
520
534
572
523
521
570
568
580
61
56
54
62
63
65
a Measured by DSC at a heating rate of 20 °C in N2.
b 5% weight loss temperature measured by TGA at a heating rate
of 10 °C/min in N2.
c 10% weight loss temperature measured by TGA at a heating rate
of 10 °C/min in N2.
d Char residual at 700 °C in N2.
of the polymers.
Dynamic thermogravimetry in nitrogen was used to
study the thermal stability of the various polymers; the re-
sults of the study are given in Table 2. The polymers had
excellent stabilities against thermal decomposition. The
temperatures at a 5% weight loss (TD5) are above 485 °C
and the temperatures at a 10% weight loss (TD10) are above
520 °C. However, it must be pointed out that the incorpora-
tion of polychloro substitents produced a decrease in Td in
every case, and that this effect also had to do with the nature
of the substituents. For example, polymer 3a exhibited a
5% lower weight loss temperature (Td = 525 °C) than did
nonsubstituted polymer PEKK (Td = 554 °C).16a Evidently,
polymers 3b and 3c with methyl groups exhibited lower Td
values than others, which was attributable to the thermo-
oxidatively weak C–H bonds in the –CH3 group, which
might scission before the decomposition of the polymer
backbone. However, char yields at 700 °C in nitrogen at-
mosphere exceed 50% for all polymers, comparable to
those of wholly aromatic PEKs.
Fig. 5. WAXD patterns of the polymers 3.
Solubility of Polymers
The solubility behavior of the polymers in some sol-
vents was examined and the results are shown in Table 3.
All the polymers were found to be soluble in concentrated
sulfuric acid like the conventional PEKK. It is well known
that PEKK could not be dissolved in most known organic
solvents. In sharp contrast, all the newly synthesized aro-
matic C-PEKs showed excellent solubility in aprotic polar
organic solvents, such as NMP, DMF and DMSO. Except
for polymer 3f, other polymers could also dissolve in the
less polar solvents such as chloroform and tetrahydrofuran
(THF). The good solubility of the polymers could be attrib-
Fig. 6. DSC curves of polymers 3a-3f.

194 J. Chin. Chem. Soc., Vol. 55, No. 1, 2008
Sheng et al.
(TCTPC) has been successfully synthesized from tere-
phthaloyl chloride. Several novel polychloro substituted
poly(aryl ether ketone)s with high molecular weight, high
glass transition temperatures, good thermal stability and
mechanical properties have been prepared. The resulting
C-PEKs have remarkably improved solubilities in common
organic solvents over the unsubstituted PEKK. These poly-
mers were well soluble in dipolar solvents such as DMF
and NMP. The soluble polymers can be cast into transpar-
ent and tough films from solution.
Table 3. The solubility of polymers 3
Polymer CHCl3 THF DMF DMSO NMP Conc.H2SO4
3a
+ +
+ +
+ +
+ +
+ +
– –
– –
+ +
+ +
+ +
+ +
+ +
+ –
– –
+ +
+ +
+ +
+ +
+ +
+ +
– –
+ +
+ +
+ +
+ +
+ +
+ +
– –
+ +
+ +
+ +
+ +
+ +
+ +
– –
+ +
+ +
+ +
+ +
+ +
+ +
+ +
3b
3c
3d
3e
3f
PEKK
+ +, Soluble at room temperature; + –, soluble on heating; – –,
insoluble.
ACKNOWLEDGEMENTS
Table 4. Mechanical properties of polymers 3
Tensile strength
(MPa)
Young’s
modulus (GPa)
Elongation at
break (%)
The authors are grateful to the National Natural Sci-
ence Foundation of China (No. 20264001), the Research
Program of the Educational Bureau of Jiangxi Province of
China (No. 2007-123) and the Natural Science Foundation
of Jiangxi Province of China (No. 0520028) for financial
support of this work.
Polymer
3a
3b
3c
3d
3e
3f
87.4
86.1
86.2
88.2
89.4
99.7
2.45
2.32
2.34
2.52
2.64
3.35
13
15
14
12
11
10
Received October 3, 2007.
uted to the introduction of the polychloro substituents,
which disturb the close packing of the polymer chains and
lead to the increased free volume. Therefore, it will become
easy for solvents to solubilize the polymer, which is neces-
sary in industrial processing for the polymer. However, the
solubility of polymer 3f is relatively lower with the incor-
poration of the rigid carbonyl and biphenyl moieties. Poly-
mer 3f was insoluble in chloroform at room temperature,
but could dissolve in THF with heating. Transparent and
tough films could be made from all of these new polymers
by film casting and solvent evaporation for polymer solu-
tions in chloroform, except for polymer 3f, which can be
cast into films from NMP.
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