Synthesis and characterization of soluble and thermally stable poly(ether-imide-urea)s

Article abstract of DOI:10.1246/bcsj.20130330

Two series of new modified poly(ether-imide-urea)s, P_Oa-P _Oc and P_Sa-P_Sc, with benzoxazole or benzothiazole pendent groups were successfully synthesized by diphenyl azidophosphate (DPAP)-activated one-pot polyaddition reaction of two bis(imide-dicarboxylic acid)s, 2-[3,5-bis(4-trimellitimidophenoxy)phenyl] benzoxazole (1_O) or 2-[3,5-bis(4-trimellitimidophenoxy)phenyl] benzothiazole (1_S) with various kinds of aromatic diamines a-c. In this direct method, the polymers were prepared by polyaddition reactions of the in situ-formed diisocyanate with the aromatic diamines. For comparative purposes, reference poly(ether-imide-urea)s, P_Ra-P_Rc, were also prepared by reacting a bis(imide-dicarboxylic acid) lacking pendent groups, namely, 3,5-bis(4-trimellitimidophenoxy)benzene (2) with the same diamines under similar conditions. Characterization of polymers was accomplished by inherent viscosity measurements, FTIR, ¹H NMR spectroscopy and thermogravimetry. The polymers were obtained in quantitative yields with inherent viscosities between 0.19 and 0.37 dL g^-1. The solubilities of modified poly(ether-imide-urea)s in common organic solvents as well as their thermal stability were enhanced compared to these of the corresponding unmodified poly(etherimide-urea)s. The glass-transition temperature, 10% weight loss temperature, and char yields at 800°C were, respectively, 7-28, 14-38°C, and 3-7% higher than those of the reference polymers in nitrogen atmosphere.

Full text of DOI:10.1246/bcsj.20130330

© 2014 The Chemical Society of Japan
Bull. Chem. Soc. Jpn. Vol. 87, No. 5, 631-638 (2014)
631
Synthesis and Characterization of Soluble
and Thermally Stable Poly(ether-imide-urea)s
Hojjat Toiserkani
Department of Chemistry, College of Sciences and College of Oil Engineering,
Hormozgan University, Bandar Abbas 3995, Iran
Received November 27, 2013; E-mail: Toiserkani@yahoo.com
Two series of new modified poly(ether-imide-urea)s, POa-POc and PSa-PSc, with benzoxazole or benzothiazole
pendent groups were successfully synthesized by diphenyl azidophosphate (DPAP)-activated one-pot polyaddition
reaction of two bis(imide-dicarboxylic acid)s, 2-[3,5-bis(4-trimellitimidophenoxy)phenyl]benzoxazole (1O) or 2-[3,5-
bis(4-trimellitimidophenoxy)phenyl]benzothiazole (1S) with various kinds of aromatic diamines a-c. In this direct
method, the polymers were prepared by polyaddition reactions of the in situ-formed diisocyanate with the aromatic
diamines. For comparative purposes, reference poly(ether-imide-urea)s, PRa-PRc, were also prepared by reacting a
bis(imide-dicarboxylic acid) lacking pendent groups, namely, 3,5-bis(4-trimellitimidophenoxy)benzene (2) with the same
diamines under similar conditions. Characterization of polymers was accomplished by inherent viscosity measurements,
1
FTIR, H NMR spectroscopy and thermogravimetry. The polymers were obtained in quantitative yields with inherent
viscosities between 0.19 and 0.37 dL g¹1. The solubilities of modified poly(ether-imide-urea)s in common organic
solvents as well as their thermal stability were enhanced compared to these of the corresponding unmodified poly(ether-
imide-urea)s. The glass-transition temperature, 10% weight loss temperature, and char yields at 800 °C were, respectively,
7-28, 14-38 °C, and 3-7% higher than those of the reference polymers in nitrogen atmosphere.
Polyimides present both great scientific and commercial
interest, because of their combination of outstanding key prop-
erties, including thermal and thermooxidative stability, high
mechanical strength, high modulus, good adhesion to common
substrates, excellent electrical properties, and superior chemical
resistance.1-3 However, despite the excellent combined prop-
erties, their widespread applications have been limited in some
fields, because aromatic polyimides are normally insoluble
in common organic solvents and have extremely high glass-
transition temperatures (Tg’s) or melting temperatures, which
preclude melt processing. Consequently, the search for new
polyimides with better processability, and the same thermal
stability should result in new materials for many applications.
The incorporation of ether groups or other flexibilizing linkages
into the main chain generally leads to lower glass-transition
temperature as well as a significant improvement in solubility
without greatly sacrificing other advantageous polymer prop-
erties.4-7 On the other hand, the introduction of bulky groups
into the polymer chain8-13 or the attachment of bulky lateral
groups14-21 can impart a significant increase in Tg by restricting
the segmental mobility, while providing an enhanced solubility
due to decreasing packing and crystallinity. Combining these
two structural modifications minimized the trade-off between
the processability and useful and positive properties of aro-
matic polyimides.
zole (1S) were synthesized and used for the preparation of
corresponding alternating poly(ether-imide-amide)s,22 poly-
(ether-imide-ester)s23 and poly(ether-imide-urethane)s.24
As part of our continuing efforts to develop soluble poly-
imides with good thermal stability, the current work deals with
the synthesis and characterization of two series of new modi-
fied poly(ether-imide-urea)s, POa-POc and PSa-PSc, bearing
benzoxazole or benzothiazole pendent groups derived from two
bis(imide-dicarboxylic acid)s, 1O and 1S with various kinds of
aromatic diamines a-c in dry dimethyl sulfoxide (DMSO) in
the presence of diphenyl azidophosphate (DPAP) via “one-pot”
procedure. The effect of pendent groups on solubility and
thermal properties of the resulting modified polymers is inves-
tigated by comparison with polymers missing pendent group,
reference PRa-PRc, obtained from 1,3-bis(4-aminophenoxy)-
benzene (3) and the same diamines. Since the designed poly-
(ether-imide-urea)s are composed of flexible ether linkages,
and pendent groups, they should be expected to exhibit an
enhanced solubility, and excellent thermal properties in com-
parison with reference polymers.
Experimental
Materials. All chemicals were purchased either from Merck
or Fluka Chemical Co. Diphenyl azidophosphate (DPAP) was
purchased from Merck and used as received. Dimethyl sulfox-
ide (DMSO, Merck), and triethylamine (TEA, Merck) were
purified by distillation under reduced pressure over calcium
hydride and stored over 4-¡ molecular sieves. 1,3-Phenylene-
diamine (a, Merck) was purified by sublimation before use.
In our previous studies, two benzoxazole- or benzothia-
zole-containing dicarboxylic acids bearing two preformed imide
rings, 2-[3,5-bis(4-trimellitimidophenoxy)phenyl]benzoxazole
(1O) and 2-[3,5-bis(4-trimellitimidophenoxy)phenyl]benzothia-
Published on the web January 17, 2014; doi:10.1246/bcsj.20130330

632
Bull. Chem. Soc. Jpn. Vol. 87, No. 5 (2014)
Soluble and Thermally Stable Poly(ether-imide-urea)s
Table 1. Physical Properties and Elemental Analysis of the Poly(ether-imide-urea)s
a)
Elemental analysis/%
Yield
/%
©
Composition of
repeating unit
inh
Designation
¹1
/dL g
C
H
N
Calcd
Found
Calcd
Found
Calcd
Found
Calcd
Found
Calcd
Found
Calcd
Found
Calcd
Found
Calcd
Found
Calcd
Found
68.45
68.06
68.85
68.13
67.74
66.65
67.19
66.63
67.74
67.12
66.66
66.05
67.92
67.21
68.45
67.87
67.19
66.68
3.40
3.43
3.30
3.35
3.25
3.34
3.34
3.41
3.25
3.26
3.20
3.24
3.35
3.54
3.40
3.61
3.34
3.52
11.40
11.36
11.47
11.04
11.28
11.13
11.19
11.05
11.28
11.06
11.11
10.98
11.32
11.08
11.40
11.21
11.19
11.10
POa
POb
POc
PSa
PSb
PSc
68
63
65
66
62
66
74
68
71
0.31
0.23
0.19
0.28
0.20
0.26
0.37
0.27
0.24
C49H29N7O9
C56H32N8O10
C56H32N8O9S
C49H29N7O8S
C56H32N8O9S
C56H32N8O8S2
C42H26N6O8
C49H29N7O9
PRa
PRb
PRc
C49H29N7O8S
¹1
a) Measured at a polymer concentration of 0.5 g dL in DMF at 30 °C.
Aromatic diamines including 5-(2-benzoxazolyl)-1,3-phenyl-
enediamine (b, mp 226-230 °C), and 5-(2-benzothiazolyl)-1,3-
phenylenediamine (c, mp 167-171 °C) were prepared in our
laboratory according to a method previously reported.25
Synthesis of the Monomers. Bis(imide-carboxylic acid)
monomers 1O, 1S, and 2 were synthesized by the condensation
of 5-(2-benzoxazole)-1,3-bis(4-aminophenoxy)benzene, 5-(2-
benzothiazole)-1,3-bis(4-aminophenoxy)benzene, and 1,3-bis-
(4-aminophenoxy)benzene (as a reference), with two mole
equivalents of trimellitic anhydride in glacial acetic acid,
respectively, according to our previous work.22
(DMSO-d6): ¤ 8.92 (4H of ureylene linkages), 8.38-6.85
(separate peak blocks, 25H of aromatic rings). Elemental
analysis: calculated for C49H29N7O9 (859)n: C, 68.45; H, 3.40;
N, 11.40%. Found: C, 68.06; H, 3.43; N, 11.36%.
The above one-pot polyaddition reaction was chosen as
a procedure for preparation of the other polymers. Inherent
viscosities, yields, and elemental analyses of poly(ether-imide-
urea)s are summarized in Table 1. The spectroscopic data for
the polymers are discussed in Results and Discussion section.
Measurements. Inherent viscosities (©inh) of polymers were
¹1
determined for solution of 0.5 g dL in DMF at 30 °C using a
1
Synthesis of Poly(ether-imide-urea)s.
The general
Canon-Fenske viscometer. H NMR spectra were recorded on
procedure to prepare the poly(ether-imide-urea)s is as follows:
into a hot flow-dried two-necked flask equipped with a drying
tube-capped reflux condenser, magnetic stirrer, and dropping
funnel were placed bis(imide-carboxylic acid) 1O (0.227 g,
0.30 mmol) in DMSO (2.0 mL). Then, DPAP (0.7 mL) and
triethylamine (0.8 mL) were added to the initial contents of
the flask. The final mixture was stirred 2 h at about 10 °C and
then for 3 h at 70 °C until evolution of nitrogen gas stopped.
1,3-Phenylenediamine a (0.032 g, 0.30 mmol) in DMSO (2.5
mL) was added dropwise to the initial reaction mixture, and
the final mixture was heated for 12 h at 90 °C. The viscous
polymer solution obtained was trickled on stirred methanol
to give rise to a crude precipitate, which was collected by
filtration, washed thoroughly with methanol, hot water, and
ether, respectively, and dried under reduced pressure at 40 °C
to afford 0.175 g (68%) of POa as brown powder. The inherent
viscosity of polymer, POa, was 0.31 dL g¹1 measured at a con-
a Bruker AV-500 FT-NMR spectrometer in DMSO-d6 at 25 °C
with frequencies of 500.13 MHz. FTIR spectra were recorded
on a Bruker Tensor-27 spectrometer for the measurement of
infrared absorption spectra for monomers and polymers. The
spectra of solids were obtained using KBr pellets. Thermo-
gravimetric analyses (TGA/DTG) was conducted with a Du
Pont 2000 thermal analysis instrument under nitrogen atmos-
phere (20 cm3 min¹1) at a heating rate of 10 °C min¹1. Differ-
ential scanning calorimetry (DSC) was recorded on a Perkin-
¹1
Elmer pyris 6 DSC under nitrogen atmosphere (20 cm3 min
)
¹1
at a heating rate of 10 °C min
.
Results and Discussion
Synthesis and Characterization. Bis(imide-carboxylic
acid) monomers such as 2-[3,5-bis(4-trimellitimidophenoxy)-
phenyl]benzoxazole (1O), 2-[3,5-bis(4-trimellitimidophenoxy)-
phenyl]benzothiazole (1S), and 3,5-bis(4-trimellitimidophen-
oxy)benzene (2, as reference) were synthesized by the con-
densation reaction between the appropriate aromatic diamines,
¹1
centration of 0.5 g dL in N,N-dimethylformamide (DMF) at
30 °C.
FTIR (KBr, cm¹1): 3414 (br, s), 1778 (sh, w), 1726 (sh, s),
1671 (sh, s), 1615 (sh, m), 1601 (sh, w), 1502 (sh, m), 1439
(sh, m), 1380 (sh, s), 1225 (sh, s), 1164 (sh, w), 1090 (sh, m),
5-(2-benzoxazole)-1,3-bis(4-aminophenoxy)benzene,
5-(2-
benzothiazole)-1,3-bis(4-aminophenoxy)benzene, and 1,3-bis-
(4-aminophenoxy)benzene, and two mole equivalents of tri-
mellitic anhydride in glacial acetic acid, respectively. The
1
1017 (sh, w), 939 (sh, w), 763 (sh, w), 725 (sh, m). H NMR

H. Toiserkani
Bull. Chem. Soc. Jpn. Vol. 87, No. 5 (2014)
633
Scheme 1. One-pot synthetic route to prepare new poly(ether-imide-urea)s.
details of this synthesis route and the characterization data have
been reported in our previous work.22
polymers obtained have been summarized in Table 1. Accord-
ing to the data from Table 1, the poly(ether-imide-urea)s all get
high yields (62-74%), and elemental analyses show that com-
positions found of the repeating unit are agree with those results
shown in Scheme 1. The resulting poly(ether-imide-urea)s
Two series of new modified poly(ether-imide-urea)s, POa-
POc and PSa-PSc having benzoxazole and benzothiazole
pendent group were prepared by the diphenyl azidophosphate
(DPAP) activated one-pot polycondensation reaction of bis-
(imide-carboxylic acid) monomers, 1O or 1S, with various
aromatic diamines a-c. In addition, the corresponding unmodi-
fied poly(ether-imide-urea)s, PRa-PRc (reference polymers)
were also prepared by reacting a bis(imide-dicarboxylic acid)
lacking pendent groups namely 3,5-bis(4-trimellitimidophen-
oxy)benzene (2) with the same diamines under identical experi-
mental conditions for comparative purposes.
As shown in Scheme 1, bis(imide-carboxylic acid) mono-
mers, were converted to bis(imide-carbonyl azide) components,
using DPAP in DMSO as the reaction solvent. The thermal
decomposition of the in situ-obtained bis(imide-carbonyl
azide) via Curtius rearrangement gave the corresponding di-
isocyanates. In continuation of this reaction, diisocyanates have
been reacted with various aromatic diamines a-c to prepare the
final poly(ether-imide-urea)s.
¹1
exhibited inherent viscosities of 0.19-0.37 dL g measured in
DMF at a concentration of 0.5 dL g¹1 at 30 °C. The FTIR spectra
of the polymers showed characteristic absorptions for the imide
¹1
ring at around 1780 and 1720 cm (imide-I), which is indi-
cative of the asymmetric and symmetric C=O stretching vibra-
¹1
tion, and at 1375 (imide-II), 1085 (imide-III), and 725 cm
(imide-IV) whereas the imide-I, -III, and -IV bands were
assigned to axial, transverse, and out-of-plane vibrations of the
cyclic imide structure, respectively.25 The N-H stretching band
of the urea could be observed around 3400-3200 cm¹1, the
C-O-C stretching band of ether linkages at 1220 cm¹1, and the
C=O stretching band of urea groups at 1670 cm¹1, the C=N
stretching band benzoxazole or benzothiazole groups at 1620-
¹1
1635 cm and the N-H bending and C-N stretching bands at
1550 cm¹1 could also be observed.5,15,28 Figure 1 shows typical
1
FTIR spectra of POb, PSc, and PRa. In general, the H NMR
The reactions including diisocyanate formation and poly-
addition readily proceeded in a dark yellow to brown homo-
geneous solution for all polymers preparation. The poly(ether-
imide-urea)s were prepared in total yields of about 70%
starting from bis(imide-carboxylic acid)s. These low yields
are reasonable because the yields of the Curtius rearrange-
ment reactions are known generally not to be very high.26 The
details about various aspects of this one-pot polyaddition were
reported in literature.27
spectra of the resulting poly(ether-imide-urea)s are divided
two parts, with the first showing the urea-group protons in the
most downfield region (around 9.12-8.85 ppm), and the second,
resonance signals of aromatic protons in the region of about
6.80-8.50 ppm. On the basis of the description above, we can
conclude that the polymers have the expected structures.
Properties of the Poly(ether-imide-urea)s. The organo-
solubility behavior of all polymers was tested qualitatively
in various organic solvents, with the results summarized in
Table 2. One of the aims of the present investigation was the
enhancement of the polymer solubility by introducing volumi-
nous pendent groups along the polymer backbone. All of
the modified poly(ether-imide-urea)s were soluble in polar
Also, structural features of these polymers were confirmed by
1
elemental analysis as well as FTIR and H NMR spectroscopy.
Elemental analysis values of C, H, and N of all the polymers are
close to theoretical values. The experimental data of the isolated

634
Bull. Chem. Soc. Jpn. Vol. 87, No. 5 (2014)
Soluble and Thermally Stable Poly(ether-imide-urea)s
Figure 1. FTIR spectra of POb, PSc, and PRa.
aprotic solvents (DMF, NMP, DMAc, and DMSO) and concen-
trated H2SO4, at room temperature. They also showed moderate
solubilities in m-cresol and pyridine, while they were almost
insoluble in chloroform and tetrahydrofuran upon heating at
about 70 °C. Modified poly(ether-imide-urea)s, POa-POc and
PSa-PSc displayed almost the same solubility in these solvents.
In contrast, the unmodified poly(ether-imide-urea)s (reference
polymers, PRa-PRc) dissolved at ambient temperature only in
concentrated H2SO4 and upon heating in polar aprotic solvents.
In addition, they were completely insoluble in less efficient
solvents such as m-cresol, pyridine, chloroform, and tetra-
hydrofuran. In general, the modified poly(ether-imide-urea)s

H. Toiserkani
Bull. Chem. Soc. Jpn. Vol. 87, No. 5 (2014)
635
Table 2. Solubility of the Poly(ether-imide-urea)s
Polymer
Solventa)
m-Cresol
code
DMAc
DMSO
DMF
NMP
THF
Py
H2SO4
CF
POa
POb
POc
PSa
PSb
PSc
PRa
PRb
PRc
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+h
+
+
+
+
+
+
+
+h
+
+h
+
+h
+h
+
¹
¹
+h
+h
+
+h
+h
+
+
+
+
+
+
+
+
+
+
¹
¹
¹
¹
¹
¹
¹
¹
¹
¹
¹
¹
+
+
+
¹
+h
¹
+h
+h
+
+h
+h
+
¹
¹
¹
¹
+
+
+h
¹
+h
a) Qualitative solubility was determined by dissolving 10 mg of poly(imide-urea)s in 1 mL of solvent
at room temperature or upon heating; +: soluble at room temperature; +h: soluble on heating; and
¹: insoluble even on heating; DMAc: N,N-dimethylacetamide; DMSO: dimethyl sulfoxide; DMF: N,N-
dimethylformamide; NMP: N-methylpyrrolidone; THF: tetrahydrofuran; Py: pyridine; CF: chloroform.
displayed an increased solubility in comparison with unmodi-
fied series. This was attributable in part to the packing-
disruptive structure of the bis(imide-dicarboxylic acid) mono-
mers, 1O and 1S, which resulted in a high steric hindrance for
close chain packing and, thus, reduced interchain interactions.
The chain separation effect accounts for a weakening of the
strong interactions through hydrogen bonding and the steric
factor must be dominant because the other effects, such as
dipole attraction or chain rigidity enhancement, should work
against good solubility. In general, high solubility of these
polymers in high polar solvents and high solubility of the
poly(ether-imide-ester)s and somewhat the poly(ether-imide-
urethane)s with the same structure, reported previously,22-24 in
less polar solvents can be explained by the strong solvation of
the ester linkages by pyridine, m-cresol and other less polar
solvents causing better solubility of poly(ether-imide-ester)s
in less polar solvents, whereas the strong solvation of the
urea and amide groups by polar aprotic solvents improves the
solubility of poly(ether-imide-urea)s and poly(ether-imide-
amide)s in NMP, DMAc, DMF, and DMSO.
Table 3. Thermal Properties of the Polymersa)
b)
c)
Polymer
Tg
¦Tg T10
¦T10 Char yieldd) ¦CY
code
/°C
/°C
/°C
/°C
/wt %
/wt %
POa
POb
POc
PSa
PSb
PSc
PRa
PRb
PRc
202
221
210
196
214
203
174
204
196
(28)
(17)
(14)
(22)
(10)
(7)
408
443
428
397
425
422
370
411
405
(38)
(32)
(23)
(27)
(14)
(17)
®
33
41
40
32
38
38
29
34
33
(4)
(7)
(7)
(3)
(4)
(5)
®
®
®
®
®
®
®
®
a) Values shown in parentheses are the difference between the
Tg and T10 values and char yields of the modified polymers
(with benzoxazole or benzothiazole pendent groups) and refer-
ence polymers (without pendent groups) with similar struc-
tures. b) From the second heating traces of DSC measurements
¹1
with a heating rate of 10 °C min in nitrogen. c) Decomposi-
tion temperature at which a 10% weight loss was recorded by
¹1
TGA at a heating rate of 10 °C min in nitrogen. d) Residual
Thermogravimetric analysis (TGA/DTG) and differential
scanning calorimetry (DSC) were used to evaluate the thermal
properties of the poly(ether-imide-urea)s, and the results
including glass-transition temperatures (Tg) and the temperature
at 10% weight loss (T10) in nitrogen as well as the anaerobic
char yield at 800 °C for all polymers are summarized in
Table 3. The DSC profiles were achieved at a heating rate of
weight percentage at 800 °C under nitrogen flow.
loss) as a criterion of thermal stability. The modified polymers
started to lose weight at higher temperatures than the corre-
sponding unmodified ones, since their T10 values were higher by
14-38 °C. In addition, the modification of polymers increased
their anaerobic char yield at 800 °C by 3-7%. This desirable
thermal stability of the modified polymers could be attributed to
the presence of the heat-resistant benzoxazole or benzothiazole
ring incorporated as pendent group as well as the introduction
of rigid imide rings causing an improved stability toward
heat. Representative TGA/DTG thermograms of the polymer
POb are shown in Figure 3. Furthermore, in order to have a
better comparison, temperatures at 10% weight losses (T10)
are tabulated in Table 3. In general, the thermograms of the
resulting polymers were almost similar to each other, and
poly(ether-imide-urea)s showed a two-stage decomposition at
elevated temperatures. Assuming a different stability of the urea
and imide units, the temperature maximum decomposition
¹1
10 °C min in a nitrogen atmosphere in the temperature range
from room temperature to 300 °C. The DSC thermograms of
the polymers showed glass-transition temperatures (Tg’s) in
the range between 174 and 221 °C. The nature of the diamine
moiety played a significant role on the Tg values. These went
down in the series as follows b > c > a (Table 3). This could
be attributed to the incorporation of rigid benzoxazole or
benzothiazole ring in diamine segments, which restricted the
free rotation of the macromolecular chains leading to an
enhanced Tg value. Figure 2 shows DSC curves of the poly-
mers POa, PSa, and PRa.
The thermal stability was investigated by TGA with the
T10 values (temperatures which correspond to a 10% weight

636
Bull. Chem. Soc. Jpn. Vol. 87, No. 5 (2014)
Soluble and Thermally Stable Poly(ether-imide-urea)s
of the first stage is at around 370-430 °C, which might be
attributed to the early degradation of the urea linkages.
Therefore, the 10% weight loss temperatures are mainly caused
by the decomposition of urea units. The second-stage decom-
position, started around 540-590 °C, is due to the decomposi-
tion of the imide linkages.28-31
In order to investigate the structure-property relationships,
in particular, studying the influence of the pendent groups on
some polymer properties such as Tg and T10 values and char
yield at 800 °C. In this way, the four classes of copolyimides
including those previously-prepared namely, poly(ether-imide-
amide)s,22 poly(ether-imide-ester)s,23 and poly(ether-imide-
urethane)s24 and these poly(ether-imide-urea)s, four polymers
having almost the same aromatic structure have been chosen
for comparative purposes. Scheme 2 shows their chemical
structure, and Table 4 tabulates the obtained results. The most
important difference among above copolyimides was observed
in their thermal behavior. The present poly(ether-imide-urea)s
exhibited less thermal stability than those of the poly(ether-
imide-amide)s, poly(ether-imide-ester)s (Table 4). However,
they showed higher T10 values than the poly(ether-imide-
urethane)s. These observations might be attributed to the early
degradation of the urethane linkages than those of the amide,
ester and even urea groups against high temperatures. Moreover,
Tg values of the poly(ether-imide-amide)s are remarkably
greater than other polymers. This could be attributed to the
incorporation of flexible ester, urea, and urethane units along
the polymer backbone, while the presence of amide groups with
H-bond formation ability causes a restriction in free rotation of
the macromolecular chains leading to enhanced Tg values.
Conclusion
The one-pot polyureylation reactions of bis(imide-carbox-
ylic acid)s, namely, 1O and 1S (having benzoxazole or benzo-
thiazole pendent groups, respectively) and 2 (missing pendent
groups, as reference monomer) with a number of aromatic
diamines a-c resulted in preparation of aromatic poly(ether-
imide-urea)s POa-POc, PSa-PSc, and PRa-PRc. The main
objectives of this study were to improve the solubility as well
as the thermal stability by the introduction of both heat-
resistant imide heterocyclic rings and flexible ether and urea
segments into the macromolecular chains. These new modified
polymers exhibited good thermal properties as well as excellent
solubility in comparison with unmodified ones. These charac-
teristics indicate that the benzoxazole or benzothiazole pendent
groups in the polymer backbone have played an important
role in the improvement of solubility and thermal resistance
of polymer. Thus, they are considered to be new promising
processable high-temperature polymeric materials.
Figure 2. DSC thermograms of the polymers POa, PSa,
and PRa.
Figure 3. TGA/DTG thermograms of POb.

H. Toiserkani
Bull. Chem. Soc. Jpn. Vol. 87, No. 5 (2014)
637
Scheme 2. Chemical structure of four classes of copolyimides with almost the same aromatic backbone.
Table 4. Structures and Some Thermal Characteristics of Copolyimides with Almost the Same Aromatic Moieties
a)
b)
Tg
T10
Char yieldc)
/wt %
Polymer class
Polymer structure
Ref.
/°C
/°C
O
O
O
O
NH
NH
N
O
O
N
n
O
O
Poly(ether-imide-amide)s
263
513
52
22
23
24
N
O
O
O
O
O
O
O
N
O
O
N
n
O
O
Poly(ether-imide-ester)s
Poly(ether-imide-urethane)s
Poly(ether-imide-urea)s
208
197
202
425
397
408
36
32
33
N
O
O
O
O
O
N
HN
O
NH
O
N
O
O
n
O
O
N
O
O
O
NH NH
O
N
O
HN
NH
O
O
N
n
This
Study
O
O
N
O
¹1
a) From the second heating traces of DSC measurements with a heating rate of 10 °C min in nitrogen. b) Temperature at which
¹1
10% weight loss was recorded by TGA at a heating rate of 10 °C min in nitrogen. c) Residual weight percentage at 800 °C under
nitrogen flow.
86, 289.
References
5
6
H. Toiserkani, High Perform. Polym. 2011, 23, 542.
M. Kolahdoozan, R. Mirsafaei, S. Mallakpour, Polym. Bull.
1
T. L. St. Clair, in Polyimides, ed. by D. Wilson, H. D.
Stenzenberger, P. M. Hergenrother, Chapman & Hall, New York,
1990, pp. 58-78. doi:10.1007/978-94-010-9661-4_3.
2012, 68, 1239.
7
X.-h. Huang, W. Huang, Y.-f. Zhou, D.-y. Yan, Chin. J.
2
Y. Imai, in Polyimides: Fundamentals and Applications,
Polym. Sci. 2011, 29, 506.
ed. by M. K. Ghosh, K. L. Mittal, Marcel Dekker, New York,
1996, p. 49.
8
C. A. Terraza, J.-G. Liu, Y. Nakamura, Y. Shibasaki, S.
Ando, M. Ueda, J. Polym. Sci., Part A: Polym. Chem. 2008, 46,
3
4
C. E. Sroog, Prog. Polym. Sci. 1991, 16, 561.
H. Toiserkani, M. Rafiaee, Bull. Chem. Soc. Jpn. 2013,
1510.
9
Q. Zhang, S. Li, W. Li, S. Zhang, Polymer 2007, 48, 6246.

638
Bull. Chem. Soc. Jpn. Vol. 87, No. 5 (2014)
Soluble and Thermally Stable Poly(ether-imide-urea)s
10 X. Wang, Y. Li, S. Zhang, T. Ma, Y. Shao, X. Zhao, Eur.
Polym. J. 2006, 42, 1229.
11 S. Wu, T. Hayakawa, R. Kikuchi, S. J. Grunzinger, M.-a.
Kakimoto, H. Oikawa, Macromolecules 2007, 40, 5698.
12 B. Y. Myung, J. S. Kim, J. J. Kim, T. H. Yoon, J. Polym.
Sci., Part A: Polym. Chem. 2003, 41, 3361.
13 S.-H. Hsiao, T.-L. Huang, J. Polym. Res. 2004, 11, 9.
14 C. W. Chang, C. H. Lin, P. W. Cheng, H. J. Hwang, S. A.
Dai, J. Polym. Sci., Part A: Polym. Chem. 2009, 47, 2486.
15 H. Toiserkani, K. Saidi, H. Sheibani, J. Appl. Polym. Sci.
2009, 114, 185.
16 H. Toiserkani, H. Sheibani, K. Saidi, Eur. Polym. J. 2010,
46, 185.
17 M. Ghaemy, R. Alizadeh, Eur. Polym. J. 2009, 45, 1681.
18 S. M. Kwak, J. H. Yeon, T. H. Yoon, J. Polym. Sci., Part A:
Polym. Chem. 2006, 44, 2567.
Macromol. Chem. Phys. 2001, 202, 2954.
21 J. K. Park, D. H. Lee, B. J. Song, J. B. Oh, H. K. Kim,
J. Polym. Sci., Part A: Polym. Chem. 2006, 44, 1326.
22 H. Toiserkani, J. Appl. Polym. Sci. 2012, 125, 1576.
23 H. Toiserkani, Chin. J. Polym. Sci. 2013, 31, 1528.
24 H. Toiserkani, Polym. Bull. 2013, 70, 2727.
25 H. Toiserkani, H. Sheibani, K. Saidi, Polym. Adv. Technol.
2011, 22, 1494.
26 D. J. Cram, J. S. Bradshaw, J. Am. Chem. Soc. 1963, 85,
1108.
27 N. Nishi, M. Tsunemi, K. Nakamura, S. Tokura, Die
Makromol. Chem. 1991, 192, 1811.
28 H. Behniafar, S. Haghighat, Polym. Adv. Technol. 2008, 19,
1040.
29 J. A. Mikroyannidis, Eur. Polym. J. 1986, 22, 277.
30 H. Toiserkani, Open J. Polym. Chem. 2011, 1, 1.
31 J. Liu, Z. Li, X. Luo, D. Ma, J. Polym. Sci., Part B: Polym.
Phys. 2004, 42, 216.
19 H.-S. Kim, Y.-H. Kim, S.-K. Ahn, S.-K. Kwon, Macro-
molecules 2003, 36, 2327.
20 L. Bes, A. Rousseau, B. Boutevin, R. Mercier, R. Kerboua,