Synthesis and characterization of new soluble polyamides from 9,9-bis[4-(chloroformylphenoxy)phenyl]xanthene and various aromatic diamines

Article abstract of DOI:10.1002/cjoc.201090022

9,9-Bis(4-hydroxyphenyl)xanthene (BHPX) was synthesized in 82% yield from xanthenone in a one-pot, two-step synthetic procedure. A new diacyl chloride monomer, 9,9-bis[4-(chloroformylphenoxy)phenyl]xanthene (BCPX), was synthesized in three steps from the nucleophilic fluorodisplacement of 4-fluorobenzonitrile with the dipotassium bisphenolate of BHPX, followed by alkaline hydrolysis of the intermediate bis(ether nitrile), and then chlorination with thionyl chloride. Several novel aromatic polyamides containing ether and bulky xanthene groups with the inherent viscosities (0.72-0.98 dL/g) were prepared by the low temperature polycondensation of BCPX with various aromatic diamines in N,N-dimethylacetamide (DMAc) solution containing pyridine (Py). All new polyamides were amorphous and readily soluble in various polar solvents such as DMAc, N,N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP) and Py. These polymers showed relatively high glass transition temperatures between 236 and 298 °C, decomposition temperatures at 10% weight loss ranging from 490 to 535 °C and 483 to 515 °C in nitrogen and air, respectively, and char yields at 700 °C in nitrogen higher than 50%. Transparent, flexible, and tough films of these polymers cast from DMAc solutions exhibited tensile strengths ranging from 82 to 106 MPa, elongations at break from 10% to 25%, and initial moduli from 2.0 to 2.8 GPa.

Full text of DOI:10.1002/cjoc.201090022

FULL PAPER
Synthesis and Characterization of New Soluble Polyamides
from 9,9-Bis[4-(chloroformylphenoxy)phenyl]xanthene and
Various Aromatic Diamines
Jiang, Jianwena(姜建文)
Huang, Shuipinga(黄水萍)
Huang, Zhenzhonga(黄振中)
Liu, Yuanb(刘园)
Sheng, Shouri*,a(盛寿日)
Song, Caishenga(宋才生)
a College of Chemistry and Chemical Engineering, Jiangxi Normal University, Nanchang, Jiangxi 330022, China
b Department of Pharmacy, General Hospital of Air Force, Beijing 100142, China
9,9-Bis(4-hydroxyphenyl)xanthene (BHPX) was synthesized in 82% yield from xanthenone in a one-pot,
two-step synthetic procedure. A new diacyl chloride monomer, 9,9-bis[4-(chloroformylphenoxy)phenyl]xanthene
(BCPX), was synthesized in three steps from the nucleophilic fluorodisplacement of 4-fluorobenzonitrile with the
dipotassium bisphenolate of BHPX, followed by alkaline hydrolysis of the intermediate bis(ether nitrile), and then
chlorination with thionyl chloride. Several novel aromatic polyamides containing ether and bulky xanthene groups
with the inherent viscosities (0.72—0.98 dL/g) were prepared by the low temperature polycondensation of BCPX
with various aromatic diamines in N,N-dimethylacetamide (DMAc) solution containing pyridine (Py). All new
polyamides were amorphous and readily soluble in various polar solvents such as DMAc, N,N-dimethylformamide
(DMF), N-methyl-2-pyrrolidone (NMP) and Py. These polymers showed relatively high glass transition tempera-
tures between 236 and 298 ℃, decomposition temperatures at 10% weight loss ranging from 490 to 535 ℃ and
483 to 515 ℃ in nitrogen and air, respectively, and char yields at 700 ℃ in nitrogen higher than 50%. Transpar-
ent, flexible, and tough films of these polymers cast from DMAc solutions exhibited tensile strengths ranging from
82 to 106 MPa, elongations at break from 10% to 25%, and initial moduli from 2.0 to 2.8 GPa.
Keywords 9,9-bis(4-hydroxyphenyl)xanthene, 9,9-bis[4-(chloroformylphenoxy)phenyl]xanthene, polyamide, cardo
unit
Introduction
outstanding properties is to introduce cardo groups into
the polymer backbone. Introduction of pendent loops
along the polymer backbone has been shown to impart
greater solubility and enhanced rigidity as well as better
mechanical and thermal properties to the resulting
“cardo” polymer, which is of particular importance in
aromatic heterocyclic polymers with rigid chains.13 It has
been reported that the presence of cardo groups such as
fluorene,14 phthalide,15 phthalimidine,16,17 cyclodode-
cylidene,18 adamantane,19 tricyclo[5.2.1.02,6]decane,20
norbornane21 and tert-butylcyclohexylidene22 groups into
the backbone of polyamides yields polymers with en-
hanced solubility, processability, and good thermal sta-
bility. The xanthene group could be considered as a bulky
cardo group and has been incorporated into several
polymers such as poly(aryl ether)s23,24 and poly (aryl es-
ter)s25 to improve their processabilities. This demon-
strates that the introduction of cardo xanthene groups into
the polymer backbone would be a potential modification
to the structure of rigid polymers. However, to our
knowledge, there are few references on the characteristic
Aromatic polyamides have found wide commercial
acceptance due to their unique property combinations.1
They can be fabricated into strong abrasion-resistant
fibres and films with very high moduli, good thermal
stability and high solvent resistance. However, most of
the aromatic polyamides are insoluble in organic sol-
vents; they are only soluble in concentrated mineral ac-
ids. The insolubility and also high transition tempera-
tures make these polymers difficult to process. There-
fore, much effort has been made to chemically modify
the structure of these polymers with the aim of improv-
ing their solubility and/or lowering their transition tem-
peratures to a range that facilitates their processing in
melt. To accomplish this goal, the addition of pendent
groups into the polyamide backbone2-4 and the incorpo-
ration of bulky substituents,5-8 asymmetrical moieties9,10
or flexible units3,11,12 within the parent chain have been
widely investigated.
A successful approach to improve the processability
of aromatic polyamide without extreme loss of their
*
E-mail: shengsr@jxnu.edu.cn; Tel.: 0086-0791-8120381; Fax: 0086-0791-8506404
Received June 29, 2009; revised July 20, 2009; accepted September 8, 2009.
Project supported by the National Natural Science Foundation of China (No. 20664001) and the Research Program of Jiangxi Province Department
of Education (Nos. GJJ08166, GJJ09138).
102
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Chin. J. Chem. 2010, 28, 102— 110

Synthesis and Characterization of New Soluble Polyamides
of introducing xanthene units into polyamides. In the
present study, we will report the synthesis of a series of
cardo polyamides containing xanthene groups derived
from the new cardo dicarboxylic acid chloride, 9,9-bis[4-
(chloroformylphenoxy)phenyl]xanthene (BCPX). The
solubility, crystallinity, tensile property and thermal
property of the polymers were also investigated.
9,9-Bis[4-(4-cyanophenoxy)phenyl]-xanthene (4,
BCYPX) In a 250 mL round-bottomed flask equipped
with a Dean-Stark trap and a condenser, BHPX (36.6 g,
0.1 mol) was dissolved in a mixture of DMF (200 mL)
and toluene (50 mL). Anhydrous potassium carbonate
(27.6 g, 0.2 mol) was added to this solution. The sus-
pension was heated to reflux, and water was removed by
azeotropic distillation with toluene. After the water was
completely removed, the residual toluene was distilled
out from the system. Then the reaction mixture was
cooled to about 60 ℃, and 4-fluorobenzonitrile (24.3 g,
0.2 mol) was added. After refluxing at 150 ℃ for 6 h,
the solution was allowed to cool and poured into 500
mL of water. The precipitated white powder was col-
lected by filtration, thoroughly washed with water, and
dried. The crude product was purified by recrystalliza-
tion from acetonitrile to give a white fine granular crys-
tal of dinitrile 4 (47.2 g, yield 83%), m.p. 219—220 ℃;
1H NMR (CDCl3, 400 MHz) δ: 7.60 (d, J＝8.8 Hz, 4H),
7.32 (t, J＝8.0 Hz, 2H), 7.19 (d, J＝8.0 Hz, 2H), 7.09 (t,
J＝8.0 Hz, 2H), 7.04—7.02 (m, 8H), 6.96—6.93 (m,
6H); 13C NMR (CDCl3, 100 MHz) δ: 161.18, 153.53,
152.43, 142.33, 134.20, 131.74, 129.87, 129.77, 128.34,
123.18, 119.54, 118.84, 118.23, 116.75, 106.09, 53.54;
IR (KBr) ν: 2227 (CN stretching) and 1251 (C—O—C
Experimental
Materials
Xanthone, phenol, p-fluorobenzonitrile, p-chloroni-
trobenzene, thionyl chloride, and anhydrous potassium
carbonate were used as received. Reagent grade aro-
matic diamines (Aldrich Co.) such as p-phenylenedia-
mine (7a, PPD), m-phenylenediamine (7b, MPD) and
4,4'-oxydianiline (7d, ODA) were purified by sublima-
tion. Benzidine (7c) was recrystallized from ethanol.
4,4'-Bis(4-aminophenoxy)biphenyl (7e, m.p. 198—199
℃),26 bis[4-(4-amionphenoxy)phenyl]sulfone (7f, m.p.
228—230 ℃),27 2,2-bis[4-(4-amionphenoxy)phenyl]-
propane (7g, m.p. 125—126 ℃)28 and 2,2'-dimethyl-
4,4'-bis(4-aminophenoxy)biphenyl (7h, m.p. 138—139
℃)29 were prepared by the aromatic nucleophilic sub-
stitution reaction of 4-chloronitrobenzene with the cor-
responding bisphenol precursors in the presence of po-
tassium carbonate, giving the dinitro compounds, fol-
lowed by reduction with hydrazine as the reducing agent
and palladium on active carbon as the catalyst. Com-
mercially available xylene was refluxed with sodium
and distilled under reduced pressure prior to use. DMAc
and Py were purified by distillation under reduced
pressure over calcium hydride and stored over 4 Å mo-
lecular sieves prior to use.
＋
－1
stretching) cm ; EI-MS m/z (%): 568 (M , 100). Anal.
calcd for C39H24N2O3: C 82.38, H 4.25, N 4.93; found C
82.15, H 4.35, N 4.85.
9,9-Bis[4-(4-carboxyphenoxy)phenyl]-xanthene (5,
BCAPX) Xanthene-dinitrile 4 (25.6 g, 0.045 mol),
potassium hydroxide (51 g, 0.45 mol), ethanol (150 mL),
and water (150 mL) were introduced into a 500 mL
flask, and the suspension was refluxed for 2 d to form a
clear solution, which was filtered while hot to remove
any possible impurities. After cooling to room tempera-
ture, the pH value of the filtrate was adjusted by con-
centrated hydrochloric acid to 2—3. The white precipi-
tate formed was collected by filtration, washed repeat-
edly with water, and dried under vacuum at 150 ℃ for
5 h to afford BCAPX (25.6 g, yield 94%), m.p. 247—
Monomer synthesis
9,9-Bis(4-hydroxyphenyl)xanthene (3, BHPX) In
a 250 mL, round-bottomed flask, xanthenone (1) (19.6 g,
0.1 mol) was refluxed in thionyl chloride (150 mL) for 5
h and stood for 18 h to convert to 9,9-dichlo-roxanthene
(2) according to a literature method.30 The excess thio-
nyl chloride was removed under vacuum, the intermedi-
ate 2 was washed with petroleum ether, dried under
vacuum, and then dissolved in xylene and phenol (23.5
g, 0.25 mol) was added. The mixture was refluxed for 8
h, the xylene and excess phenol were removed under
vacuum, and the crude product was recrystallized from
toluene to afford a purplish-red acicular crystal of 3
(30.0 g, yield 82%), m.p. 239—240 ℃ (Lit.25 241 ℃);
1H NMR (CDCl3, 400 MHz) δ: 7.26 (t, J＝8.0 Hz, 2H),
7.14 (d, J＝8.0 Hz, 2H), 7.04 (t, J＝8.0 Hz, 2H), 6.93 (d,
J＝8.0 Hz, 2H), 6.83 (d, J＝8.8 Hz, 4H), 6.70 (d, J＝
8.8 Hz, 4H), 4.68 (br s, 2H); 13C NMR (CDCl3, 100
MHz) δ: 155.96, 151.92, 136.64, 130.93, 130.90, 130.25,
128.41, 123.57, 116.48, 115.01, 52.74; IR (KBr) ν: 3065,
3033, 1611, 1595, 1508, 1444, 1238, 1175, 870, 759
1
249 ℃; H NMR (DMSO-d6, 400 MHz) δ: 12.08 (s,
2H), 7.91 (dd, J＝8.8, 8.4 Hz, 4 H), 7.36 (t, J＝7.6 Hz,
2H), 7.25 (d, J＝8.0 Hz, 2H), 7.17 (t, J＝7.6 Hz, 2H),
7.08 (d, J＝8.8 Hz, 8H), 6.98—6.95 (m, 6H); 13C NMR
(CDCl3, 100 MHz) δ: 171.36, 162.18, 154.26, 152.51,
141.84, 132.44, 131.57, 129.94, 129.91, 128.21, 123.79,
123.08, 119.23, 117.69, 116.68, 53.52; IR (KBr) ν:
2500—3450 (H-bonded O—H stretch), 1681 (C＝O
－1
stretching), 1238＋(C—O—C stretching) cm . EI-MS
m/z (%): 606 (M , 100). Anal. calcd for C39H26O7: C
77.22, H 4.32; found C 77.03, H 4.41.
9,9-Bis[4-(chloroformylphenoxy)-phenyl]xanthene
(6, BCPX) A mixture of 5 (36.40 g, 0.06 mol), thionyl
chloride (150 mL) and two drops of DMF were refluxed
for 4 h under stirring. Then, the mixture was vacuum
distilled to remove the residue thionyl chloride and
cooled to 0—4 ℃. The white precipitate was afforded
and collected by filtration. The crude product was puri-
－1
cm . Anal. calcd for C25H18O3: C 81.95, H 4.95; found
C 81.90, H 4.87.
Chin. J. Chem. 2010, 28, 102— 110
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103

Jiang et al.
FULL PAPER
fied by recrystallization from anhydrous petroleum ether
to furnish BCPX (32.8 g, yield 85%), m.p. 167—169
℃; 1H NMR (CDCl3, 400 MHz) δ: 8.09 (dd, J＝6.8, 6.8
Hz, 4H), 7.31 (t, J＝8.4 Hz, 2H), 7.22 (d, J＝8.0 Hz,
2H), 7.11 (t, J＝7.6 Hz, 2H), 7.06—7.02 (m, 8H),
6.95—6.92 (m, 6H); 13C NMR (CDCl3, 100 MHz) δ:
167.09, 163.70, 153.42, 152.47, 142.55, 133.94, 131.76,
129.84, 129.75, 128.33, 127.33, 123.71, 119.76, 117.44,
116.77, 53.61; IR (KBr) ν: 1765 (C＝O stretching),
Hz, 4H), 7.45—7.32 (m, 12H), 7.20—7.08 (m, 8H),
7.00—6.85 (m, 12H); IR (KBr) ν: 3321 (N—H), 1658
－1
(C＝O), 1244 (C—O—C), 1148 (SO2) cm .
1
Polyamide (8g): H NMR (DMSO-d6, 400 MHz) δ:
10.24 (s, 2H), 8.00 (d, J＝8.4 Hz, 4H), 7.76 (d, J＝8.4 Hz,
4H), 7.41—7.30 (m, 10H), 7.20—7.08 (m, 16H), 6.86—
6.75 (m, 6H), 1.72 (s, 6H); IR (KBr) ν: 3316 (N—H),
－1
2968 (C—H), 1656 (C＝O), 1240 (C—O—C) cm .
1
Polyamide (8h): H NMR (DMSO-d6, 400 MHz) δ:
－1
1249 (C—O—C stretching) cm ; EI-MS m/z (%): 642
10.26 (s, 2H), 8.01 (d, J＝8.4 Hz, 4H), 7.77 (d, J＝8.4
Hz, 4H), 7.41 (s, 2H), 7.38—7.28 (m, 10H), 7.24—6.83
(m, 18H), 2.15 (s, 6H); IR (KBr) ν: 3318 (N—H), 2925
(M＋, 14.8), 607 (100). Anal. calcd for C39H24Cl2O5: C
72.79, H 3.76; found C 72.56, H 3.68.
－1
(C—H), 1655 (C＝O), 1238 (C—O—C) cm .
Polymerization
Measurements
In a typical experiment, polyamide 8d, derived from 6
and 4,4'-oxydianiline (7d), was prepared as follows: in a
100 mL flask, a solution of 40 mL of DMAc containing
pyridine (0.10 g) and 6.00 mmol of 7d (1.2014 g) was
prepared and cooled to －10 ℃ on a dry ice-acetone
bath, and then 6.00 mmol of 9,9-bis[4-(chloroformyl-
phenoxy)phenyl]xanthene (BCPX) (3.8611 g) was
added. The mixture was stirred in －10—0 ℃ for 5 h.
The reaction was then continued overnight at room
temperature. The resulting highly viscous polymer solu-
tion was poured slowly with stirring into 300 mL of
methanol. The white fiberlike precipitate formed was
washed repeatedly with methanol and hot water, col-
lected by filtration, and dried at 150 ℃ under vacuum
for 6 h to give polyamide 8d (4.48 g, yield 97%).
1H NMR (DMSO-d6, 400 MHz) δ: 10.22 (s, 2H), 8.02 (s,
4H), 7.77 (s, 4H), 7.55—6.57 (m, 20H); IR (KBr) ν:
3313 (N—H stretching), 1655 (C＝O stretching), and
The NMR spectra were recorded on a Bruker
Avance 400 MHz spectrometer in dimethyl sulfoxide-d6
(DMSO-d6) or chloroform (CDCl3). IR spectra of the
monomers and polymers in KBr pellets were deter-
mined on a Perkin-Elmer SP One FT-IR spectropho-
tometer. Mass spectra (EI, 70 eV) were recorded on a
HP 5989B mass spectrometer. Microanalyses were per-
formed with a Carlo Erba 1106 Elemental analyzer.
Melting points were determined on an X4 melting point
apparatus and are uncorrected. The glass-transition
temperatures (Tg) were measured on a Perkin-Elmer
DSC-7 instrument at a heating rate of 10 ℃/min under
nitrogen protection. The second scan was immediately
initiated after the sample was cooled to room tempera-
ture. The Tg values were reported from the second scan
after the first heating and quenching, and taken from the
midpoint of the change in the slope of the baseline. The
thermal stability of the polymers from 50 to 700 ℃
was determined with a Seiko SSC-5200 thermogravim-
etric analysis (TGA) at a heating rate of 20 ℃/min un-
der a protective nitrogen atmosphere (120 mL/min) or in
air. Wide-angle X-ray diffraction patterns were recorded
at room temperature (ca. 25 ℃) on powder with a Ri-
gaku Geiger Flex D-Max III X-ray diffractometer, using
Ni-filtered Cu Kα radiation (operating at 40 kV and 15
mA; the scanning rate being 2 (°)/min over a range of
2θ＝2°—40°). The mechanical properties were meas-
ured on an Instron 1122 testing instrument with 120×5
mm specimens in accordance with GB1040-79 at a
drawing rate of 50 mm/min. The inherent viscosities
were measured at 0.5 g/dL concentration in DMAc with
an Ubbelohde viscometer at 30 ℃, in which the poly-
amides were pretreated by drying in an oven at 120 ℃
for 1 h to remove the adsorbed moisture.
－1
1243 (C—O—C stretching) cm . The other polyam-
ides were also prepared via a similar procedure as de-
scribed for polyamide 8d by the polymerization of 1
equiv. of BCPX with 1 equiv. of the corresponding
aromatic diamines.
1
Polyamide (8a): H NMR (DMSO-d6, 400 MHz) δ:
10.21 (s, 2H), 8.52 (s, 1H), 8.14 (d, J＝8.0 Hz, 2H),
7.80 (d, J＝8.4 Hz, 4H), 7.70—7.67 (m, 1H), 7.32—
6.88 (m, 20H); IR (K－Br) ν: 3310 (N—H), 1658 (C＝O),
1
1241 (C—O—C) cm .
1
Polyamide (8b): H NMR (DMSO-d6, 400 MHz) δ:
10.20 (s, 2H), 8.01 (d, J＝8.4 Hz, 4H), 7.74 (d, J＝8.4
Hz, 4H), 7.45—6.95 (m, 24H); IR (KBr) ν: 3308 (N—
－1
H), 1653 (C＝O), 1238 (C—O—C) cm .
1
Polyamide (8c): H NMR (DMSO-d6, 400 MHz) δ:
10.18 (s, 2H), 8.03 (d, J＝8.4 Hz, 4H), 7.78 (d, J＝8.4
Hz, 4H), 7.34—7.03 (m, 14H), 6.93—6.87 (m, 10H); IR
(KBr) ν: 3310 (N—H), 1658 (C＝O), 1241 (C—O—C)
－1
cm .
Results and discussion
1
Polyamide (8e): H NMR (DMSO-d6, 400 MHz) δ:
Monomer synthesis
10.22 (s, 2H), 8.05 (d, J＝8.4 Hz, 4H), 7.80 (d, J＝8.4
Hz, 4H), 7.40—7.30 (m, 12H), 7.25—7.01 (m, 10H),
6.96—6.85 (m, 10H); IR (KBr) ν: 3315 (N—H), 1657
Scheme 1 outlines the synthetic route applied to the
synthesis of the bisphenol monomer, 9,9-bis(4-
hydroxyphenyl)xanthene 3 (3, BHPX). In general,
bisphenols could be prepared by the condensation of
ketone compounds with excess phenol catalyzed by acid
－1
(C＝O), 1242 (C—O—C) cm .
1
Polyamide (8f): H NMR (DMSO-d6, 400 MHz) δ:
10.20 (s, 2H), 8.05 (d, J＝8.4 Hz, 4H), 7.80 (d, J＝8.4
104
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Chin. J. Chem. 2010, 28, 102— 110

Synthesis and Characterization of New Soluble Polyamides
such as hydrogen chloride and 3-mercaptopropionic
acid. However, the reaction of xanthenone and phenol
under the similar conditions did not afford the desired
BHPX, which might be resulted from the steric hin-
drance of the phenyl groups of the xanthenone. Previ-
ously, BHPX was synthesized from 9,9-dichloroxan-
thene with excess phenol in the presence of
3-mercaptopropionic acid,25 but the yield of BHPX was
low (14%). After a series of experiments, 82% yield of
BHPX was obtained by reaction of xanthone with thio-
nyl chloride, affording 9,9-dichloroxanthene (2), fol-
lowed by treatment with phenol in refluxing xylene in a
one-pot, two-step synthetic procedure. The structure of
DMF. All the structures of the intermediate BCYPX,
BCAPX and BCPX were also confirmed by elemental
1
analysis and infrared, H NMR, and 13C NMR spec-
troscopy.
Figure 1 displays the 1H NMR and 13C NMR spectra
of BCPX in CDCl3 solution, respectively. Assignments
to all protons and carbons are given in the figure. In the
1H NMR spectrum, the aromatic protons (H-14) ortho to
the chlorocarbonyl groups and those (H-2, H-3 and H-4)
on the xanthene unit were clearly distinguished, whereas
the aromatic protons (H-10 and H-13) ortho to the ether
groups, those (H-9) ortho to the xanthene unit, and
those (H-1) on the xanthene unit were overlapped. How-
ever, all carbon nuclei in BCPX gave well-separated
peaks in the 13C NMR spectrum. The resonance of car-
bonyl carbon occurred at the farthest downfield (δ
167.09).
1
BHPX was confirmed by elemental analysis, FT-IR, H
and 13C NMR spectroscopic techniques.
Scheme 1 Preparation of 9,9-bis(4-hydroxyphenyl)xanthene
(BHPX)
Polymer synthesis and characterization
The low-temperature solution polycondensation
technique was used for the synthesis of a series of cardo
polyamides (8a—8h) containing xanthene group as
shown in Scheme 3. In the low-temperature solution
polycondensation, the polyamides were prepared in a
one-step pathway by the direct polycondensation reac-
tion of 1 equiv. of the BCPX (6) with 1 equiv. of aro-
matic diamine (7) in DMAc solution containing a trace
of pyridine cooled by an external ice-acetone bath. The
reaction temperature was maintained from －10 to 0 ℃
in the initial 5 h. In order to obtain maximum molecular
weight, the reaction was then allowed to proceed over-
night at room temperature.
The polyamides were isolated as tough fibers in
quantitative yields with inherent viscosities that ranged
from 0.72 to 0.98 dL/g (Table 1). The molecular weight
of these polymers was high enough to obtain transparent,
tough, and flexible polymer films by casting from their
DMAc solutions.
As shown in Scheme 2, the intermediate bis(ether
benzonitrile) (4, BCYPX) was obtained from the nu-
cleophilic fluoro displacement of p-fluorobenzonitrile
with the potassium phenolate of BHPX in DMF. The
BCYPX was then readily converted into bis(ether car-
boxylic acid) (5, BCAPX) in good yield and high purity
by alkaline hydrolysis, which was converted to the cor-
responding diacyl chloride (6, BCPX) by treatment with
thionyl chloride in the presence of a trace amount of
Scheme 2 Synthesis of the new dicarboxylic acid chloride (BCPX)
Chin. J. Chem. 2010, 28, 102— 110
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105

Jiang et al.
FULL PAPER
Figure 1 1H NMR (A) and 13C NMR (B) spectra of BCPX in CDCl3 solution.
Scheme 3 Preparation of cardo polyamides containing xanthene structures
106
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Chin. J. Chem. 2010, 28, 102— 110

Synthesis and Characterization of New Soluble Polyamides
Table 1 Inherent viscosity and solubility behavior of various polyamidesa
－
1
Polymer
8a
η
inh/(dL•g )
NMP
＋＋
＋＋
＋＋
＋＋
＋＋
＋＋
＋＋
＋＋
DMAc
＋＋
＋＋
＋＋
＋＋
＋＋
＋＋
＋＋
＋＋
DMF
＋＋
＋＋
＋＋
＋＋
＋＋
＋＋
＋＋
＋＋
DMSO
＋
m-Cresol
＋＋
＋＋
＋＋
＋＋
＋＋
＋＋
＋＋
＋＋
Py
THF
－
CHCl3
－
0.92
＋＋
＋＋
＋＋
＋＋
＋＋
＋＋
＋＋
＋＋
8b
0.82
＋＋
＋
s
－
8c
0.88
－
－
8d
0.86
＋－
＋
s
－
8e
0.75
－
－
8f
0.80
＋＋
＋＋
＋
＋＋
＋＋
－
－
8g
0.98
－
8h
0.72
－
a Measured at 3.0 % (w/V). ＋＋, soluble at room temperature; ＋, soluble on heating at 60 ℃; ＋－, partially soluble; －, insoluble at
room temperature, even on heating; s＝swelling. Solvent: DMSO: dimethyl sulfoxide; THF: tetrahydrofuran.
The molecular structures of these polyamides were
confirmed by IR and NMR spectroscopy. Figure 2 com-
pares the IR spectrum of the typical polyamide 8a,
where the ch－aracteristic absorptions of the polyamide 8a
the formation of amide linkages. These results further
demonstrated that the polyamides containing the xan-
thene moieties had the expected chemical structures.
1
－1
at 3313 cm (N—H stretching), 1655 cm (C＝O
－1
stretching), 1500—1550 cm (combined N—H bend-
ing and C—N stretching), and the strong absorption of
－1
aryl ether group stretching in the region of 1243 cm
1
were also observed. Figure 3 shows the H NMR and
13C NMR spectra of the typical polyamide 8a, in which
all the protons and the carbons could be assigned to the
polymer structure. The resonance peaks appearing in the
1
region of δ 10.22 in the H NMR spectrum also support
Figure 2 FT-IR spectrum of the polyamide 8a.
Figure 3 1H NMR (A) and 13C NMR (B) spectra of the polyamide 8a in DMSO-d6 solution.
Chin. J. Chem. 2010, 28, 102— 110
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107

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Polymer properties
Table 2 Thermal properties of polyamides
a
d
Td5b/℃
523
527
520
528
535
513
495
490
Td10c/℃
Rw /%
The crystallinity of the prepared polyamides was
evaluated via wide-angle X-ray diffraction measure-
ments. All of the polyamides presented amorphous pat-
terns. This is reasonable because the bulky xanthene
cardo group and flexible ether linkage significantly in-
creased the disorder in the chains, therefore, leading to
loose chain packing. The amorphous nature of these
polymers was reflected in their good solubility.
Polymer
8a
Tg /℃
286
260
298
280
250
242
236
275
502
58
61
62
57
60
56
51
54
8b
508
8c
510
8d
512
8e
515
8f
501
The solubility of the polyamides in several organic
solvents at 3.0% (w/V) also is summarized in Table 1. All
the polyamides are readily soluble in DMAc, NMP, DMF,
m-cresol, and even in pyridine, and some of them also in
DMSO and THF (Table 1). Polyamides 8f and 8g were
also soluble in THF, attributable to the presence of sul-
fonyl and isopropylene linkages in the diamine moiety.
The polyamides containing p-phenylene (8a) and
4,4'-biphenylene units (8c, 8e and 8h) in the main linkage
had somewhat limited solubility. These three polymers
were insoluble in THF and CHCl3, and their lower
solubility may indicate strong hydrogen bonding between
chains or good packing ability due to the presence of rigid
rod-like p-phenylene and 4,4'-biphenylene segments.
The thermal properties of the polyamides were
evaluated by DSC as well as by thermogravimetric
analysis (TGA). Figure 4 illustrates typical TG curves
for the representative polyamide 8a in both air and ni-
trogen atmospheres. All the polymers did not show sig-
nificant weight loss below 450 ℃ either in nitrogen or
air. The temperatures at 10% weight loss were recorded
in the range of 490—535 ℃ in nitrogen and 483—515
℃ in air, as shown in Table 2. They left a high char
yield ranged from 51% to 62% in a nitrogen atmosphere
due to high aromaticity. It is worthy mentioning that the
polyamide 8g had the lowest char yield in this series of
polyamides, due to the presence of less-stable isopro-
pylene linkages in its diamine moiety.
8g
490
8h
483
a
Baseline shift in the second heating DSC trace, with a heating
rate of 10 ℃/min in nitrogen. b Temperature at which 5% weight
loss was recorded by TG at a heating rate of 20 ℃/min in nitro-
gen. c Temperature at which 10% weight loss was recorded by TG
at a heating rate of 20 ℃/min in air. d Residual weight (%) when
heated to 700 ℃ at a scan rate of 20 ℃/min in nitrogen.
order of segment flexibility of the diamine moiety. No
melting peak (Tm) was detected by DSC, which sup-
ported their generally amorphous characters. The poly-
amide 8c exhibited the higher Tg value (298 ℃) be-
cause of the effect of the rigid biphenylene polymer
backbone. The lowest Tg of 236 ℃ was observed for
polyamide 8g derived from the multiring flexible dia-
mine 7g. In general, the introduction of flexible ether
linkages or less symmetrical m-phenylene unit leads to a
decreased Tg. For example, p-phenylenediamine-based
polyamide 8a exhibited higher Tg of 286 ℃ than those
of polyamides 8b and 8d showing Tg of 260 and 250 ℃,
derived from m-phenylenediamine and 4,4'-oxydianiline,
respectively. In addition, the incorporation of bulky
methyl groups into the polymer backbone inhibited the
polymer backone free rotation, which led to an increase
in the Tg values of the resulting polymers. Thus, the
polyamide 8h derived from the diamine 7h exhibited
higher Tg than its counterpart 8e derived from the dia-
mine 7e. Seen from Table 2, there is a large window
between the Tg and the decomposition temperature for
all the polyamides, which could be advantageous in the
processing of these polymers.
Strong, transparent films could be easily obtained
from DMAc solutions of these polymers. The mechani-
cal properties of these polyamide films are summarized
in Table 3. The polymer films had tensile strengths
ranging from 82 to 106 MPa, elongations at break from
10% to 25%, and tensile moduli from 2.0 to 2.8 GPa,
indicating that these polymer films were tough and
flexible.
The thermal and mechanical properties of the new
resulting aromatic polyamides were compared with
those of the polyamides containing similar fluorene
cardo structures.14 Some data of the two typical poly-
mers were listed in Table 4. The Tg of the present
polyamide 8a is lower than that of the polyamide having
fluorene units. However, the mechanical property of 8a
Figure 4 Typical TGA curves for polyamide 8a in nitrogen (A)
and in air (B).
The DSC thermograms of the polyamides obtained
from the second heating trace showed Tg values between
236 and 298 ℃ (Table 2), following the decreasing
108
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Chin. J. Chem. 2010, 28, 102— 110

Synthesis and Characterization of New Soluble Polyamides
Table 3 Mechanical properties of various polyamide filmsa
Polymer
8a
Tensile strength/MPa
Elongation at break/%
Tensile modulus/GPa
94
86
106
99
80
84
88
82
16
13
15
18
15
25
21
10
2.4
2.3
2.6
2.4
2.5
2.0
2.1
2.8
8b
8c
8d
8e
8f
8g
8h
a The polymer films were obtained by casting from their DMAc solutions.
Table 4 Thermal and mechanical properties of polyamides with xanthene and fluorene units
Tensile
Elongation
Tensile
a
b
Polyamide
Tg /℃ Td /℃
strength/MPa at break/% modulus/GPa
286
523
94
16
2.4
8a
303
542
76
27
1.7
Ref 14
a Baseline shift in the second heating DSC trace, with a heating rate of 10 ℃/min in nitrogen. b 10% weight loss temperature recorded by
TG at a heating rate of 20 ℃/min in nitrogen.
was comparable to that of the fluorene-containing
polyamide. In addition, the present polyamides showed
an almost comparable thermal stability with their similar
counterparts.
well as good solubility in various organic solvents. All
these properties make the present diphenylxanthene-
based polyamides be considered new potential candi-
dates for processable high-performance thermoplastic
materials.
Conclusion
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