Novel flame-retardant and thermally stable poly(amide-imide)s based on bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetracarboxylic diimide and phosphine oxide in the main chain: Synthesis and characterization

Article abstract of DOI:10.1002/jccs.200900091

Six novel poly(amide-imide)s PAIs 5a-f were synthesized through the direct polycondensation reaction of six chiral N,N'-(bicyclo[2,2,2]oct-7-ene- tetracarboxylic)-bis-L-amino acids 3a-f with bis(3-amino phenyl) phenyl phosphine oxide 4 in a medium consist

Full text of DOI:10.1002/jccs.200900091

Journal of the Chinese Chemical Society, 2009, 56, 609-618
609
Novel Flame-retardant and Thermally Stable Poly(amide-imide)s Based on
Bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetracarboxylic Diimide and Phosphine
Oxide in the Main Chain: Synthesis and Characterization
Khalil Faghihi,* Mohsen Hajibeygi and Meisam Shabanian
Organic Polymer Chemistry Research Laboratory, Department of Chemistry, Faculty of Science,
Arak University, Arak 38156, Iran
Six novel poly(amide-imide)s PAIs 5a-f were synthesized through the direct polycondensation reac-
tion of six chiral N,N¢-(bicyclo[2,2,2]oct-7-ene-tetracarboxylic)-bis-L-amino acids 3a-f with bis(3-amino
phenyl) phenyl phosphine oxide 4 in a medium consisting of N-methyl-2-pyrrolidone (NMP), triphenyl
phosphite (TPP), calcium chloride (CaCl2) and pyridine. The polymerization reaction produced a series of
flame-retardant and thermally stable poly(amide-imide)s 5a-f with high yield and good inherent viscosity
of 0.39-0.83 dLg-1. The resultant polymers were fully characterized by means of FTIR, 1H NMR spectros-
copy, elemental analyses, inherent viscosity, specific rotation and solubility tests. Thermal properties and
flame retardant behavior of the PAIs 5a-f were investigated using thermal gravimetric analysis (TGA and
DTG) and limited oxygen index (LOI). Data obtained by thermal analysis (TGA and DTG) revealed that
these polymers show good thermal stability. Furthermore, high char yields in TGA and good LOI values
indicated that resultant polymers exhibited good flame retardant properties. N,N¢-(bicyclo[2,2,2]oct-7-
ene-tetracarboxylic)-bis-L-amino acids 3a-f were prepared in quantitative yields by the condensation re-
action of bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride 1 with L-alanine 2a, L-valine 2b,
L-leucine 2c, L-isoleucine 2d, L-phenyl alanine 2e and L-2-aminobutyric acid 2f in acetic acid solution.
These polymers can be potentially utilized in flame retardant thermoplastic materials.
Keywords: Flame-retardant polymers; Poly(amide-imide)s; Thermally stable polymers; Chiral
amino acid.
INTRODUCTION
Aromatic polyamides possess excellent mechanical
performance materials with a good compromise between
thermal stability and processability when compared with
polyamides or polyimides of analogous structures.6,7
Phosphines, phosphine oxides, phosphonium com-
pounds, phosphonates, elemental red phosphorus, phos-
phites and phosphate are all used as flame retardants.8-11
The general types of phosphorus moieties have been incor-
porated into different polymeric backbones, such as epoxy
resin, poly(amic acid), polycarbonate, poly(vinyl chlo-
ride), polyester, polyimide and poly(methyl methacry-
late).12-19 Among the polymers with phosphorus moieties,
the polymers with phosphine oxide moieties have major
advantages, such as good flame-retardant properties, high
thermal oxidative stability, enhanced solubility in organic
solvents, improved miscibility and good adhesion to other
compounds.20-26
properties and thermal stability; however, they are difficult
to process because of limited solubility and high glass tran-
sition (Tg) or melt temperature due to chain stiffness and
intermolecular hydrogen bonding between amide groups.1
The processing of these thermoplastic polymers has been
greatly hindered because they lack softening or melting be-
havior at usual processing temperatures, and they tend to
degrade before or at the softening temperature.2 Various at-
tempts have been made to bring down the Tg or melting
temperature of aromatic polyamides to make them proc-
essable by introducing linked and flexible bridging units3-5
into the polymer chains. Unfortunately, the loss of thermal
stability and significant decrease in mechanical properties
on heating are usually a consequence of the reduced chain
stiffness. Aromatic poly(amide-imide)s (PAIs) are high
In this article, a series of novel flame-retardant PAIs
* Corresponding author. Mobile: 0098-9188630427; Fax: 0098-861-2774031; E-mail: k-faghihi@araku.ac.ir

610 J. Chin. Chem. Soc., Vol. 56, No. 3, 2009
Faghihi et al.
5a-f containing phosphine oxide moiety were synthesized
by the direct polycondensation reactions of six chiral N,N¢-
(bicyclo[2,2,2]oct-7-ene-tetracarboxylic)-bis-L-amino ac-
ids 3a-f with bis(3-amino phenyl) phenyl phosphine oxide
4 in a medium consisting of N-methyl-2-pyrrolidone, tri-
phenyl phosphite, calcium chloride and pyridine. These
polymers that have phosphine oxide moieties in the main
chain show flame retardant and thermally stable behavior.
These properties can make these polymers attractive for
practical application such as processable high-performance
engineering plastics. On the other hand, due to the presence
of chiral segments in the polymer backbone, these PAIs are
optically active. The synthesis and application of optically
active polymers are novel topics worthy of considera-
tion.27-30
Table 1.
The chemical structure and purity of the optically ac-
tive diimide-diacids 3a-f were proved by using elemental
analysis, FTIR, 1H NMR and 13C NMR spectroscopic tech-
niques and these data shown in Table 2.
As an example, the FTIR spectrum of N,N¢-(bicyclo-
[2,2,2]oct-7-ene-tetracarboxylic)-bis-L-valine 3b showed
a broad peak between 2500 and 3400 cm-1, which was as-
signed to the COOH groups. Peaks appearing at 1709-1751
cm-1 (acid C=O and symmetric imide stretching), 1390 and
700 cm-1 (imide characteristic ring vibration) confirmed
the presence of an imide ring and carboxylic groups in this
compound (Fig. 1).
The 1H NMR spectrum of diimide-diacid 3b is shown
in Fig. 2. The protons H(a) relevant to O-H carboxylic
groups appeared at 12.88 ppm. Peaks in 4.12-4.15 ppm ap-
pearing as doublets were assigned to the CH(b) protons,
which is a chiral center; peaks between 0.66-0.94 ppm
were assigned to aliphatic CH3(c,d); peaks in 2.32-2.39
ppm were assigned to H(e). Protons relevant to the olefin
bicyclo ring appeared at 5.99-6.09 ppm, H(h). Peaks be-
tween 3.24-3.42 ppm were assigned to H(f) (4H) and H(g)
(2H).
RESULTS AND DISCUSSION
Monomer synthesis
The asymmetric diimide-diacids 3a-f were synthe-
sized by the condensation reaction of bicyclo[2,2,2]oct-7-
ene-2,3,5,6-tetracarboxylic dianhydride 1 with two equi-
molars of L-alanine 2a, L-valine 2b, L-leucine 2c, L-iso-
leucine 2d, L-phenyl alanine 2e and L-2-aminobutyric acid
2f in an acetic acid solution (Scheme I). The yields and
some physical properties of these compounds are shown in
The 13C NMR spectrum of diimide-diacid 3b showed
9 signals, including C1 and C6 in carboxylic acids and car-
bonyl imide rings, and C7, C8 in carbon atoms olefin in a
Scheme I
Table 1. Synthesis and some physical properties of chiral diimide-diacid derivatives 3a-f
a
25
Diacid Amino acid compound
R
Mp (°C)
Yield (%)
[á]D
3a
3b
3c
3d
3e
3f
L-Alanine
CH3
249-250
318-320
289-290
293-295
247-248
251-253
92
93
94
92
91
93
+155.7
+138.4
+146.8
+156.2
+160.2
+130.2
L-Valine
(CH3)2CH
L-Leucine
(CH3)2CHCH2
(C2H5)(CH3)CH
PhCH2
L-Isoleucine
L-Phenyl alanine
L-2-Aminobutyric acid CH3CH2
a Measured at a concentration of 0.5 g/dL in DMF at 25 °C.

Synthesis of Novel Flame Retardant Poly(amide-imide)s
J. Chin. Chem. Soc., Vol. 56, No. 3, 2009 611
Table 2. 1H-NMR, 13C-NMR, FTIR spectra and elemental analyses data of diacid derivatives 3a-f
Diimide-diacid
Spectral data
1H-NMR (DMSO-d6, d ppm): 12.87-12.93 (s, br, 2H), 5.95-5.98 (t, 2H), 4.50-4.57
(q, 1H), 3.37 (s, 2H), 3.16-3.25 (m, 4H), 1.23-1.25 (d, 6H). 13C-NMR (DMSO-d6, d
ppm): 176.82, 170.61, 130.64, 47.55, 42.47, 33.89, 14.49. FTIR (KBr, cm-1): 2561-
3100 (m, sh, br), 1770 (w), 1705 (s, br), 1628 (w), 1467 (w), 1396 (m), 1309 (m),
1207 (m), 1126 (w), 976 (w), 675 (w), 611 (w). Elemental analysis: calcd for
C18H18N2O8: C, 55.39; H, 4.65; N, 7.18; found: C, 54.45; H, 4.56; N, 7.11.
1H-NMR (DMSO-d6, d ppm): 12.88 (s, br, 2H), 5.99-6.09 (m, 2H), 4.12-4.15 (d,
2H), 3.45 (D2O exchange, s, 2H), 3.18-3.25 (D2O exchange, t, 4H), 2.32-2.39 (m,
2H), 0.92-0.94 (d, 6H), 0.66-0.68 (d, 6H). 13C-NMR (DMSO-d6, d ppm): 177.23,
169.55, 131.51, 57.70, 42.61, 33.84, 27.96, 21.28, 19.60. FTIR (KBr, cm-1): 2500-
3400 (m, br), 1709-1770 (s, br), 1390 (s), 1199 (s, sh), 1068 (m), 775 (w), 700 (m),
603 (w). Elemental analysis: calcd for C22H26N2O8: C, 59.19; H, 5.87; N, 6.27;
found: C, 58.98; H, 5.87; N, 6.25.
3a
3b
3c
3d
3e
1H-NMR (DMSO-d6, d ppm): 12.70 (s, br, 2H), 5.93-6.01 (m, 2H), 4.44-4.49 (dd,
2H, J = 6, 3 Hz), 3.40 (s, 2H), 3.21-3.30 (m, 4H), 1.85 (m, 2H), 1.65 (m, 2H), 1.25
(m, br, 2H), 0.75-0.81 (q, 12H). 13C-NMR (DMSO-d6, d ppm): 177.09, 170.46,
130.97, 50.73, 42.44, 36.62, 33.80, 24.60, 23.47, 21.14. FTIR (KBr, cm-1): 2500-
3200 (m, br), 1770 (w), 1710 (s, br), 1628 (w), 1460 (m), 1380 (m), 1309 (m), 1207
(w), 1126 (w), 976 (w), 670 (w), 600 (w). Elemental analysis: calcd for
C24H30N2O8: C, 60.75; H, 6.37; N, 5.90; found: C, 60.25; H, 6.22; N, 5.88.
1H-NMR (DMSO-d6, d ppm): 12.8 (s, br, 2H), 5.97-6.03 (m, 2H), 4.18-4.21 (d,
2H), 3.22-3.30 (m, 6H), 2.14-2.19 (m, 2H), 1.30-1.37 (m, 2H), 0.85-0.91 (d, 6H),
0.71-0.74 (t, 6H). 13C-NMR (DMSO-d6, d ppm): 177.59, 169.66, 131.27, 57.03,
42.40, 33.67, 25.24, 16.90, 10.87. FTIR (KBr, cm-1): 2500-3400 (m, br), 1772 (w),
1744 (s, sh), 1709 (s, sh), 1390 (s), 1232 (w), 1225 (m), 806 (w), 717 (w), 599 (w),
314 (m). Elemental analysis: calcd for C24H30N2O8: C, 60.75; H, 6.37; N, 5.90;
found: C, 60.45; H, 6.21; N, 5.91.
1H NMR (DMSO-d6, d ppm): 13.15 (s, br, 2H), 7.21-7.23 (q, 6H), 7.02-7.03 (t,
4H), 4.85-4.91 (dd, br, 2H, J = 6, 6 Hz), 3.25-3.31 (dd, 2H, J = 12, 3 Hz), 3.10-3.12
(d, 2H, J = 6 Hz), 3.01-3.05 (d, 4H, J = 12 Hz), 2.92-2.94 (d, 2H, J = 6 Hz). 13
C
NMR (DMSO-d6, d ppm): 176.69, 169.94, 132.02, 129.32, 128.53, 126.98, 53.07,
42.24, 42.11, 33.45, 33.24. FTIR (KBr, cm-1): 2600-3500 (m, br), 1776 (w), 1703
(s, br), 1498 (w), 1398 (w), 1394 (s), 1234 (m, br), 1174 (s), 933 (w), 698 (m).
Elemental analysis: calcd for C30H26N2O8: C, 66.41; H, 4.83; N, 5.16; found: C,
66.41; H, 4.82; N, 5.10.
1H NMR (DMSO-d6, d ppm): 12.95 (s, br, 2H), 6.01-6.10 (m, 2H), 4.33-4.38 (dd,
2H, J = 6, 3 Hz), 3.43 (D2O-exchang, s, br, 2H), 3.20-3.27 (D2O-exchang, q, 4H),
1.91-1.93 (m, 2H), 1.79-1.81 (m, 2H), 0.66-0.71 (t, 6H). 13C NMR (DMSO-d6, d
ppm): 177.14, 170.19, 131.06, 56.50, 42.41, 33.79, 21.23, 11.06. FTIR (KBr, cm-1):
2650-3400 (m, br), 1776 (s, br), 1498 (w), 1390 (s), 1224 (m, br), 1170 (s), 933
(w), 698 (m). Elemental analysis: calcd for C20H22N2O8: C, 57.41; H, 5.30; N, 6.70;
found: C, 57.34; H, 5.29; N, 6.70.
3f
bicyclo ring (Fig. 3). These peaks in the 13C NMR spectrum
along with elemental analyses data confirmed the proposed
structure of compound 3b.
tion reaction of an equimolar mixture of diimide-diacids
3a-f with bis(3-amino phenyl) phenyl phosphine oxide 4 in
a medium consisting of N-methyl-2-pyrrolidone, triphenyl
phosphite, calcium chloride and pyridine (Scheme II). The
syntheses and some physical properties of these novel PAIs
5a-f are given in Table 3. The entire polycondensation re-
Polymer synthesis
PAIs 5a-f were synthesized by direct polycondensa-

612 J. Chin. Chem. Soc., Vol. 56, No. 3, 2009
Faghihi et al.
action readily proceeded in a homogeneous solution; tough
and stringy precipitates formed when the viscous PAIs so-
lution was obtained in good yields. The resultant polymers
due to the presence of chiral amino acids 2a-f in the main
Fig. 1. FTIR spectrum of diimide-diacid 3b.
Fig. 2. 1H NMR spectrum of diimide-diacid 3b.

Synthesis of Novel Flame Retardant Poly(amide-imide)s
J. Chin. Chem. Soc., Vol. 56, No. 3, 2009 613
Fig. 3. 13C NMR spectrum of diimide-diacid 3b.
chain of polymers are optically active and Specific Rota-
tions were measured at a concentration of 0.5 g/dL in
DMSO at 25 °C. Also the resultant polymers have a range
of color between white and pale yellow.
were in good agreement with the calculated values for the
proposed structure (Table 4). The solubility of PAIs 5a-f
was investigated as 0.01 g of polymeric sample in 2 mL of
solvent. All of the polymers are soluble in DMSO and
H2SO4 and partially soluble in organic solvents such as
DMF, NMP and DMAc and are insoluble in solvents such
as chloroform, dichloromethane, methanol and ethanol.
Polymer characterization
The elemental analyses of the resultant PAIs 5a-f
Scheme II

614 J. Chin. Chem. Soc., Vol. 56, No. 3, 2009
Faghihi et al.
Table 3. Synthesis and some physical properties of PAIs 5a-f
Table 4. Elemental analysis of PAIs 5a-f
a
Diimide-diacid Polymer Yield (%) hinh (dL/g)a
Color
Polymer
Formula
C%
H%
N%
25
[á]
D
3a
3b
3c
3d
3e
3f
5a
5b
5c
5d
5e
5f
89
83
85
81
80
83
0.41
0.45
0.47
0.83
0.39
0.48
65.2
71.6
81.0
68.3
81.2
77.8
PY
W
5a
C36H31N4O7P
(662.63)n
Calcd
Found
Calcd
Found
Calcd
Found
Calcd
Found
Calcd
Found
Calcd
Found
65.25
64.15
66.84
65.78
67.55
66.14
67.55
66.04
70.75
68.89
66.08
65.23
4.72
4.66
5.47
5.23
5.80
5.21
5.80
5.35
4.82
4.64
5.11
5.01
8.46
8.34
7.80
7.65
7.50
7.13
7.50
7.34
6.88
6.71
8.11
8.01
W
5b
5c
5d
5e
5f
C40H39N4O7P
(718.74)n
W
PY
W
C42H43N4O7P
(746.79)n
C42H43N4O7P
(746.79)n
a Measured at a concentration of 0.5 g/dL in DMSO at 25 °C.
b W = White, PY = Pale Yellow
C48H39N4O7P
(814.01)n
C38H35N4O7P
(690.03)n
The structures of these polymers were confirmed as
1
PAIs by means of FTIR, H-MNR spectroscopy and ele-
mental analyses. FTIR characterizations of all PAIs are
listed in Table 5. The representative FTIR spectrum of PAI
5b is shown in Fig. 4. The polymer exhibited characteristic
absorption bands at 1709 and 1774 cm-1 for the imide ring
(symmetric and asymmetric C=O stretching vibration), a
broad peak approximately at 1690 cm-1 related to amide
groups (C=O stretching vibration), and 1384 cm-1 (C-N
stretching vibration). The absorption bands of amide groups
appeared at 3340 cm-1 (N-H stretching).
Table 5. FTIR Charcterization of PAIs 5a-f
Polymer
Spectral data
5a
FT-IR Peaks (cm-1): 3330 (m, br), 2966 (w, sh), 1774
(w), 1709 (s, br), 1589 (m), 1541 (m), 1481 (m), 1412
(m, sh), 1380 (m, br), 1308 (w), 1192 (m), 1116 (w),
692 (m).
5b
5c
5d
5e
5f
FT-IR Peaks (cm-1): 3340 (m, br), 2972 (w, sh), 1774
(w), 1709 (s, br), 1589 (m), 1541 (m), 1481 (m), 1415
(m, sh), 1384 (m, br), 1309 (w), 1190 (m), 1116 (w),
788 (w), 692 (m).
FT-IR Peaks (cm-1): 3340 (m, br), 2957 (m), 1774
(w), 1709 (s, br), 1589 (m), 1541 (m), 1481 (m), 1415
(m) 1384 (m, sh), 1309 (w) 1186 (m), 690 (m), 501
(w).
FT-IR Peaks (cm-1): 3331 (m, br), 2966 (m), 1774
(w), 1709 (s, br), 1589 (m), 1541 (m), 1481 (m), 1412
(m, sh), 1380 (m, br), 1308 (w), 1192 (m), 1114 (w),
692 (m), 499 (w).
FT-IR Peaks (cm-1): 3352 (m, br), 2972 (w), 1774
(w), 1709 (s, br), 1589 (m), 1541 (m), 1481 (m), 1384
(s), 1309 (w), 1190 (m), 1186 (m), 787 (w), 692 (m),
501 (w).
The 1H NMR spectra of PAIs 5b and 5f showed peaks
that confirm their chemical structures (Figs. 5, 6). Fig. 5
1
displays the H-NMR spectrum of PAI 5c. The aromatic
protons related to tiphenyl phosphine oxide appeared in the
region of 7.13-7.87 ppm and the peak in the region of 10.01
ppm is assigned to N-H of the amide groups in the main
1
chain of the polymer. And Fig. 6 displays the H NMR
spectrum of PAI 5f. The aromatic protons related to tri-
phenyl phosphine oxide appeared in the region of 7.12-
7.86 ppm, and the peak in the region of 10.00 ppm is as-
signed to N-H of the amide groups in the main chain of the
polymer. A decaying peak related to carboxylic acid’s pro-
tons and peaks appearing related to amide groups and tri-
phenyl phosphine oxide protons in the polymer chain, con-
firmed the proposed structure of PAIs 5a-f.
FT-IR Peaks (cm-1): 3329 (m, br), 2960 (m, sh), 1774
(w), 1709 (s, br), 1589 (m), 1540 (m), 1480 (m), 1383
(s), 1190 (m), 1187(m), 787 (m), 692 (m), 501 (w).
These polymers exhibited good resistance to thermal
decomposition up to 270-310 °C in nitrogen and began to
decompose gradually above that temperature. The temper-
ature of 5% weight loss for all the polymers ranged from
270 to 310 °C and the residual weight at 600 °C ranged
from 59.99 to 62.16% in nitrogen. The high char yields of
these PAIs in the high temperature region are important. It
shows that these polymers have good thermal stability.
Thermal properties
The thermal properties of PAIs 5c, 5d and 5f were in-
vestigated by TGA in a nitrogen atmosphere at a heating
rate of 10 °C/min (Fig. 7). All of these polymers showed
similar decomposition behavior. Initial decomposition tem-
perature, 5 and 10% weight loss temperature (T5, T10), and
char yields are summarized in Table 6.

Synthesis of Novel Flame Retardant Poly(amide-imide)s
J. Chin. Chem. Soc., Vol. 56, No. 3, 2009 615
Also the flame retardant property of these polymers was
evaluated by measuring their LOI values. They showed
LOI data between 31 and 33.
than 26 would show self-extinguishing behavior26 and are
considered to be flame retardant. Therefore high char yield
data, along with good LOI values between 31 and 33, indi-
cated that these polymers have good flame retardant prop-
Generally, materials exhibiting LOI values greater
Fig. 4. FTIR spectrum of PAI 5b.
Fig. 5. 1H NMR spectrum of PAI 5c.

616 J. Chin. Chem. Soc., Vol. 56, No. 3, 2009
Faghihi et al.
Fig. 6. 1H NMR spectrum of PAI 5f.
Table 6. Thermal behavior of PALs 5c, 5d and 5f
Polymer
T5 (°C)a
T10 (°C)a
Char yieldb
LOIc
5c
5d
5f
300-305
310-315
270-275
365-370
345-350
335-340
62.12
59.99
60.03
32
31
33
a Temperature at which 5% or 10% weight loss was recorded by
TGA at a heating rate of 10 °C/min under N2.
b Weight percentage of material left after TGA analysis at a
maximum temperature of 600 °C under N2.
c LOI, Limited oxygen index
moieties into the backbone increased the thermal stability
and flame-retardant properties. These properties can make
these polymers attractive for practical applications such as
processable high-performance engineering plastics.
Fig. 7. TGA curves of PAIs 5c, 5d and 5f.
erties.
EXPERIMENTAL
CONCLUSIONS
A novel series of PAIs 5a-f containing phosphine ox-
Materials
Bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetracarboxylic di-
anhydride 1 (from Aldrich), L-alanine 2a, L-valine 2b, L-
leucine 2c, L-isoleucine 2d, L-phenyl alanine 2e and L-2-
aminobutyric acid 2f (from Merck) were used without pre-
vious purification. According to the synthetic procedure
reported previously,23-24 bis(3-amino phenyl) phenyl phos-
phine oxide 4 was prepared from bis(3-nitro phenyl) phen-
ide moieties were synthesized by direct polycondensation
reaction of six asymmetric diacids 3a-f with bis(3-amino
phenyl) phenyl phosphine oxide 4 by using triphenyl phos-
phite, NMP, calcium chloride and pyridine as condensing
agents. The high char yields and good LOI data of these
polymers showed that the introduction of phosphine oxide

Synthesis of Novel Flame Retardant Poly(amide-imide)s
J. Chin. Chem. Soc., Vol. 56, No. 3, 2009 617
yl phosphine oxide. Solvent: N-methyl-2-pyrrolidone (NMP;
from Fluka), pyridine (from Acros), triphenyl phosphite
(TPP; from Merck) were used as received. Commercially
available calcium chloride (CaCl2; from Merck) was dried
under vacuum at 150 °C for 6 hrs.
no phenyl) phenyl phosphine oxide 4, 0.1 g (0.9 mmol) of
calcium chloride, 0.84 mL (3.00 mmol) of triphenyl phos-
phite, 0.18 mL of pyridine and 2.00 mL of N-methy-2-pyr-
rolidone were placed into a 25-mL round-bottomed flask,
which was fitted with a stirring bar. The reaction mixture
was heated under reflux on an oil bath at 120 °C for 8 hrs.
Then, the reaction mixture was poured into 50 mL of meth-
anol and the precipitated polymer was collected by filtra-
tion and washed thoroughly with hot methanol and dried at
60 °C for 12 hrs under vacuum to leave 0.194 g (83%)
white solid polymer 5b.
Apparatus and techniques
1H NMR and 13C NMR spectra were recorded on a
Bruker 300 MHz instrument (Germany). Fourier transform
infrared (FTIR) spectra were recorded on a Galaxy series
FTIR 5000 spectrophotometer (England). Spectra of solid
were performed by using KBr pellets. Vibration transition
frequencies were reported in wave numbers (cm-1). Band
intensities were assigned as weak (w), medium (m), shoul-
der (sh), strong (s) and broad (br). Inherent viscosities were
measured by a standard procedure by using a Technico
Regd Trade Mark Viscometer. Specific Rotations were
measured by an A-Kruss polarimeter. Limited oxygen in-
dexes (LOI) were measured on a Stanton Redcroft flame
meter. Thermal Gravimetric Analysis (TGAand DTG) data
for polymers were taken on a Mettler TA4000 System un-
der N2 atmosphere at a rate of 10 °C/min. Elemental analy-
ses were performed on Vario EL equipment by Arak Uni-
versity.
Received November 14, 2008.
REFERENCES
1. Saxena, A.; Rao, V. L.; Prabhakaran, P. V.; Ninan, K. N. Eur.
Polym. J. 2003, 39, 401.
2. Bier, G. Adv. Chem. Ser. 1969, 91, 612.
3. Yang, C. P.; Chen, Y. P.; Woo, E. M. Polymer 2004, 45, 5279.
4. Boulares, A.; Tessier, M.; Marechal, E. Polymer 2000, 41,
3561.
5. Ge, Z.; Yang, S.; Tao, Z.; Liu, J.; Fan, L. Polymer 2004, 45,
3627.
6. Liaw, D. J.; Hsu, P. N.; Chen, W. H.; Lin, S. L. Macro-
molecules 2002, 35, 4669.
Monomer synthesis
7. Faghihi, Kh.; Naghavi, H. J. Appl. Polym. Sci. 2005, 96,
1776.
N,N¢-(bicyclo[2,2,2]oct-7-ene-tetracarboxylic)-bis-L-
amino acids 3a-f
8. Weil, E. D.; Levchik, S. V.; Ravey, M.; Zhu, W. M. Phospho-
rus, Sulfur Silicon Relat. Elem. 1999, 146, 17.
9. Green, J. J. Fire. Sci. 1992, 10(6), 470.
10. Aaronson, A. M. Phosphorus Flame Retardant for a Chang-
ing World. Phosphorus Chemistry, Developments in Ameri-
can Science, ACS Symposium Series 486, Washington,
1992; p 218.
1 g (4.03 mmol) of bicyclo[2,2,2]oct-7-ene-2,3,5,6-
tetracarboxylic dianhydride 1, 8.06 mmol of L-amino acids
2a-f, 50 mL of acetic acid and a stirring bar were placed
into a 250-mL round-bottomed flask. The mixture was stir-
red at room temperature overnight and refluxed for 4 hrs.
The solvent was removed under reduced pressure, and the
residue was dissolved in 100 mL of cold water, then the so-
lution was decanted and 5 mL of concentrated HCl was
added. A white precipitate was formed, filtered off, and
dried to give compounds N,N¢-(bicyclo[2,2,2]oct-7-ene-
tetracarboxylic)-bis-L-amino acids 3a-f.
11. Annakutty, K. S.; Kishore, K. J. Sci. Ind. Res. 1989, 48(10),
479.
12. Xu, J.; Jiao, Y.; Zhang, B.; Qu, H.; Yang, G. J. Appl. Polym.
Sci. 2006, 101, 731.
13. Yang, S. C.; Kim, J. P. J. Appl. Polym. Sci. 2008, 108, 2297.
14. Tian, C.; Wang, H.; Liu, X.; Ma, Z.; Guo, H.; Xu, J. J. Appl.
Polym. Sci. 2003, 89, 3137.
Bis(3-amino phenyl) phenyl phosphine oxide 4
This compound was prepared according to our previ-
ous methods.23-24
15. Galip, H.; Hasipoglu, H.; Gunduz, G. J. Appl. Polym. Sci.
1999, 74, 2906.
Polymer synthesis
16. Liu, J.; Gao, Y.; Wang, F.; Wu, M. J. Appl. Polym. Sci. 2000,
75, 384.
The PAIs 5a-f were prepared by the following general
procedure: Taking polymer 5b as an example: 0.145 g
(0.326 mmol) of N,N¢-(bicyclo[2,2,2]oct-7-ene-tetracar-
boxylic)-bis-L-valine 3b, 0.1 g (0.326 mmol) of bis(3-ami-
17. Kashiwagi, T.; Morgan, A. B.; Antonucci, J. M.; Vanlandingham,
M. R.; Harris, R. H.; Award, W. H.; Shields, J. R. J. Appl.
Polym. Sci. 2003, 89, 2072.

618 J. Chin. Chem. Soc., Vol. 56, No. 3, 2009
Faghihi et al.
18. Wu, Q.; Lu, J.; Qu, B. Polym. Int. 2003, 52, 1326.
19. Wang, Z. Y.; Feng, Z. Q.; Liu, Q. J. Appl. Polym. Sci. 2007,
105, 3317.
24. Faghihi, Kh. J. Appl. Polym. Sci. 2006, 102, 5062.
25. Faghihi, Kh.; Hajibeygi, M. J. Appl. Polym. Sci. 2004, 92,
3447.
20. Espinosa, M. A.; Galia, M.; Cadiz, V. J. Polym. Sci. Polym.
Chem. 2004, 42, 3516.
26. Ying-Ling, L.; Yie-Chan, C.; Tsung-Yu, C. Polym. Int. 2003,
52, 1256.
21. Liu, Y. L.; Jeng, R. J.; Chiu, Y. S. J. Polym. Sci. Polym.
Chem. 2001, 39, 1716.
27. Faghihi, Kh. Macromol. Res. 2004, 12, 258.
28. Cianga, L. Eur. Polym. J. 2003, 39, 2271.
29. Fghihi, Kh. J. Appl. Polym. Sci. 2008, 109, 74.
30. Angiolini, L.; Benelli, T.; Giorgini, L.; Salatelli, E. Polymer
2005, 46, 2424.
22. Rusch-Salazar, L. A.; Sheares, V. V. J. Polym. Sci. Polym.
Chem. 2003, 41, 2277.
23. Faghihi, Kh.; Zamani, Kh. J. Appl. Polym. Sci. 2006, 101,
4263.