New optically active Organo-soluble poly(amide-Imide)s from [N,N?-(4,4?- Diphtaloyl)-BIS-l-amino Diacid]s and 1,2-bis[4,4'-aminophenoxy] ethane: Synthesis and characterization

Article abstract of DOI:10.4067/S0717-97072013000300020

Six new dicarboxylic acids 3a-f were synthesized by the reaction of 3,3?,4,4?-biphenyltetracarboxylic dianhydride (BPDA) 1 with L-amino acids 2a-f in a solution of glacial acetic acid/pyridine (Py) at refluxing temperature. Then six new optically active p

Full text of DOI:10.4067/S0717-97072013000300020

J. Chil. Chem. Soc., 58, Nº 3 (2013)
NEW OPTICALLY ACTIVE ORGANO-SOLUBLE POLY(AMIDE-IMIDE)S FROM [N,N΄-(4,4΄-
DIPHTALOYL)-BIS-L-AMINO DIACID]S AND 1,2-BIS[4,4’-AMINOPHENOXY] ETHANE: SYNTHESIS AND
CHARACTERIZATION
AKRAM FEYZI, KHALIL FAGHIHI*, AHAMD RAEISI, MARYAM KOUSHKI, MANSOURE FARAHANI
Organic Polymer Chemistry Research Laboratory, Department of Chemistry, Faculty of Science, Arak University, Arak, 38156-8-8349, Iran
(Received: October 11, 2012 - Accepted: April 29, 2013)
ABSTRACT
Six new dicarboxylic acids 3a-f were synthesized by the reaction of 3,3΄,4,4΄-biphenyltetracarboxylic dianhydride (BPDA) 1 with L-amino acids 2a-f in a
solution of glacial acetic acid/pyridine (Py) at refluxing temperature. Then six new optically active poly(amide-imide)s (PAI)s with good inherent viscosities were
synthesized by direct polycondensation reaction of [N,N΄-(4,4΄-diphtaloyl)-bis-L-amino diacid]s with 1,2-bis[4,4’-aminophenoxy] ethane (APE) 4 in a medium
of N-methyl-2-pyrrolidone (NMP)/ triphenyl phosphite (TPP)/ calcium chloride (CaCl2)/pyridine. Not only PAIs are optically active but also soluble in various
organic solvents. These resulting new polymers can be used in column chromatography for the separation of enantiomeric mixtures. The resulted polymers were
fully characterized by means of FTIR, 1H-NMR spectroscopy, elemental analyses, inherent viscosity, specific rotation, solubility tests and UV-Vis spectroscopy.
Also thermal properties of the PAIs 3a-f were investigated using thermal gravimetric analysis (TGA).
Keywords: Poly(amide-imide); Thermal properties; Organo-soluble polymer; Inherent viscosity.
recorded on 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), shoulder (sh), strong (s) and broad (br). Inherent viscosities
were measured by a standard procedure by using a Technico Regd Trad Mark
Viscometer. UV-Vis absorptions were recorded at 25°C in the 270–790 nm
spectral regions with a Perkin-Elmer Lambda 15 spectrophotometer on DMF
solution by using cell lengths of 1 cm. Specific Rotations were measured by an
A-Kruss polarimeter. Thermal Gravimetric Analysis (TGA and DTG) data of
polymers were taken on a Mettler TA4000 System under N atmosphere at rate
of 10°C/min. Elemental analyses were performed by Vario2EL equipments.
Monomer synthesis
INTRODUCTION
Since their development in the 1960s, polyimides have become an
important class of polymers, finding a wide range of applications in the
aerospace and microelectronics industries. Aromatic polyimides are well
known high-performance polymers because of their excellent thermal stability,
mechanical and electrical properties and chemical resistance [1, 2]. However,
polyimides are often insoluble and intractable characteristics resulting in
processing difficulties which limit their applications [3].
Modification of high performance polymers by increasing the solubility
and lowering the transition temperatures while maintaining thermal stability
are of particular interest. Copolycondensation is one of the possible ways for
modification of polymer properties. Thus, processing of polyimides many
copolyimides, such as poly(amide-imide)s, poly(ester-imide)s, and other
copolymers have been prepared [4-9]. The synthesis of poly(amide-imide)s is
more attractive than the other methods of copolymerization, because solubility
and processability can be improved without significantly sacrificing the
thermal and mechanical properties, they are useful in numerous applications
in electrical wire enamel, adhesives, and injection-molding and extrusion
products [10-12]. These polymers are a type of chemicals materials, which
could become one of the new sources of a family of environmentally friendly.
We use amino acids as chiral agents which are often naturally occurring
compounds therefore synthetic polymers based on amino acids are expected to
be biodegradable and biocompatible.
This paper reports the preparation and basic characterization of
photosensitive and thermally stable poly(amide–imide)s (PAI)s 5a-f by the
direct polycondensation reaction of [N,N΄-(4,4΄-diphtaloyl)-bis-L-amino
diacid]s with 1,2-bis[4,4’-aminophenoxy] ethane (APE) 4 in a medium
consisting of N-methyl-2-pyrrolidone (NMP), triphenyl phosphite (TPP),
calcium chloride (CaCl ) and pyridine (Py). As reported previously, APE
has been synthesized thr2ough a two step reaction starting from 4-nitro phenol
and 1,2- dibromo ethane in the presence of potassium carbonate, followed by
catalytic reduction with hydrazine monohydrate 10% Pd/C [13-15].
[N, N΄-(4,4΄-diphtaloyl)-bis-L-amino diacid]s 3a-f
2.942 g (10.00 mmol) of 3, 3΄, 4, 4΄- biphenyltetracarboxylic dianhydride
1, 20.00 mmol of L-amino acids 2a–f, 80 mL of mixture of acetic acid/pyridine
(3:2) and a stirring bar were placed into a 250-mL round-bottomed flask. The
mixture was stirred at room temperature overnight and refluxed for 4-10 h. The
solvent was removed under reduced pressure, and the residue was dissolved in
100 mL of cold acidic water. A white to cream precipitate was formed, filtered
off, and dried to give compounds [N, N΄-(4, 4΄-diphtaloyl)-bis-L-amino diacid]
s 3a–f.
Polymer synthesis
A mixture of di carboxylic acid 3a-f (1 mmol), di amine APE 4 (1 mmol),
calcium chloride (0.350 g), TPP (0.8 ml), pyridine (1.2 ml) and NMP (4.0 ml)
was refluxed for 10 h. After cooling, the reaction mixture was poured into
methanol (50 ml) to precipitate the corresponding polymer. The precipitated
polymer was then separated by vacuum filtration and washed with methanol
(30 ml) and hot water (100 ml) and dried at 120°C under vacuum for 24 h. IR
and NMR spectroscopic results of the obtained polymers will be discussed in
the Results and Discussion section.
RESULTS AND DISCUSSION
Monomer synthesis
Asymmetric di carboxylic acids 3a–f were synthesized by the
condensation reaction of 3,3΄,4,4΄- biphenyltetracarboxylic dianhydride 1
with two equimolars of L-alanine 2a, L-valine 2b, L-leucine 2c, L-2-amino-2-
phenylacetic acid 2d, L-phenyl alanine 2e and L-2-aminobutyric acid 2f in an
acetic acid/pyridine solution. In this work, we used six diacids 3a-f for direct
polycondensation (Scheme 1). Di acid 3e was synthesized previously [17]. The
yields and some physical properties of these compounds are shown in Table
1. Chemical structure and purity of the optically active di carboxylic acids
3a–f were proved by using elemental analysis, FTIR, 1H-NMR and 13C-NMR
spectroscopic techniques. These data are shown in Table 2.
EXPERIMENTAL
Materials
3, 3΄, 4, 4΄- Biphenyltetracarboxylic dianhydride (1; Aldrich), L-alanine 2a,
L-valine 2b, L-leucine 2c, L-2-amino-2-phenylacetic acid 2d, L-phenylalanine
2e and L-2-aminobutyric acid 2f (Merck) were used without previous
purification. Diamine APE 4 (mp = 115- 117°C) was prepared according to
our previous work [16]. NMP (Fluka), Py (Acros) and TPP (Merck) were used
as received. Commercially available CaCl2 (Merck) was dried under vacuum
at 150 °C for 6 h.
Techniques
1H-NMR and 13C-NMR spectra were recorded on a Bruker 300 MHz
instrument (Germany). Fourier transform infrared (FTIR) spectra were
e-mail: k-faghihi@araku.ac.ir
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J. Chil. Chem. Soc., 58, Nº 3 (2013)
1H-NMR (DMSO- d , δ ppm): 12.70- 12.56(s, br, 2H),
8.23(s, br, 4H), 7.92-67.95(m, 2H), 7.16(m, 10H), 5.12-
5.16(dd, 2H), 3.47-3.51(m, 4H). 13C-NMR (DMSO-
d , δ ppm): 170.17, 177.16, 167.13, 145.07, 137.76,
1634.52, 132.17, 130.83, 129.17, 128.80, 127.03,
124.27, 123.00, 52.86, 34.45. FT-IR Peaks (cm-1):
3067-3400 (m, sh,br), 2960 (w), 1774 (w), 1718 (s,
br), 1604 (w), 1510 (w), 1373 (m), 1300 (w), 1224
(m), 1105 (m), 1091 (w), 941 (w), 740 (m). Elemental
analysis: calcd for C32H O8N : C, 67.36; H, 5.26; N,
4.91. found: C, 66.85; H,305.10;2N, 4.71.
3d
Scheme 1. Synthesis of the dicarboxylic acids 3a-f.
1H-NMR (DMSO- d6, δ ppm): 12.67- 12.46(s, br,
2H), 8.31-8.36(m, 4H), 8.23-8.28(m, 2H), 7.34-
7.50(m, 10H), 6.07(s, 2H). 13C-NMR (DMSO- d6, δ
ppm): 169.36, 167.00, 145.13, 135.41, 135.41, 134.48,
132.53, 131.27, 129.15, 129.03, 128.79, 128.44,
127.85, 124.68, 123.07, 55.85. FT-IR Peaks (cm-1):
3060-3400 (m, sh,br), 2960 (w), 1774 (w), 1718 (s, br),
1593 (w), 1527 (w), 1375 (m), 1317 (w), 1201 (m),
1140 (m), 1066 (w), 920 (w), 700 (m). Elemental
analysis: calcd for C35H O8N : C, 70.01; H, 4.02; N,
4.67. found: C, 69.74; H,243.87;2N, 4.18.
Table 1. Yields and some physical properties of chiral the di carboxylic
acids 3a-f.
25 (a)
Entry
Amino acid
Yield (%)
Mp (°C)
[α]D
3e
3a
3b
3c
L-Alanine
L-Valine
94
92
83
287-289
270-271
275-277
-7.5
+4.5
+2.1
L-Leucine
L-2-amino-2-phenyl
acetic acid
3d
3e
3f
91
94
88
245-246
295-297
263-265
-8.2
-6.5
1H-NMR (DMSO- d6, δ ppm): 12.65-12.43(s, br,
2H), 8.32-8.35(m, 4H), 8.04-8.06(m, 2H), 4.68-
4.74(m, 2H), 2.04-2.18(m, 4H), 0.84-0.89(t, 6H).
13C-NMR (DMSO- d , δ ppm): 170.91, 167.53,
145.10, 134.41, 132.461, 131.31, 124.55, 122.97,
53.86, 22.00, 11.28. FT-IR Peaks (cm-1): 3340 (w),
2933 (w), 1772 (m), 1714 (s), 1670 (s), 1606 (s), 1458
(m), 1375 (m), 1300 (w), 1228 (m), 1176 (m), 1070
(w), 949 (m), 740 (s), 522 (m). Elemental analysis:
calcd for C H O8N2: C, 62.06; H, 4.31; N, 6.03.
found: C, 6214.4220; H, 4.11; N, 5.83.
L-Phenyl alanine
L-2-Aminobutyric
acid
+14.6
(a) Measured at a concentration of 0.5 g/dl in DMF at 25oC.
3f
Table 2. 1H-NMR, 13C-NMR, FTIR spectra and elemental analyses data of
the di carboxylic acids derivatives 3a-f.
Diimide-
Spectral data
diacid
1H-NMR (DMSO- d6, δ ppm): 12.87-12.93 (s, br,
2H), 8.28-8.32 (m, 4H), 8.00-8.03 (m, 2H), 4.90-4.92
(q, 2H), 1.56-1.58 (d, 6H). 13C-NMR (DMSO- d6, δ
ppm): 171.49, 167.15, 144.75, 134.08, 132.63, 131.34,
These FTIR data showed absorption around 2500 and 3400 cm-1, which
was assigned to the COOH groups. Peaks appearing at around 1700- 1770 cm -1
(acid C=O and symmetric imide stretching), 1390- 700 cm -1 imide charasteristic
ring vibration) confirmed the presence of imide ring and carboxylic groups
in these compounds. Also 13C-NMR data showed carboxylic acid and imide
carbons and aromatic carbons in related signals.
124.40, 122.53, 47.58, 15.18.FT-IR Peaks (cm-1):
3a
3100-3419 (m, sh,br), 2928 (w), 1772 (w), 1710 (s,
br), 1620 (w), 1425 (w), 1384 (m), 1300 (w), 1248
(m), 1149 (m), 1084 (w), 937 (w), 742 (m). Elemental
analysis: calcd for C22H O8N : C, 60.55; H, 3.67; N,
6.42. found: C, 60.04; H,163.31;2N, 6.32.
As an example, the 1H-NMR spectrum of diacid 3f showed peaks between
0.84 and 0.89 ppm as a triplet, which was assigned for two CH3 group (d) peak
between 2.04 and 2.18 ppm as a multiplet, which was assigned to the CH2 (c)
protons and peaks between 4.68 and 4.74 ppm as a doublet of doublet, which
was assigned to the CH (b) protons, which are chiral centers. The peaks at 8.04-
8.35 ppm were assigned to aromatic protons (e, f and g). Also a broad peak
in 12.95 ppm was assigned to COOH groups (Fig. 1).The measured results
in elemental analyses of these compounds were closely corresponded to the
calculated ones, demonstrating that the expected compounds were obtained.
1H-NMR (DMSO- d6, δ ppm): 12.92-13.10 (s, br,
2H), 8.22-8.35(m, 4H), 8.04-8.06(m, 2H), 4.48-4.51(d,
2H), 2.60-2.62(m, 2H), 0.84-1.07(dd, 6H). 13C-NMR
(DMSO- d6, δ ppm): 170.17, 167.49, 145.13, 134.39,
132.49, 131.20, 124.56, 122.95, 57.61, 28.45, 21.27,
3b
19.70. FT-IR Peaks (cm-1): 2986-3410 (m, sh,br),
2933 (w), 1772 (w), 1710 (s, br), 1620 (w), 1431
(w), 1377 (m), 1300 (w), 1267 (m), 1194 (m), 1080
(w), 900 (w), 746 (m). Elemental analysis: calcd
for C26H O8N2: C, 63.41; H, 4.87; N, 5.69. found: C,
62.50; H2,44.21; N, 4.99.
Polymer synthesis
The direct polycondensation of a dicarboxylic acid and the diamine
is one of the well-known methods for (PAI)s synthesis. In this work, we
synthesized (PAI)s 5a–f containing ether and methylene moieties by direct
polycondensation reactions of six chiral [N,N΄-(4,4΄-diphtaloyl)-bis-L-amino
diacid]s 3a–f with 1,2-bis[4,4’-aminophenoxy] ethane 4 by using triphenyl
phosphite (TPP) and pyridine as condensing agents (Scheme 2).
1H-NMR (DMSO- d6, δ ppm): 12.85- 12.95(s, br, 2H),
8.29-8.40(m, 4H), 7.99-8.07(m,2H), 4.77-4.85(m,2H),
1.88-2.2(dd, 4H), 1.35-1.65(m, 2H), 0.84-0.91(m,12H).
13C-NMR (DMSO- d , δ ppm): 171.16, 167.48,
145.17, 134.39, 132.62,6131.34, 124.53, 122.96, 50.78,
25.12, 23.42, 21.29. FT-IR Peaks (cm-1): 3176-3400
(m, sh,br), 2960 (w), 1774 (w), 1695 (s, br), 1622 (w),
1431 (w), 1379 (m), 1300 (w), 1244 (m), 1157 (m),
1091 (w), 918 (w), 748 (m). Elemental analysis: calcd
for C28H O8N2: C, 64.61; H, 5.38; N, 5.38. found: C,
63.24; H2,84.99; N, 5.07.
All the polycondensations proceeded readily in a homogeneous solution.
Tough and stringy precipitates formed when the viscous polymer solutions
were trickled into the stirring methanol.
Yields and some physical properties of these new (PAI) s 5a-f are given
in Table 3. All the polymers were obtained in high yields (82-94%), and the
inherent viscosities (0.30-0.45 dl/g) was measured in DMF solutions. Due to
the presence of chiral amino acid moieties 2a-f in the polymer backbone, the
polymers 5a-f are optically active and the specific rotations are given in Table
3. Also the resulting polymers have a range of color between cream and light
brown.
3c
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J. Chil. Chem. Soc., 58, Nº 3 (2013)
FT-IR Peaks (cm-1): 3358 (w), 2916 (w), 1776 (w), 1720 (s,
br), 1616 (m), 1515 (s), 1388 (s), 1295 (m), 1252 (m), 1107
(w), 1099 (w), 1055 (w), 825 (w), 723 (s), 524 (m).
5e
5f
FT-IR Peaks (cm-1): 3340 (w), 2933 (w), 1772 (m), 1714 (s),
1670 (s), 1606 (s), 1458 (m), 1375 (m), 1300 (w), 1226 (m),
1176 (m), 1070 (w), 949 (m), 740 (s), 522 (m).
Fig.2. FTIR spectrum of PAI 5f
The 1H-NMR spectrum of PAI 5a showed peaks that confirm its chemical
structure (Fig. 3). The aromatic protons and four methylene protons related
these last ones to the diamine 4, appeared in the region of 6.73-8.31 ppm and
4.24-4.48 ppm respectively. A single peak at 9.74 ppm is assigned for N-H
amide groups in the polymer chain. Also the elemental analyses of the resulting
(PAI)s 5a-f were in good agreement with the calculated values for the proposed
structure (Table 5).
Fig.3. 1H-NMR spectrum (DMSO-d6) of PAI 5a
Table 5. Elemental analysis of PAIs 5a-f.
Polymer
Formula
C36H28N4O8
(644.28)n
%C
%H
4.34
3.95
5.14
4.65
5.49
5.23
4.16
4.98
4.52
4.21
4.75
4.65
%N
8.69
7.89
7.99
7.71
7.68
7.43
7.28
6.87
7.03
6.69
8.32
8.08
5a
Calcd
Found
Calcd
Found
Calcd
Found
Calcd
Found
Calcd
Found
Calcd
Found
67.10
66.74
68.59
68.10
69.25
69.10
71.89
69.84
72.38
72.32
67.88
67.82
Fig. 1. 1H-NMR spectrum (DMSO- d6) of di carboxylic acid 3f
Scheme 2. Synthesis rout of (PAI)s 5a-f
5b
5c
5d
5e
5f
C40H36N4O8
(700.32)n
Table 3. Yields and some physical properties of (PAI) s 5a–f.
C42H40N4O8
(728.34)n
Yield
(%)
25 (a)
diacid polymer
η inh(dL/g) (a)
[α]D
Color
3a
3b
3c
3d
3e
3f
5a
5b
5c
5d
5e
5f
89
0.31
0.30
0.41
0.42
0.45
0.39
+105
Light Yellow
Cream
C46H32N4O8
(768.38)n
92
82
83
94
84
+117
+94.5
+111.5
+101.5
+66.5
Cream
C48H36N4O8
(796.40)n
Dark cream
Light brown
Cream
C38H32N4O8
(672.30)n
(a) Measured at a concentration of 0.5 g/dl in DMF at 25 oC.
Solubility of the PAIs
Solubility of (PAI)s 5a-f was investigated as 0.01 g of polymeric sample
in 2 mL of solvent. These poly(amide-imide)s have good solubility in aprotic
organic solvents. Remarkably, all of these PAIs were easily soluble at room
temperature in aprotic polar solvents such as NMP, N, N´-dimethylacetamide
(DMAc), N,N´-dimethylformamide (DMF), and insoluble in solvents such
as chloroform, ethanol and methanol. It is due to the flexibility effect of the
etheric structure of the diamine (Table 6).
Polymer characterization
The structure of polymers was confirmed as (PAI) s by means of FTIR
spectroscopy and elemental analyses. Representative FTIR spectrum of PAI 5f
was shown in Figure 2. The polymer showed the C=O asymmetric stretching
of imide at 1772 cm-1, the C=O symmetric stretching of imide at 1714 cm-1 and
C-N stretching at 1375 cm-1 . The absorption bands of amide groups appeared
at 3340 cm-1 (N-H stretching). All of these PAIs exhibited strong absorption
around 1380 and 730 cm-1, which shows the presence of the heterocyclic imide
groups. FTIR spectroscopy data for all of PAIs 5a-f are listed in table 4.
Table 6. Solubility of PAIs 5a-f.
Solvent
DMAc
DMSO
DMF
5a
+
+
+
+
−
−
−
−
−
5b
+
+
+
+
−
−
−
−
−
5c
+
+
+
+
−
−
−
−
−
5d
+
+
+
+
−
−
−
−
−
5e
+
+
+
+
−
−
−
−
−
5f
+
+
+
+
−
−
−
−
−
Table 4. FTIR characterization of PAIs 5a-f.
Polymer
Spectra data
FT-IR Peaks (cm-1): 3350 (m, br), 3066 (w), 2945 (w), 1776
(m), 1714 (s, br), 1672 (s), 1593 (s), 1492 (s), 1380 (m), 1320
(w), 1245 (m), 1140 (m), 1052 (m), 922 (m), 743 (m).
5a
NMP
FT-IR Peaks (cm-1): 3375 (w), 3065 (w), 1776 (w), 1720 (s),
1625 (w), 1524 (s), 1385 (m), 1248 (m), 1122 (w), 1056 (w),
1082 (m), 925 (s), 726 (w).
MeOH
EtOH
CHCl3
CH2Cl2
H2O
5b
5c
5d
FT-IR Peaks (cm-1): 3354 (w), 2924 (w), 1776 (m), 1722 (s,
br), 1610 (m), 1515 (s), 1386 (s), 1248 (s), 1176 (w), 1088
(w), 1053 (w), 825 (w), 725 (s), 617 (w), 524 (w).
FT-IR Peaks (cm-1): 3345 (w), 2961 (m), 1776 (w), 1716 (s),
1675 (m), 1638 (w), 1587 (m), 1465 (m), 1385 (s), 1321 (w),
1201 (m), 1113 (w), 725 (w).
+ , Soluble at room temerature. _ , Insoluble at room temperature
UV-Vis Absorption characteristics
Photo-sensitive property of the new poly(amide-imide)s 5a–f in the DMF
solution was studied by a UV spectrophotometer. All polymer solutions exhibit
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J. Chil. Chem. Soc., 58, Nº 3 (2013)
the same two positions of absorption maximum in UV-Vis spectra at 330–
337 nm. The absorption maximum at around 340 nm corresponds to n→ π*
transition of the nonbonding electrons which is present in nitrogen and oxygen
atoms in the polymer backbone. The UV-Vis absorption spectrum of PAI 5f
in DMF is shown in Fig. 4. The spectrum of PAI 5f exhibited a typical peak
around 330 nm (n→ π* transition).
CONCLUSIONS
In this article, we have successfully synthesized 6 dicarboxylic acid 3a-f
containing amino acidic moieties. A series of new thermally stable PAIs 5a-f
were prepared from chiral [N, N΄-(4, 4΄-diphtaloyl)-bis-L-amino diacid]s 3a-f
with 1,2-bis[4,4’-aminophenoxy] ethane 4 by direct polycondesation method.
The results presented here also clearly demonstrate that incorporating the
imide group into the polymer main chain as well as combination of the wholly
aromatic backbone and several functional groups enhanced the thermal stability
of the new polymers. These polymers are expected to have high solubility due
to the presence of the alkyl groups in the polymer chain. These properties could
make these PAIs attractive for practical applications such as processable high-
performance engineering plastics, column chromatography for the separation
of the enantiomeric mixtures.
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TGA and derivative of thermogravimetric (DTG) analysis at a rate of
10 ºCmin-1 in a nitrogen atmosphere were utilized to examine the thermal
properties of the PAIs. Obtained results are summarized in Table 7. Figure 5
shows TGA results of the PAIs 5b and 5d; respectively.
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at 800 ºC (char yield). The results revealed that the PAIs were thermally stable
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8.- Kh. Faghihi and H. Moghanian, Chinese J. Polym. Sci., 28(5):695-704
(2010).
9.- Kh. Faghihi and M. Hajibeygi, Chinese J. Polym. Sci., 28(4):517-525
(2010).
10.- Kh. Faghihi and M. Hajibeygi, Macromol. Res., 13:14-18 (2005).
11.- Kh. Faghihi, J. Appl. Polym. Sci., 109:74-81 (2008).
12.- Kh. Faghihi, M. Hajibeygi and M. Shabanian, J. Chin. Chem. Soc-Taip.,
56:609-618 (2009).
The char yield can be applied as a decisive factor for estimating the limited
oxygen index (LOI) of polymers using Van Krevelen and Hoftyzer’s equation
[18]:
13.- D.J. Liaw and W.H. Chen, Polym., 44:3865-3870 (2003).
14.- S. Mallakpour and M. Kolhdoozan, J. Appl. Polym. Sci.,104:1248-1254
(2007).
LOI = 17.5 + 0.4CR
Where CR is the char yield.
PAIs 5b and 5d had LOI values around 35, which were calculated from
their char yield. On the basis of the LOI values, such macromolecules can be
classified as self-extinguishing polymers.
15.- Kh. Faghihi, A. Feyzi, and H. Nasr Isfahani, Desig. Monom. Polym.,
13:131-142 (2010).
16.- Kh. Faghihi, M. Nourbakhsh and M. Hajibeygi, Chinese J. Polym. Sci.,
28(6):941-949 (2010).
Table 7. Thermal behavior of PAIs 5b and 5d.
17.- Z.Y. Yang, J.SH. Yao and R.B. Guo, Adv. Mater. Research, 282-283:116-
119 (2011).
18.- D.W. VanKrevelen and P.J. Hoftyzer, Properties of Polymers, Elsevier,
New York, (1976).
polymer
5b
T5(˚C)a
T10(˚C)a Char yield (%)b
LOI c
35.5
35.9
420
460
45
5d
412
450
46
a Temperature at which 5% or 10% weight loss was recorded by TGA at a
heating rate of 10 ˚C/min under N .
Weight percentage of mate2rial left after TGA analysis at a maximum
b
temperature of 800 ˚C under N2.
c Limiting Oxygen Index (LOI).
Fig.5. TGA curves of the (PAI)s 5b and 5d.
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