Synthesis and characterization of new heat resistance and organosoluble poly(ether-amide)

Article abstract of DOI:10.4314/bcse.v27i3.10

New series of olefinic poly(ether-amide)s (OPEA)s 6a-f was synthesized from 4,4′-bis(1,4- diphenoxybutane)diacrylic acid 4 and aromatic diamine 5a-f via a direct polycondensation reaction. The resulting polymers were characterized by Fourier transform inf

Full text of DOI:10.4314/bcse.v27i3.10

Bull. Chem. Soc. Ethiop. 2013, 27(3), 413-419.
Printed in Ethiopia
DOI: http://dx.doi.org/10.4314/bcse.v27i3.10
ISSN 1011-3924
 2013 Chemical Society of Ethiopia
SYNTHESIS AND CHARACTERIZATION OF NEW HEAT RESISTANCE AND
ORGANOSOLUBLE POLY(ETHER-AMIDE)
*
Meisam Shabanian and Nemat Basaki
Department of Chemistry, Farahan Branch, Islamic Azad University, Farahan, Iran
(
Received September 25, 2012; revised March 16, 2013)
ABSTRACT. New series of olefinic poly(ether-amide)s (OPEA)s 6a-f was synthesized from 4,4′-bis(1,4-
diphenoxybutane)diacrylic acid 4 and aromatic diamine 5a-f via a direct polycondensation reaction. The resulting
1
polymers were characterized by Fourier transform infrared spectra (FTIR), nuclear magnetic resonance ( H-
NMR), solubility test and inherent viscosity. The thermal properties of the polymers 6a-c were investigated by
thermogravimetric analysis (TGA). Polymer 6c due to presence of SO
thermal properties compare with polymer 6a and 6b.
2
group as a polar group shows better
KEY WORDS: Polycondensation, Polyamide, Ether group, Thermal properties
INTRODUCTION
Aromatic polyamides are noted for high transparency, excellent mechanical properties, heat
resistance, good char yield, low flammability, good barrier properties, and outstanding strength-
to-weight ratios and solvent resistance [1-4]; however, they are difficult to process because of
g
limited solubility and high glass transition (T ) [5-7]. The processing of these polymers has been
greatly hindered because they lack softening or melting property at usual processing
temperature, and they tend to decompose at the softening temperature. Many efforts have been
made to create structurally modified aromatic polyamides having better solubility and
processability. It is known that the solubility of polyamides is often increased when flexible
2 2 3 2
bonds such as [-CH -, -O-, -SO -, -C(CF -) ], bulky pendent groups, polar components or large
pendent groups are incorporated into the polymer backbone due to the altering crystallinity and
intermolecular interactions [8-13], synthesis of polyamides with noncoplaner unit in the
polymer chains [14], preparation of copolymers such as poly(amide-imide)s [15-18], poly(ester-
imide)s [19], poly(amide-ester-imide)s [20] and the introduction of bulky side groups into the
polymer chains [21-23] resulted a series of modified polyamides.
It has been recognized that the incorporation of aryl-ether linkages generally imparts an
enhanced solubility, processability, and toughness of aromatic polyamides without substantial
diminution of thermal properties [24]. Aromatic polymers that contain aryl ether linkages
generally have lower glass transition temperatures, greater chain flexibility, and tractability in
compared to their corresponding polymers without these groups in the chain [25-27]. The lower
glass transition temperatures and also improved solubility are attributed to the flexible linkages
that provide a polymer chain with a lower energy of internal rotation [28].
In this article, new series of olefinic poly(ether-amide)s 6a-f were synthesized by reacting
4,4′-bis(1,4-diphenoxybutane) diacrylic acid 4 and various diamine 5a-f via a direct
polycondensation reaction in a medium consisting of N-methyl-2-pyrrolidone, triphenyl
phosphite, calcium chloride and pyridine.
EXPERIMENTAL
Materials
All chemicals were purchased from Fluka Chemical Co. (Switzerland), Aldrich Chemical Co.
(
Milwaukee, USA), Merck Chemical Co. (Germany) and Acros Organics NV/SA (Belgium).
_
*
_________
Corresponding author. E-mail: shabanian.m44@gmail.com

414
Meisam Shabanian and Nemat Basaki
Techniques
The Fourier transform infrared spectra (FTIR) were measured using the Bruker Vertex 80 V
-
1
spectrometer over the wavenumber range of 600-4000 cm . NMR measurements were
performed with a Bruker 300 MHz and Bruker 500 MHz spectrometer. DMSO-d was used as
the solvent and the solvent signal was used for internal calibration (DMSO-d : δ ( C) = 39.6
6
1
3
6
1
ppm, δ ( H) = 2.5 ppm). Inherent viscosities were measured by a standard procedure by using a
Technico Regd Trad Mark Viscometer. Thermal gravimetric analysis (TGA) data for the
polymers were taken on a Mettler TA4000 System in the range between room temperature and
8
00 °C at a heating rate of 10 ºC/min in nitrogen atmosphere.
Monomer synthesis
Synthesis of 4,4′-bis(1,4-diphenoxybutane) diacrylic acid 4. At first 4,4′-bis(1,4-
diphenoxybutane) dialdehyde 3 was synthesized from the reaction of 4-hydroxybenzaldehyde
(
34 mmol) 1 and 17 mmol of dry K CO in 30 mL dimethyl formamide (DMF) with 17 mmol of
2 3
1
at 120 °C, then was cooled and poured onto crushed ice. The solid was precipitated, washed
,4-dibromo butane 2 in 5 mL dry dimethyl formamide. The reaction mixture was heated for 6 h
1
with the cold water and filtered at room temperature until product was obtained. H-NMR
(
(
DMSO-d
6
, TMS) δ: 1.9 (s, 4H), 4.11-5.15 (d, 4H), 7.10-7.13 (d, 4H), 7.84-7.87 (d, 4H), 9.86
s, 2H) ppm. Then 5 mmol of 4,4′-bis(1,4-diphenoxybutane) dialdehyde 3 were placed in a 100
mL beaker with 11 mmol malonic acid using 1 mL morpholine under solvent-free conditions.
The mixture compounds were heated until completely melted. Then the heating was removed
and 20 mL of 5% HCl was added in the reaction mixture slowly with stirring and the stirring
continued at room temperature for 2 h. After that the white precipitate was filtered and washed
with 20 mL H O and filtered until white product was obtained. M.p. 323-325 ºC, FTIR (KBr):
2
2
1
400-3500 (s, br), 1688 (s), 1627 (s), 1602 (s), 1510 (s), 1429 (s), 1310 (s), 1219 (s), 1171 (m),
-
1 1
018 (s, br), 827 (m), 680 (m), 510 (w) cm . H-NMR (DMSO-d , TMS) δ: 1.87 (s, 4H), 4.08
6
(
2
6
s, 4H), 6.34-6.40 (d, 2H), 6.98-7.11 (d, 4H), 7.51-7.57 (d, 2H), 7.62-7.86 (d, 4H), 12.36 (s, br,
1
3
H) ppm. C-NMR (DMSO-d
7.73, 25.73 ppm.
6
) δ: 168.32, 160.77, 144.23, 130.42, 127.19, 115.87, 115.25,
Synthesis of olefinic poly(ether-amide)s
Polyamides 6a-f were synthesized by direct polycondensation reaction. As an example the
preparation of OPEA 6e is described below. OPEA 6e was prepared from the reaction of 4,4′-
bis(1,4-diphenoxybutane) diacrylic acid 4 with 4,4'-diaminodiphenyl-ether 5e. In a 25 mL
round-bottomed flask which was fitted with a stirring bar were placed diacid 4 (0.64 mmol),
4
,4'-diaminodiphenylether 5e (0.64 mmol), calcium chloride (0.20 g, 1.80 mmol), triphenyl
phosphite (1.68 mL, 6.00 mmol), pyridine (0.36 mL) and N-methyl-2-pyrrolidone (2 mL). The
reaction mixture was heated under reflux on an oil bath at 60 °C for 1 h, then 90 °C for 2 h, and
1
20 °C for 6 h. The OPEA 6e formed was viscous, then the reaction mixture was poured into 50
mL of methanol and the precipitated polymer was collected by filtration and washed thoroughly
with hot methanol and dried at 60 °C for 12 h under vacuum to leave solid OPEA 6e.
Polymer 6a. FTIR (KBr): 3320 (m), 2947 (m), 1689 (s), 1589 (m), 1541 (m), 1481 (m), 1384
-
1
(
m), 1186 (m), 690 (w), 501 (w) cm .
Polymer 6b. FTIR (KBr): 3310 (w), 3075 (m), 2957 (m), 1685 (s), 1622 (s), 1578 (m), 1539
m), 1480 (m), 1424 (m), 1380 (m), 1278 (m), 1170 (m), 1079 (m), 950 (w), 729 (m), 699 (m)
(
cm .
-
1
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Synthesis of new poly(ether-amide)
415
Polymer 6c. FTIR (KBr): 3328 (w), 3032 (m), 2960 (m), 1688 (s), 1615(s), 1522 (m), 1540 (m),
1
-
483 (m), 1427 (m), 1380 (m), 1308 (m), 1180 (m), 1071 (m), 962 (w), 727 (m), 650 (m) cm .
1
Polymer 6d. FTIR (KBr): 3287 (w), 3025 (m), 2955 (m), 1670(s), 1550 (m), 1481 (m), 1435
(
-
1
m), 1385 (m), 1310 (m), 1165 (m), 1064 (m), 952 (w), 730 (m), 652 (m) cm .
Polymer 6e. FTIR (KBr): 3267 (w), 3020 (m), 2945 (m), 1669 (s), 1549 (m), 1479 (m), 1435
(
-
m), 1388 (m), 1268 (m), 1165 (m), 1062 (m), 952 (w), 731 (m), 655 (m) cm .
1
Polymer 6f. FTIR (KBr): 3332 (w), 3018 (m), 2975 (m), 1684 (s), 1549 (m), 1479 (m), 1435
(
-
1
m), 1388 (m), 1259 (m), 1165 (m), 1068 (m), 952 (w), 726 (m), 651 (m) cm .
RESULTS AND DISCUSSION
Monomer synthesis
Dicarboxylic acid 4 containing aryl ether and methylene group was synthesized by using two
step reactions. At first 4,4′-bis(1,4-diphenoxybutane)dialdehyde 3 was prepared from the
reaction of one equimolar 1,4-dibromobutane 2 and two equimolars 4-hydroxybenzaldehyde 1.
Then dialdehyde compound 3 was reacted with malonic acid at presence of catalytic amount of
morpholine under a solvent free condition. The chemical structure and purity of dicarboxylic
1
13
acid compound 4 were confirmed by FTIR, H-NMR, and C-NMR spectroscopy.
Polymer synthesis
Olefinic poly(ether-amide)s 6a-f were synthesized via direct polycondensation reaction of diacid
4
with aromatic diamine 5a-f via direct polycondensation reaction in a medium consisting of N-
methyl-2-pyrrolidone (NMP), triphenyl phosphite (TPP), calcium chloride and pyridine (Scheme
). The OPEAs 6a-f were obtained in good yields (Table 1).
1
Table 1. Some physical properties of OPEAs 6a-f.
a
b
Polymer
Yield (%)
η
inh (dL/g)
Color
Y
6
6
a
93
96
95
91
94
89
0.72
b
0.66
Y
6
c
0.67
C
6
d
0.61
C
6
e
0.58
Y
6f
0.57
B
a b
Measured at a concentration of 0.5g/dL in DMF at 25˚C. B = Brown, C = Cream, Y= Yellow.
Polymer characterization
The structure of polymer was confirmed by H-NMR and FTIR spectroscopies. FTIR data of
1
-
1
OPEAs 6a-f exhibited characteristic absorption bands around 1670 cm for the amide group
(
C=O stretching vibration) and the N-H stretching absorption bands of amide groups around
-
280 cm (N-H stretching). The H-NMR spectrum of polymer 6e showed peaks that confirm its
1
1
3
chemical structure (Figure 1). The aromatic and olefinic protons related to polymer backbone
appeared in the region of 6.6-7.8 ppm. The protons related to methylene group appeared at 1.9
and 4.1 ppm and the peak in the region of 10.5 ppm is assigned for NH of the amide groups in
the polymer chain.
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Meisam Shabanian and Nemat Basaki
Scheme 1. Synthesis route of olefinic poly(ether-amide) 6a-f.
1
Figure 1. H-NMR spectrum of OPEA 6e.
Solubility test
One of the main objectives of this study was producing modified polyamides with improved
solubility. The incorporation of monomers with flexible group such as ether moieties in the
polymer backbone, led to these polymers have good solubility in various solvents, especially
organic aprotic solvents. The solubility of OPEAs 6a-f was investigated as 0.01 g of polymeric
Bull. Chem. Soc. Ethiop. 2013, 27(3)

Synthesis of new poly(ether-amide)
417
sample in 2 mL of solvent. Remarkably, all of OPEAs were easily soluble at room temperature
in aprotic polar solvents such as N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide
(DMAc), N,N-dimethylformamide (DMF) and insoluble in solvents such as acetone,
chloroform, ethanol and methanol (Table 2).
Table 2. Solubility of OPEAs 6a-f.
Solvent
DMAc
6a
+
+
+
+
–
6b
+
+
+
+
–
6c
+
+
+
+
–
6d
+
+
+
+
–
6e
+
+
+
+
–
6f
+
+
+
+
–
DMSO
DMF
NMP
Cyclohexanone
CHCl
3
–
–
–
–
–
–
Acetone
EtOH
–
–
–
–
–
–
–
–
–
–
–
–
MeOH
–
–
–
–
–
–
2
H O
–
–
–
–
–
–
Solubility: + : soluble; –: insoluble.
Thermal properties
Thermal stability of the OPEA 6a-c determined under inert atmosphere is shown in Figure 2.
The initial decomposition temperatures of 5% and 10% weight losses (T and T10) and the char
5
yield at 800 °C are summarized in Table 3. Thermal decomposition temperatures of the
polymers were found in the range 237-241 °C. Compared with the thermal decomposition
behavior of OPEA 6a, OPEA 6b and 6c with two benzene rings show higher 5 wt% and 10 wt%
and delay the decomposition. The weight retained at 800 °C shows higher char residue at high
temperature and improves significantly with percent of SO
2
group.
Figure 2. TGA curves of OPEAs 6a-c.
Table 3. Thermal and fire measurements of OPEAs 6a-c.
a
a
b
Polymer
OPEA 6a
OPEA 6b
OPEA 6c
T
5
(˚C)
T
10 (˚C)
Char yield
33.34
241
234
237
273
315
33.10
316
34.96
a
2
Temperature at which 5% or 10% weight loss was recorded by TGA at a heating rate of 10 ˚C/min under N .
b
Weight percentage of material left after TGA analysis at a maximum temperature of 800 ˚C.
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Meisam Shabanian and Nemat Basaki
CONCLUSIONS
In this article, an efficient method for the synthesis of 4,4′-bis(1,4-diphenoxybutane) diacrylic
acid 4, containing ether and olefinic groups, has been developed under solvent free condition in
presence of morpholine as a catalyst. New poly(ether-amide)s with good inherent viscosity were
prepared by the direct polycondensation reaction of the synthesized diacid and aromatic diamine
5
a-f. The results presented herein also clearly demonstrate that incorporating the ether group
into the polymer main chain as well as combination of the wholly aromatic backbone and
several functional groups remarkably enhanced the solubility in organic solvents of the new
2
polymers. The thermal stability and char residue of the OPEA 6c due to presence SO have been
increased as compared with the OPEA 6a. These properties could make these OPEAs attractive
for practical applications such as processable high-performance engineering plastics.
ACKNOWLEDGEMENTS
The authors wish to acknowledge the support of this work by the research council of Farahan
branch, Islamic Azad University, Farahan, Iran.
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