Preparation of new optically active and thermally stable poly(amide-imide) containing bicyclo segment and ether group in the main chain by direct polycondensation in two different media

Article abstract of DOI:10.4067/S0717-97072010000400018

A new series of optically active and thermally stable poly(amide-imide)s (PAIs) with good inherent viscosities based on bicyclo diacids and etheric diamine in the main chain were synthesized from the direct polycondensation reaction of N,N?-(bicyclo[2,2,2

Full text of DOI:10.4067/S0717-97072010000400018

J. Chil. Chem. Soc., 55, Nº 4 (2010)
PREPARATION OF NEW OPTICALLY ACTIVE AND THERMALLY STABLE POLY(AMIDE-IMIDE)
CONTAINING BICYCLO SEGMENT AND ETHER GROUP IN THE MAIN CHAIN BY DIRECT
POLYCONDENSATION IN TWO DIFFERENT MEDIA
Khalil Faghihi1*, MeisaM shabanian2
1Polymer Research laboratory, Department of Chemistry, Faculty of science, islamic azad University, arak branch, arak, iran.
2 islamic azad University, arak branch, Young Researchers Club, araky, iran
(Received: May 31, 2010 - Accepted: November 15, 2010)
ABSTRACT
A new series of optically active and thermally stable poly(amide-imide)s (PAIs) with good inherent viscosities based on bicyclo diacids and etheric diamine
in the main chain were synthesized from the direct polycondensation reaction of N,N΄-(bicyclo[2,2,2]oct-7-ene-tetracarboxylic)-bis-l-amino acids 3a-g with
1,2-Bis[4-aminophenoxy]ethane 7 by direct polycondensatios with two different media such as direct polycondensation in a medium consisting of n-methyl-2-
pyrrolidone (NMP)/triphenyl phosphite (TPP)/calcium chloride (CaCl2)/pyridine (Py) and direct polycondensation in a tosyl chloride (TsCl)/pyridine (Py)/n,n-
dimethylformamide (DMF) system. Also 3a-g were synthesized by the condensation reaction of bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride 1
with two equimolars of various amino acids such as l-alanine 2a, l-valine 2b, l-leucine 2c, l-isoleucine 2d, l-phenylalanine 2e, l-2-aminobutyric acid 2f and
l-histidine 2g in an acetic acid solution.
The polymerization reactions produced a series of thermally stable and optically active organosoluble PAIs. The resulting polymers were fully characterized
1
by means of FT-IR and H-NMR spectroscopy, elemental analyses, inherent viscosity, specific rotation, solubility tests and differential scanning calorimeter
(DSC). Also thermal properties of the PAIs 8a-g were investigated using thermal gravimetric analysis (TGA) and derivative of thermaogravimetric (DTG) analysis.
Key word: Thermal properties; Optically active; Organosoluble; Poly(amide-imide)
INTRODUCTION
EXPERIMENTAL
High-performance polymeric materials are currently receiving
considerable attention for their potential applications in advanced technologies
demands. Aromatic polyimides are well known high-performance polymers
that show excellent thermal, mechanical and electrical properties.1, 2 However,
applications may be rather limited due to their high softening or melting
temperatures and their insoluble nature in most organic solvents.3
Modification of high performance materials 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
medication of polymer properties. Thus, for the processing of polyimides
many copolyimides, such as poly(amide-imide)s, poly(ester-imide)s, and other
copolymers have been prepared.4-9 Aromatic polymers that contain aryl ether
linkages and other flexible units such as –NHCO– and –SO2- generally have
lower glasstransition temperatures, greater chain flexibility and tractability in
compare to their corresponding polymers these groups in the chain.10-12 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.13
Nature uses chirality as one of the key structural factors to perform a series
of complicated functionalities, such as molecular recognition and catalytic
activities.14 Synthesis and characterization of optically active polymers have
been a challenging theme in the field of polymer synthesis in recent years
for their important applications of optically active polymers as catalysts for
asymmetric synthesis and as chiral stationary phases (CSP) for the direct
optical resolution of enantiomers.15-17 Optically active polymers can be
obtained by polymerization of optically active monomers or by stereo selective
polymerization of racemic or prochiral monomers using optically active
catalysts.18, 19
In this article, a series of new optically active and thermally stable
organosoluble PAIs 8a-g containing bicycle and ether moiety were synthesized
bythedirectpolycondensationreactionsofsevenchiralN,N΄-(bicyclo[2,2,2]oct-
7-ene-tetracarboxylic)-bis-l-amino acids 3a-g with 1,2-Bis[4-aminophenoxy]
ethane 7 by two different media such as direct polycondensation in a medium
consisting of n-methyl-2-pyrrolidone (NMP)/triphenyl phosphite (TPP)/
calcium chloride (CaCl2)/pyridine (Py) and direct polycondensation in a tosyl
chloride (TsCl)/pyridine (Py)/n,n-dimethylformamide (DMF) system.
Materials
Bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride
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, L-histidine 2g, 1,2-dibromoethane
4, p-nitrophenol 5 and tosyl chloride (TsCl; from Merck) were used without
previous purification. Solvent: N-methyl-2-pyrrolidone (NMP; from Fluka),
pyridine (from Acros), triphenyl phosphite (TPP; from Merck) and N,N-
dimethylformamide (DMF; from Merck) were used as received. Commercially
available calcium chloride (CaCl2; from Merck) was dried under vacuum at
150ºC for 6 hrs.
Techniques
1H-NMR and 13C-NMR spectra were recorded on a Bruker 300 MHz
instrument (Germany). Fourier transform infrared (FT-IR) spectra were
recorded on Galaxy series FT-IR 5000 spectrophotometer (England). Spectra
of solid were performed by using KBr pellets. Vibration transition frequencies
were reported in wave number (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. Specific Rotations were measured by an A-Kruss polarimeter.
Thermal Gravimetric Analysis (TGA and DTG) data for polymers were taken
on a Mettler TA4000 System under N2 atmosphere at rate of 10◦C/min and
differential scanning calorimetry (DSC) was conducted with a DSC Metller
110 (Switzerland) at a heating rate of 10 ºCmin-1 in a nitrogen atmosphere. The
temperature range was from 25 to 350°C. The glass transition temperature (Tg)
of PAI was recorded based on the second scanning. Elemental analyses were
performed by Vario EL equipment in Arak University.
Monomer synthesis
Synthesis of N,N΄-(bicyclo[2,2,2]oct-7-ene-tetracarboxylic)-bis-l-amino
acids 3a-g
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-g, 50 mL of acetic acid and a
stirring bar were placed into a 250-mL round-bottomed flask. The mixture was
stirred at room temperature for 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 solution 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-g.8
1,2-bis[4,4’-aminophenoxy]ethane 7
e-mail: k-faghihi@araku.ac.ir
491

J. Chil. Chem. Soc., 55, Nº 4 (2010)
1,2-bis[4-aminophenoxy]ethane 7 was synthesized according to the
pervious work.20
The chemical structure and purity of the optically active diacids 3a-g
were proved by using elemental analysis, FT-IR, 1H-NMR and 13C-NMR
spectroscopic techniques and these data shown in Table 2.
Polymer synthesis
Poly(amide-imide)s 8a-g were synthesized by two different methods that
as an example the preparation of PAI 8a explains in the following.
Method A: Direct polycondensation in a medium consisting of n-methyl-
2-pyrrolidone (nMP)/triphenyl phosphite (TPP)/calcium chloride (CaCl2)/
pyridine (Py)
1
Table 2 H-NMR, 13C-NMR, FT-IR spectra and elemental analyses data
of diacid derivatives 3a-g.
Diimide-diacid
Spectral data
0.107 g (0.275 mmol) of n,n΄-(bicyclo[2,2,2]oct-7-ene-tetracarboxylic)-
bis-l-alanine 3a, 0.067 g (0.275 mmol) of 1,2-Bis [4-aminophenoxy] ethane
7, 0.1 g (0.9 mmol) of calcium chloride, 0.84 mL, (3.00 mmol) of triphenyl
phosphite, 0.1 mL of pyridine and 1.5 mL n-methyl-2-pyrrolidone (NMP) were
placed into a 25-mL round-bottomed flask, which was fitted with a stirring
bar. The reaction mixture was heated under reflux at 120˚C for 8 hrs. 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 hrs under vacuum to leave 0.151 g (92%) pale yellow
solid polymer 8a.
1H-NMR (DMSO-d6, δ ppm): 12.87-12.93 (s, br, 2H),
5.95-5.98 (t, 2H), 4.50-4.57 (q, 1H, J= 7 Hz), 3.37 (s,
2H), 3.16-3.25 (m, 4H), 1.23-1.25 (d, 6H). 13C-NMR
(DMSO-d6, δ ppm): 176.82, 170.61, 130.64, 47.55,
42.47, 33.89, 14.49. FT-IR (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 C H N O
: C, 55.39; H, 4.65; N, 7.18; found: C, 54.451;8H1,84.2568;
N, 7.11.
3a
Method B: Direct Polycondensation in a Tosyl Chloride (TsCl)/Pyridine
(Py)/ n,n-Dimethylformamide (DMF) system
1H-NMR (DMSO-d , δ ppm): 12.88 (s, br, 2H), 5.99-
6.09 (m, 2H), 4.12-64.15 (d, 2H, J= 9 Hz), 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, J= 6 Hz), 0.66-
0.68 (d, 6H, J= 6 Hz). 13C-NMR (DMSO-d6, δ ppm):
177.23, 169.55, 131.51, 57.70, 42.61, 33.84, 27.96,
21.28, 19.60. FT-IR (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 C22H N2O8: C, 59.19; H, 5.87; N, 6.27; found: C,
58.98; H2,65.87; N, 6.25.
A solution of 0.1 mL pyridine, 0.078 g (0.411 mmol) of TsCl after 30 min
stirring at room temperature was treated with 0.1 mL, (1.36 mmol) of DMF for
additional 30 min. The reaction mixture was added dropwise to a solution 0.053
g (0.137 mmol) of diacid 3a in 0.1 mL of pyridine. The mixture was maintained
at room temperature for 30 min, and then to this mixture, a solution 0.033 g
(0.137 mmol) of 1,2-Bis[4-aminophenoxy]ethane 7 in 0.1 mL of Pyridine was
added dropwise and the whole solution was stirred at room temperature for 30
min and at 110ºC for 2 hrs. As the reaction proceeded, the solution became
viscous, then was precipitated in 30 mL of methanol and filtered off, dried
under vacuum to leave 0.121 g (74%) brown solid polymer 8a.
3b
RESULTS AND DISCUSSION
1H-NMR (DMSO-d6, δ 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-d , δ ppm): 177.09, 170.46, 130.97, 50.73,
42.44, 36.662, 33.80, 24.60, 23.47, 21.14. FT-IR (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 C24H N2O8: C, 60.75; H, 6.37; N, 5.90; found: C,
60.25; H3,06.22; N, 5.88.
Synthesis of monomers
The asymmetric diacids 3a-g were synthesized by the condensation
reaction of bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride 1 with
two equimolars of l-alanine 2a, l-valine 2b, l-leucine 2c, l-isoleucine 2d,
l-phenyl alanine 2e, l-2-aminobutyric acid 2f and l-histidine 2g in an acetic
acid solution (scheme 1). The yields and some physical properties of these
compounds are shown in Table 1.
3c
1H-NMR (DMSO-d6, δ ppm): 12.8 (s, br, 2H), 5.97-
6.03 (m, 2H), 4.18-4.21 (d, 2H, J= 9 Hz), 3.22-3.30
(m, 6H), 2.14-2.15 (d, 2H, J= 3 Hz), 1.30-1.37 (m,
2H), 0.89-0.91 (d, 6H, J= 6 Hz ), 0.71-0.74 (t, 6H).
13C-NMR (DMSO-d , δ ppm): 177.59, 169.66, 131.27,
57.03, 42.40, 33.67,625.24, 16.90, 10.87. FT-IR (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 C24H N2O8: C, 60.75; H, 6.37; N, 5.90; found: C,
60.45; H3,06.21; N, 5.91.
3d
Scheme 1: Preparation of diacids 3a-g
Table 1 Some physical properties of chiral diacid derivatives 3a-g
Amino acid
compound
a
1H NMR (DMSO-d6, δ 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). 13C NMR (DMSO-d6, δ ppm): 176.69,
169.94, 132.02, 129.32, 128.53, 126.98, 53.07, 42.24,
42.11, 33.45, 33.24. FT-IR (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 C30H N2O : C, 66.41; H, 4.83; N,
5.16; found: C, 66.41; H,264.82;8N, 5.10.
25
D
Entry
R
Mp(˚C)
Yield(%)
[ ]
á
3a
3b
3c
L-Alanine
L-Valine
CH3
249-250
318-320
289-290
92
93
94
+155.7
+138.4
+146.8
(CH3)2CH
L-Leucine
(CH3)2CHCH2
3e
3d
3e
L-Isoleucine
(C2H5)(CH3)CH
PhCH2
293-295
247-248
92
91
+156.2
+160.2
L-Phenyl
alanine
L-2-
Aminobutyric
acid
3f
CH3CH2
251-253
310-312
93
85
+130.2
+128.4
3g
L-histidine
CH2-imidazole
a Measured at a concentration of 0.5 g/dL in DMF at 25˚C.
492

J. Chil. Chem. Soc., 55, Nº 4 (2010)
1H NMR (DMSO-d6, δ 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-d , δ ppm): 177.14, 170.19,
131.06, 56.50, 42.41, 33.79,621.23, 11.06. FT-IR (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 C20H N2O : C, 57.41; H, 5.30; N,
6.70; found: C, 57.34; H,225.29;8N, 6.70.
3f
1H-NMR (DMSO-d , δ ppm): 14.48 (s, br, 4H), 9.11 (s,
2H), 7.30 (s, 2H), 56.38-5.80 (s, 2H), 4.98-5.01 (t, 2H),
3.03-3.32 (m, 10H). 13C-NMR (DMSO-d6, δ ppm):
176.53, 168.91, 134.22, 130.21, 128.84, 117.86, 51.49,
42.44, 33.31, 23.56. FT-IR (KBr, cm-1): 2500-3400 (s,
br), 1770 (w), 1707 (s, br), 1626 (m), 1521 (w), 1383
(s), 1228 (s), 1163 (s), 1074 (m), 927 (w), 827 (s), 710
(m), 624 (m). Elemental analysis: calcd. for C24H N O
: C, 55.17; H, 4.24; N, 16.09; found: C, 55.03; H2,24.6238;
N, 16.00.
3g
Fig. 2: 13C-NMR spectrum of diacid 3f
1,2-bis[4-aminophenoxy]ethane 7 was synthesized according this method:
At first 1,2-bis[4,4’-nitrophenoxy] ethane 6 was prepared from the reaction of
two equimolars p-nitrophenol 5 and one equimolar 1,2-dibromo ethane 4. Then
dinitro compound 6 was reduced by using 10% Pd-C, ethanol and hydrazine
monohydrate (Scheme 1).
The FT-IR spectra of all n,n΄-(bicyclo[2,2,2]oct-7-ene-tetracarboxylic)-
bis-l-amino acids 3a-g 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 and 700 cm-1
(imide characteristic ring vibration) confirmed the presence of imide ring and
carboxylic groups in these compounds.
As an example, the 1H-NMR spectrum of diacid 3f is showed in Figure 1.
The protons H(a) relevant to O-H carboxylic groups appeared at 12.95 ppm.
Peak in 4.33-4.38 ppm as a doublet of doublet which were assigned to the H(c)
protons, which is a chiral center, peaks between 0.66-0.71 ppm were assigned
to aliphatic CH3(g), peak in 1.79-1.93 ppm were assigned to H(f). Protons
relevant to olefin bicyclo ring appeared at 6.01-6.10 ppm, H(b). Peaks between
3.20-3.43 ppm were assigned to H(e) (4H) and H(d) (2H), that appeared in D2O
exchange 1H-NMR spectrum. Also the 13C-NMR spectrum of diacid 3f showed
8 signals, including C(b) and C(a) in carboxylic acids and carbonyl imide
rings, and C(c) in carbon atoms olefin in bicyclo (Figure 2). These peaks in
1H-NMR and 13C-NMR spectra along with elemental analyses data confirmed
the proposed structure of compound 3f.
Scheme 2: Synthesis of diamine 7
The chemical structure and purity of dinitro compound 6 were proved with
elemental analysis, 1H-NMR and FT-IR spectroscopy and diamine compound
1
7 were proved with elemental analysis, FT-IR, H-NMR, and 13C-NMR
spectroscopy.
The measured results in elemental analyses of these compounds were
closely corresponded to the calculated ones, demonstrating that the expected
compounds were obtained. The FT-IR spectrum of diamine 7 showed two
peaks at 3406 and 3327 cm-1, which were assigned to the NH2 groups.
6.66-6.69 (d, 4H, J= 9 Hz), 6.48-6.51 (d, 4H, J= 9 Hz), 4.63 (s, 4H), 4.07
(s, 4H) ppm. 13C-NMR (300 MHz, DMSO-d6): δ; 150.0, 143.0, 115.8, 115.3,
67.3 ppm. Elemental
1H-NMR spectrum of diamine 7 showed peaks as a doublet of doublet at
6.66-6.69 ppm and 6.48-6.51 ppm were assigned to the H(a) and H(b) related
to aromatic protons, and a singlet peak at 4.07 ppm which was assigned to the
H(d) protons of the NH2 groups in this compound (Fig. 3).
Fig. 1: 1H-NMR spectrum of diacid 3f
493

J. Chil. Chem. Soc., 55, Nº 4 (2010)
the solution was treated with DMF for 30 min. The reaction mixture was added
to a solution of diacid in Py. After 30 min, a solution of diamine in Py was
added and the whole solution was maintained at room temperature, and then at
refluxing temperature.22
The polymers with high inherent viscosities were obtained at 2 hrs time.
The syntheses and some physical properties of these new PAIs 8a-g are
given in Table 4. The entire polycondensation reaction readily proceeds in a
homogeneous solution, tough and stringy precipitates formed when the viscous
PAIs solution was obtained in moderate yields. Although PAIs 8a-g obtained
in a shorter period in media B, but these polymers obtained with higher inherent
viscosities and good yields in media A.
One of the main methods for synthesis of optically active polymers is
incorporation of chiral segments in the monomer structure. In this work we
used of chiral amino acid moieties for synthesis of chiral diacids 3a-g. Also
Specific Rotations of the resulting polymers were measured at a concentration
of 0.5 g/dL in DMF at 25˚C (Table 3 and 4).
Table 3 Yield and some physical properties PAIs 8a-g by media A.
a
Diacid
Polymer
Yield(%) ηinh(dL/g)a
Colorb
25
D
á
[ ]
3a
3b
3c
3d
3e
3f
8a
8b
8c
8d
8e
8f
92
91
86
91
91
92
83
0.75
0.85
0.78
0.59
0.66
0.69
0.51
+88
+110
+110
+76
W
Y
Fig. 3: 1H-NMR spectrum of diamine 4
W
Y
Polymer synthesis
+96
PY
Y
The direct polycondensation of a dicarboxylic acid and diamine is one
of the well-known methods for PAI synthesis. In this article, we synthesized
PAIs 8a-g containing dibenzalacetone moiety by the direct polycondensation
reactions of seven chiral N,N΄-(bicyclo[2,2,2]oct-7-ene-tetracarboxylic)-bis-l-
amino acids 3a-g with 1,2-bis[4,4’-aminophenoxy]ethane 7 in two different
media such as direct polycondensation in a medium consisting of n-methyl-
2-pyrrolidone (NMP)/triphenyl phosphite (TPP)/calcium chloride (CaCl2)/
pyridine (Py) (method A, Scheme 3) and direct polycondensation in a tosyl
chloride (TsCl)/pyridine (Py)/n,n-dimethylformamide (DMF) system (Media
B, Scheme 3).
+86
3g
8g
+124
PY
a , Measured at a concentration of 0.5g/dL in DMF at 25˚C.
b, PY= Pale Yellow,Y=Yellow, W=White.
Table 4 Yield and some physical properties PAIs 8a-g by media B.
Diacid
Polymer
Yield(%)
ηinh(dL/g)a
Colorb
3a
3b
3c
3d
3e
3f
8a
8b
8c
8d
8e
8f
74
77
83
75
81
68
82
0.50
0.38
0.46
0.28
0.61
0.54
0.30
+102
+92
+68
+56
+110
+58
+62
B
Y
PB
Y
PY
B
3g
8g
PB
a , Measured at a concentration of 0.5g/dL in DMF at 25˚C.
b, B= Brown, PB= Pale Brown, PY= Pale Yellow, Y=Yellow.
Polymer properties
The Spectroscopic results such as CHN, FT-IR and 1H-NMR data
confirmed the structure of these polymers. The elemental analyses of the
resulting PAIs 8a-g were in good agreement with the calculated values for the
proposed structure (Table 5).
Scheme 3: Synthesis of PAIs 8a-g in two different media
In media A for direct polycondensation used TPP/Py/CaCl as activating
agent according to a typical procedure that was shown in Scheme23. A triphenyl
phosphite (TPP)-activated polycondensation (phosphorylation reaction)
technique for the synthesis of polyamides was reported by Yamazaki et al.21
The syntheses and some physical properties of these new PAIs 8a-g are
given in Table 3. The entire polycondensation reaction readily proceeds in a
homogeneous solution, tough and stringy precipitates formed when the viscous
PAIs solution was obtained in good yields.
In method B for the direct polycondensation of diacids 3a-g and aromatic
diamine 7, a Vilsmeier adduct was prepared by dissolving TsCl in a mixed
solvent of Py and DMF. The polycondensation was carried out as the following
way: TsCl was dissolved in Py and after a certain period of time (aging time);
494

J. Chil. Chem. Soc., 55, Nº 4 (2010)
Table 5 Elemental analysis results of PAIs 8a-g.
Table 6 FT-IR characterization of PAIs 8a-g.
Polymer
Spectral data (n, cm-1)
Polymer
Formula
C32H30N4O8
(598.21)n
C%
H%
5.05
4.98
5.85
5.79
6.20
6.21
6.20
6.18
5.10
5.06
5.47
5.39
4.69
4.62
N%
9.36
9.18
8.56
8.22
8.21
8.04
8.21
7.98
7.46
7.27
8.94
8.80
15.33
14.98
3269 (w), 2915 (w), 1774 (w), 1709 (s), 1605 (m),
1518 (m), 1380 (m), 1219 (m), 1158 (m), 1065 (w),
969 (w), 830 (w), 725 (w).
8a
Calcd.
Found
Calcd.
Found
Calcd.
Found
Calcd.
Found
Calcd.
Found
Calcd.
Found
Calcd.
Found
64.21
63.64
66.04
63.54
66.85
66.11
66.85
66.08
70.39
70.02
65.17
64.89
62.46
61.98
8a
8b
8c
8d
8e
8f
C36H38N4O8
(654.71)n
3246 (m), 2926 (m), 1776 (w), 1710 (s, br), 1605 (s),
1516 (s), 1383 (s), 1235 (s), 1178 (m), 1087 (w), 981
(m), 830 (m), 725 (w), 704 (w).
8b
8c
8d
8e
8f
C38H42N4O8
(682.76)n
3245 (w), 2915 (w), 1776 (w), 1712 (s), 1602 (m),
1518 (m), 1383 (m), 1219 (m), 1177 (m), 1065 (w),
929 (w), 832 (w), 725 (w).
C38H42N4O8
(682.76)n
3252 (w,), 2918 (w), 1774 (w), 1709 (s), 1605 (m),
1516 (m), 1382 (m), 1248 (m), 1115 (m), 1080 (s),
983 (w), 837 (w), 725 (w).
C44H38N4O8
(750.79)n
3244 (w), 2928 (m), 1776 (w), 1712 (s), 1605 (m),
1516 (m), 1386 (m), 1250 (m), 1111 (m), 1082 (m),
983 (w), 837 (w), 729 (w).
C34H34N4O8
(626.66)n
3238 (w), 3055 (w), 2928 (w), 1772 (w), 1709 (s),
1604 (w), 1510 (s), 1386 (m), 1305 (w), 1228 (s, br),
1120 (w), 1066 (w), 831 (w), 723 (w).
8g
C38H34N8O8
(730.25)n
3243 (w, br), 2918 (m, br), 1774 (w), 1710 (s, br),
1610 (m), 1510 (m), 1383 (m), 1251 (m), 1112 (m),
1082 (s), 983 (w), 837 (w), 725 (w).
The representative FT-IR spectrum of PAI 8f was shown in Figure 4.
The polymer exhibited characteristic absorption bands at 1772 cm-1 for the
imide ring (asymmetric C=O stretching vibration), 1709 cm-1 (symmetric C=O
stretching and amide stretching vibration) in the main chain, 1386 cm-1 (C-N
stretching vibration). The absorption bands of amide groups appeared at 3335
cm-1 (N-H stretching). FT-IR characterizations of all PAIs are given in Table 6.
8g
Figure 5 displays 1H-NMR spectrum of PAI 8a that the aromatic protons
related to diamine appeared in the region of 6.70-6.78 and 7.24-7.40 ppm and
the peak in the region of 9.52 ppm is assigned for N-H of amide groups in the
main chain of polymer. Decaying peak related to carboxylic acid protons and
appearing peaks related to amide groups and aromatic protons of diamine in the
polymer chain, confirmed the proposed structure of PAI 8a.
Fig. 4: FT-IR spectrum of PAI 8f
Fig. 5: 1H-NMR spectrum of PAI 8a
Solubility of the PAIs
Oneofthemainobjectivesofthisstudywasproducingmodifiedpoly(amide-
imide)s with improved solubility. By the incorporation of monomers with ether
and bicyclo moiety these polymers are expected to have higher solubility.
The solubility of PAIs 8a-g was investigated as 0.01 g of polymeric sample
in 2 mL of solvent. Remarkably, all of these PAIs were easily soluble at
room temperature in aprotic polar solvents such as n-methyl-2-pyrrolidinone
(NMP), n,n-dimethylacetamide (DMAc), n,n-dimethylformamide (DMF)
and insoluble in solvents such as acetone, chloroform, ethanol and methanol.
495

J. Chil. Chem. Soc., 55, Nº 4 (2010)
Thermal properties
REFERENCES
TGA and derivative of thermaogravimetric (DTGA) analysis at a rate
of 10ºCmin-1 in a nitrogen atmosphere were utilized to examine the thermal
decomposition of these PAIs, and the obtained results are summarized in Table
7. Figure 6 show TGA results of all the PAIs.
The thermal stability of the polymers was studied on the basis of 5 and
10% weight losses (T5 and T10, respectively) of the polymers and the residue at
600ºC (char yield). The results revealed that the PAIs were thermally stable up
to 320ºC. TGA data showed that the resulting polymers were good thermally
stable. Also the DSC analyses for the polymers showed Tg between 175 and
215 ºC respectability (Table 7). Thermal stability and Tg value of the polymers
8e and 8g with aromatic rings were higher than the other polymers, because
these polymers has a rigid aromatic structure in the side chain.
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Marcel Dekker: New York (1996).
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(2001).
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(2009).
Table 7 Thermal behavior of all the PAIs.
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Chem., 13, 1373, (1975).
Polymer
8a
Tga
T5(˚C)b
T10(˚C)b
370
Char yield c
44.5
200
185
175
185
210
195
215
330
8b
320
340
43.62
8c
275
360
42.52
8d
220
310
43.21
8e
330
380
51.83
8f
270
375
38.25
8g
260
370
47.91
a Glass transition temperature was recorded at a heating rate of 10ºCmin-1
in a nitrogen atmosphere.
b
Temperature at which 5% or 10% weight loss was recorded in TGA
analysis at a heating rate of 10 ˚C/min under N2.
c
Weight percentage of material left after TGA analysis at a maximum
temperature of 600 ˚C under N2.
22. Mallakpour, S., Kolahdoozan, M. J. appl. Polym. sci., 104, 1248, (2007).
Fig. 6: TGA curves of all the PAIs
CONCLUSIONS
A series of new thermally stable and optically active organosoluble PAIs
8a-g containing containing bicyclo and ether groups moiety were synthesized
by the direct polycondensation reactions of seven chiral diacids 3a-g with
diamine 7 by two different methods. By introducing ether and bicyclo moiety
into the polymer backbone the rigid conformation of the chains is modified
increasing the solubility in polar aprotic solvents. Because the resulting
polymers contained optically pure l-amino acid moieties, they showed
optical rotations and were optically active. The presented results 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 remarkably enhanced the thermal stability of the new polymers.
Potential applications of amino acid based polymers include chiral stationary
phases for the resolution of enantiomers in chromatographic techniques, and
biomaterials.
496