Optically active: Microwave-assisted synthesis and characterization of l-lysine-derived poly (amide-imide)s

Article abstract of DOI:10.1007/s00726-010-0767-0

l-lysine hydrochloride was transformed to ethyl l-lysine dihydrochloride. This salt was reacted with trimellitic anhydride to yield the corresponding diacid (1). Microwave-assisted polycondensation results a series of novel Poly (amide-imide)s (PAI _a-i ). These polymers have inherent viscosities in the range of 0.23-0.66 dl g^-1, display optical activity from +8.02 to +15.11 (as there is no obvious regioselectivity between alpha and epsilon amino groups of the chiral diacid during the polymerization step then random orientation of diacid moieties along the polymer backbone can be predicted and the concept of "tacticity" cannot be addressed in this research), and are readily soluble in polar aprotic solvents. They start to decompose (T _10%) above 362°C and display glass-transition temperatures at 119-153°C. All of the above polymers were fully characterized by UV, FT-IR and ¹H NMR spectroscopy, elemental analysis, thermogravimetric analyses, DSC, inherent viscosity measurement and specific rotation.

Full text of DOI:10.1007/s00726-010-0767-0

Amino Acids (2011) 41:485–494
DOI 10.1007/s00726-010-0767-0
ORIGINAL ARTICLE
Optically active: microwave-assisted synthesis
and characterization of L-lysine-derived poly (amide-imide)s
•
Ali Reza Alborzi Saeed Zahmatkesh
•
•
Karim Zare Javad Sadeghi
Received: 15 August 2010 / Accepted: 28 September 2010 / Published online: 14 October 2010
Ó Springer-Verlag 2010
Abstract L-lysine hydrochloride was transformed to ethyl
L-lysine dihydrochloride. This salt was reacted with
trimellitic anhydride to yield the corresponding diacid (1).
Microwave-assisted polycondensation results a series of
novel Poly (amide-imide)s (PAIa–i). These polymers have
inherent viscosities in the range of 0.23–0.66 dl g-1, dis-
play optical activity from ?8.02 to ?15.11 (as there is no
obvious regioselectivity between alpha and epsilon amino
groups of the chiral diacid during the polymerization
step then random orientation of diacid moieties along the
polymer backbone can be predicted and the concept of
‘‘tacticity’’ cannot be addressed in this research), and are
readily soluble in polar aprotic solvents. They start to
decompose (T10%) above 362°C and display glass-transition
temperatures at 119–153°C. All of the above polymers were
Introduction
The interest for developing new biodegradable and/or
biocompatible polymers, especially polyesters and poly-
amides, has largely encouraged the use of monomers based
on naturally occurring products (Gonsalves and Mungara
1996; Steinbuchel 2002). Both carbohydrate- (Thiem and
Bachmann 1994; Varela and Orgueira 1999) and amino
acid- (Gonsalves and Mungara 1996) derived monomers
are being currently used as building blocks to generate
novel polymeric structures with enhanced biodegradability.
L-Lysine in particular has been repeatedly used for
making polyamides with potential as biomaterials
(Gachard et al. 1997; Saotome and Schultz 1967; Crescenzi
et al. 1968; Katsarawa et al. 1985; Espartero et al. 1993).
For instance, L-lysine with good functionalities has been
used to prepare some polytartaramides (Majo et al. 2004).
Optically active polymers are one of the most important
classes of high performance engineering materials which
are suitable candidates for use as the chiral stationary
phases in high performance liquid chromatography (HPLC)
(Nakano 2001; Cirilli et al. 2003; Coa et al. 2007;
Mallakpour and Kowsari 2005; Yuan et al. 2005) as well as
asymmetric catalysis applications (Itsuno 2005; Hu et al.
2001, 2002; HB et al. 2000; Canali et al. 1999). The syn-
thesis and application of these polymers is a considerable
topic, which has been paid more attention recently
(Hajipour et al. 2005). Most of the natural polymers are
optically active and have special chemical activities, such
as catalytic properties that exist in genes, proteins and
enzymes. Some other applications are construction of
chiral media for asymmetric synthesis, chiral stationary
phases for resolution of enantiomers in chromatographic
techniques (Akelah and Sherrington 1981), chiral liquid
crystals in ferroelectrics and nonlinear optical devices
1
fully characterized by UV, FT-IR and H NMR spectros-
copy, elemental analysis, thermogravimetric analyses,
DSC, inherent viscosity measurement and specific rotation.
Keywords Thermal properties ꢀ Optically active ꢀ
L-lysine ꢀ Poly (amide-imide) ꢀ Microwave-assisted
polymerization
A. R. Alborzi ꢀ K. Zare ꢀ J. Sadeghi
Department of Chemistry, Islamic Azad University,
Firouzabad, Fars, Iran
S. Zahmatkesh (&)
Department of Science, Payame Noor University (PNU),
Tehran, Iran
e-mail: zahmatkesh1355@yahoo.com
123

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A. R. Alborzi et al.
Monomer synthesis
(Wulff 1989; Fontanille and Guyot 1987). These synthetic
polymers based on optically pure amino acids can induce
crystallinity with their ability to form higher ordered
structures that exhibit enhanced solubility characteristics
(Birchall et al. 2001). These properties have caused them to
be good candidate for drug delivery systems, biomimetic
systems, biodegradable macromolecules, biomaterials, and
also as chiral purification media (Mallakpour and Yousefian
2008). So, more considerations to improve different
synthetic procedures of optically active polymers exist.
Recently, we have synthesized optically active polymers by
different methods (Hajipour et al. 2009; Zahmatkesh and
Hajipour 2009, 2010).
Synthesis of Ethyl L-lysine dihydrochloride
(Majo et al. 2004)
In a 50 ml round-bottomed flask equipped with a reflux
condenser and a stirring bar, 8 ml of thionyl chloride was
added drop wise to the stirring absolute ethanol (2.5 ml)
at -10°C. L-lysine hydrochloride (7.3 g, 0.04 mol) was
added to the mixture and refluxed for 6 h. The solvent
was evaporated under reduced pressure and the residue
was washed with diethyl ether for three times. Yield:
87%; m.p.: 136–137°C; IR (cm-1): 3,421, 3,350–2,514,
2,019, 1,740, 1,603, 1,583, 1,501, 1,217, 851, 740;
1H-NMR (D2O, ppm): 1.07 (3H), 1.29 (2H), 1.49 (2H),
1.76 (2H), 2.78 (2H), 3.91 (1H), 4.08 (2H); Elemental
analysis for C8H18N2O2ꢀ2HCl, Calculated: C (38.87%), H
(8.16%), N (11.33%), Found: C (38.62%), H (8.31%), N
(11.40%).
In this research, we report the synthesis and character-
ization of nine novel Poly (amide-imide)s based on L-lysine
through microwave-assisted polycondensation. These
polymers showed good optical activity (?8.02 to ?15.11).
The outstanding characteristics of these polymers include
thermal stability, good solubility, optical activity, poten-
tially being ion exchangeable.
Synthesis of ethyl L-lysine-N,N0-ditrimellitoyl diacide (1)
Materials and methods
Into a 25-ml round-bottomed flask, 2,000 g (10.42 9
10-3 mol) of trimellitic anhydride, 1.282 g (5.21 9 10-3
mol) of Ethyl L-lysine dihydrochloride, a mixture of acetic
acid/pyridine (5 ml, 3:2) and a stirring bar were placed.
The mixture was stirred at room temperature for 2 h and
then refluxed for 6 h. The solvent was removed under
reduced pressure. 5 ml of cold concentrated HCl was
added. A white precipitate was formed and filtered off. The
white diacid (1) was extracted from this crude product
with chloroform. Yield: 2.32 g (79%); m.p.: 168°C;
[a]2D5 = ?3.14° (0.050 g in 10 ml DMF); IR (cm-1):
3,400–2,400, 1,702, 1,498, 1,418, 1,296, 1,148, 1,069,
The trimellitic anhydride (Merck) was recrystallized from
acetic anhydride. 1,2-phenylene diamine, 1,3-phenylene
diamine, 1,4-phenylene diamine and 2,6-diamino pyridine
were purified by sublimation under the reduced pressure.
4,40-diamino diphenyl sulfone, 4,40-diamino diphenyl ether
and 4,40-diamino biphenyl were recrystallized from EtOH/
H2O. DMF was purified by distillation under reduced
pressure over barium oxide. The other chemicals (Merck)
1
were used as received. H NMR spectra were recorded on
an 500 MHz and 13C NMR on an 125 MHz (Bruker
Avance) instrument, using DMSO-d6 as solvent and tetra-
methylsilane as shift reference (tube diameter 5 mm). IR
spectra were recorded on a Shimadzu FT-IR-680 instru-
ment using KBr pellets. UV spectra were recorded on a
Perkin-Elmer lambada 5 instrument. Specific rotations
were measured by an A. Kruss. Optronic P3002 RS (Ger-
many) Polarimeter in DMF as solvent. Thermogravimetric
analyses (TGA) were recorded on a Mettler TA4000 with
heating rate of 6°C min-1 under air atmosphere. DSC
analyses were preformed on a Mettler DSC-30 under
nitrogen atmosphere. Inherent viscosities of polymers were
measured by a standard procedure using a Cannon–Fenske
Routine Viscometer (Germany) at 25°C using DMF as
solvent. Melting points were measured in open capillaries
with a IA9000 series digital Melting Point Apparatus.
Elemental analyses were preformed in a Heraeus CHNS-
RAPID instrument.
1
1,018, 916, 803, 750, 748; H-NMR (500 MHz, CDCl3,
ppm): 1.2 (3H), 1.3 (2H), 1.7 (1H), 1.8 (1H), 2.1 (1H), 2.2
(1H), 3.7 (2H), 4.2 (2H), 4.8 (1H), 7.9 (1H), 8.0 (1H), 8.1
(1H), 8.2 (1H), 8.4 (1H), 8.5 (1H); 13C NMR (125 MHz,
CDCl3, ppm): d 14.4, 23.6, 27.7, 28.2, 38.0, 52.4, 62.5,
123.8, 124.1, 124.8, 125.2, 132.2, 132.4, 134.9, 135.1,
136.2, 136.4, 136.5, 136.6, 166.8, 166.9, 167.6, 167.7,
169.3, 170.1, 170.2
Synthesis of ethyl L-lysine-N,N0-ditrimellitoyl
diacylchloride (2)
Into a 25-ml round-bottomed flask were placed 0.558 g
(1.0 9 10-3 mol) of diacid (1), 5 ml (an excess amount) of
thionyl chloride and two drops of DMF. The mixture was
stirred for 20 min and then refluxed for 2 h. Unreacted
123

Microwave-assisted synthesis and characterization of L-lysine-derived poly (amide-imide)s
487
Diamine synthesis (Hajipour et al. 2007)
Synthesis of phenyl-2,6-bis(4-nitrophenyl) pyridine
thionyl chloride was removed under reduced pressure and
the residue was washed with n-hexane, to leave 0.486 g
(82%) of white crystals. d.p.: 175°C. [a]2D5 = ?4.08°
(0.050 g in 10 ml DMF). IR (KBr cm-1): 3,023, 2,784,
1,862, 1,785, 1,720, 1,464, 1,384, 1,226, 1,017, 922, 877,
754, 718, 680, 507.
Yield (%) = 60; m.p. (°C) [250; IR (cm-1): 1,585,
1,543, 1,510, 1,375, 1,345, 1,090, 845, 815, 750, 740;
Scheme 1 Protection of
L-lysine acidic group
1) Stirre
-Cl.+H3N
NH3+.Cl-
OEt
H2N
NH3+.Cl-
+ EtOH +
SOCl
2
2) Reflux
C
O
C
O
OH
O
HOOC
AcOH/Py (3:2)
+
-Cl.+H3N
NH3+.Cl-
O
2
Reflux
C OEt
O
O
O
O
HOOC
COOH
N
N
C OEt
O
O
O
1
Scheme 2 Diacid 1 synthesis
Fig. 1 IR spectrum of diacid 1
123

488
A. R. Alborzi et al.
1H NMR d: (ppm): 7.56–7.62 (m, 8H), 7.77–7.79
(s, 2H), 8.07 (dd, 2H), 8.37–8.44 (m, 3H); MS (m/z):
399, 398, 397 (Mꢀ?, 100%), 351, 306, 305, 304, 302,
152, 151.
Synthesis of phenyl-2,6-bis(4-aminophenyl) pyridine
Yield (%) = 92; m.p. (°C) = 155; IR (cm-1): 3,335,
3,200, 1,620, 1,580, 1,535, 1,505, 1,440, 1,385, 1,280,
Fig. 2 1H NMR spectrum of
diacid 1
123

Microwave-assisted synthesis and characterization of L-lysine-derived poly (amide-imide)s
489
Fig. 3 13C NMR spectrum of
diacid 1
Scheme 3 Chlorination of
diacid 1
O
O
O
O
HOOC
COOH
SOCl2
Reflux
N
N
C
O
O
O
O
O
O
ClOC
COCl
N
N
C
O
O
2
1
1
1,235, 1,175, 825, 750, 680; H NMR d: (ppm): 7.00–8.20
(m, 15H), 3.99 (NH2, s, 4H); MS (m/z): 340, 338, 337
(Mꢀ?, 100%), 336, 322, 245, 169.
1,010, 856, 822, 733, 688, 483; H NMR d: (ppm): 7.3
(2H), 7. 7 (2H), 7.9 (2H), 8.1 (2H), 8.4 (2H).
Synthesis of 4-(p-chlorophenyl)-2,6-bis(4-aminophenyl)
pyridine
Synthesis of 4-(p-chlorophenyl)-2,6-bis(4-nitrophenyl)
pyridine
The same procedure was followed: recrystallized from
EtOH, Bright yellow; Yield (%) = 90; m.p. (°C) = 378;
IR (cm-1): 3,500–3,000, 1,610, 1,603, 1,540, 1,519, 1,369,
1,233, 1,180, 1,091, 1,013, 824, 748, 518; 1H NMR d:
The same procedure was followed: recrystallized from
EtOH, Yellow; Yield (%) = 55; m.p. (°C) [250; IR
(cm-1): 3,424, 1,595, 1,544, 1,515, 1,384, 1,343, 1,090,
123

490
A. R. Alborzi et al.
O
C
was added, and the mixture was ground for 5 min. The
reaction mixture was irradiated in a microwave oven for
10 min (600 W, interval 10 s/min). The resulting homog-
enous glassy compound film was dissolved in DMF and
then isolated by adding methanol/H2O (50:50) and tritu-
rating, followed by filtration. It was washed several times
with methanol and vacuum dried.
NH4OAC
HOAC/T
+
CH3
ArCHO
2
O2N
O2N
N
NO2
N2H4.H2O Pd/C
DMF/EtOH/ reflux
Ar
N
PAIa: Pale yellow; yield (%) = 85; [a]2D5 = ?10.25;
UV (k max) = 268; IR (cm-1): 3,375, 1,716, 1,544, 1,388,
H2N
NH2
1
1,250, 729; H NMR d: (ppm): 1.1 (3H), 1.3 (2H), 1.6
(2H), 2.1 (2H), 3.5 (2H), 4.1 (2H), 4.8 (1H), 6.7–8.5 (10H),
10.6 (2H).
PAIb: Pale green; yield (%) = 90; [a]2D5 = ?10.14; UV
(k max) = 348; IR (cm-1): 3,470, 1,775, 1,716, 1,517,
1,390, 1,318, 1,251, 730; H NMR d: (ppm): 1.1 (3H), 1.3
(2H), 1.6 (2H), 2.1 (2H), 3.5 (2H), 4.1 (2H), 4.8 (1H),
Ar
,
Ar:
Cl
1
Scheme 4 Synthesis of phenyl-2,6-bis(4-aminophenyl) pyridine and
4-(p-chlorophenyl)-2,6-bis(4-aminophenyl) pyridine
7.2–8.3 (10H), 8.5 (2H).
PAIc: dark yellow; yield (%) = 70; [a]2D5 = ?8.81; UV
(k max) = 264; IR (cm-1): 3,465, 2,933, 1,729, 1,717,
(ppm): 3.6 (4H), 6.7 (4H), 7.3 (2H), 7.4 (2H), 7.5 (2H), 8.0
(4H); 13C NMR d: (ppm): 114.6, 115.3, 128.5, 128.8,
129.5, 130, 135, 138, 148.7, 157.6.
1
1,388, 1,281, 1,247, 1,172, 1,107, 726; H NMR d: (ppm):
1.1 (3H), 1.3 (2H), 1.6 (2H), 2.1 (2H), 3.5 (2H), 4.1 (2H),
4.8 (1H), 7.2–8.3 (9H), 8.4 (2H).
PAId: pale green; yield (%) = 85; [a]2D5 = ?11.18; UV
(k max) = 362; IR (cm-1): 3,415, 1,776, 1,717, 1,501,
1,391, 1,249, 1,186, 1,106, 818, 730; H NMR d: (ppm):
1.1 (3H), 1.3 (2H), 1.6 (2H), 2.1 (2H), 3.5 (2H), 4.1 (2H),
Microwave-assisted polymerization
1
General procedure into a porcelain dish, a mixture of
diacyl chloride (1.0 mmol) and DABCO (1.0 mmol) as a
catalyst was placed. After grounding the reagents for
5 min, diamine (1.0 mmol) was added and the mixture was
ground for further 5 min. 0.25 ml of O-cresol as a solvent
4.8 (1H), 7.2–8.6 (14H), 10.6 (2H).
PAIe: Pale yellow; yield (%) = 80; [a]2D5 = ?12.01;
UV (k max) = 264; IR (cm-1): 3,371, 1,716, 1,539, 1,500,
O
O
O
O
Cl
Cl
N
N
O-cresol/DABCO
MW irradiation
n
H2N Ar NH2
+
CO2Et
O
O
O
O
O
O
O
O
Ar
*
N
H
N
H
*
N
N
n
CO2Et
PEEIa-f
O
Ar:
N
a
b
c
d
e
H2 N
NH2
H2 N
NH2
N
N
O
S
O
Cl
i
g
h
f
Scheme 5 Microwave-assisted polymerization
123

Microwave-assisted synthesis and characterization of L-lysine-derived poly (amide-imide)s
491
Results and discussion
Table 1 Optimization of microwave-assisted polycondensation on
PAIa
Power Time (min) Interval (10 s min-1
)
g9inh (dl g-1
)
[a]2D5
?6.4
Ethyl L-lysine dihydrochloride was prepared with the
reaction of a mixture of EtOH and thionyl chloride with
L-lysine hydrochloride. L-lysine hydrochloride was added
to the mixture drop wise at -10°C and then refluxed for
6 h. The dark solid was washed three times with diethyl
ether to leave a bright with solid (87%). FT-IR spectros-
copy shows a strong and broad peak at 3,350–2,514 cm-1
corresponding to the ammonium N–H stretching and a
strong peak at 1,740 cm-1 corresponding to the C=O
stretching of ester moiety. 1H-NMR (D2O, ppm) spec-
troscopy shows the corresponding peaks such as 3.91 (1H)
due to the chiral center and 1.07 (3H) and 2.78 (2H) peaks
due to the ethyl moiety (Scheme 1). The best solvent to
prepare Ethyl L-lysine-N,N0-ditrimellitoyl diacide (1) was
acetic acid/pyridine mixture, since we have the salt form of
chiral diamine as starting material here. The best method
for purification of this synthetic diacid was found to be
extraction with chloroform (Scheme 2). The chemical
structure of diacid 1 was confirmed by spectroscopic
analysis (Figs. 1, 2, 3). FT-IR spectroscopy shows a strong
and broad peak at 3,600–2,700 cm-1 corresponding to the
COOH stretching, a strong peak at 1,740 cm-1 corre-
sponding to the C=O stretching of ester moiety, a strong
peak at 1,702 cm-1 corresponding to the symmetric C=O
stretching of imidic moiety and two peaks at 1,411 and
750 cm-1 due to the cyclic imide groups. 1H-NMR (CDCl3
ppm) spectroscopy shows 14 peaks and the corresponding
peaks such as 4.8 (1H) due to the chiral center and 10.21
(2H) due to the acidic moiety. 13C-NMR (CDCl3 ppm)
spectroscopy shows 26 peaks due to the 26 different
carbons. Corresponding white diacyl chloride (2) was
prepared in refluxing SOCl2 for 2 h (Scheme 3). FT-IR
spectroscopy shows the corresponding carbonyl stretching
of acyl chloride at 1,862 cm-1. Synthesis of phenyl-2,6-
bis(4-aminophenyl) pyridine and 4-(p-chlorophenyl)-2,6-
bis(4-aminophenyl) pyridine is presented in Scheme 4.
Microwave-assisted polymerization was applied to pre-
pare the poly (amide-imide)s (Scheme 5). To optimize the
polymerization conditions, we did six experiments on
PAIa. The optimum condition is as follow: power =
600 W; time = 10 min with interval times of 10 s min-1
of running. It is found that at higher power, the lower
viscosity and lower specific rotation is obtained; which can
be attributed to polymer degradation. At lower power, the
higher specific rotation but lower viscosity is obtained; the
results are shown in Table 1. All polymers have been
obtained in good yields (65–90%) and high viscosity
(0.23–0.66) with optical activity (?8.02 to ?15.11) and
being thermally stable [T(10%) 0.362–425°C] High speed
and high yield are the advantages of this polymerization
method. As there is no obvious regioselectivity between
900
900
600
600
300
300
15
15
10
15
20
20
-
?
?
?
?
?
0.31
0.30
0.36
0.31
0.29
0.21
?6.4
?10.3
?6.3
?7.9
?8.5
Table 2 Solubility of polymers
Solvents PAIa PAIb PAIc PAId PAIe PAIf PAIg PAIh PAIi
NMP
?
?
?
?
?
-
-
-
-
-
?
?
?
?
?
-
-
-
-
-
?
?
?
?
?
-
-
-
-
-
?
?
?
?
?
-
-
-
-
-
?
?
?
?
?
-
-
-
-
-
?
?
?
?
?
-
-
-
-
-
?
?
?
?
?
-
-
-
-
-
?
?
?
?
?
-
-
-
-
-
?
?
?
?
?
-
-
-
-
-
DMSO
DMAc
DMF
H2SO4
CH2Cl2
CHCl3
EtOH
MeOH
H2O
Concentration: 5 mg ml-1, ?, soluble at room temperature; -,
insoluble at room temperature
1
1,388, 1,246, 1,176, 1,105, 833, 730; H NMR d: (ppm):
1.1 (3H), 1.3 (2H), 1.6 (2H), 2.1 (2H), 3.5 (2H), 4.1 (2H),
4.8 (1H), 6.6–8.4 (14H), 10.5 (2H).
PAIf: Gray; yield (%) = 85; [a]2D5 = ?13.46; UV
(k max) = 264; IR (cm-1): 3,370, 1,776, 1,716, 1,593,
1,532, 1,395, 1,320, 1,253, 1,148, 1,107, 835, 730; 1H
NMR d: (ppm): 1.1 (3H), 1.3 (2H), 1.6 (2H), 2.1 (2H), 3.5
(2H), 4.1 (2H), 4.8 (1H), 6.1 (1H), 6.6 (2H), 7.5 (2H), 7.8
(2H), 7.9 (1H), 8.0 (1H), 8.1 (1H), 8.2 (1H), 8.3 (1H), 8.4
(1H),10.8 (1H), 13.8 (1H).
PAIg: Bright yellow; yield (%) = 85; [a]2D5 = ?12.61;
UV (k max) = 263; IR (cm-1): 3,362, 1,775, 1,716, 1,604,
1
1,525, 1,392, 1,250, 1,187, 843, 731; H NMR d: (ppm):
1.1 (3H), 1.3 (2H), 1.6 (2H), 2.1 (2H), 3.5 (2H), 4.1 (2H),
4.8 (1H), 6.6–9.2 (21H), 10.3 (2H).
PAIh: Bright yellow; yield (%) = 90; [a]2D5 = ?15.11;
UV (k max) = 294; IR (cm-1): 3,379, 1,775, 1,717, 1,603,
1,525, 1,387, 1,250, 1,094, 827, 731; H NMR d: (ppm):
1.1 (3H), 1.3 (2H), 1.6 (2H), 2.1 (2H), 3.5 (2H), 4.1 (2H),
1
4.8 (1H), 6.6–9.2 (20H), 10.2 (1H), 10.3 (1H).
PAIi: Pale yellow; yield (%) = 65; [a]2D5 = ?8.02; UV
(k max) = 258; IR (cm-1): 3,471, 1,776, 1,716, 1,388,
1
1,249, 732; H NMR d: (ppm): 1.1 (3H), 1.3 (2H), 1.6
(2H), 2.1 (2H), 3.5 (2H), 4.1 (2H), 4.8 (1H), 7.2-8.6 (10H),
10.3 (1H), 13.2 (1H).
123

492
A. R. Alborzi et al.
Fig. 4 FT-IR spectrum of PAIe
Fig. 5 1H NMR spectrum of
PAIe
alpha and epsilon amino groups of the chiral diacid during
the polymerization step, then random orientation of diacid
moieties along the polymer backbone can be predicted and
the concept of ‘‘tacticity’’ cannot be addressed in this
research. Head-to-tail regiorandomness may likely affect
some physical properties of the polymers such as crystal-
linity. These polymers are organosoluble in common
polar aprotic solvents (Table 2). The novel polymers were
fully characterized by spectroscopic analysis (UV, FT-IR,
1H NMR), elemental analysis, thermal analysis (TGA,
DSC), viscometric measurements, optical rotation
measurements and solubility tests. As an example, the
corresponding spectra of PAIe are represented in Figs. 4, 5,
6, 7, respectively. Thermal properties of these polymers
are investigated by TGA/DTG under air atmosphere
at 6°C min-1 and by DSC under nitrogen atmosphere at
123

Microwave-assisted synthesis and characterization of L-lysine-derived poly (amide-imide)s
493
Table 3 Thermal behavior of polymers
Polymer
Decomposition
temperature
(°C) Ta10%
Glass-transition
temperature
(Tg)b
Char
yield
(%)c
PAIa
PAIb
PAIc
PAId
PAIe
PAIf
PAIg
PAIh
a
370
362
365
363
370
425
400
420
–
3.9
2.6
2.9
3.8
3.2
3.1
4.6
4.4
–
–
–
–
–
142
–
Temperature at which 10% weight loss was recorded by TGA at a
heating rate of 10°C min-1 under air atmosphere
b
Glass-transition temperature
c
Percentage weight of material left after TGA analysis at maximum
temperature 600°C under air atmosphere
1,530 cm-1. All of these PAIs exhibited strong absorption
at around 1,380 and 720 cm-1, which shows the presence
1
of the heterocyclic imide groups. The H NMR spectra of
PAIs shows a peak at 4.8 ppm due to the chiral center. The
polymers show a maximum absorption in UV spectra at
around 264–348 nm. The elemental analysis result for
PAId is also in good agreement with calculated/expected
percentages of carbon, hydrogen and nitrogen contents
in the polymer-repeating unit (calculated for C38H28N4O8:
C (68.20), H (4.20), N (8.30); found: C (67.43), H (4.56),
N (7.65)). These polymers can be partially hydro-
lyzed to present the pendent carboxylic acid groups
Fig. 6 TGA spectrum of PAIe
10°C min-1 (Table 3). In FT-IR spectra of these polymers
some characteristic peaks could be seen, including the N–H
stretching of amide group at around 3,350 cm-1, C=O
asymmetric stretching of imide group, the C=O symmetric
stretching of imide and amide groups at 1,727–1,716 cm-1
C–N stretching at around 1,387 cm-1, C–N stretching at
,
Fig. 7 DSC spectrum of PAIe
123

494
A. R. Alborzi et al.
Hajipour AR, Zahmatkesh S, Zarei A, Khazdooz L, Ruoho AE (2005)
Synthesis and characterization of novel optically active poly(-
amide–imide)s via direct amidation. Euro Polym Jnl 41:2290
Hajipour AR, Zahmatkesh S, Ruoho AE (2007) Synthesis and
characterization of heterocyclic, and optically active poly
(amide-imide)s by phosphorylation polycondensation. Polym
Bull 59:145–159
Hajipour AR, Roosta P, Zahmatkesh S, Ruoho AE (2009) Synthesis
and characterization of novel optically active poly(ester-imide-
imine)s. e-polymers 011
HB Y, Hu QS, Pu L (2000) Synthesis of a rigid and optically active
poly(BINAP) and its application in asymmetric catalysis.
Tetrahedron Lett 41:1681–1685
Hu OS, Sun C, Monaghan CE (2001) Synthesis of optically active
polymers with chiral units attached to rigid backbones and their
application for asymmetric catalysis. Tetrahedron Lett
42:7725–7728
Hu OS, Sun C, Monaghan CE (2002) Optically active dendronized
polymers as a new type of macromolecular chiral catalysts for
asymmetric catalysis. Tetrahedron Lett 43:927–930
Itsuno S (2005) Chiral polymer synthesis by means of repeated
asymmetric reaction. Prog Polym Sci 30:540–558
Katsarawa RD, Kharadze DP, Japaridze NS, Omiadze TN, Avalishi-
vili MN, Zaalishvili MM (1985) Heterochain polymers based on
natural amino acids. Synthesis of polyamides from NaNe-
bis(trimethylsilyl)lysine alkyl esters. Makromol Chem 186:939–
954
(ion-exchangeable polymers). Solubility and the flexibility
of these polymers are enhanced by incorporating the soft
segment in the polymer backbone.
Conclusions
A fast and effective procedure to prepare a serious of
optically active poly (amide-imide)s containing ethyl
L-lysine ester has been introduced. Since there is no obvi-
ous regioselectivity between alpha and epsilon acyl chlo-
ride groups of the lysine ester containing diacid during the
polymerization step then random orientation of lysine
moieties along the polymer backbone can be predicted.
These polymers are very soluble, optically active, poten-
tially ion exchangeable and thermally stable. The resulting
1
polymers are identified by FT-IR, UV, H NMR spectros-
copy and elemental analysis; and characterized by yield of
reaction, inherent viscosity, and specific rotation.
Acknowledgments We gratefully acknowledge the funding support
received for this project from Firouzabad Islamic Azad University.
Majo MA, Alla A, Bou JJ, Herranz C, Munoz-Guerra S (2004)
Synthesis and characterization of polyamides obtained from
tartaric acid and L-lysine. Euro Polym Jnl 40:2699
Mallakpour S, Kowsari E (2005) Synthesis of organosoluble and
optically active poly(ester-imide)s by direct polycondensation
with tosyl chloride in pyridine and dimethylformamide. Polym
Bull 55:51–59
Mallakpour S, Yousefian H (2008) Direct polyamidation in molten
tetrabutylammonium bromide: novel and efficient green media.
Polym Bull 60:191–198
Nakano T (2001) Optically active synthetic polymers as chiral
stationary phases in HPLC. J Chromatogr A 906:205–225
Saotome K, Schultz RC (1967) Optically active polyamides with
regular structural sequences prepared from a-amino acid.
Makromol Chem 109:239–249
Steinbuchel A (ed) (2002) Biopolymers, vol. 3–4, 7–8. Wiley,
Weinheim
Thiem J, Bachmann F (1994) Carbohydrate-derived polyamides.
Trends Polym Sci 2(12):425–432
Varela O, Orgueira HA (1999) Synthesis of chiral polyamides from
carbohydrate-derived monomers. Adv Carbohydr Chem Bio-
chem 55:137–174
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