Interfacial synthesis and properties of l-lysine-derived optically active poly(ester-imide)s

Article abstract of DOI:10.1016/j.cclet.2010.11.016

l-Lysine hydrochloride was transformed to ethyl l-lysine dihydrochloride. This salt was reacted with trimellitic anhydride to yield the corresponding diacid (1). Interfacial polycondensation results novel poly(ester-imide)s (PEI_a-i). These polymers have inherent viscosities in the range of 0.23-0.47 dl g^-1, display optical activity, and are readily soluble in polar aprotic solvents. They start to decompose (T_10%) above 350 °C and display glass-transition temperatures at 100.42-172.81 °C. All of the above polymers were fully characterized by UV, FT-IR and ¹H NMR spectroscopy, elemental analysis, TGA, DSC, inherent viscosity measurement and specific rotation.

Full text of DOI:10.1016/j.cclet.2010.11.016

Available online at www.sciencedirect.com
Chinese Chemical Letters 22 (2011) 607–610
www.elsevier.com/locate/cclet
Interfacial synthesis and properties of L-lysine-derived optically
active poly(ester-imide)s
b
b
Saeed Zahmatkesh a, Ali Reza Alborzi b, , Javad Sadeghi , Karim Zare
*
a Department of Science, Payame Noor University (PNU), Tehran, Iran
b Department of Chemistry, Islamic Azad University, Firouzabad, Fars, Iran
Received 30 August 2010
Available online 5 March 2011
Abstract
L-Lysine hydrochloride was transformed to ethyl L-lysine dihydrochloride. This salt was reacted with trimellitic anhydride to
yield the corresponding diacid (1). Interfacial polycondensation results novel poly(ester-imide)s (PEIa–i). These polymers have
inherent viscosities in the range of 0.23–0.47 dl gꢀ1, display optical activity, and are readily soluble in polar aprotic solvents. They
start to decompose (T10%) above 350 8C and display glass-transition temperatures at 100.42–172.81 8C. All of the above polymers
were fully characterized by UV, FT-IR and 1H NMR spectroscopy, elemental analysis, TGA, DSC, inherent viscosity measurement
and specific rotation.
# 2010 Ali Reza Alborzi. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
Keywords: Chiral; Optically active; L-Lysine; Poly(ester-imide); Interfacial polymerization
The interest for developing new biodegradable and/or biocompatible polymers, especially polyesters and
polyamides, has largely encouraged the use of monomers based on naturally occurring products [1,2]. Both
carbohydrate [3] and amino acid [1] 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 [4,5]. 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) [6] as well as asymmetric catalysis applications [7,8]. 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 [9], chiral liquid crystals in
ferroelectrics and nonlinear optical devices [10]. These synthetic polymers based on optically pure amino acids can
induce crystallinity and cause better solubility [11]. These properties have caused them to be good candidate for drug
delivery systems, biomimetic systems, biodegradable macromolecules, biomaterials, and also as chiral purification
media [12]. So, more considerations to improve different synthetic procedures of optically active polymers exist.
Recently, we have synthesized optically active polymers by different methods [12]. In this research, we report the
synthesis and characterization of nine novel poly(ester-imide)s based on L-lysine through interfacial polycondensa-
* Corresponding author.
1001-8417/$ – see front matter # 2010 Ali Reza Alborzi. Published by Elsevier B.V. on behalf of Chinese Chemical Society. All rights reserved.
doi:10.1016/j.cclet.2010.11.016

[()TD$FIG]
608
S. Zahmatkesh et al. / Chinese Chemical Letters 22 (2011) 607–610
1) Stir
2) Reflux
-Cl.+H3N
NH3+.Cl-
OEt
H2N
NH3+.Cl-
OH
+EtOH+SOCl
2
C
O
C
O
O
O
O
HOOC
2
HOOC
COOH
AcOH/Py (3:2)
Reflux
-Cl.+H3N
NH3+.Cl-
O
+
N
N
C OEt
O
C
O
OEt
O
O
O
O
N
O
O
N
1
ClOC
COCl
SOCl2
Reflux
C
O
O
O
2
Scheme 1. Protection of L-lysine acidic group.
tion. The outstanding characteristics of these polymers include thermal stability, good solubility, optical activity, and
potentially being ion exchangeable.
1. Experimental
Synthesis of ethyl L-lysine dihydrochloride [5]: According to the reported article (using EtOH as starting material):
yield: 87%; mp: 136–137 8C; IR (cmꢀ1): 3421, 3350–2514, 2019, 1740, 1603, 1583, 1501, 1217, 851, 740; 1H NMR
(D2O): d 1.07 (t, 3H, 7 Hz), 1.29 (br, 2H), 1.49 (br, 2H), 1.76 (br, 2H), 2.78 (br, 2H), 3.91 (t, 1H, 4.3 Hz), 4.08 (br, 2H);
elemental analysis for C8H18N2O2ꢁ2HCl, Calcd. C (38.87%), H (8.16%), N (11.33%), found: C (38.62%), H (8.31%),
N (11.40%).
Synthesis of ethyl L-lysine-N,N0-ditrimellitoyl diacide (1): Into a 25 mL round-bottomed flask, 2.000 g
(10.42 ꢂ 10ꢀ3 mol) of trimellitic anhydride, 1.282 g (5.21 ꢂ 10ꢀ3 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 r.t. for 2 h and then
refluxed for 6 h. The solvent was extracted under reduced pressure. 5 mL of cold concentrated HCl was added. Awhite
precipitate was formed and filtered off. The white diacid (1) was extracted from this crude product with chloroform.
25
Yield: 2.32 g (79%); mp: 168 8C; ½aꢃD +3.14 (0.050 g in 10 mL DMF); IR (cmꢀ1): 3400–2400, 1702, 1498, 1418,
1296, 1148, 1069, 1018, 916, 803, 750, 748; 1H NMR (500 MHz, CDCl3): d 1.2 (t, 3H, 7.06 Hz), 1.3 (br, 2H), 1.7 (br,
1H,), 1.8 (br, 1H), 2.1 (br, 1H), 2.2 (br, 1H), 3.7 (t, 2H, 4.1 Hz), 4.2 (q, 2H, 3.9 Hz), 4.8 (t, 1H, 4 Hz), 7.9 (s, 1H), 8.0 (s,
1H), 8.1 (s, 1H), 8.2 (s, 1H), 8.4 (s, 1H), 8.5 (s, 1H), 10.2 (s, 2H); 13C NMR (125 MHz, CDCl3): 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): According to the reported article [12]; yield:
25
0.486 g (82%) of white crystals. dp: 175 8C. ½aꢃD +4.08 (0.050 g in 10 mL DMF). IR (KBr, cmꢀ1): 3023, 2784, 1862,
1785, 1720, 1464, 1384, 1226, 1017, 922, 877, 754, 718, 680, 507.
[()TD$FIG]
O
O
O
O
O
O
O
O
O
O
O
O
Ar
*
O
O
*
Cl
n
Cl
N
N
n
N
N
n
+
HOArOH
CO2Et
CO2Et
PEIa-i
HO
OH
O
O
O
O
O
S
O
C
OH
Ar:
N
N
C O-
O
O
O
O
O
a
b
c
d
e
f
h
i
g
Scheme 2. Interfacial polymerization.

Table 1
Characteristic data of the polymers.
1H NMR (500 MHz, DMSO-d6)
hinh (dl gꢀ1 a
)
T10%
(Tg)c
b
25
a
Polymer
UV (lmax, nm)
in DMF
½aꢃD
PEIa
PEIb
PEIc
248.86
258.47
260.87
1.1 (3H, br), 1.2 (2H, br), 1.6 (2H, br), 2.1 (2H, br),
3.5 (2H, br), 4.1 (2H, br), 4.8 (1H, br), 6.0–10.3 (14H, br)
1.1 (3H, br), 1.2 (2H, br), 1.5 (2H, br), 2.1 (2H, br),
3.5 (2H, br), 4.0 (2H, br), 4.8 (1H, br), 7.7–8.5 (10H, br)
1.0 (3H, br), 1.2 (2H, br), 1.6 (2H, br), 2.0 (2H, br),
3.5 (2H, br), 4.0 (2H, br), 4.8 (1H, br), 4.9 (1H, br), 5.9 (1H, br),
6.9–8.4 (16H, br).
0.37
0.28
0.32
+28.908
+15.508
+25.508
368
376
366
158
11.42, 139.98
138.35
PEId
PEIe
262.08
257.27
Low solubility cause unclear spectrum
0.41
0.24
+30.308
+17.108
476
361
172.81
132.3
1.1 (3H, br), 1.5 (2H, br), 1.7 (2H, br), 2.0 (2H, br),
3.5 (2H, br), 4.1 (2H, br), 4.8 (1H, br), 7.0–7.18 (2H, br),
7.55–7.71 (2H, br), 7.8–8.2 (6H, br), 8.4–8.5 (2H, br).
1.0 (3H, br), 1.2 (2H, br), 1.6 (2H, br), 2.1 (2H, br),
3.5 (2H, br), 4.1 (2H, br), 4.8 (1H, br), 7.8–8.4 (10H, br)
1.0 (3H, br), 1.2 (2H, br), 1.5 (2H, br), 2.1 (2H, br),
3.5 (2H, br), 4.1 (2H, br), 4.8 (1H, br), 7.4 (2H, br), 7.8 (2H, br), 7.9 (3H, br),
8.1 (1H, br), 8.2 (1H, br), 8.26 (1H, br), 8.3 (1H, br), 8.37 (1H, br)
1.1 (3H, br), 1.12 (2H, br), 1.2 (1H, br), 1.4–1.6 (2H, br),
2.0 (2H, br), 3.5 (2H, br), 4.1 (1H, br), 4.8 (1H, br), 6.7 (2H, br),
7.0 (2H, br), 7.4–8.5 (14H, br)
PEIf
PEIg
257.27
258.47
0.23
0.30
+15.808
+24.708
371
356
111.32
–
PEIh
PEIi
260.87
260.87
0.47
0.34
+35.208
+27.208
395
409
128.37
112.65
1.1 (3H, br), 1. 2 (2H, br), 1.5 (2H, br), 1.6 (6H, br),
2.1 (2H, br), 3.5 (2H, br), 4.1 (2H, br), 4.8 (1H, br),
6.6 (2H, br), 6.9–7.0 (2H, br), 7.2 (2H, br), 7.3 (2H, br),
8.0 (1H, br), 8.2 (1H, br), 8.3 (1H, br), 8.5 (1H, br), 9.1 (1H, br), 9.2 (1H, br)
a
Measured in DMF (0.5 g dlꢀ1) at 25 8C.
Temperature at which 10% weight loss was recorded by TGA at a heating rate of 10 8C/min under air atmosphere.
Glass transition temperature recorded by DSC at a heating rate of 10 8C/min under air atmosphere.
b
c

610
S. Zahmatkesh et al. / Chinese Chemical Letters 22 (2011) 607–610
Synthesis of N,N0-(pyromellitoyl)-bis-p-aminophenol and synthesis of dihydroxy-[7a,14c] dihydro-naphto[2,1-b]
naphtha[10,20: 4,5] furo[3,2-d] furan: according to the reported article [12].
Poly(ester-imide)s synthesis, general procedure: For the general procedure into a 25 mL round-bottomed flask in an
ice bath, 1 mmol of diacyl chloride, 7 mL of dichloromethane and a stirring bar were placed. A solution of diol
(1 mmol) in water (10 mL), sodium hydroxide (6.3 mL, 0.1 mol/L) and catalytic amount of tetraethylammonium
bromide was prepared. This solution was added dropwise to the flask during 10 min with stirring the mixture
vigorously. After stirring for 3 h, the polymer was filtered of, washed with methanol and vacuum dried.
2. Results and discussion
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 1). The chemical structure of diacid 1 was confirmed by
spectroscopic analysis. All polymers have been obtained in good yields (65–95%) and high viscosity (0.23–0.47) with
optical activity (+15.5 to +35.2) and being thermally stable (T10%: 356–476 8C) (Scheme 2). High speed and high yield
are the advantages of this polymerization method. These polymers are organo soluble in common polar aprotic
1
solvents. The novel polymers were fully characterized by spectroscopic analysis (UV, FT-IR, H NMR), elemental
analysis, thermal analysis (TGA, DSC), viscometric measurements, optical rotation measurements and solubility tests
(Table 1).
Thermal properties of these polymers are investigated by TGA/DTG under air atmosphere at 6 8C/min and by DSC
under nitrogen atmosphere at 10 8C/min. These polymers can be partially hydrolyzed to present the pendent
carboxylic acid groups (ion-exchangeable polymers). Solubility and the flexibility of these polymers are enhanced by
incorporating the soft segment in the polymer backbone.
Acknowledgment
We gratefully acknowledge the funding support received for this project from Firouzabad Islamic Azad University.
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