Properties of copolyamido esters prepared by anionic copolymerization of ω-dodecalactam, ε-caprolactam, and ε-caprolactone

Article abstract of DOI:10.1134/S1070427209040193

The possibility of anionic copolymerization of ω-dodecalactam, ε-caprolactam, and ε-caprolactone in the presence of catalytic amounts of sodium caprolactamate and 2,4-toluene diisocyanate as activator was examined.

Full text of DOI:10.1134/S1070427209040193

ISSN 1070-4272, Russian Journal of Applied Chemistry, 2009, Vol. 82, No. 4, pp. 639−643. © Pleiades Publishing, Ltd., 2009.
Original Russian Text © A.V. Ivanova, R.R. Spiridonova, R.F. Bakhtiyarov, M.Sh. Bikchentaev, S.S. Galibeev, A.M. Kochnev, 2009, published in Zhurnal
Prikladnoi Khimii, 2009, Vol. 82, No. 4, pp. 644−648.
MACROMOLECULAR CHEMISTRY
AND POLYMERIC MATERIALS
Properties of Copolyamido Esters Prepared by Anionic
Copolymerization of ω-Dodecalactam, ε-Caprolactam,
and ε-Caprolactone
A. V. Ivanova, R. R. Spiridonova, R. F. Bakhtiyarov, M. Sh. Bikchentaev,
S. S. Galibeev, and A. M. Kochnev
Kazan State University of Technology, Kazan, Tatarstan, Russia
Received September 1, 2008
Abstract—The possibility of anionic copolymerization of ω-dodecalactam, ε-caprolactam, and ε-caprolactone
in the presence of catalytic amounts of sodium caprolactamate and 2,4-toluene diisocyanate as activator was
examined.
DOI: 10.1134/S1070427209040193
breaking stress, from 150 to 400 kg cm–2 and relative
elongation at break, from 200 to 1100%. Copolymers
of ω-dodecalactam (ω-DLM) and ε-CLN were studied
only in [4], with sodium hydride used for generating
catalytically active lactamate anions and ε-CLN itself
acting as activator. The structures of the copolymers
were examined by IR spectroscopy and X-ray phase
analysis. The dependence of the melting points and heats
of melting of the products on the content of the initial
monomers was revealed. However, the mechanical
properties of the CPAEs obtained were unsatisfactory
because of low molecular weights.
The class of oxygen-containing heterocyclic com-
pounds includes a wide range of substances: lactams,
lactones, oxiranes, carbonates, peroxides, lactides,
trioxanes, dioxolanes, etc. Of most practical interest are
lactams and lactones, because their anionic polymerization
via ring opening allows preparation of macromolecular
compounds exhibiting a set of valuable characteristics and
therefore finding wide practical use. At the same time,
such materials have certain drawbacks. Polylactones have
low flow point, low resistance to polar solvents, and poor
strength; polylactams have low elasticity, low specific
impact resilience, poor heat resistance, and high melting
point limiting their reprocessing by plastic deformation
in a melt.
Previously we prepared copolymers based on ω-DLM
and ε-CLN with good physicomechanical properties
[5]. However, the comonomers used in the process are
relatively expensive and are imported. To make the
products obtained cheaper, with their properties being
preserved, we decided to use as a third comonomer
ε-CLM, which is cheap and is commercially produced
in Russia.
By anionic copolymerization of lactams and lactones
of various structures, it is possible to prepare copolyamido
esters (CPAEs) combining rigid polyamide and flexible
polyester components, which allows control over
physicomechanical properties. Furthermore, both
comonomers have similar structure and are capable of
polymerization under similar conditions.
Thus, the goal of this study was preparation of
terpolymers by anionic copolymerization of ω-DLM,
ε-CLM, and ε-CLN in the presence of catalytic amounts
of sodium caprolactamate and of 2,4-toluene diisocyanate
as activator and elucidation of the effect exerted by the
monomer ratio on the copolymer properties.
CPAEs based on ε-caprolactam (ε-CLM) and
ε-caprolactone (ε-CLN) were prepared and studied in
[1–3]. Their mechanical properties, as well as melting
points, vary depending on copolymer composition:
639

640
IVANOVA et al.
Table 1. Yield of copolyamido esters synthesized at various
ratios of ω-dodecalactam, ε-caprolactam, and ε-caprolactone
the activator (3 mol % 2,4-toluene diisocyanate) were
added with continuous stirring. After the viscosity of
the reaction mixture increased, afterpolymerization was
performed for 120 min to decrease the amount of the
unchanged monomer.
The resulting SPAEs were purified to remove unchang-
ed monomers by extraction with acetone for 8 h.
The IR spectra were recorded on a Perkin–Elmer IR
Fourier Spectrometer (PC-16 model). Thermogravimetric
studies of the samples were performed with a Q-1500
derivatograph (MOM, Hungary) at a heating rate of
3 deg min–1. Thermomechanical curves were taken on
an installation for complex analysis. The spin–lattice
relaxation time T1 and the phase population were
measured on a pulse NMR relaxometer with an
operating frequency of 20 MHz. DSC studies were
performed with a DSC 1 calorimeter (Mettler Toledo)
at a heating rate of 5 deg min–1. To determine the melt
flow index (MFI), we used an IIRT capillary viscometer.
The load weight and capillary diameter were 2.16 kg
and 2.095 mm, respectively. The Shore hardness was
measured with a portable electronic hardness gage with
a TN-200 needle indenter. Samples for determination
of physicomechanical characteristics were cut out from
plates prepared by direct hot pressing at 60 to 230°C.
Samples were tested no earlier than 24 h after the
preparation and were conditioned at the test temperature
for 4 h. In σt determination, the clamps of the tensile-
testing machine were moved at a rate of 100 mm min–1.
The water absorption of the polymers was evaluated in
percents as weight gain after swelling in distilled water
for 24 h.
EXPERIMENTAL
ω-DLM and ε-CLM were recrystallized from absolute
benzene, dried in a vacuum oven at 50°C, and stored in
a desiccator under argon. ε-CLN was purified by vacuum
distillation. Na-CLM was prepared as 25% solution in
ε-caprolactam by reaction of the latter with sodium metal
in the bulk at 110–115°C for 30 min. The product was
stored in a desiccator over CaCl2.
The copolymers were synthesized in an argon flow by
the following procedure: 1 mol % Na-CLM was dissolved
in a mixture of ε-CLM and ω-DLM at 180°C, after which
the calculated amount of the comonomer (ε-CLN) and
We prepared the terpolymers in 72 to 91% yield
(Table 1). The terpolymers were pale yellow solids. The
homo- and copolymers were insoluble in chloroform
and acetone and partially soluble in dimethylformamide
(DMF) and dimethyl sulfoxide (DMSO).
In the IR spectra of the CPAEs obtained, after extrac-
tion with acetone we found characteristic absorption
bands of amides (Amide A 3300, Amide B 3070, Amide
I 1640, Amide II 1540 cm–1). The absorption band at
1700 cm–1 corresponds to C=O stretching vibrations
in tertiary amides, and that at 1730 cm–1, to stretching
vibrations of the carbonyl group in aliphatic esters.
T, °C
Fig. 1. TG curves of copolyamido esters prepared at
various molar ratios ω-dodecalactam : ε-caprolactam :
ε-caprolactone in the initial monomer mixture. ω-DLM:
ε-CLM : ε-CLN: (1) 33 : 33 : 33, (2) 15 : 70 : 15, (3)
70 : 15 : 15, (4) 15 : 15 : 70, (5) 0 : 0 : 100, (6) 100 : 0 :
0, and (7) 0 : 100 : 0.
A TGA study of the CPAEs obtained (Fig. 1) showed
that the weight loss was monotonic. This fact indirectly
suggests that the copolymers rather than mixtures of
homopolymers were obtained. This is also confirmed by
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PROPERTIES OF COPOLYAMIDO ESTERS PREPARED BY ANIONIC COPOLYMERIZATION
641
Table 2. Spin–lattice relaxation time T1 of copolyamido esters
a pulse NMR examination of the CPAEs.All the samples
are characterized by a single spin–lattice relaxation time
T1 (Table 2), and this time increases with an increase in the
content of flexible lactone units in the polymer structure.
Two relaxation times T2a and T2b suggest the presence in
the copolymer of crystalline and amorphous phases.
interval of melting, which is due to their nonuniformity
in molecular weight. This fact is apparently associated
with the use of monomers differing in the reactivity and
occurrence of various competing reactions in the course
of copolymerization.
The softening points determined from the thermo-
mechanical curves varied in the range 80–180°C. The
lowest values were observed with an excess of the
polyester component (Fig. 3).
The DSC curves have a single melting peak. In
the case of CPAEs, this fact confirms the copolymer
formation, in agreement with the previously made
assumptions (Fig. 2). The DSC curves of the copolymers,
compared to those of the homopolymers, have a broader
As the copolymers have different softening points,
MFI was measured at different temperatures also. The
Table 3. Melt flow index of the terpolymers obtained
T, °C
Fig. 2. DSC curves of copolyamido esters prepared at
various molar ratios ω-dodecalactam : ε-caprolactam:
ε-caprolactone in the initial monomer mixture. (T)
Temperature. ω-DLM : ε-CLM : ε-CLN: (1) 100 : 0 : 0,
(2) 0 : 100 : 0, (3) 15 : 70 : 15, (4) 70 : 15 : 15, (5) 33 :
33 : 33, and (6) 0 : 0 : 100.
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642
IVANOVA et al.
the corresponding polyamides and polyesters (Table 4).
The Shore hardness of the copolymers varies from 92 to
98 and depends on the initial composition insignificantly
(Table 4).
Table 4. Density and Shore hardness A of the copolyamido
esters obtained
To optimize the search for synergistic compositions,
we used the simplex-lattice method of the experimental
design and plotted the diagrams of the breaking stress,
relative elongation, and water absorption for the CPAEs
with the fractions of the three comonomers varying from
15 to 70 mol %.
Two areas of optimum properties can be revealed. The
first area is centered at the initial monomer ratio ω-DLM
: ε-CLM : ε-CLN = 52 : 24 : 24 and is characterized by
the breaking stress in the range 40–47 MPa, relative
elongation in the range 540–640%, and water absorption
in the range 0.48–0.82%. With respect to the whole set
of the properties, such copolymers considerably surpass
the corresponding homopolymers. As for particular
characteristics, lactams exhibit the highest breaking
stress and poly-ε-CLN, the best elastic properties. These
results are not surprising, as polyamide blocks have
a more rigid-chain structure. It should be noted that one of
major drawbacks of polyamides is relatively high water
absorption, about 6% for ε-CLM, which negatively affects
the properties of articles thereof.
MFI values for the copolymers (Table 3) are in the range
2–8.5 g/10 min in the temperature interval 100–220°C,
whereas the MFI values of the lactam homopolymers are
in the temperature range from 200 to 230°C. The results
obtained, taking into account the rheological nomogram,
show that all the copolymers can be processed into articles
by pressure casting.
However, from the viewpoint of the cost, of most
interest is the second area with ε-CLM as major
component. In this case, the breaking stress of CPAE
(53 MPa) is similar to that of the strongest homopolymer,
ω-DLM (50 MPa), the relative elongation (830%)
appreciably exceeds that of homo-ε-CLN (625%), and
the water absorption (3.5%) is almost two times lower
than that of ε-CLM (5.7%).
The densities of the copolymers varied from 0.97 to
1.15 g cm–3, which is comparable with the densities of
CONCLUSIONS
(1) By performing anionic copolymerization of
ω-dodecalactam, ε-caprolactam, and ε-caprolactone in the
presence of catalytic amounts of sodium caprolactamate
and of 2,4-toluene diisocyanate as activator, we
prepared copolymeric products and examined them by
thermogravimetric analysis, pulse NMR, and differential
scanning calorimetry.
T, °C
Fig. 3. Thermomechanical curves of copolyamido esters
prepared at various molar ratios ω-dodecalactam :
ε-caprolactam : ε-caprolactone in the initial monomer
mixture. (χ) Deformation and (T) temperature. ω-DLM :
ε-CLM : ε-CLN: (1) 15 : 15 : 70, (2) 33 : 33 : 33, (3) 70 :
15 : 15, and (4) 15 : 70 : 15.
(2) Using the simplex-lattice method of experimental
design, we suggested the optimum compositions of the
copolyamido esters at which good physicomechanical
characteristics are combined with relatively low water
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PROPERTIES OF COPOLYAMIDO ESTERS PREPARED BY ANIONIC COPOLYMERIZATION
643
Chem. Commun., 1985, vol. 50, no. 4, pp. 834–839.
absorption and with lower processing temperatures
compared to lactam homopolymers.
4. JPN Patent 62252425A.
5. Ivanova, A.V., Yakimov, R.V., Galibeev, S.S., and Gafarov,
A.M., in Sbornik trudov regional’noi i 40-i nauchnoi
studencheskoi konferentsii “Nauka. Student. Tvorchestvo”
(Coll. of Works of the Regional and 40th Scientific Students’
Conf. “Science. Student. Creative Power”), Cheboksary,
2006, p. 239.
REFERENCES
1. Czechoslovak Patent 229890.
2. JPN Patent 59124930A.
3. Valter, B., Terekhova, M., Petrov, E., et al., Coll. Czech.
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