Application of sulfonamide derivative of calixarene for improvement of mechanical properties and thermal stability of polyurethane composite

Article abstract of DOI:10.1007/s10847-015-0539-2

A calixarene derivative, 5,11,17,23-tetrakis (hydroxyl ethyl sulfonamide) calix[4]arene, was synthesized through a linear reaction from parent calix[4]arene. This sulfonamide calixarene derivative was used as a precursor to produce calixarene-polyurethane composite. Structural properties of calixarene-based synthesized precursors were studied using spectroscopic techniques such as ¹H-NMR, ¹³C-NMR, and IR. Also, mechanical properties of produced polyurethane composite such as fracture elongation, modulus, and tensile strength were studied which indicated that these properties were deeply dependent upon calixarene ratio in composite. An increase in calixarene ratio resulted in a decrease the fracture elongation. In contrast, an increase in calixarene ratio caused a considerable decrease of modulus and tensile strength. The modulus and tensile strength were increased by 16.98 and 20 % as the calixarene/polyol ratio reached 3 %. Finally, TGA and DSC studies showed that calixarene ratio considerably enhanced the thermal stability of polyurethane.

Full text of DOI:10.1007/s10847-015-0539-2

J Incl Phenom Macrocycl Chem
DOI 10.1007/s10847-015-0539-2
ORIGINAL ARTICLE
Application of sulfonamide derivative of calixarene
for improvement of mechanical properties and thermal
stability of polyurethane composite
Saeed Taghvaei-Ganjali1 Mona Rasouli-Saniabadi1 Maryam Sadat Mirmoeini1
•
•
Received: 21 December 2014 / Accepted: 8 June 2015
Ó Springer Science+Business Media Dordrecht 2015
Abstract A calixarene derivative, 5,11,17,23-tetrakis
(hydroxyl ethyl sulfonamide) calix[4]arene, was synthe-
sized through a linear reaction from parent calix[4]arene.
This sulfonamide calixarene derivative was used as a pre-
cursor to produce calixarene-polyurethane composite.
Structural properties of calixarene-based synthesized pre-
cursors were studied using spectroscopic techniques such
Introduction
Calixarenes are cyclic oligomers made up of phenol units.
It has been established that the phenolic hydroxy groups
appended on the lower rim form strong intermolecular
hydrogen bonds, serving as the main driving force for the
stabilization of the ‘cone’ conformation [1–4]. They are a
class of host compounds that combine a polar and an apolar
molecular region, both capable of interacting with a variety
of guest molecules [4–7]. The synthesis and purification of
functionalized calixarenes have been optimized very suc-
cessfully, which makes them a very promising class of
synthetic host molecules, particularly when selective
chemical transformations convert the parent compound
into highly organized host molecules, e.g., calixcrowns,
calix-spherands etc. Such functionalized calixarenes form
complexes with metal cations, substituted ammonium ions,
and even neutral molecules like acetone, toluene, etc. [4–
7]. Addition of calixarene to some polymers like poly-
urethane can result in many significant structural changes
which consequently reflect the mechanical properties.
The synthesis of calixarene derivatives and using them
as a precursor to react with polyurethane in order to form
calixarene-polyurethane composite and their application in
ionic complexes and biomolecules have been widely
investigated [7–9].
1
as H-NMR, 13C-NMR, and IR. Also, mechanical proper-
ties of produced polyurethane composite such as fracture
elongation, modulus, and tensile strength were studied
which indicated that these properties were deeply depen-
dent upon calixarene ratio in composite. An increase in
calixarene ratio resulted in a decrease the fracture elon-
gation. In contrast, an increase in calixarene ratio caused a
considerable decrease of modulus and tensile strength. The
modulus and tensile strength were increased by 16.98 and
20 % as the calixarene/polyol ratio reached 3 %. Finally,
TGA and DSC studies showed that calixarene ratio con-
siderably enhanced the thermal stability of polyurethane.
Keywords Calixarene derivatives Á Calixarene-
polyurethane composite Á Mechanical properties Á
Tensile strength Á Modulus
The calixarene linked to polymer substrates has
spawned a considerable interest as a promising composite
in calixarene chemistry [10–14]. The calix[4]arene vari-
ability of ion selectivity and ability to substitute with dif-
ferent molecules are due to their special structure including
holes with definite size. Additionally, they are often used as
host molecule to trap ions and molecules [14–21].
& Saeed Taghvaei-Ganjali
taghvaei@hotmail.com; s_taghvaei@iau-tnb.ac.ir
1
In this work, a sulfonamide derivative of calixarene
containing hydroxyl groups on upper rim position was
Department of Chemistry, Islamic Azad University, North
Tehran Branch, Tehran, Iran
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J Incl Phenom Macrocycl Chem
5, 11, 17, 23-Tetra tertio butyl calix[4]arene
synthesized and used as a precursor to produce calixarene-
polyurethane composite.
The structure of 5,11,17,23-tetra tertio butyl calix[4]arene
derivative is shown in Fig. 1. The synthesis procedure was
as follows: Stoichiometric value, 100 g, of granulated p-
tert-butylphenol was pulverized and poured into a 3-necked
round bottom flask equipped with a mechanical agitator,
reflux, and a thermometer. In another pot, 33.3 g of sodium
hydroxide was dissolved into 100 mL formaldehyde
(37 %) and added into mentioned round bottom flask and
was stirred for 40 min in room temperature. The reaction
pot was heated in a paraffin bath up to 130 °C for 2 h until
the solution color changed from light yellow to dark yel-
low. A foamy substance was obtained as the reaction sys-
tem was cooled to room temperature. Then, 1000 mL of
diphenyl ether was added into mentioned flask and the
temperature was increased up to 120 °C. Nitrogen gas was
purged into the flask while one of necks was kept open to
exit vapor for 2–3 h. As the solution color was changed
from yellow to gray and the water evaporation was stop-
ped, the open neck was closed and the flask reactants were
refluxed at 250 °C for 4 h. The contents color was changed
into brown and black. The system reached room tempera-
ture after 4 h and 1.5 L ethyl acetate was added and stirred
for 30 min. After 2 days, white crystals were obtained and
the precipitates were filtered. The produced crystals were
washed with ethyl acetate, glacial acetic acid, distilled
water, and acetone to obtain pure calix[4]arene crystals.
The structure and configuration of composite reflect a
variety of parameters such as thermal stability, phase
behavior, and also mechanical properties including modu-
lus, tensile strength, and fracture elongation. Therefore, the
effect of calixarene and its ratio, especially because of its
crosslinking role, on composite configuration is the main
aim of this study.
Experimental
Materials
All the reagents were of analytical grade and used without
further purification. Para-tert-butyl Phenol was purchased
from the Acros Company. Formaldehyde, sodium hydrox-
ide, chlorosulfonic acid, monoethanol amine, sodium metal,
and benzophenone were purchased from the Merck Com-
pany. Diphenyl-methane di-isocyanate (MDI) (purity:
99.9 %) was purchased from the Huntsman company.
Measurements
1H-NMR 500 MHz and 13C-NMR 125 MHz Bruker AM
model were used for NMR spectroscopic analyses. FT-IR
Bruker tensor27 and Perkinelmer was used for IR spec-
troscopy. Mechanical properties measurements were per-
formed using HP testing machine (Inspekt 100, Hegewald
& Peschke, Germany). All mechanical properties mea-
surements were performed in triplicates and the average
value and their standard deviations were reported. The
RSD % ranges of measurements were reported 7.2–7.32,
4.6–14.01, and 6.94–10.49 for modulus, tensile strength,
and fracture elongation, respectively.
1
Yield 58 %; mp [ 340 °C; HNMR: (500 MHz, CDCl3,
TMS), d (ppm), 1.2 (36H, s, (CH3)3C) 3.5, 4.2 (8H, d,
ArCH2Ar), 7.0 (8H, s, ArH), 10.3 (4H, s, OH);13C-NMR:
(125 MHz, CDCl3), d (ppm), 30.5 (ArCH2Ar), 32.4
(CH3)3C), 34 (CH3)3C), 126.1 (Ar), 128.2 (ArCH2Ar),
144.5 (ArC(CH3)3), 146.8 (ArOH); IR (KBr): 3200 cm-1
.
5, 11, 17, 23-Tetrakis (chlorosulfonyl) calix[4]arene
Differential scanning calorimetry (DSC) and thermogravi-
metric analysis (TGA) measurements were performed using
NETZSCH DSC 200F3 model TGA-DSC simultaneous ther-
mal analyzer, with a nitrogen flow rate of 30 mL min-1 at
heating scan rate of5 °C min-1 to consider the phase behavior
and thermal stability of calixarene-polyurethane composite. In
DSC, 10 mg of sample was placed into aluminum pans (di-
mensions: 8 mm diameter, 0.5 mm thick) and placed into a
differential scanning calorimeter along with an empty refer-
ence pan. Also, the TGA was performed in a similar way with
heating rate of 10 °C min-1 from 200 to 600 °C.
The structure of 5,11,17,23-tetrakis (chlorosulfonyl)
calix[4]arene derivative is shown in Fig. 2. The synthesis
procedure was as follows: All experimental facilities were
dried using Bunsen burner to remove humidity. A nitrogen
flow was passed through the system for 5 min. In a 3-necked
500 mL balloon equipped with a reflux condenser and nitro-
gen purging system, 4 g of crystallite calix[4]arene synthe-
sized in previous step was added to 160 mL of dry
O
OH-
Synthesis of calix[4]arene derivatives
+
H
H
The synthesis procedure of calix[4]arene derivatives and
spectral evidences of produced structures are discussed in
following sections.
HO
OH
OH
OH
OH
Fig. 1 Synthesis of 5, 11, 17, 23-tetra tertio butyl calix[4]arene
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J Incl Phenom Macrocycl Chem
Fig. 2 Synthesis of 5, 11, 17,
23-tetrakis (chlorosulfonyl)
calix[4]arene
SO2Cl
OH
SO2Cl SO2Cl
SO2Cl
HSO3Cl
CH2Cl2
HO
OH
OH
OH
HO
OH
OH
Synthesis of calixarene-polyurethane composite
dichloromethane and then stirred for 20 min to obtain a
homogeneoussuspension. Afterthe systemcooledto-10 °C,
40 mL of chlorosulfonic acid was dropped into solution
through a funnel for 2 h. The system was purged again with
nitrogen before heating and was refluxed for 20 min.
The synthesized calixarene was kept in oven at 80 °C for
an hour in order to evaporate water or any residual sol-
vents. As the dried samples were pulverized using a mortar,
stoichiometric values of calixarene weighed and added to
10 g polyol. The prepared mixture was stirred and agitated
using an agitator and ultrasonic bath to obtain a homoge-
neous mixture. Then, 12 g diisocyanate was added to
above mixture and stirred till the cream time reached. The
same procedure was used to produce composites with
different calixarenes/polyol ratios (0.5, 1, 1.5, 2, 2.5, and 3)
in similar conditions at room temperature. The ratio of
diisocyanate/polyol was 10:12 for all composites. Also,
pure polyurethane foam was produced to compare with
calixarene containing polyurethane composites. The
structure of obtained composite and reaction scheme are
shown in Fig. 4.
Since the precipitation process was exothermic, the
reaction balloon was placed into an ice bucket to keep the
room temperature condition. Then, 700 mL ether was added
to mixture during an hour and slowly stirred to change the
solution color from brown to pale yellow consisting the
suspended white precipitates. After a day, fine precipitates
were separated by sintered glass and dried with diethyl ether.
Yield 93 %; mp [250 °C; 1HNMR; (500 MHz, DMSO-d6,
TMS), d (ppm), 3.94 (8H, s, ArCH2Ar), 7.39 (8H, s, ArH),
8.87 (4H,s, OH); 13C-NMR (125 MHz, DMSO-d6), d (ppm),
30.4 (ArCH2Ar), 126.4 (ArH), 127.3 (ArCH2Ar), 138 (Ar-
SO2), 151.4 (ArOH); IR (KBr): 1163, 1356 cm-1
.
5, 11, 17, 23-Tetrakis (hydroxyl ethyl sulfonamide)
calix[4]arene
Results and discussion
The structure of 5,11,17,23-tetrakis(hydroxyl ethyle sul-
fonamide) calix[4]arene derivative is shown in Fig. 3. The
synthesis procedure was as follows: All reaction steps were
carried out in completely dry medium. Nitrogen gas was
passed through the system for 5 min. In a double necked
balloon (balloon A), 4 g of calixarene was added to 50 mL
of dry THF while a nitrogen flow was passed through one
of the bottle necks. The whole system was kept in ice
medium. In balloon B, 0.29 mL mono ethanol amine was
added to 50 mL dry THF under the nitrogen flow. Both A
and B balloons were kept in ice medium for a better dis-
solution of contents. Then, the content of balloon A was
added gradually into balloon B and was stirred for 30 min.
About 20 mL of HCl 0.1 M was added to system to obtain
a pale yellow precipitation which washed then with
methanol after filtration using a Buchner funnel. Yield
25 %; mp = 251 °C;1H-NMR (500 MHz, DMSO, TMS),
d (ppm), 2.80 (8H, s, ArCH2Ar), 3.06 (8H, t, CH2N), 3.22
(4H, s, R-OH), 3.39 (8H, t, CH2O), 7.04 (4H, s, OH), 7.54
(8H, s, ArH), 8.87 (4H, s, NH); 13C-NMR (125 MHz,
DMS), d (ppm), 37.9 (ArCH2Ar), 46.1 (CH2N), 60.4
(CH2O), 127.4 (ArH), 130.2 (ArH), 158.4 (ArSO2), 159
The spectroscopic studies including 1H-NMR, 13C-NMR, and
IR were performed to confirm the structural details of
5,11,17,23-tetrakis(hydroxyl ethyl sulfonamide) calix[4]arene.
1H-NMR spectrum of 5, 11, 17, 23-tetrakis
(hydroxyl ethyl sulfonamide) calix[4]arene
1H-NMR of mentioned product, in DMSO-d6 solvent, is
shown in Fig. 5. Since the NMR solvent medium is a
polar solvent, the bridge singlet hydrogens can be attrib-
uted to fast conversion of conformations in room tem-
perature which is not detectable by the method. Both
hydrogens were detected in 2.80 ppm. The phenolic aro-
matic proton was appeared in singlet at 7.54 ppm. Also, 4
hydroxyl protons of aromatic rings and NH sulfonamide
protons were appeared in 7.04 and 8.87 ppm, respec-
tively. The NH sulfonamide are unshielded since they are
acidic and delocalized on nitrogen atom. 8 NCH2 and
CH2 protons were appeared in 3.06 and 3.22 ppm,
respectively. Finally, 4 hydroxyl aliphatic protons were
seen at 3.22 ppm.
(ArOH), IR: (KBr): 1144, 1331, 2900–3500 cm-1
.
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J Incl Phenom Macrocycl Chem
Fig. 3 Synthesis of 5, 11, 17,
23-tetrakis (hydroxyl ethyl
sulfonamide) calix[4]arene
OH
OH
OH
OH
SO2Cl
OH
SO2Cl SO2Cl
SO2Cl
NH
SO2
NH
NH
NH
SO2
NH2CH2CH2OH
THF
SO2
SO2
HO
OH
OH
HO
OH
OH
OH
Fig. 4 Synthesis of calixarene-
polyurethane composite
OH
OH
OH
OH
OH
NH
SO2
NH
NH
NH
OCN
NCO
SO2
OH
SO2
SO2
OH
OH
HO
OH
OH
H
N
O
H
N
O
H
N
H
O
MDI
O
MDI
O
O
N
O
O
O
O
O
O
O
O
NH
NH
NH
NH
SO2
SO2
SO2
SO2
HO
OH
OH
OH
13C-NMR spectrum of 5, 11, 17, 23-tetrakis
(hydroxyl ethyl sulfonamide) calix[4]arene
Two strong peaks of sulfonamide were detected in 1144 and
1331 cm-1 which are associated with –SO2–NH–. The
mentioned IR evidences verify the functional groups of this
calixarene derivative and the substitution of chlorine by –NH
(CH2)2OH according to reaction scheme depicted in Fig. 3.
13C-NMR spectrum of this calixarene in the same medium
(DMSO-d6 dc 40.0 ppm) is shown in Fig. 6. The men-
tioned spectrum shows 8 carbon types. The aliphatic bridge
methylenes, O-linked aliphatic carbons, and N-linked ali-
phatic carbons were appeared in 37.93, 60.44, and
46.13 ppm, respectively. Also, 4 aromatic carbons were
detected in lower fields since they are linked to hydrogen.
Mechanical properties of composite
The hard foam of polyurethane is formed of an exothermic
reaction between diisocyanate, polyol, and calixarene
derivatives releasing carbon dioxide. Calixarene was used
as cross linking agent since it has 4 hydroxyl groups in
upper rim position. When calixarene was used as cross
linking agent in polyurethane chains, the resulted com-
posites showed better mechanical properties including
modulus, tensile strength, and fracture elongation.
IR spectrum of 5, 11, 17, 23-tetrakis (hydroxyl ethyl
sulfonamide) calix[4]arene
The IR spectrum is shown in Fig. 7. A wide peak in
2900–3500 cm-1 is attributed to phenol and also NH groups.
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J Incl Phenom Macrocycl Chem
Fig. 5 1H-NMR spectrum of
5, 11, 17, 23-tetrakis (hydroxyl
ethyl sulfonamide)
calix[4]arene
Fig. 6 13C-NMR spectrum
of 5, 11, 17, 23-tetrakis
(hydroxyl ethyl sulfonamide)
calix[4]arene
Tensile strength is defined as the threshold resistance against
stretching or maximum stress that a material can endure while
being stretched or pulled before failing or breaking.
resulted in modulus increase. The calixarenes interact with
polyurethane chains through many active sites. For exam-
ple, sulfonamide derivative of calixarene acts through 4
hydroxyl sites as shown in Fig. 3. According to Fig. 9
diagram, the modulus was increased by 16.98 % as the
calixarene ratio increased from 0 to about 3 % (w/w).
According to obtained data, the modulus of polyurethane
composites is deeply dependent upon the calixarene ratio
which indicated that the calixarene presence results in
higher hardness of the polyurethane foam product.
Since the aromatic parts of calixarene often increase the
tensile strength, it’s expected that calixarene having phe-
nolic and aromatic parts increases the tensile strength
which is in agreement with the findings observed in present
work according to Fig. 8. As can be seen, the tensile
strength of polyurethane composite was increased as the
calixarene ratio increased.
The elasticity or modulus is defined as the stress/strain
ratio. As can be seen, an increase in calixarene ratio
Finally, the fracture elongation or fracture strain was
studied as an index of elastic property of the polymer. In
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J Incl Phenom Macrocycl Chem
Fig. 7 FT-IR spectrum of 5,
11, 17, 23-tetrakis (hydroxyl
ethyl sulfonamide)
calix[4]arene
contrast to two afore-mentioned mechanical parameters,
the fracture elongation was decreased as the calixarene
ratio increased according to Fig. 10.
As can be seen, the fracture strain was not significantly
changed in calixarene ratio lower than 1.5 %(w/w) while it
was noticeably dramatically decreased in higher ratios of
calixarene in such a way that it was decreased by 12.52 %
as the calixarene increased from 1.5 to 3 %(w/w).The
nature of fracture elongation differs from that of two other
mechanical properties since the cross linking of calixarene
and hard parts of diisocianate form a hard lattice and pre-
vent the composite structure to have a considerable elon-
gation. The overall mechanical properties results are
summarized in Table 1.
Fig. 8 Tensile strength of calixarene-polyurethane composite versus
calixarene/polyol ratio
Fig. 9 Modulus of calixarene-polyurethane composite versus the
calixarene/polyol ratio
Fig. 10 Fracture elongation of calixarene-polyurethane composite
versus calixarene/polyol ratio
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J Incl Phenom Macrocycl Chem
Table 1 Average mechanical properties of polyurethane and cal-
ixarene-polyurethane composite containing different ratios of
calixarene
Calixarene/polyol
percentage (w/w%)
Modulus
(MPa)
Tensile
strength
(MPa)
Fracture
elongation
(%)
0
3.71
3.75
4.01
4.34
0.40
0.41
0.44
0.48
17.25
17.12
16.10
15.09
1.5
2
3
Fig. 11 FT-IR spectra of calixarene-polyurethane composite
The calixarene-polyurethane composite is crystalized
when it is stretched meaning that the amorphous parts are
crystalized as a results of stretching due to H and O atoms
in urethane which allows the formation of hydrogen bonds
in polymer chain preventing the motion of polyurethane
chains and remaining in the lattice. The crystallization
resulted from stretching can be observed on the tensome-
tery and the polymer gets white because of stretching.
Stretching and releasing polyurethane may result in reori-
entation of molecules in primary structure. In this work,
calixarenes were used as cross linking agents. Using tet-
raols in polymer structure, the polymer became harder and
its modulus was increased while its fracture elongation
decreased. The hard parts may have the crystalline state
playing the role of physical bonds in polymer. Strength and
resistance against tension are often increased when the hard
parts are longer, symmetric, and proportionate which are
the main cause of attractive intermolecular forces. Since
the aromatic parts increase the tensile strength and decrease
the stress, calixarene presence results in an increase in
modulus.
100.00
90.00
80.00
70.00
60.00
50.00
40.00
30.00
20.00
10.00
0.00
200
250
300
350
400
450
500
550
600
Temperature(°C)
Fig. 12 TGA diagram of calixarene-polyurethane composite at the
temperature range 200–600 °C with heating rate of 10 °C min-1
FT-IR spectra of the synthesized calixarene-polyurethane
composite is shown in Fig. 11. As can be seen, the broad band
observed at 2800–3215 cm-1 is attributed to the presence of a
–NH and –OH stretching vibration. The absorption peak
around 1720 cm-1 corresponds to –NHC=OO in the ester
while the peak around 1525–1595 cm-1 is attributed to –N–H
bending.
20
30
40
50
60
70
T (°C)
Fig. 13 DSC heating thermograms of calixarene-polyurethane com-
posite at the 5 °C min-1 scan rate
Thermal stability of composite
polyol increase the hardness and consequently enhance the
thermal stability because of hardness and cross linking role,
respectively. According to Fig. 12, the system undergoes a
significant degradation of higher rate compared to the
composite degradation as the temperature exceeds 360 °C
which is mainly attributed to the degradation of calixarene
derivative component.
The thermal stability of composite was analyzed using
TGA and DSC techniques according to Figs. 12 and 13.
The polyurethane is usually stable up to 215 °C [22].
However, the produced composite in this work showed
thermal stability up to 300 °C due to the presence of
calix[4]arene. The cross linking role of calixarene enhances
the hardness of composite resulting in a higher thermal
stability. Also, addition of a hard segment like diisocyanate
often increases the hardness of product. Strictly speaking,
both hard segments of diisocyanate and soft segments of
Additionally, the phase behavior of calixarene-poly-
urethane composite was investigated using the DSC tech-
nique. As can be seen in Fig. 13, the DSC thermogram
shows an exothermic peak in temperature range 40–50 °C
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J Incl Phenom Macrocycl Chem
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Conclusion
Calixarene derivatives were used to form a composite with
polyurethane in order to improve the mechanical properties
of obtained products such as modulus, tensile strength, and
fracture elongation. Straightforward procedures were
applied to produce derivatives and the structure of products
were verified using IR, 1HNMR, and 13CNMR spec-
troscopy. The measurements of mechanical properties
showed that the modulus and tensile strength were
increased by 16.98 and 20 %, respectively, as the cal-
ixarene ratio increased from 0 to 3 % (w/w) which was
attributed to the cross linking role of calixarene. Contrarily,
the fracture elongation parameter was decreased by
12.52 % as the calixarene ratio increased from 0 to 3 % (w/
w). Finally, the TGA and DSC studies indicated that the
calixarene considerably enhances the thermal stability of
polyurethane which was attributed to cross linking role of
hydroxyl groups of calixarene and also the hard segments
of diisocyanate.
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