Fabrication of proton exchange membrane for non-humidified fuel cells based on polyimide Matrimid® and hydrophobic protic ionic liquid
New proton exchange membrane based on polyimide Matrimid® (PI) and hydrophobic protic ionic liquid, 1-methylimidazolium bis(trifluoromethylsulfonyl)imide (MIM-TFSI), has been prepared by casting from methylene chloride/dimethylformamide solution. Infrared analysis revealed physicochemic...
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V.P. Kukhar Institute of Bioorganic Chemistry and Petrochemistry of the National Academy of Sciences of Ukraine
2023
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Catalysis and petrochemistry| _version_ | 1872009064412610560 |
|---|---|
| author | Rogalsky, Sergiy P. Tarasyuk, Oksana P. Cherniavska, Tetiana V. Babkina, Natalia V. Dzhuzha, Oleg V. Shybyryn, Olena V. Makhno, Stanislav M. |
| author_facet | Rogalsky, Sergiy P. Tarasyuk, Oksana P. Cherniavska, Tetiana V. Babkina, Natalia V. Dzhuzha, Oleg V. Shybyryn, Olena V. Makhno, Stanislav M. |
| author_institution_txt_mv | [
{
"author": "Sergiy P. Rogalsky",
"institution": "V.P. Kukhar Institute of Bioorganic Chemistry and Petrochemistry of the NAS of Ukraine, 1, Murmanska Str, Kyiv, Ukraine, 02094"
},
{
"author": "Oksana P. Tarasyuk",
"institution": "V.P. Kukhar Institute of Bioorganic Chemistry and Petrochemistry of the NAS of Ukraine, 1, Murmanska Str, Kyiv, Ukraine, 02094"
},
{
"author": "Tetiana V. Cherniavska",
"institution": "Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine"
},
{
"author": "Natalia V. Babkina",
"institution": "Institute of Macromolecular Chemistry of National Academy of Sciences of Ukraine 48 Kharkivske shose, Kyiv, 02160, Ukraine"
},
{
"author": "Oleg V. Dzhuzha",
"institution": "V.P. Kukhar Institute of Bioorganic Chemistry and Petrochemistry of the NAS of Ukraine, 1, Murmanska Str, Kyiv, Ukraine, 02094"
},
{
"author": "Olena V. Shybyryn",
"institution": "V.P. Kukhar Institute of Bioorganic Chemistry and Petrochemistry of the NAS of Ukraine, 1, Murmanska Str, Kyiv, Ukraine, 02094"
},
{
"author": "Stanislav M. Makhno",
"institution": "Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine"
}
] |
| author_sort | Rogalsky, Sergiy P. |
| baseUrl_str | https://kataliz.org.ua/index.php/journal/oai |
| collection | OJS |
| datestamp_date | 2024-12-24T10:38:54Z |
| description | New proton exchange membrane based on polyimide Matrimid® (PI) and hydrophobic protic ionic liquid, 1-methylimidazolium bis(trifluoromethylsulfonyl)imide (MIM-TFSI), has been prepared by casting from methylene chloride/dimethylformamide solution. Infrared analysis revealed physicochemical interactions between 1-methylimidazolium cations and imide groups of PI. The results of mechanical testing indicate significantly reduced tensile strength of PI/MIM-TFSI composite membrane compared to neat polymer. Moreover, the dynamical mechanical analysis results revealed sharp drop in storage modulus (E´) of the polymer film above 60 °C.
To improve the elastic properties of the membrane, PI was successively cross-linked with polyetheramine Jeffamine® D-2000 (10 mol. %) in methylene chloride/dimethylformamide solution, as well as in solid film at 100 °C. This approach allowed to prepare PI/Jeffamine/MIM-TFSI (70 wt. %) composite film which has an acceptable E' value of 210 MPa at 140 °C. According to thermal gravimetric analysis data, PI/Jeffamine/MIM-TFSI composite has a thermal degradation point (i.e. 5 % weight loss) of 286 °C. The ionic conductivity of PI/Jeffamine/MIM-TFSI composite membrane is around 10–4 S/cm at room temperature and reaches the minimal level of 10–3 S/cm, required for fuel cell applications, above 100 °C. Overall, the results of this study indicate that the cross-linking of polyimide Matrimid with flexible polyetheramine Jeffamine is an efficient approach for preparing dense composite membrane with high content of the protic ionic liquid. Such polymer-electrolyte membrane has the reasonable combination of good stiffness, thermal stability, and ionic conductivity and therefore is a promising candidate for use in fuel cells operating at elevated temperatures in water-free conditions. |
| doi_str_mv | 10.15407/kataliz2023.34.112 |
| first_indexed | 2026-03-12T15:50:23Z |
| format | Article |
| fulltext |
112 Каталіз та нафтохімія, 2023, №34
Catalysis and Petrochemistry, 2023, 34
UDC 544.6.018.462
https://doi.org/10.15407/kataliz2023.34.112
Fabrication of proton exchange membrane for non-humidified fuel cells based on
polyimide Matrimid® and hydrophobic protic ionic liquid
Sergiy P. Rogalsky 1 *, Oksana P. Tarasyuk 1, Tetiana V. Cherniavska 2, Natalia V. Babkina 3,
Oleg V. Dzhuzha 1, Olena V. Shybyryn 1, Stanislav M. Makhno 2
1 V.P. Kukhar Institute of Bioorganic Chemistry and Petrochemistry of National Academy of Sciences of Ukraine
50 Kharkivske shose, Kyiv, 02160, Ukraine, e-mail: sergey.rogalsky@gmail.com
2 Chuiko Institute of Surface Chemistry of National Academy of Sciences of Ukraine
17 General Naumov Str., Kyiv, 03164, Ukraine
3 Institute of Macromolecular Chemistry of National Academy of Sciences of Ukraine
48 Kharkivske shose, Kyiv, 02160, Ukraine
New proton exchange membrane based on polyimide Matrimid® (PI) and hydrophobic protic ionic liquid,
1-methylimidazolium bis(trifluoromethylsulfonyl)imide (MIM-TFSI), has been prepared by casting from
methylene chloride/dimethylformamide solution. Infrared analysis revealed physicochemical interactions between
1-methylimidazolium cations and imide groups of PI. The results of mechanical testing indicate significantly
reduced tensile strength of PI/MIM-TFSI composite membrane compared to neat polymer. Moreover, the
dynamical mechanical analysis results revealed sharp drop in storage modulus (E´) of the polymer film above
60 °C.
To improve the elastic properties of the membrane, PI was successively cross-linked with polyetheramine
Jeffamine® D-2000 (10 mol. %) in methylene chloride/dimethylformamide solution, as well as in solid film at
100 °C. This approach allowed to prepare PI/Jeffamine/MIM-TFSI (70 wt. %) composite film which has an
acceptable E' value of 210 MPa at 140 °C. According to thermal gravimetric analysis data, PI/Jeffamine/MIM-
TFSI composite has a thermal degradation point (i.e. 5 % weight loss) of 286 °C. The ionic conductivity of
PI/Jeffamine/MIM-TFSI composite membrane is around 10–4 S/cm at room temperature and reaches the minimal
level of 10–3 S/cm, required for fuel cell applications, above 100 °C. Overall, the results of this study indicate that
the cross-linking of polyimide Matrimid with flexible polyetheramine Jeffamine is an efficient approach for
preparing dense composite membrane with high content of the protic ionic liquid. Such polymer-electrolyte
membrane has the reasonable combination of good stiffness, thermal stability, and ionic conductivity and
therefore is a promising candidate for use in fuel cells operating at elevated temperatures in water-free conditions.
Keywords: polyimide, protic ionic liquid, proton exchange membrane, cross-linking, ionic conductivity
Introduction
Polyimide Matrimid® (PI) (Fig. 1) has very unusual and desirable properties combining high
thermal stability (above 450 °C), high glass transition temperature (above 330 °C), and good solubility in
common organic solvents which make it suitable as a matrix resin for specific technical applications. Thus,
Matrimid® is originally developed for use in the microelectronics industry, as well as in the gas separation
industry [1]. Recently, PI has become a popular material for the design of polymer-electrolyte membranes
(PEMs) for high temperature fuel cell applications [2-4]. For such purposes, PEM should combine high
stiffness and ionic conductivity of at least 10–3 S/cm in the temperature range 120-200 °C [5].
Protic ionic liquids (PILs), which are low temperature molten salts of Brønsted acids and
Brønsted bases, has proved to be extremely promising proton conducting electrolytes [6, 7]. PILs have
numerous advantages such as high thermal stability, low volatility, non-flammability, electrochemical
stability, and high ionic conductivity in a wide temperature range. However, taking into account the
dielectric nature of PI matrix, composite PI/PIL membranes must contain at least 60-70 wt. % of ionic liquid
in order to reach the level of conductivity required for fuel cells [2-4, 8]. Thus, the microporous support
Каталіз та нафтохімія, 2023, №34 113
Catalysis and Petrochemistry, 2023, 34
based on PI Matrimid® was impregnated with hydrophilic PIL, triethylammonium trifluoromethanesulfonate
(TFSu-TEA), to prepare composite PEM with ionic liquid content up to 76 wt. % [2]. At 130 °C, the
membrane exhibits proton conductivity of 20 mS/cm that is very close to that of the pure PIL. At the same
time, PI/TFSu-TEA membrane retains a relatively high storage modulus (E´ = 202 MPa) up to 160 °C [2]. In
another study, the composite PI/PILs membranes were prepared by immobilization of hydrophobic PILs,
namely 1-alkylimidazolium bis(trifluoromethylsulfonyl)imide salts, in the porous PI [3]. Water immiscible
PILs are considered especially promising due to their potential resistance to leaching during fuel cell
operation. The composite membranes contained 63-72 wt. % of PILs and showed the minimal required level
of ionic conductivity of 10–3 S/cm at 160 °C [3].
Fig. 1. Chemical structure of polyimide Matrimid® 5218
From a practical point of view, the use of dense PI as a matrix for composite PEM seems more
economical and convenient compared to porous polymer. However, the main problem of this approach is
to prepare PEM with high ionic liquid content while keeping satisfactory mechanical properties at
elevated temperatures. Thus, a dense composite membrane based on PI Matrimid® containing 50 wt. %
of the hydrophobic PIL, 2-butylaminoimidazolinium bis(trifluoromethylsulfonyl)imide (BAIM-TFSI),
showed significant decrease of storage modulus from 1780 to 75 MPa upon heating to 120 °C [4]. The
cross-linking of the PI with polyetheramine Jeffamine® D-400 allowed to prepare PI/Jeffamine/BAIM-
TFSI (50 %) membrane with E' value of 300 MPa at 130 °C. The ionic conductivity of this cross-linked
composite membrane reached the level of 10–2 S/cm at 130 °C suggesting therefore its potential use in
medium temperature fuel cells operating in water-free conditions [4]. However, a significant reduction
in E´ value of PI/Jeffamine/BAIM-TFSI composite occurred at higher temperatures.
In this study, new PEM based on polyimide Matrimid® and hydrophobic PIL, namely
1-methylimidazolium bis(trifluoromethylsulfonyl)imide (MIM-TFSI), has been obtained. To improve
the tensile properties of the composite membrane at elevated temperatures, combined chemical
modification of PI was realized both in the solution and in the solid state by using polyetheramine
Jeffamine® D-2000 as the cross-linking agent. The prepared PI/Jeffamine/MIM-TFSI membrane was
characterized in terms of mechanical properties, thermal stability, and proton conductivity in a wide
range of temperatures.
Experimental
Following chemicals were used for the synthesis of ionic liquid and for the elaboration of
PI-based composites: 1-methylimidazole (for synthesis, Sigma-Aldrich), lithium
bis(trifluoromethylsulfonyl)imide (97 %, Acros), N,N-dimethylformamide, hydrochloric acid (37 %),
methylene chloride (Uoslab, Ukraine). Polyimide Matrimid® 5218 powder and polyetheramine
Jeffamine® D-2000 were kindly supplied by Huntsman (Switzerland).
The ionic liquid MIM-TFSI was synthesized according to the following procedure (Scheme 1).
1-methylimidazole (5 g, 0.06 mol) was dissolved in 30 ml of water and the solution was neutralized with
O O
O
O
O
NN
CH3
CH3H3C
114 Каталіз та нафтохімія, 2023, №34
Catalysis and Petrochemistry, 2023, 34
hydrochloric acid (10 ml). To the stirred solution of 1-methylimidazolium chloride was added lithium
bis(trifluoromethylsulfonyl)imide (17.2 g, 0.06 mol) dissolved in 60 ml of water. The formed water
immiscible layer was separated and dried at 120 °C for 24 h. MIM-TFSI was obtained as an amorphous
solid of white color having melting point 49-50 °C.
1H NMR (400 MHz, DMSO-D6): δ = 3.86 (s, 3H, CH3), 7.65 (t, J = 1.7 Hz, 1H, C4-H), 7.67 (t, J = 1.7 Hz,
1H, C5-H), 9.03 (t, J = 1.1 Hz, 1H, C2-H).
19F NMR (188 MHz, DMSO-D6): δ = -75.2 (s, 6F).
N
N
H
CH3
N
N
H
CH3
+
Cl
_ (CF3SO2)2NLi
H2O, - LiCl
+ _
(CF3SO2)2N
(MIM-TFSI)
Scheme 1. Synthesis of protic ionic liquid MIM-TFSI
PI solution in methylene chloride (1 g/20 ml) was prepared. To this solution was added MIM-
TFSI (2.4 g) dissolved in dimethylformamide (5 ml), and the mixture was stirred for 2 h. The solution
was poured onto glass support and the solvent evaporated at room temperature for 24 h until a solid film
was formed. Residual solvents were removed in vacuum 1 mbar at 60 °C for 12 h. Thus, composite
membrane PI/MIM-TFSI containing 70 wt. % of PIL was prepared.
Following method was used to prepare composite membrane based on cross-linked PI. 1 g
(0.0018 mol) of PI was dissolved in 20 mL of methylene chloride followed by the addition of 10 molar
percent of Jeffamine® D-2000 with respect to PI. The solution was stirred for 24 h at room temperature
after that the solution of MIM-TFSI (2.4 g) in dimethylformamide (5 ml) was added, and the mixture
was further stirred for 2 h. The solution was poured onto glass support and the solvent evaporated at
room temperature for 24 h until a solid film was formed. It was then kept for 12 h at 40 °C and 12 h at
100 °C. Residual solvents were removed in vacuum 1 mbar at 60 °C for 12 h. Thus, composite
membrane PI/Jeffamine/MIM-TFSI containing 70 wt. % of PIL was prepared. Control samples of cross-
linked PI were prepared without the addition of ionic liquid.
The vibrational properties of MIM-TFSI and its composites with PI were studied using a Vertex-
70 Bruker (Germany) Fourier Transform Infrared (FT-IR) spectrometer equipped with a DTGS detector.
The spectrum of pure ionic liquid was obtained from a tablet with KBr. PI-based composite films were
placed into contact with the single reflection diamond ATR (Attenuated Total Reflection) crystal and the
spectra were collected at room temperature over the range 400-4000 cm–1 at a resolution of 1 cm–1.
The mechanical testing of the polymer membranes was performed using P-50 universal tensile
testing machine (Milaform, Russia) at a deformation rate of 10 mm/min. Polymer films were cut into
specimens with the size of 50100.2 mm. An average tensile strength value was calculated from the
tensile strength of 3 individual samples. Dynamic mechanical analysis (DMA) investigations were
carried out on a dynamic mechanical analyzer Q 800 (TA Instruments) in the tension mode at a
frequency of 10 Hz and a heating rate of 2.0 °С/min. The samples for DMA study had a size of
1240.2 mm. The storage modulus (E') was recorded as a function of temperature.
Thermal gravimetric analysis was made using a Q-1500D thermal analyzer. About 100 mg of the
sample was heated from 30 °C to 900 °C with a heating rate of 10 °C/min in air.
Каталіз та нафтохімія, 2023, №34 115
Catalysis and Petrochemistry, 2023, 34
The ionic conductivity of ionic liquid and PI/Jeffamine/MIM-TFSI composite membrane was
measured with the help of impedance spectrometer Solartron SI 1260 in the temperature range from 25
to 160 °C.
Results and Discussion
FTIR-ATR spectra of PI Matrimid, MIM-TFSI, and their composite are presented in Fig. 2. For the
ionic liquid, the main cation characteristic bands are the N-H stretching mode at 3288 cm–1, the ring C4,5-H
stretching mode at 3168 cm–1, and the ring C2-H stretching mode at 3116 and 3083 cm–1. The band at
2986 cm–1 is assigned to the symmetric stretching vibrations of CH3 group. The band at 1587 cm–1
corresponds to the stretching mode of CH3N group, and the stretching bands of CH3NCN groups are
observed at 1281 and 1330 cm–1 [9]. The bands at 1447 and 1430 cm–1 are assigned to asymmetric and
symmetric bending vibrations of CH3 groups, respectively. In the region 1170-400 cm–1, the IR spectrum
is dominated by contributions from TFSI anion. The strong bands at 1226, 1240, and 1307 cm–1 are
attributed to CF3 symmetric stretching vibrations, whereas the bands at 1200 and 1178 cm–1 correspond to
CF3 asymmetric stretching mode [9, 10]. Two SO2 asymmetric stretching modes are observed at 1330 and
1355 cm–1, and the band at 1333 cm–1 is assigned to SO2 symmetric stretching mode [10]. Further strong
band is SNS asymmetric stretching, C-C stretching, and NCH3 twisting at 1059 cm–1. The band at 658 cm–
1 corresponds to SNS bending vibrations. In the region between 500 and 750 cm–1 a few strong bending
modes are observed which are assigned to CF3 asymmetric bending at 571 cm–1, SO2 asymmetric bending
at 600 and 616 cm–1, and CF3 symmetric bending at 743 cm–1 [9, 10].
Fig. 2. IR spectra: 1 - MIM-TFSI, 2 - PI Matrimid, 3 - PI/MIM-TFSI (70 %)
The spectrum of PI Matrimid contains characteristic bands at 1779 cm–1 and 1716 cm–1 assigned to
asymmetric and symmetric stretching modes of imide C=O group, respectively, and a small intensity band at
1674 cm–1 is attributed to the stretching vibrations of ketone C=O group [11]. The strong band at 1365 and
1092 cm–1 are attributed to the C-N-C axial and trans stretching modes [12, 13], and the bands at 714 and
1424 cm–1 are assigned to the out of plane bending vibrations of NCO and NCC bonds [11]. The small
intensity bands at 1487, 1511, and 1620 cm–1 are assigned to C–C stretching vibrations of aromatic rings.
The weak bands at 2868, 2927, and 2959 cm–1 are attributed to aliphatic C-H stretching vibrations of the
five-membered cycle of PI. The bands at 859 and 1162 cm–1 corresponds to out of plane and in plane
bending mode of aromatic CCH groups, respectively [11].
2500 3000 3500 4000
3288
T
ra
ns
m
itt
an
ce
, a
.u
.
Wavenumber, cm-1
1
2
3
3280
b)
400 600 800 1000 1200 1400 1600 1800 2000
720
714
1096
1092
1375
1365
1716
1674
T
ra
ns
m
itt
an
ce
, a
.u
.
Wavenumber, cm-1
1
2
3
a)
1714
1670
116 Каталіз та нафтохімія, 2023, №34
Catalysis and Petrochemistry, 2023, 34
For PI/MIM-TFSI composite films, the peak position of the bands corresponding to vibrations of
both imide and ketone C=O groups slightly shifted to lower frequencies, from 1716 to 1714 cm–1 and from
1674 to 1670 cm–1, respectively (Fig. 2 a). The peak of N-H stretching mode of MIM-TFSI has also shifted
from 3288 to 3280 cm–1 (Fig. 2 b). This may indicate the hydrogen bonding between N-H groups of
1-methylimidazolium cation and C=O groups of PI (Scheme 2). Moreover, with the introduction of
MIM-TFSI, the C-N-C vibrational modes of the imide cycle shifted to higher frequencies: from 1365 to
1375 cm–1, from 1092 to 1096 cm–1, and from 714 to 720 cm–1 (Fig. 2 a). According to these results, it can be
suggested that π-π interaction between 1-methylimidazolium cation and imide cycle of PI occurs (Scheme 2).
Such physicochemical interactions probably cause good compatibility of MIM-TFSI with the polymer
matrix.
O
N
N
O
O
CH3 CH3
CH3
O
O
N
N
H
CH3
S
N
S
O
O
F3C
O
O
CF3
N
N
H
CH3
S
N
S
O
O
F3C
O
O
CF3
+ +
__
Scheme 2. Possible physicochemical interactions between PI and MIM-TFSI
The results of mechanical testing of PI-based composite membranes are summarized in Table 1. The
high content of the ionic liquid in PI/MIM-TFSI membrane leads to dramatically reduced tensile strength (by
approximately 86 %) compared with neat polymer. However, cross-linking of PI with 10 mol. % of
polyetheramine Jeffamine® D-2000 significantly improved its mechanical properties. Thus,
PI/Jeffamine/MIM-TFSI composite film has a tensile strength which is almost 58 % of that of a neat PI. At
the same time, low elongation at break indicates a high rigidity of the polymer membrane.
Table 1. Mechanical properties of composite membranes
Sample Tensile strength, MPa Elongation at break, %
PI Matrimid (control) 382 71
PI/MIM-TFSI (70 %) 5.51 152
PI/Jeffamine (10 mol. %) 482 91
PI/Jeffamine/MIM-TFSI (70 %) 222 6.51
DMA study was further performed to assess the mechanical response of PI/MIM-TFSI membranes
to higher temperatures. Polyimide Matrimid has a high storage modulus (E = 1340-1200 MPa) in the
temperature range 20-200 °C (Fig. 3, curve 1), indicating its excellent elastic properties as a polymer
matrix for PEM. PI/MIM-TFSI composite film has a significantly narrowed the temperature range of
mechanical stiffness from 20 to 60 °C (Fig. 3, curve 2, Table 2). The sharp reduction of E value is
probably caused by the plasticizing effect of ionic liquid on PI leading to soft material.
Recent studies have shown that polyimide Matrimid easily reacts with aliphatic diamines to form
cross-linked structures [4, 14] (Scheme 3). As one can see from Fig. 3 and Table 2, cross-linking of PI
with 10 mol. % of polyetheramine Jeffamine® D-2000 significantly improved its viscoelastic properties.
Thus, PI/Jeffamine/MIM-TFSI membrane demonstrated good stiffness similar to common Nafion-based
PEMs [15, 16] up to 140 °C (Fig. 3, curve 3). The obtained results agreed with previously reported ones
Каталіз та нафтохімія, 2023, №34 117
Catalysis and Petrochemistry, 2023, 34
and indicate that the intermolecular cross-linking increases the resistance of PI/PIL composite
membranes to deformation [4].
Table 2. Viscoelastic characteristics of PI/MIM-TFSI membranes
Sample Е
Т = 25 ºС,
МPа
Е
Т = 60 ºС,
МPа
Е
Т = 120 ºС,
МPа
Е
Т = 130 ºС, МPа Е
Т = 140 ºС, МPа
PI 1342 1259 1061 1045 1053
PI/MIM-TFSI (70 %) 828 224 - - -
PI/Jeffamine (10 %)/ MIM-
TFSI (70 %)
1012 805 400 296 210
O
NN
O
O
O
O
CH3
CH3
O
NH2 NH2
n
*
O
n
O
NHN
OO
O O
NH
O
NH
N
OO
O O
NH
CH3
CH3H3C
+
CH3H3C
CH3H3C
Scheme 3. Cross-linking of polyimide Matrimid with polyetheramine Jeffamine
Fig. 3. DMA curves of E´: 1 - polyimide Matrimid, 2 - PI/MIM-TFSI (70 %), 3 - PI/Jeffamine/MIM-TFSI
(70 %)
The results of TGA data for PI, MIM-TFSI, and their composites are summarized in Fig. 4 and
Table 3. Ionic liquid has a thermal degradation point (i.e. 5 % weight loss) of 381 °C with a maximum
rate at 456 °C (Fig. 4, curve 2) that indicates sufficient thermal stability for high temperature fuel cell
applications. Polyimide Matrimid has outstanding thermal properties being stable to at least 456 °C with
a maximum degradation rate at 595 °C (Fig. 4, curve 1). PI/MIM-TFSI composite also showed excellent
thermal stability (Fig. 4, curve 3) with a thermal degradation point at 397 °C. Cross-linking of PI with
Jeffamine significantly reduced the thermal degradation point of the polymer, as well as PI/MIM-TFSI
50 100 150 200 250 300 350 400
1
10
100
1000
Temperature,C
32
1E
',
M
P
a
118 Каталіз та нафтохімія, 2023, №34
Catalysis and Petrochemistry, 2023, 34
composite (Fig. 3, curve 4, Table 3). This is probably due to the opening of PI rings, as well as the
presence of flexible aliphatic chains in the polymer structure (Scheme 3).
Fig. 4. TGA curves: 1 - PI, 2 - MIM-TFSI, 3 - PI/MIM-TFSI (70 %), 4 - PI/Jeffamine/MIM-TFSI (70 %)
Table 3. TGA data for composite PI membrane
Sample Tm=5 %, °C Tm=10 %, °C Tm=20 %, °C Tm=50 %, °C
PI 456 500 551 638
MIM-TFSI 381 400 417 447
PI/MIM-TFSI (70 %) 397 440 471 601
PI/Jeffamine 316 344 373 600
PI/Jeffamine/MIM-TFSI (70%) 286 377 416 464
The ionic conductivity of MIM-TFSI ionic liquid is 1.9·10–3 S/cm at its melting point. This value
increases by almost one order of magnitude above 100 °C (Fig. 5, Table 4). PI/Jeffamine/MIM-TFSI
composite membrane has poor conductivity of 3.3·10–4-8.7·10–4 S/cm in the temperature range from 25
to 80 °C. This is probably caused by low free volume of the system which creates barriers for efficient
proton transfer in the dielectric PI matrix. With a further increase in temperature, the conductivity of the
membrane significantly increases reaching the minimal level of 10–3 S/cm required for PEM above
100 °C (Fig. 5, Table 4). This can be explained by enhanced free ionic mobility of MIM-TFSI in the
polymer membrane [4, 8]. It is worth noting that the similar results were obtained for PEM based on
microporous polyimide Matrimid impregnated with MIM-TFSI [3].
Fig. 5. Ionic conductivity as a function of temperature for MIM-TFSI ionic liquid - 1 and
PI/Jeffamine/MIM-TFSI membrane - 2 at 1 kHz
100 200 300 400 500 600 700 800 900
0
20
40
60
80
100
W
ei
gh
t,
%
Temperature, °C
1
2
3
4
40 80 120 160
-3,6
-3,4
-3,2
-3,0
-2,8
-2,6
-2,4
-2,2
-2,0
-1,8
lo
g
(
, S
/c
m
)
Temperature, C
1
2
Каталіз та нафтохімія, 2023, №34 119
Catalysis and Petrochemistry, 2023, 34
Table 4. Electrical conductivities of PI/Jeffamine/MIM-TFSI composite membranes as a function of
temperature
Sample
, S/cm
25 °C 80 °C 120 °C 140 °C 160 °C
MIM-TFSI 3.5·10–4 6·10–3 1.2·10–2 1.4·10–2 1.6·10–2
PI/Jeffamine/ MIM-TFSI (70%) 3.3·10–4 8.7·10–4 1.5·10–3 2.7·10–3 4.4·10–3
Conclusions
In this study, dense polymer-electrolyte membrane (PEM) based on polyimide Matrimid® (PI)
and hydrophobic protic ionic liquid 1-methylimidazolium bis(trifluoromethylsulfonyl)imide (MIM-
TFSI) has been prepared by casting from methylene chloride/dimethylformamide solution. IR analysis
revealed hydrogen bonding between 1-methylimidazolium cations of the ionic liquid and carbonyl
groups of PI, as well as π-π interaction between 1-methylimidazolium cations and imide heterocycles.
Such physicochemical interactions probably cause good compatibility of PI with MIM-TFSI. The results
of mechanical testing indicated significantly reduced tensile strength (by approximately 86 %) of
PI/MIM-TFSI (70 wt. %) composite film compared to neat polymer. Moreover, DMA analysis revealed
a narrow temperature range of mechanical stiffness of this composite from 20 to 60 °C. It can be
explained by the plasticizing effect of ionic liquid on PI at elevated temperatures.
To improve the elastic properties of the PI/MIM-TFSI membrane, PI was cross-linked with
polyetheramine Jeffamine® D-2000 (10 mol. %) in two successive stages: in methylene
chloride/dimethylformamide solution at room temperature, as well as in solid film at 100 °C. The
prepared PI/Jeffamine/MIM-TFSI (70 %) composite membrane demonstrated an acceptable storage
modulus E' (400-210 MPa) in the temperature range 120-140 °C. According to TGA results, cross-
linking of PI significantly reduces the thermal stability of the polymer. However, PI/Jeffamine/MIM-
TFSI composite has a thermal decomposition point of 286 °C which allows its use in high temperature
fuel cells. The results of electrochemical impedance spectroscopy suggested that PI/Jeffamine/MIM-
TFSI membrane has poor ionic conductivity (of the order of 10–4 S/cm) in the temperature range from 25
to 100 °C. Above 100 °C, the conductivity of the membrane reaches the minimal level of 10–3 S/cm
required for fuel cell applications. Thus, the cross-linking of polyimide Matrimid with flexible
polyetheramine Jeffamine allows to prepare a dense composite membrane with high content of the protic
ionic liquid. The new PEM demonstrated acceptable mechanical stiffness up to 140 °C, as well as good
thermal stability and ionic conductivity that indicates its availability for use in fuel cells operating at
elevated temperatures under anhydrous conditions.
Acknowledgement
The authors are grateful to the Huntsman society (Switzerland) for free giving of Matrimid® 5218 powder.
References
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Надійшла до редакції 04.10.2022 р.
Каталіз та нафтохімія, 2023, №34 121
Catalysis and Petrochemistry, 2023, 34
Одержання протонообмінної мембрани для безводних паливних елементів на
основі полііміду Matrimid® та гідрофобної протонної іонної рідини
Сергій П. Рогальський 1 *, Оксана П. Тарасюк 1, Тетяна В. Чернявська 2,
Наталія В. Бабкіна 3, Олег В. Джужа 1, Олена В. Шибирин 1, Станіслав М. Махно 2
1 Інститут біоорганічної хімії та нафтохімії ім. В.П. Кухаря Національної академії наук України
Харківське шосе, 50, Київ, 02160, Україна, sergey.rogalsky@gmail.com
2 Інститут хімії поверхні ім. О.О. Чуйка Національної академії наук України
вул. Генерала Наумова, 17, Київ, 03164, Україна
3 Інститут хімії високомолекулярних сполук Національної академії наук України
Харківське шосе, 48, Київ, 02160, Україна
Одержано нову протонобмінну мембрану на основі полііміду Matrimid® (ПІ) і гідрофобної
протонної іонної рідини біс(трифторметилсульфоніл)іміду 1-метилімідазолію (МІМ-ТФСІ) поливом з
розчину в суміші метиленхлорид/диметилформамід. Аналіз методом інфрачервоної спектроскопії свідчить
про фізико-хімічну взаємодію між катіонами 1-метилімідазолію та імідними групами ПІ. Згідно з
результатами механічних досліджень, композитна плівка ПІ/МІМ-ТФСІ має суттєво знижену міцність на
розрив (на 86 %) у порівнянні з чистим полімером. Крім того, методом динамічного механічного аналізу
встановлено різке зменшення модуля пружності (E´) полімерної мембрани за температури вище 60 °C.
Для покращення віскоеластичних властивостей протонобмінної мембрани проведено хімічне
зшивання ПІ за допомогою поліетераміну Jeffamine® D-2000 в суміші метиленхлорид/диметилформамід, а
також у твердій фазі за температури 100 °C. Застосування такого методу дало можливість отримати
композитну плівку ПІ/Jeffamine/МІМ-ТФСІ із вмістом іонної рідини 70 масових відсотків, яка має
задовільну величину E´ (210 MПа) за температури 140 °C. Згідно з результатами термогравіметричного
аналізу, композит має температуру початку деструкції 286 °C. Іонна провідність композитної мембрани
ПІ/Jeffamine/МІМ-ТФСІ має порядок 10–4 См/см за кімнатної температури і досягає мінімального рівня
10–3 См/см, необхідного для застосування в паливних елементах, за температури вище 100 °C. Таким
чином, результати цієї роботи свідчать, що зшивання полііміду Matrimid гнучким поліетером Jeffamine є
ефективним методом одержання суцільної композитної мембрани з високим вмістом протонної іонної
рідини. Така мембрана має оптимальне поєднання механічної жорсткості, термічної стійкості та іонної
провідності і є перспективною для застосування в паливних елементах, які функціонують за підвищеної
температури і за відсутності зволоження.
Ключові слова: поліімід, протонна іонна рідина, протонобмінна мембрана, зшивання, іонна
провідність
|
| id | oai:katalizorgua:article-98 |
| institution | Catalysis and petrochemistry |
| keywords_txt_mv | keywords |
| language | English |
| last_indexed | 2026-03-12T15:50:23Z |
| publishDate | 2023 |
| publisher | V.P. Kukhar Institute of Bioorganic Chemistry and Petrochemistry of the National Academy of Sciences of Ukraine |
| record_format | ojs |
| resource_txt_mv | katalizorgua/02/798833fe95e637a5044b8f65bee48202.pdf |
| spelling | oai:katalizorgua:article-982024-12-24T10:38:54Z Fabrication of proton exchange membrane for non-humidified fuel cells based on polyimide Matrimid® and hydrophobic protic ionic liquid Fabrication of proton exchange membrane for non-humidified fuel cells based on polyimide Matrimid® and hydrophobic protic ionic liquid Rogalsky, Sergiy P. Tarasyuk, Oksana P. Cherniavska, Tetiana V. Babkina, Natalia V. Dzhuzha, Oleg V. Shybyryn, Olena V. Makhno, Stanislav M. polyimide, protic ionic liquid, proton exchange membrane, cross-linking, ionic conductivity polyimide, protic ionic liquid, proton exchange membrane, cross-linking, ionic conductivity New proton exchange membrane based on polyimide Matrimid® (PI) and hydrophobic protic ionic liquid, 1-methylimidazolium bis(trifluoromethylsulfonyl)imide (MIM-TFSI), has been prepared by casting from methylene chloride/dimethylformamide solution. Infrared analysis revealed physicochemical interactions between 1-methylimidazolium cations and imide groups of PI. The results of mechanical testing indicate significantly reduced tensile strength of PI/MIM-TFSI composite membrane compared to neat polymer. Moreover, the dynamical mechanical analysis results revealed sharp drop in storage modulus (E´) of the polymer film above 60 °C. To improve the elastic properties of the membrane, PI was successively cross-linked with polyetheramine Jeffamine® D-2000 (10 mol. %) in methylene chloride/dimethylformamide solution, as well as in solid film at 100 °C. This approach allowed to prepare PI/Jeffamine/MIM-TFSI (70 wt. %) composite film which has an acceptable E' value of 210 MPa at 140 °C. According to thermal gravimetric analysis data, PI/Jeffamine/MIM-TFSI composite has a thermal degradation point (i.e. 5 % weight loss) of 286 °C. The ionic conductivity of PI/Jeffamine/MIM-TFSI composite membrane is around 10–4 S/cm at room temperature and reaches the minimal level of 10–3 S/cm, required for fuel cell applications, above 100 °C. Overall, the results of this study indicate that the cross-linking of polyimide Matrimid with flexible polyetheramine Jeffamine is an efficient approach for preparing dense composite membrane with high content of the protic ionic liquid. Such polymer-electrolyte membrane has the reasonable combination of good stiffness, thermal stability, and ionic conductivity and therefore is a promising candidate for use in fuel cells operating at elevated temperatures in water-free conditions. Отримано нову протонобмінну мембрану на основі полііміду Matrimid® (ПІ) і гідрофобної протонної іонної рідини біс(трифторметилсульфоніл)іміду 1-метилімідазолію (МІМ-ТФСІ) поливом з розчину в суміші метиленхлорид/диметилформамід. Аналіз методом інфрачервоної спектроскопії свідчить про фізико-хімічну взаємодію між катіонами 1-метилімідазолію та імідними групами ПІ. Згідно з результатами механічних досліджень, композитна плівка ПІ/МІМ-ТФСІ має суттєво знижену міцність на розрив (на 86 %) у порівнянні з чистим полімером. Крім того, методом динамічного механічного аналізу встановлено різке зменшення модуля пружності (E´) полімерної мембрани за температури вище 60 °C. Для покращення віскоеластичних властивостей протонобмінної мембрани проведено хімічне зшивання ПІ за допомогою поліетераміну Jeffamine® D-2000 в суміші метиленхлорид/диметилформамід, а також у твердій фазі за температури 100 °C. Застосування такого методу дало можливість отримати композитну плівку ПІ/Jeffamine/МІМ-ТФСІ із вмістом іонної рідини 70 масових відсотків, яка має задовільну величину E´ (210 MПа) за температури 140 °C. Згідно з результатами термогравіметричного аналізу, композит має температуру початку деструкції 286 °C. Іонна провідність композитної мембрани ПІ/Jeffamine/МІМ-ТФСІ має порядок 10–4 См/см за кімнатної температури і досягає мінімального рівня 10–3 См/см, необхідного для застосування в паливних елементах, за температури вище 100 °C. Таким чином, результати цієї роботи свідчать, що зшивання полііміду Matrimid гнучким поліетером Jeffamine є ефективним методом отримання суцільної композитної мембрани з високим вмістом протонної іонної рідини. Така мембрана має оптимальне поєднання механічної жорсткості, термічної стійкості та іонної провідності і є перспективною для застосування в паливних елементах, які функціонують за підвищеної температури і за відсутності зволоження. V.P. Kukhar Institute of Bioorganic Chemistry and Petrochemistry of the National Academy of Sciences of Ukraine 2023-09-07 Article Article application/pdf https://kataliz.org.ua/index.php/journal/article/view/98 10.15407/kataliz2023.34.112 Catalysis and petrochemistry; No. 34 (2023): Catalysis and petrochemistry; 112-121 Каталіз та нафтохімія; № 34 (2023): Каталіз та нафтохімія; 112-121 2707-5796 2412-4176 10.15407/kataliz2023.34 en https://kataliz.org.ua/index.php/journal/article/view/98/81 Copyright (c) 2023 Catalysis and petrochemistry |
| spellingShingle | polyimide protic ionic liquid proton exchange membrane cross-linking ionic conductivity Rogalsky, Sergiy P. Tarasyuk, Oksana P. Cherniavska, Tetiana V. Babkina, Natalia V. Dzhuzha, Oleg V. Shybyryn, Olena V. Makhno, Stanislav M. Fabrication of proton exchange membrane for non-humidified fuel cells based on polyimide Matrimid® and hydrophobic protic ionic liquid |
| title | Fabrication of proton exchange membrane for non-humidified fuel cells based on polyimide Matrimid® and hydrophobic protic ionic liquid |
| title_alt | Fabrication of proton exchange membrane for non-humidified fuel cells based on polyimide Matrimid® and hydrophobic protic ionic liquid |
| title_full | Fabrication of proton exchange membrane for non-humidified fuel cells based on polyimide Matrimid® and hydrophobic protic ionic liquid |
| title_fullStr | Fabrication of proton exchange membrane for non-humidified fuel cells based on polyimide Matrimid® and hydrophobic protic ionic liquid |
| title_full_unstemmed | Fabrication of proton exchange membrane for non-humidified fuel cells based on polyimide Matrimid® and hydrophobic protic ionic liquid |
| title_short | Fabrication of proton exchange membrane for non-humidified fuel cells based on polyimide Matrimid® and hydrophobic protic ionic liquid |
| title_sort | fabrication of proton exchange membrane for non-humidified fuel cells based on polyimide matrimid® and hydrophobic protic ionic liquid |
| topic | polyimide protic ionic liquid proton exchange membrane cross-linking ionic conductivity |
| topic_facet | polyimide protic ionic liquid proton exchange membrane cross-linking ionic conductivity polyimide protic ionic liquid proton exchange membrane cross-linking ionic conductivity |
| url | https://kataliz.org.ua/index.php/journal/article/view/98 |
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