Synthesis of new monomer 3,3′-diamino-4,4′-bis{p- [(diethoxyphosphoryl)methyl]phenylamino}diphenyl sulfone and polybenzimidazoles on its basis

Full text of DOI:10.1134/S0012500809120040

ISSN 0012ꢀ5008, Doklady Chemistry, 2009, Vol. 429, Part 2, pp. 315–320. © Pleiades Publishing, Ltd., 2009.
Original Russian Text © I.I. Ponomarev, E.I. Goryunov, P.V. Petrovskii, Ivan I. Ponomarev, Yu.A. Volkova, D.Yu. Razorenov, A.R. Khokhlov, 2009, published in Doklady Akademii
Nauk, 2009, Vol. 429, No. 5, pp. 621–626.
CHEMISTRY
Synthesis of New Monomer 3,3'ꢀDiaminoꢀ4,4'ꢀbis{pꢀ
[(diethoxyphosphoryl)methyl]phenylamino}diphenyl Sulfone
and Polybenzimidazoles on Its Basis
I. I. Ponomarev, E. I. Goryunov, P. V. Petrovskii, Ivan I. Ponomarev,
Yu. A. Volkova, D. Yu. Razorenov, and Academician A. R. Khokhlov
Received June 3, 2009
DOI: 10.1134/S0012500809120040
Polyheteroarylenes (PHAs) are of great interest for mers derived from 5ꢀphosphonoisophthalic acid [9],
application as thermoꢀ, heatꢀ, fireꢀ, and chemicallyꢀ
resistant systems and some of them also as compoꢀ
nents of solidꢀpolymer protonꢀconducting memꢀ
branes of hydrogen (methanol)–air fuel cells (FCs)
[1]. Thus, for example, film materials based on PHA
containing ionogenic acid groups (SO3H, COOH)
were successfully tested in such FCs. The chemical
structure of these polymeric electrolytes can be easily
modified in desired direction, they show high moisꢀ
ture absorption and sufficient proton conduction at
highꢀmolecularꢀweight filmꢀforming PBI based on
10ꢀdihydroxyꢀ10ꢀoxoꢀ10Hꢀdibenzo[ ][1,4]oxaphosꢀ
phinineꢀ2,8ꢀdicarboxylic acid [8,10].
b,e
The measurements of proton conductivity of
pressed or film samples based on the above polymers
showed values within 10–3 to 10–5 S/cm, whereas the
conductivity of PBIs doped with phosphoric acid
reached 0.15 S/cm [5–7]. Such a large difference in
proton conductivity is likely due to the fact that doped
systems contain up to 5–6 molecules of H3PO4 per
monomer unit of polymer, which is equivalent to
temperatures below 100 С in a wet state. The further
°
development in this field is associated with a possibilꢀ
ity to obtain polymers showing protonꢀconducting
15⎯18 P–OH groups, while the obtained PPBIs comꢀ
prise only 1–2 groups, which is insufficient for effiꢀ
cient proton transport.
properties at temperatures above 120 C under anhyꢀ
°
drous conditions. Polymers comprising phosphoryl
groups can meet this requirement because they can
provide proton transfer in the absence of water [1, 2].
In this work, we have synthesized highꢀmolecularꢀ
weight PPBIs containing 4–5 P–OH groups
covalently attached to the polymer chain and assessed
their physicochemical properties and possibility of
application in a real fuel cell.
Polybenzimidazoles (PBIs) are one of the most
studied types of PHAs used in fuelꢀcell membranes as
polymer–electrolyte complexes with orthophosphoric
acid [2–7]. It has been found, however, that free
orthophosphoric acid migrates from membrane into
electrode space while the fuel cell is in use, this
decreases proton conductance and cell efficacy.
Therefore, it is rather reasonable to develop methods
for the synthesis of PBIs that involve ionogenic acid
phosphorusꢀcontaining groups chemically bound to
the polymer chain. To provide high chemical and therꢀ
mal stability of this polymer, it is optimal to include
phosphorus atom into the main chain of polymer via
P–C bonds [8]. Only few reports on the synthesis of
phosphorylated polybenzimidazoles (PPBIs) are
available in the literature: phosphonethylated ones
prepared by polymerꢀanalogous reactions [8], copolyꢀ
EXPERIMENTAL
4,4'ꢀDichlorodiphenyl sulfone (
zoic acid ( ), diethyl 4ꢀaminobenzylphosphonate (
polyphosphoric acid (PPA), Eaton’s reagent (ER),
ꢀmethylpyrrolidone (NMP), and formic acid were
1), 4,4'ꢀoxydibenꢀ
6
3),
N
purchased from SigmaꢀAldrich and used without
additional purification.
3,3ꢀBis(pꢀcarboxyphenyl)phthalide (7) received
from Soyuzglavreaktiv was purified by recrystallizaꢀ
tion from methanol with activated carbon and dried in
vacuum (0.133 Pa) at 90–100
10Hꢀ10
5ꢀphenoxaphosphineꢀ2,8ꢀdicarboxylic acid
) was obtained by procedure [10].
°
C, 10ꢀhydroxyꢀ10ꢀoxoꢀ
Nesmeyanov Institute of Organoelement Compounds,
Russian Academy of Sciences, ul. Vavilova 28, Moscow,
119991 Russia
λ
(
8
315

316
PONOMAREV et al.
Synthesis of Initial Compounds
ent). The suspension was cooled to ambient temperaꢀ
ture, poured on ice and distilled water was added to
total volume of 1000 mL. The precipitate was filtered
off, washed with water to pH 7, and recrystallized from
1000 mL of acetic acid to give 71.69 g (95%) of comꢀ
4,4'ꢀDichloroꢀ3,3'ꢀdinitrodiphenyl sulfone (2)
(Scheme 1) was obtained by inꢀhouse procedure. 4,4'ꢀ
Dichlorodiphenyl sulfone (
dissolved under stirring in 250 mL of concentrated
H2SO4 at 80 C in a 500ꢀmL twoꢀnecked flask
1) (57.4 g, 0.2 mol) was
pound
2
. After drying (100
°
C, Pres = 10–2 Torr) mp
°
200–201.5
°
C.
equipped with a helicalꢀblade stirrer. After dissolution
(1–1.5 h), 37.4 g (0.44 mol) of NaNO3 was added in
small portions with stirring over 20–30 min. The
resultant white suspension was stirred for 5 h (moniꢀ
toring by TLC for product formation, toluene as eluꢀ
4
1H NMR (CDCl3,
δ
, ppm): 8.43 (d, 2H, JHH
=
2.0 Hz), 8.07 (dd, 2H, 3 HH = 8.4 Hz, 4
J JHH = 2.0 Hz),
7.78 (d, 2H, dd, 2H, 3
J
HH = 8.4 Hz).
Cl
Cl
Cl
Cl
4
H SO /NaNO
2 4
3
SO2
SO2
80°C
1
3
NO2
NO2
2
1
2
2
NO2
HN
SO2
NO2
3
3'
4'
1
OC2H5
4
2H2N
CH2 P O
NH
OC2H5
3
N-МП, Et3N, 80°C
4
CH2
CH2
O
O
P(OC2H5)2
P(OC2H5)2
NH2
HN
SO2
NH2
NH
60–80°C; 80 atm
Pd/C (5%)
5
CH2
CH2
O
O
P(OC2H5)2
P(OC2H5)2
Scheme 1
1H NMR (DMSOꢀd6
3JHH = 7.0 Hz), 3.28 (d, 4H, 2
,
δ
, ppm): 1.19 (t, 12H,
HP = 21.6 Hz), 3.97 (dq,
4,4'ꢀBis{
lamino}ꢀ3,3'ꢀdinitrodiphenyl sulfone (4) (Scheme 1)
was obtained by reaction of diethyl 4ꢀaminobenꢀ
zylphosphonate ( ) with sulfone . Compound (16 g,
0.044 mol) was added in argon flow at ambient temꢀ
perature to 26 mL of
ꢀmethylpyrrolidone containing 9.2 Hz, 4
5.6 g (0.02 mol) of sulfone . After homogeneous soluꢀ
tion formed, the temperature was raised to 80 C and
the reaction was continued until disappearance of
compound in the reaction mixture (monitoring by
TLC, toluene–acetone, 5 : 1, as eluent). After comꢀ
pletion of the synthesis ( 6 h), the reaction mixture
pꢀ[(diethoxyphosphoryl)methyl]phenyꢀ
J
8H, 3
J
HH = 7.2 Hz, 3
J
HP = 7.4 Hz), 7.08 (d, 2H, 3JHH
=
=
3
2
3
3
9.2 Hz), 7.28–7.38 (m, 8H), 7.90 (dd, 2H, JHH
N
J
HH = 2.4 Hz), 8.56 (d, 2H, 4
31Р {1H} NMR (DMSOꢀd6
, ppm): +27.8 (s).
3,3'ꢀDiaminoꢀ4,4'ꢀbis{ ꢀ[(diethoxyphosphoryl)meꢀ
JHH = 2.4 Hz).
2
,
δ
°
p
2
thyl]phenylamino}diphenyl sulfone (5) (Scheme 1)
was obtained by reduction of 7.91 g (0.01 mol) of sulꢀ
~
fone
4
with hydrogen in an autoclave (60–80
°
C,
was cooled to ambient temperature and diluted with
150 mL of ethanol. The resulting bright yellow fine
precipitate was filtered off, dried in air, and recrysꢀ
tallized from ethanol to give 12.02 g (80%) of comꢀ
PH = 80 atm) over 5% Pd/C in 210 mL of ethanol
2
during 8 h. The hot solution of
filtered through silica gel layer and cooled. Tetramine
5 crystallized as fine beige crystals. After drying in vacꢀ
4 after reduction was
pound
4
, mp 154–156
°
C.
DOKLADY CHEMISTRY Vol. 429
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2009

SYNTHESIS OF NEW MONOMER
317
3
3
uum (100
°
C, Pres = 10–2 Torr), 6.21 g (85%) of the 8H, JHH = 7.2 Hz, JHP = 7.4 Hz), 5.28 (br s, 4H),
product was obtained with mp 118–120
°
C.
6.95–7.16 (m, 14H), 7.39 (s, 2H).
31P{1H} NMR (DMSOꢀd6
,
δ, ppm): +28.43 (s, P).
For C34H44N4O8P2S anal. calcd. (%): C, 55.51;
H, 6.22; N, 7.58; P, 8.40; S, 4.52.
Found (%): C, 55.88; H, 6.07; N, 7.67; P, 8.48;
S, 4.39.
Synthesis of PPBI in Polyphosphoric Acid (PPA)
and Eaton’s Reagent (ER) Medium
1H NMR (DMSOꢀd6
,
δ
, ppm): 1.18 (t, 12H,
Polymer 4POH DPO (
9) was obtained in PPA and
3JHH = 7.0 Hz), 3.13 (d, 4H, 2
JHP = 21.2 Hz), 3.94 (dq,
ER from monomers and
5
6
(Scheme 2).
HO OH
P
H C
2
O
N
O
C
O
S
O
O
O
N
N
N
O
C
HO
OH
6
n
4POH ДФО (9)
4POH DPO
CH
2
O
P
OH
HO
HO OH
P
2
NH2
HN
SO2
NH2
NH
H C
O
5
N
C
O
CH2
CH2
O
P(OC2H5)2
N
O
O
O
P(OC2H5)2
S
N
N
O
C
ER; PPA
O
HO
OH
n
O
O
4POH Cardo (10)
O
O
P
CH
2
7
OH
HO
HO OH
P
O
H C
2
N
N
O
O
C
O
S
10
P
N
O
O
8
P OH
O
2
O
C
O
OH
OH
OH
N
8
n
5POH PDA
5POH ФДК (11)
CH
O
2
P
OH
HO
Scheme
2
DOKLADY CHEMISTRY Vol. 429
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2009

318
PONOMAREV et al.
Properties of phosphorusꢀcontaining polybenzimidazoles prepared in polyphosphoric acid (PPA) and Eaton’s reagent
(ER) medium
Solubility
ηred
0.5%, 25
in H2SO4)
, dL/g
Tdeg, °C
TGA, air)
Polymer
Medium
(
°
C
τ, h
NH4OH
(28%)
HCOOH
(100%)
(
H2SO4
CF3COOH
4POH DPO
(9
)
PPA
ER
0.53
0.80
40
30
+
+
+
+
++
++
+++
+++
500
475
4
POH Cardo (10
)
ER
3.24
30
+
+
++
++
+++
450
5POH PDA 11
(
)
PPA
ER
0.42
1.33
40
35
+
+
+
+
+++
+++
475
475
Note: The sign “+” indicates polymer solubility below 1%, “++” indicates that polymer is soluble, “+++” indicates that polymer is readily
soluble, “ ” indicates that polymer is soluble in part.
Synthesis in PPA medium. A twoꢀnecked flask 95% yields (Scheme 2). The table shows the properties
equipped with a mechanical stirrer was charged with of polymers
0.731 g (0.001 mol) of monomer and 0.258 g
(0.001 mol) of monomer . Polyphosphoric acid
(4.37 g) was added to the monomers and the mixture
was heated to 75 C. After 2ꢀh keeping, the temperaꢀ
ture was raised to 120 C, 2.1 g of P2O5 was added, and
the mixture was kept for 4 h. The temperature was eleꢀ
vated to 180 C and the reaction was continued for
32 h. The reaction mixture was cooled to 120 C and
9–11.
5
6
Study of Individual Compounds and Polymers
1H and 31P NMR spectra of the studied compounds
were recorded on a Bruker Avance 400 spectrometer
operating at 400.13 and 161.98 MHz, respectively, in
°
°
°
DMSOꢀ
d
6 or HCOOD solutions. Chemical shifts in
δ
°
scale were calculated using residual proton signals of
the deuterated solvent as an internal reference (1H)
and 85% H3PO4 as an external reference (31P).
the resultant polymer was precipitated with water. The
precipitate was collected by filtration, washed with
water, and dried in vacuum (0.133 Pa) at 100
°
C for 5 h
Dynamic TGA was carried out with a MOM
Qꢀ1000 derivatograph (Hungary) in air at a heating
rate of 5 K/min, sample weight of 40–60 mg.
to give 0.94 g (95%) of polymer
9
.
1H NMR (HCOOD,
22.0 Hz), 8.65–9.22 (m, aromatic protons).
δ, ppm): 4.90 (d, JHP
=
2
Melting points were measured on a Boetius heating
bench and not corrected.
31P{1H} NMR (HCOOD,
, ppm): +25.91 (s).
δ
Reaction course and purity of isolated products were
monitored by TLC using Silufol UVꢀ254 plates, visualꢀ
ization under UV light or by exposing to iodine vapors.
Synthesis in ER medium. A twoꢀnecked flask
equipped with a mechanical stirrer was charged with
0.7308 g (0.001 mol) of monomer
of monomer , and 3 mL of ER. The monomers were
dissolved in argon flow for 1 h at 100 C with stirring.
5, 0.2582 g (0.001 mol)
6
Reduced viscosity was measured at 25 C with a
°
°
capillary Ubbelohde viscometer at polymer concenꢀ
tration of 0.5 g/dL.
The resultant homogeneous solution was strengthened
with 2 g of P2O5 and stirred additionally for 1 h.
The temperature was elevated to 145
then 2 mL of ER was added. The reaction was carried
out for 24 h, the temperature was decreased to 100
and the polymer was precipitated with water. The preꢀ
cipitate was collected by filtration and Soxhlet
extracted with isopropanol. The polymer was dried in
°
C over 2 h and
RESULTS AND DISCUSSION
°
C
Tetramine 5 was obtained for the first time accordꢀ
ing to Scheme 1.
At the first stage, the nitration of 4,4'ꢀdichloꢀ
rodiphenyl sulfone (
H2SO4 at 80 C afforded 4,4'ꢀdichloroꢀ3,3'ꢀdiniꢀ
trodiphenyl sulfone ( ) in high yield. The latter was
further used for the synthesis of 4,4'ꢀbis{ ꢀ[(diethoxyꢀ
phosphoryl)methyl]phenylamino}ꢀ3,3'ꢀdinitrodipheꢀ
nyl sulfone ( ) by reaction with 2 equivalents of diethyl
4ꢀaminobenzylphosphonate ( ) in ꢀmethylpyrroliꢀ
done in the presence of triethylamine. Dinitro comꢀ
pound was reduced with hydrogen over Pd/C (5%) in
in more than EtOH solution in an autoclave at 60–80 C. After crysꢀ
1) with sodium nitrate in 98%
vacuum (0.133 Pa) at 100
(96.1%).
°
C for 5 h. Yield 0.95 g
°
2
1H NMR (HCOOD,
22.0 Hz), 8.65–9.22 (m, aromatic protons).
δ
, ppm): 4.90 (d, JHP
=
2
p
4
31P{1H} NMR (HCOOD,
δ, ppm): +25.91 (s).
3
N
Polymers 4POH Cardo (10) and 5POH PDA (11
)
were obtained in PPA and ER similarly to polymer
from monomers and as well as and
9
4
7
5
8
5
°
DOKLADY CHEMISTRY Vol. 429
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2009

SYNTHESIS OF NEW MONOMER
319
tallization of reduction product
5
from ethanol, its
It is known that, in general, the polycondensation
of 1,3ꢀdiaminoꢀ4,6ꢀdianilines with dicarboxylic acids
in PPA medium leads to Nꢀphenylꢀsubstituted PBIs
[2] (Scheme 3).
composition and chemical structure were confirmed
by elemental analysis and 1H and 31P{1H} NMR specꢀ
troscopy.
X
X
X
R
X
HN
NH
N
N
N
N
PPA
+
HOOC–R–COOH
100–200°C
–4H2O
H2N
NH2
n
Scheme
3
We assumed that the polycondensation reaction of 3.24 dL/g, which indicates rather high molecular
the above monomers will proceed similarly both weights of obtained PPBIs, which, however, exhibit
5–8
in PPA and ER [11], which in recent time is widely limited solubility in formic and trifluoroacetic acids
used for the synthesis of PHA and PBI (see, in particꢀ and in concentrated ammonia solutions upon heating
ular, [11–13]). Polymer concentrations in the syntheꢀ to 60–80 C. A solution of polymer 5POH PDA (11) in
°
ses varied within 10–20%. The syntheses involved aqueous ammonia shows distinct thixotropic properꢀ
strengthening of both PPA and ER by adding phosꢀ ties and gives elastic physical gel upon cooling, whose
phoric anhydride during polycondensation (taking slow drying at ambient temperature results in good
into account water evolved). The use of this technique films.
makes it possible to increase considerably the molecuꢀ
The table also shows that all obtained polymers,
lar weight of resulting PPBI. The syntheses in PPA and
according to the data of dynamic TGA in air (heating
ER were carried out at 180–200
respectively.
°
C and 140–145 C,
°
rate of 5 K/min), have high thermal stability comparaꢀ
ble with that of the best known polymers of PBI family
[1–3]. Their onset degradation temperatures are above
We used the following dicarboxylic acids as
comonomers for sulfone : 4,4'ꢀoxydibenzoic acid ( ),
because its polymers show high filmꢀforming properꢀ
ties [2], 3,3ꢀbis( ꢀcarboxyphenyl)phthalide ( ),
whose use provides cardo polymers and enhances their
solubility [2, 13], and 10ꢀhydroxyꢀ10ꢀoxoꢀ10Hꢀ10
5ꢀ
) as a carꢀ
5
6
500 C.
°
p
7
The preliminary testing of proton conductivity of a
film of 5POH PDA (11) obtained from a gel in 28%
aqueous ammonia solution followed by treatment with
2% H2SO4 showed conductivity about 1–2 mS/cm at
λ
phenoxaphosphineꢀ2,8ꢀdicarboxylic acid (
8
rier of one P–OH group [8, 10].
160 C, whereas PPBI obtained in the work [10] based
°
1Н and 31Р NMR spectra confirm the chemical
structure of polymers 11, which contain after preꢀ
on PDA under these conditions showed 100 times
lower proton conductivity. For the practical applicaꢀ
tion of membranes in highꢀtemperature fuel cell, the
proton conductivity should be at least of 5 mS/cm at
9–
cipitation only free phosphonate groups showing
phosphorus chemical shifts at 25.9 ppm [8]. Thus, the
polycyclocondensation and isolation of polymers 9–
150–200 C, better value is 50 mS/cm and above.
°
Therefore, the use of films of obtained PPBIs in a pure
form seems to be doubtful. The attempts to dope them
with phosphoric acid lead to rather mechanically weak
membranes providing no opportunity to make effiꢀ
cient membraneꢀelectrode assembly (MEA). The
obtained PPBIs were successfully used as thickening
agents for phosphoric acid for application as storage
for protonꢀconducting electrolyte in a threeꢀlayer
membrane based on traditional PBIs. The resource
testing of these MEAs (with working surface area of
5 cm2) in a hydrogen–air fuel cell with the use of
11 is accompanied by the total hydrolysis of diethyl
phosphonate group of monomer and complete retenꢀ
tion of benzylphosphonate side groups.
The structure of the polymers was also confirmed
by the data of IR spectroscopy. IR spectra show wide
bands of associated hydroxy groups in the region of
2500–3800 cm–1 and strong bands of stretching vibraꢀ
tions of phosphonate groups within 1150–1280 cm–1.
The table shows that ηred values for 0.5% solutions
of the polymers in H2SO4 at 25 C are of 0.42–
°
DOKLADY CHEMISTRY Vol. 429
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2009

320
PONOMAREV et al.
Celtec P1000® industrial electrodes (BASF) in a galꢀ
vanostatic mode (current density of 0.4 A/cm2,
6. Samms, S.R., Wasmus, S., and Savinell, R.F., J. Elecꢀ
trochem. Soc., 1996, vol. 143, p. 1225.
7. Savinell, R.F., Yeager, E., Tryk, D., et al., J. Electroꢀ
chem. Soc., 1994, vol. 141, p. L46.
160
°
C) showed stable potential difference of U =
Δ
0.560–0.580 V during 2200 h of continuous operation.
8. Rybkin, Yu.Yu., Candidate (Chem.) Dissertation
,
INEOS RAN, 2005.
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DOKLADY CHEMISTRY Vol. 429
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2009