Chemical modification of cardo poly(benzimidazole) with 10-azidoheptadecafluorodecane using "click" reaction

Full text of DOI:10.1134/S0012500812110079

ISSN 0012ꢀ5008, Doklady Chemistry, 2012, Vol. 447, Part 1, pp. 249–253. © Pleiades Publishing, Ltd., 2012.
Original Russian Text © Iv.I. Ponomarev, I.I. Ponomarev, Yu.A. Volkova, D.Yu. Razorenov, I.V. Blagodatskikh, I.O. Volkov, A.R. Khokhlov, 2012, published in Doklady Akademii
Nauk, 2012, Vol. 447, No. 2, pp. 171–175.
CHEMISTRY
Chemical Modification of Cardo Poly(benzimidazole)
with 10ꢀAzidoheptadecafluorodecane
Using “Click” Reaction
Iv. I. Ponomarev, I. I. Ponomarev,
Yu. A. Volkova, D. Yu. Razorenov, I. V. Blagodatskikh,
I. O. Volkov, and Academician A. R. Khokhlov
Received July 20, 2012
DOI: 10.1134/S0012500812110079
Poly(benzimidazole)s (PBIs) are one of the most alkylation with propargyl bromide (PB) [5] followed by
promising and studied classes of polymers used as its transformation into PBI–F with the use of 1,3ꢀdipolar
membranes in highꢀtemperature hydrogen fuel cells addition of 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10ꢀheptaꢀ
(HTFC) as polymerꢀelectrolyte complexes with decafluorodecyl azide (3). For this purpose, we have
orthophosphoric acid (PA) [1, 2]. With the aim to studied for the first time the consecutive model reactions
improve the performance characteristics of PBI memꢀ of 2ꢀarylꢀsubstituted benzimidazoles with propargyl broꢀ
branes, they are subjected to chemical modification. mide (PB) and then with compound
3, using model 2ꢀ
For example, to enhance their proton conductivity, we phenylbenzimidazole (2ꢀPBI,
previously prepared and successfully tested phosphonꢀ
1) as an example.
ethylated PBI [3], Nꢀarylꢀsubstituted PBI with five
EXPERIMENTAL
Dimethyl sulfoxide (DMSO),
–P–OH groups per monomer unit of the polymer [4],
and phosphorylated polybenzimidazolotriazoles [5] in
the construction of the membraneꢀelectrode block
(MEB) of fuel cells.
N
ꢀmethylpyrroliꢀ
done (NMP), 2ꢀphenylbenzimidazole (2ꢀPBI), propꢀ
argyl bromide (PB), sodium hydroxide, potassium
carbonate, triethylamine NEt3, copper(I) iodide,
sodium azide, and 85% orthophosphoric acid (PA)
were purchased from Sigma–Aldrich and used as
received. 10ꢀIodoꢀ1,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8ꢀ
heptadecafluorodecane from P&M Company was also
used without additional purification. Matrix polybenꢀ
zimidazole (PBI–O–PT) was obtained by procedures
In the design of novel highꢀperformance MEB for
fuel cells, the problems involve not only the improveꢀ
ment of PBI membranes but also the issues of
improvement of performance of catalytic, or active
layers (AL), and gasꢀdiffusion layers (GDL) of the
MEB. The question on the necessity of the presence of
small amounts of PBI in these MEB layers remains
open [1, 2, 6], in particular, water evolved as a product
of electrochemical reactions on the cathode causes the
leakage of phosphoric acid (PA) from the MEB. To
prevent this undesirable process, the AL of the MEB
should contain an attractor of orthophosphoric acid
(PA), for example, PBI, but insoluble in PA and havꢀ
ing enhanced gas permeability. Conventional PBIs do
not meet these requirements [1, 2].
developed by us [3, 5]. A polymer sample with ηred
2.1 dL/g (0.5% solution in NMP at 25°C) was used for
the alkylation of PB.
=
Methods for Studying Individual Compounds
and Polymers
1H, and 31P NMR spectra of obtained compounds
were recorded on a Bruker Avanceꢀ400 spectrometer
(operating at 400.13 and 161.98 MHz, respectively) in
DMSOꢀd6 or HCOOD solutions. The values of chemꢀ
ical shifts were calculated using residual proton signals
of deuterated solvent as an internal reference for H
and 85% H3PO4 as an external reference for 31Р NMR
spectra.
In this work we have tested a chemical approach that
consists in a twoꢀstep polymer analogous reaction of
filmꢀforming highꢀmolecularꢀweight PBI–O–PT by
1
Nesmeyanov Institute of Organoelement Compounds,
Russian Academy of Sciences, ul. Vavilova 28, Moscow,
119991 Russia
249

250
PONOMAREV et al.
IR absorption spectra were recorded on a Nicolet tory funnel to give virtually quantitative yield of the
MagnaꢀIR 750 Fourierꢀtransform spectrophotometer compound suitable for further use.
in the range 4000–400 cm–1 as thin films of KBr pelꢀ
For C10H4F17N3 anal. calcd. (%): F, 66.03.
М =
lets.
Xꢀray photoelectron spectra were recorded on a
Kratos XSAMꢀ800 instrument (Great Britain) with
the use of magnesium characteristic radiation (hν =
1253.6 eV) at residual pressure 10–8 Pa in a constant
resolution mode. The power of Xꢀray gun during specꢀ
tra recording was no higher than 45 W (15 kV, 3 mA).
Sample charging was monitored using carbon compoꢀ
nent with the lowest binding energy (285.0 eV). Quanꢀ
titative analysis was performed on the basis of inteꢀ
grated intensity of photoelectron lines taking into
account the coefficients of elemental sensitivity by the
previously described procedure [7].
489.13.
Found (%): F, 66.33.
1Н NMR (СDCl3
,
δ
, ppm,
J, Hz): 2.33 (tt, 2H,
CH2CF2, 3 HH 7.4, 3
J JHF 18.2), 3.55 (t, 2H, CH2CH2CF2,
3JHH 7.5).
19F{1H} NMR (
4JFF 10.1), –115.27 (t, 2F, CF2CH2, 4
to –122.9 (m, 2F, CF2CF2CH2), –122.6 to –123.2
(m, 4F, CF3CF2(CF2)2), –123.5 to –124.0 (m, 2F,
CF3(CF2)3CF2), –124.3 to –124.8 (m, 2F,
CF3(CF2)4CF2), –127.2 to 127.6 (m, 2F, CF3CF2).
δ
, ppm,
J, Hz): –82.49 (t, 3F, CF3,
JFF 13.8), –122.4
Synthesis of 1ꢀ{[1'ꢀ(3'',3'',4'',4'',5'',5'',6'',6'',7'',7'',
Light scattering experiments were carried out on a
FotoKor Kompleks (FotoKor, Russia) with crossꢀcorꢀ
relation photon counting system and an He–Ne laser
8'',8'',9'',9'',10'',10'',10''ꢀheptadecafluorodecyl)ꢀ1'
1',2',3'ꢀtriazolꢀ4'ꢀyl]methyl}ꢀ2ꢀphenylꢀ1 ꢀbenzimidaꢀ
zole (4). Compound (2.32 g, 0.01 mol) and 4.89 g
(0.01 mol) of azide was heated at reflux for 4 h in 30 mL
Hꢀ
H
2
(
λ
= 633 nm). Correlator was used in the logarithmic
configuration. Measurements were conducted at 25
in the scattering angle range 30 –140°. The particle
3
°С
of ethanol in the presence of 0.2 g (0.001 mol) of CuI and
°
0.5 mL of NEt3. Reaction course was monitored by TLC
size distribution was calculated by CONTIN software.
using toluene–methanol as an eluent. After reactants
2
and disappeared, the reaction solution was filtered
through a thin layer of silica gel and allowed to crystallize
in a refrigerator. The resultant colorless crystals had mp
3
Synthesis of Individual Compounds
Synthesis of 2ꢀphenylꢀ1ꢀpropꢀ2'ꢀinylꢀ1
H
ꢀbenzimiꢀ
dazole ( ). A mixture of 1.94 g (0.01 mol) of 2ꢀPBI (
1.40 g (0.011 mol) of potassium carbonate, and 1.30 g
(0.011 mol) of propargyl bromide (PB) in 10 mL of
2
1),
145–146
For C26H16N5F17 anal. calcd. (%): C, 43.29; H,
2.24; N, 9.71; F, 44.77. = 721.41.
Found (%): C, 43.02; H, 2.27; N, 9.41; F, 44.37.
°C.
M
NMP was stirred at 50°С in a dry argon flow for 10 h
with intermittent sonication. The reaction was moniꢀ
tored by TLC using toluene as an eluent. The reaction
solution was poured into water, neutralized with acetic
1Н (СDCl3;
δ
, ppm,
J
, Hz): 2.77 (tt, 2H, CH2CF2,
3JHH 7.3, JHF 18.0), 4.59 (t, 2H, CH2CH2CF2, JHH
3
3
acid to pH 6, and compound
diethyl ether (3 30 mL). The extract was dried with
calcium chloride, filtered, concentrated to 20 mL, and
placed in a refrigerator. The colorless crystals of were
separated by filtration and dried in a vacuum at 60
The yield of crystalline compound was 2.1 g (90%),
mp 71–73 (lit. 72 ).
2 was extracted with
7.3), 5.50 (s, 2H, CH2N), 7.26 (s, 1H, H5’), 7.25–7.34
(m, 2Н, Н5,6), 7.37 (d, 1H, Н4, JHH 7.8), 7.45–7.53
×
3
(m, 3H,
7.83 (d, 1H, Н7, 3
19F{1H} NMR (
4JFF 9.9), –114.18 (t, 2F, CF2CH2, 4
m
ꢀ +
p
ꢀ
С6Н5), 7.70–7.78 (m, 2H,
HH 7.6).
, ppm,
oꢀС6Н5),
2
J
°C.
2
δ
J
, Hz): –80.70 (t, 3F, CF3,
°C
°C
JFF 13.1), –121.4
1H NMR (DMSOꢀd6
НС
С, 4 HH 2.5), 5.16 (d, 2H, СН2, 4
7.38 (m, 2H, Н5,6], 7.57–7.66 (m, 3H,
.68–7.75 (m, 2H, Н4,7), 7.84–7.90 (m, 2H,
,
δ, ppm,
J, Hz): 3.52 (t, 1H,
to –121.9 (m, 2F, CF2CF2CH2), –121.7 to –122.2 (m,
4F, CF3CF2(CF2)2), –122.4 to –122.9 (m, 2F,
CF3(CF2)3CF2), –123.2 to –123.6 (m, 2F,
≡
J
JHH 2.5), 7.28–
mꢀ +
pꢀ
С6Н5),
7
о
ꢀС6Н5). CF3(CF2)4CF2), –125.9 to –126.3 (m, 2F, CF3CF2).
Synthesis of 3,3,4,4,5,5,6,6,7,7,8,8,9,9,10,10,10ꢀ
Alkylation of PBI–O–PT with propargyl bromide.
heptadecafluorodecyl azide (3). The compound was PBI–O–PT (0.532 g, 1 mmol) was dissolved in 6 mL
prepared by the reaction of 5.74 g (0.01 mol) of 10ꢀ of NMP, 0.3 g (~2.2 mmol) of K2CO3 was added, and
iodoꢀ1,1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8ꢀheptadecafluꢀ
orodecane with 0.65 g (0.01 mol) of NaN3 in 20 mL of
the mixture was stirred for 30 min in water ultrasound
bath at 40–50 . Next, a solution of 0.5 g (~4.4 mmol)
°C
dry DMF at constant stirring at ambient temperature of propargyl bromide (PB) freshly distilled over methꢀ
for 24 h. After completion of the reaction, the solution ylhydroquinone in 5 mL of NMP was added dropwise
was diluted with a threefold amount of water, and the over 30 min, and the stirring was continued for 24, 48,
yellowish oily product (3) was separated in a separaꢀ 72, and 96 h with imtermittent sonication for 20–
DOKLADY CHEMISTRY Vol. 447
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2012

CHEMICAL MODIFICATION OF CARDO POLY(BENZIMIDAZOLE)
251
1
30 min at 40–50°C, and sampling for H NMR to
1.2
0.8
0.4
0
analyze the alkylation extent. The polymer was preꢀ
cipitated with water, acidified with acetic acid to pH 5,
filtered and the powder was refluxed twice in distilled
water for 1–2 h to remove the solvent. The powder was
1
2
dried at 100
°C in a vacuum. Depending on conditions
and reactant ratio, the alkylation extent can be 25–
100%. PBI–O–PT–Pg is readily soluble in amide solꢀ
vents and DMSO.
1,3ꢀDipolar addition of 3,3,4,4,5,5,6,6,7,7,8,8,
9,9,10,10,10ꢀheptadecafluorodecyl azide (3) to PBI–
O–PT–Pg to give PBI–F. PBI–O–PT–Pg (0.606 g,
1 mmol) was dissolved in 6 mL of DMSO, a solution
0.1
1
10
100
1000
Rh nm
,
of 1.0 g (~2.2 mmol) of azide 3 in 5 mL of DMSO and
a solution of 0.04 g of CuI and 0.5 mL of NEt3 in 3 mL
Fig. 1. Hydrodynamic radius (R ) distribution of particles in
h
of DMSO was added. The reaction mixture was stirred
PBIꢀF solutions in 85% formic acid (
1
) and in 0.05 M LiCl
for 8 h at 60–80
aqueous ammonia solution. The precipitate was sepaꢀ
rated by filtration, dried at 100 in a vacuum, and
°C and then precipitated with a 1%
solution in 85% formic acid (2). Scattering angle is 60°,
concentration is 1.7 mg/mL.
°C
analyzed by NMR and IR spectroscopy and elemental
analysis. For PBI–O–PT–Pg with alkylation degree of
RESULTS AND DISCUSSION
In this work, we have studied in detail the model
100%, the addition of perfluorinated azide
3 occurred
in 100% yield. The reaction led to fluorinated polybenꢀ
zimidazolotriazole PBI–F containing 40.2% of fluoꢀ
rine at a calculated value of 40.7%. The polymer is solꢀ
uble in 85% HCOOH and partially soluble in hexafluꢀ
oroisopropanol.
reactions of 2ꢀPBI (
1) with propargyl bromide (PB)
and the subsequent reaction of intermediate alkyne
2
4
with fluorinated azide
(Scheme 1).
3
to form model product
N
N
BrH2C–
NꢀMP, K2CO3,
20–30
≡ (PB)
N
N
H
°C
1
2
2ꢀPBI
N
N
EtOH, CuI, NEt3
2
+ C8F17CH2CH2N3
60–80°C
CF2 CF2 CF2
CF3
3
4
N
N
N
CF2 CF2 CF2 CF2
Scheme 1.
3290 cm–1; the latter disappears after addition of
, and the spectrum of the product of the click
reaction shows the prevalence of intense bands of
The chemical structure of compounds
2 and 4 was
confirmed by the data of 1Н and 31P NMR and FTIR azide
3
spectroscopy.
4
stretching vibrations of C–F groups in the range
1145–1290 cm–1.
On passing from 2ꢀPBI (1) to its propargylꢀconꢀ
taining derivative
2, according to FTIR spectroscopy,
the broad absorption band of NH groups at 3200–
The data obtained in the study of model reactions
3400 cm–1 disappears and a typical band of stretching were further used to study polymer analogous reacꢀ
vibrations of terminal acetylene
≡СН appears at tions of PBI–O–PT (Scheme 2).
DOKLADY CHEMISTRY Vol. 447
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252
PONOMAREV et al.
N
N
N
N
N
N
O
O
3
n
BrH2C–
NꢀMP, 2.2
Ultrasound, 20–50
≡
(
PB
K2CO3,
C, 72 h
)
N
H
N
H
n
°
O
O
O
O
n
n
PBI–O–PT
PBI–O–PT–Pg
N
N
N
O
N
DMSO, CuI, NEt3
60–80
PBI–O–PT–Pg + 3
n
C8F17CH2CH2N3
°
C
O
N
N
N
N
3
N
N
O
C8F17CH2CH2
C8F17CH2CH2
n
PBI–F
Scheme 2.
The polymer analogous reactions were monitored entropy of counterions, is the factor that favors the staꢀ
by 1Н and 19F NMR, IR spectroscopy, GPC [5], and
light scattering.
bility of intraꢀ and intermolecular aggregates. The
decrease in the hydrodynamic size of the aggregates
upon addition of lowꢀmolecularꢀweight electrolyte
agrees well with the features of the behavior of associꢀ
ating polyelectrolytes [8].
The methods of dynamic and static light scattering
indicate the formation of partially aggregated soluꢀ
tions of PBI–F in HCOOH below the coil overlapping
concentration both in a saltꢀfree medium and in soluꢀ
tions containing LiCl. Figure 1 shows the size distribuꢀ
tion curves that exhibit the presence of two diffusional
modes, which can be assigned to the diffusion of macꢀ
Strong films were cast from 5% solutions of PBI–F
in 85% HCOOH. Their surface was studied by XPS.
The general Xꢀray photoelectron spectrum shows carꢀ
bon, oxygen, nitrogen, and fluorine lines (Fig. 2). The
surface composition of studied sample was found to
coincide with the composition theoretically calculated
from the chemical formula. This is confirmed by the
results of quantitative XPS analysis performed on the
romolecules (
Rh = 5 0.5 nm) and aggregates (Rh
=
83 and 60
4
3
nm in saltꢀfree and salt solutions,
respectively). Taking into account the dual nature of
the PBI–F chain containing fluoroalkyl fragments, it
is natural to suppose that the aggregation results from
the formation of hydrophobic fluoroalkyl domains. At
the same time, the electrostatic repulsion between
particles, along with the contribution of translational
basis of the integrated intensities of N1
O1 lines, as well as of the component with binding
energy of 292.1 eV in the C1 spectrum responsible for
s, F1s, C1s, and
s
s
the presence of CF2 groups in surface layers.
Prepared PBI–F according to DTGA in air shows
good thermal stability comparable with that of other
members of the PBI family [1–6]. Its intense degradaꢀ
C1s
tion temperature is above 500°С, while the degradaꢀ
tion onset temperature is about 350°С on account of
F1s
the presence of methylene groups.
The PBI–F polymer is of considerable interest for
the modification of ALs and GDLs of the MEB
because it can provide better gas permeability (due to
the loosening of its packing by long perfluorinated
substituents) to the centers of electrochemical reacꢀ
tion in the AL, while the 1,2,3ꢀtriazole ring of the side
chain, like the benzimidazole ring of the main chain,
will form a complex with PA, thus improving proton
removal from the zone of the electrochemical reaction
toward the protonꢀconducting membrane.
O1
s
F
KLL
N1
s
1000
750
500
b, eV
250
0
E
Our assumptions are confirmed by experimental
data. Thus, the doping of PBI–F film with PA occurs up
to 800%, i.e., twice as much as that of pure PBI–O–PT.
Fig. 2. General Xꢀray photoelectron spectrum of the studꢀ
ied sample of PBI–F film.
DOKLADY CHEMISTRY Vol. 447
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CHEMICAL MODIFICATION OF CARDO POLY(BENZIMIDAZOLE)
253
At the same time, PBI–F is insoluble in PA at 160
°С,
Chemistry and Materials Science) and the Russian
which plays a key role for the use of the material in the Foundation for Basic Research (project no. 11–03–
AL since the products soluble in PA are transferred to 12115ꢀofiꢀmꢀ2011).
the active centers of catalyst and block them. We manꢀ
aged to assemble a sevenꢀlayer MEB on the basis of the
doped PBI–F membrane [9], which provides a closedꢀ
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°С
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DOKLADY CHEMISTRY Vol. 447
Part 1
2012