Ionic liquids: Structuration agents in a fluorinated matrix

Article abstract of DOI:10.1039/c0cc04273k

The use of ionic liquids as functional building blocks based on pyridinium, imidazolium and phosphonium cations to achieve materials combining a structuration at nanoscale with the dramatic mechanical properties of the resulting ionomers has been successf

Full text of DOI:10.1039/c0cc04273k

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Synthesis procedure and 1H NMR (CDCl3) and 13C NMR (CDCl3)
Synthesis of compounds 1a, 1b
In a 100 mL flask was placed under a positive nitrogen pressure, triphenylphosphine (1
equiv., 20 mmol, 5 g) and a solid of alkyl iodide and bromide [1 equiv., 20 mmol i.e; 13 g for
octadecyl iodide (C18H37I) and 11 g for octadecyl bromide] were diluted in toluene (20 mL).
The stirred suspension was allowed to react for 24 h at 120 °C, and a yellow precipitate was
formed. The reaction mixture was then filtered, and washed repeatedly with pentane.
Octadecyltriphenylphosphonium iodide (C18P I-) 1a. White solid, Yield = 90%, m.p. = 86 °C,
1
Tg = 11 °C. H NMR (CDCl3): δ 0.80-0.90 (m, 3H, CH3); 1.10-1.35 (m, 28, CH2Me); 1.50-
1.70 [m, 4H, PCH2(CH2)2]; 3.50-3.70 (m, 2H, PCH2); 7.70-7.90 (m, 15H, H arom). 13C NMR
(CDCl3): δ 14.00 (CH3); 22.67 (CH2Me); 23.20; 29.37-29.66; 30.24; 31.85 (PCH2); 118.45;
130.43; 133.70; 135.15 (P-Carom.).
Octadecyltriphenylphosphonium bromide (C18P Br-) 1b. White solid, Yield = 90%, m.p. = 85
1
°C, Tg = 12 °C. H NMR (CDCl3): δ 0.80-0.85 (m, 3H, CH3); 1.05-1.30 (m, 28, CH2Me);
1.55-1.75 [m, 4H, PCH2(CH2)2]; 3.50-3.65 (m, 2H, PCH2); 7.70-7.85 (m, 15H, H arom). 13C
NMR (CDCl3): δ 14.00 (CH3); 22.52 (CH2Me); 23.00; 28.90-29.66; 30.20; 32.00 (PCH2);
118.85; 130.80; 133.50; 135.45 (P-Carom.).
* Synthesis of octadecyltriphenylphosphonium hexafluorophosphate 1c
-
Octadecyltriphenylphosphonium hexafluorophosphate (C18PPF6 ) 1c was prepared by anionic
exchange according to the following procedure: In
a
100 mL flask,
octadecyltriphenylphosphonium iodide (C18P I-) (5.000 g, 13.14 mmol, 1 equiv.) was
dissolved into dichloromethane (25 mL). The mixture was stirred for 30 min at room
temperature. A solution of hydrogen hexafluorophosphate (HPF6) (3.830 g, 26.28 mmol, 2
equiv.) diluted in water (25 mL) was stirred for 30 min and added to the
octadecyltriphenylphosphonium iodide solution. The stirred suspension was allowed to react
for 24 h at room temperature. The reaction mixture was then introduced in a separatory
funnel, and the organic layer was washed repeatedly with distilled water (4x 25 mL). The
mixture was dried over anhydrous magnesium sulfate, concentrated under reduced pressure.
The solvent was removed by evaporation under vacuum. White solid, Yield = 90%, %, m.p. =

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80 °C, Tg = -2 °C. 1H NMR (CDCl3): δ 0.80-0.90 (m, 3H, CH3); 1.10-1.35 (m, 28, CH2Me);
1.45-1.70 [m, 4H, PCH2(CH2)2]; 3.40-3.55 (m, 2H, PCH2); 7.55-7.85 (m, 15H, H arom). 13C
NMR (CDCl3): δ 14.00 (CH3); 22.35 (CH2Me); 23.50; 29.12-29.74; 30.35; 31.75 (PCH2);
118.75; 130.22; 133.50; 135.05 (P-Carom.).
* Synthesis of N-octadecyl-N'-octadecylimidazolium iodide 2c
Three steps are necessary for the synthesis of N-octadecyl-N'-octadecylimidazolium iodide
(C18C18Im I-). The first one is the deprotonation of the imidazole ring with a solution of
sodium methoxide prepared as follows: Sodium (1 equiv., 0.465 g, 20 mmol) is dissolved in
dry freshly distilled methanol (10 mL) in a septum sealed, 100 mL round-bottomed, three-
necked flask equipped with a condenser, a nitrogen inlet and a magnetic stirrer. Then,
imidazole (1 equiv., 1.37 g, 20 mmol) and a small amount of acetonitrile (10 mL) were
introduced into the solution of sodium methoxide at room temperature. After 15 min, the
white suspension was formed and concentrated under reduced pressure. The dried white
powder was diluted in acetonitrile and a powder of octadecyl iodide (C18H37I) was added
under nitrogen atmosphere. The mixture was heated at 85 °C during 24 h. After the first
alkylation, the same procedure was used for the second alkylation. After cooling to room
temperature, the solvent was removed by evaporation under vacuum, and the beige solid
obtained was filtered, washed repeatedly with pentane and dried. White powder, Yield = 97%,
1
%, m.p. = 64 °C, Tg = 35 °C. H NMR (CDCl3): δ 0.75-0.90 (m, 6H, 2CH3), 1.15-1.30 (m,
64H, 32 CH2], 1.80-1.90 (m, 2H, NCH2CH2), 4.30 (t, 2H, CH2N=), 7.45 (m, 1H, H arom),
7.65 (m, 1H, H arom), 9.15 [s (b), 1H, H arom]. 13C NMR (CDCl3): δ 14.10 (2CH3); 22.67
(2CH2Me); 26.23; 28.97; 29.35-29.69; 30.24; 31.91 (CH2); 50.10; (CH2N=); 50.32 (CH2N-);
121.69; 122.48 (=CN); 136.88 (N-C=N).
* Synthesis of octadecylpyridinium iodide 3
In a 100 mL flask was placed under a nitrogen pressure, octadecyl iodide (C18H37I) (10
mmol)] and distilled pyridine (1.5 equiv.). The stirred suspension was allowed to react for 24
h at room temperature. A yellow precipitate was formed. The reaction mixture was then
filtered, washed repeatedly with pentane. Most of the solvent was removed under vacuum.
1
Octadecylpyridinium iodide 3 was isolated after drying and fully characterized by H and 13C
NMR. White solid, Yield = 90%, m.p. = 102 °C, Tg = 44 °C. 1H NMR (CDCl3): δ 0.84 (t, J =
7.3 Hz, 3H, CH3), 1.15-1.30 (m, 30H, 15 CH2), 1.90-2.02 (m, 2H, NCH2CH2), 4.90 (t, J = 7.5

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Hz, 2H, NCH2), 8.05 (t, J = 7.2 Hz, 2H arom), 8.45 (t, J = 7.8 Hz, 1H, H arom), 9.35 (d, J =
5.4 Hz, 2H, H arom). 13C NMR (CDCl3): δ 14.04 (CH3); 22.58; 25.91; 28.99; 29.25-29.60;
31.81-31.84 (CH2); 62.02 (CH2N=); 128.57 (C=C); 144.82; 145.50 (=CN).
Thermogravimetric analysis (TGA)
Figure 1 – Effect of the anion chemical nature associated to phosphonium ionic liquids:
evolution of the weight loss as a function of temperature (TGA, DTG) of the
(●) C18P Br-, (■) C18P I-, (♦) C18P PF6
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Supplementary Material (ESI) for Chemical Communications
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Differential scanning calorimetry (DSC)
Nomenclature
structure
Melting
Temperature (m.p)/ Glass
transition (Tg)
(°C)
Octadecyltriphenylphosphonium
iodide
m.p. = 86
Tg = 11
C18H37
P
C18P I-
I-
Octadecyltriphenylphosphonium
bromide
m.p. = 85
Tg = 12
C18H37
P
C18P Br-
Br-
Octadecyltriphenylphosphonium
hexafluorophosphate
m.p. = 80
Tg = -2
C18H37
P
-
C18P PF6
-
PF6
Octadecylpyridinium iodide
m.p. = 102
Tg = 44
C18Py I-
N
C18H37
I-
N-octadecyl-
m.p. = 64°C
Tg = 35
N
N
H37C18
C18H37
I-
N’octadecylimidazolium iodide
C18C18Im I-

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-
DSC curves of the PTFE/C18P I-, Br-, PF6
Table 1: Atomic percentage of species detected on the surface of PTFE films
X-Ray Photoelectron Spectroscopy
Atomic %
PTFE
C-F
59
97
C-C
30
3
PTFE 1%
C18P I-
PTFE 5%
C18P I-
93
88
5
PTFE 1%
12
C18C18Im I-