Vioux
1
UM
R 5
253 -
Insti
tut
de C
him
ie M
olé
cu
lair
eet
des M
até
riau
x d
e M
on
tpellie
r
UMR 5253 - CNRS, UM2, ENSCM, UM1
André Vioux
Ionogels: Ionic liquid based Ionogels: Ionic liquid based hybrid materialshybrid materials
Leuven Summer School on Ionic Liquids 2010
Outline
�Scope: ionogels
� What is it?
� What is not
�Different classes of ionogels, and their preparation
� From low molecular weight gelators to polymers
� From nanoparticulate additives to sol-gel processing
�Confinement effects: liquid behaviour?
� Physicochemical properties
� Dynamic molecular simulation
�Applications: multipurpose materials
� Electrolyte materials
� Nanocontainers, nanoreactors,
�Conclusion: ionogels as modular tunable materials
(a)
T Ueki et al. Macromolecules 2008
The concept: IL properties without leaking
What is a gel?
Thomas Graham used the term of « gel » in 1861.
Dorothy Jordon Lloyd (1926) :« the gel is easier to recognize than to define »
The inversed-tube test:
P. Flory (1974): A liquid–solid system �which features a continuous structure with
macroscopic dimensions�which is stable at the time scale of analysis�which behaves as a solid (rheology)
percolating solid network
�Physical gels (polymer gels, jellies, slurries or pastes)
�Chemical gels (cross-linked; brittle or flexible)
Vioux
2
(a)
A solid material which endows the IL with dimensional stability
Negligible vapor pressure of I.L.
Stable solid–liquid systems
Solid and liquid networks percolate throughout each other
The solid network may be organic, inorganic or hybrid
What is an ionogel (or ion gel) ? What is not: polymerisable ILs
(a)
H Ohno et al. Macromol Symp 2007
(a)
R K Donato et al. J. Appl Polym Sci 2010
Clays: e.g.
montmorillonite
Gilman et al.
Chem Mater
2002
carbon nanotubes
Bellayer et al.
Adv Funct Mater
2005
MWNT
What is not: use of Ils as compatibilizers
Borderline: SILP
Riisager, A. and al. Top. Catal. 2006, 40, 91
Supported IL Phases
Thin film of IL
Free flowing powders with up
to 25% wt of IL loading
Application in catalysis (SILC)
Vioux
3
Different classes of ionogels
�Organic gels
� Low molecular weight gelators
� Polymers and biopolymers
�Inorganic gels
� Ceramic nanoparticles, carbon nanotubes
� Sol-gel chemistry in ILs
�Hybrid O/I gels
� (Bio)polymers + (nano)fillers
� Hybrid solid network
PMMA
silica
PMMA/SiO2
K Lunstroot et al. PCCP 2010
M A Néouze et al. Chem Comm 2005
F Gayet et al. Chem Mater 2009
Organic ionogels
� Polymers
Solvent casting
Swelling of polymers with ILs
Polymerization of monomers in ILs
Key parameter:
Miscibility with the polymer
�Low molecular weight gelators
L-glutamic acids, derivatives of aspartame, cholesterol, amino acids
IL wt % > 50: need for some cross-linker
High compatibility of PMMA with imidazolium ILs
Scott et al Chem. Commun. 2002 Susan et al., JACS 2005
Thermal behaviour of PMMA ionogels
Jiang et al., React Funct Polym 2006
Mass fractions
DSCTGA
ILIL
PMMAPMMA
[BMIm][PF6]
Temperature dependence of ionic conductivity for PMMA ionogels
Mole fractions
Vogel-Tamman-
Fulcher
Susan et al., JACS 2005
« polymer-in-
salt » behavior
[EMIm][TFSI]
Vioux
4
Crosslinking + strengthening : covalently bonded silica nanofillers
f-PMMA:TEOS mass ratios = 70:30 or 60:40
Up to 90 wt % IL loading
Gayet et al. J Mater Chem 201045 50 55 60 65 70 75 80 85
10-5
10-4
10-3
105
106
107
σ / S
.cm
-1
Ionic Liquid Content / % wt
You
ng
Mo
du
lus E
/ P
a
Good compromise:
�Mechanical stability
�High ionic conductivity
[BMIm][TFSI]
Thermoreversible sol-gel transition
T P Lodge et al. Science 2008
red = PS (solvophobe) blue = PEO (solvophile)
[EMIm][TFSI]
T P Lodge et al. Nature Mater 2008
Ionogel gate dielectrics for flexible electronics
[EMIm][TFSI]
transistor
Special case of polysaccharides
Microwave pulse heating
120-170 °C
Dissolution of cellulose
R Rogers et al, JACS 2002
Regeneration into water
or gelation on humidity
7 days
Kadokawa et al, Carbohydr Res 2008
Vioux
5
Inorganic ionogels: Bucky gels
� Dispersion of SWCNT in ILs : « bucky tubes »
Fukushima Science 2003, 300, 2072
1wt% of SWCNTs ground into [BMIM[BF4]
Composites: elastic conductors for flexible electronicsTsuyoshi Sekitani et al., Science 2008, 1468
From the name of architect Richard Buckminster “Bucky” Fuller
Ionogels from oxide nanoparticles
Dispersions of silica nanoparticles in [Cnmim][X]
M Watanabe et al., J Phys Chem B 2008
Silica particle concentrations:
(a) neat [EMIm][TFSI], (b) 1 wt %,
(c) 3 wt %, (d) 5 wt %, and (e) 15 wt %
Gels with 90% of ILs
size<14 nm [C4mim][NTf2]
I Honma et al Chem Mater 2007
Coagulation of particles
Uruguay
Argentina
Estuary of Rio de La Plata: mixing of fresh water
(containing suspended solids) and ocean water (highly
saline) causes the aggregation of particles
Atlantic
Inorganic vs organic ionogels
(a)
K Ueno et al. J Phys Chem 2008
[BMIm][TFSI]
5 w% SiO2
about 10-2 Scm-1 at 30 °C
Vioux
6
Sol-gel processing in ILs
2 HC(O)OH + (CH3O)4Si SiO2 + 2 CH3OH + HC(O)OCH3
Sheng Dai et al. Chem. Commun., 2000, 243
“aerogel-like” SBET 720 m²/g; Vp 1.4 cm3/g
Non-aqueous route
IL as template and drying control chemical additive
Aqueous route
Y. Zhou et al., Chem. Mater., 2004, 16, 554H2O / HCl + (CH3O)4Si
lamellar
microporous
structure
Dp = 1.3 nm
[BMIm][TFSI]
Inorganic ionogels by sol-gel
No extraction of the IL : synthesis of ionogels
Vioux A. et al. Patent WO 2005/007746Chem. Commun. 2005, 1082
Progr.Solid State Chem. 2006, 33, 217
� Formic acid route
� Acidic hydrolysis
or
TEOS / EtOH / IL / HCl-H2O (5M)
Y Deng et al, Tetrahedron Lett 2004; Adv Synth Catal 2005; Eur J Chem 2005
The sol-gel method depends on the IL
TMOS / MTMOS 50:50
Role of the anion
ILs as catalysts : see also A. Pierre et al. Catal. Commun. 10, 359, 2009
N NCH3Bu
+
H
HCOOH HCl / H2O Neutral H2O
BMIm Cl 2 days liquid after 4 weeks liquid after 4 weeks
Transparent monolithliquid liquid
BMIm BF4 4h 3 days 3 days
White precipitate Transparent monolith Transparent monolith
BMIm NTf2 < 12 h 5 days 3 h
Transparent monolith Two phases: liquid + solid
No gelation
Cl<NTF2<BF4 Cl<<<<BF4∼∼∼∼NTF2 Cl<<NTF2<<BF4
Inorganic vs organic ionogels
(a)log (
σT
)1000 / T /K-1
x= i.l. / silicaIonic liquid
2.0 2.5 3.0 3.5 4.0-3
-2
-1
0
1
x=0.25
x=0.5
x=1
[BMI][TFSI]
x= [BMIm][TFSI] / SiO2 molar ratio
x ↑↑↑↑ ⇒⇒⇒⇒ log(σσσσionogelT) ↑↑↑↑ up to log(σσσσi.l.T)
Vioux
7
Confinement effects: solid or liquid?
�Interconnected porosity�Mesoporous skeleton
0.0 0.2 0.4 0.6 0.8 1.0
0
200
400
600
800
1000
0 10 20 30 40 50 60 70 80-0.5
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
dV
/ d
logD
(cm
3.g
-1)
pore diameter (nm)
vo
lum
e s
orb
ed
(cm
3.g
-1)
relative pressure (P/P0)
200 300 400 500
0,00
0,02
0,04
0,06
0,08
⇒ 3.10-2 S.cm-1 at 200°C
Only ½ lower than bulk ionic liquid
Temperature / K
σσσσ / S.cm-1
[BMIm][TFSI]
Ionogel x= 0.5
�3-D interpenetrated continuous networks
�Ionic liq. vol. ≈ 3x SiO2 vol.
After washing with acetonitrile
SBET = 785 m2g-1
Vp = 1.51 cm3g-1
Dp = 12 nm
i.l. / SiO2 molar ratio x= 0.5
Differential Scanning Calorimetry
-100 -50 0 50 100 150 200-30
-25
-20
-15
-10
-5
0
5
10 exo
arb
itra
ry u
nits
Temperature (°C)
Crystallization –37°C (236 K)then melting – 6°C (267 K)
cooling –80 °C.min-1
heating 5 °C.min-1
bulk ionic liquid
[BMI][TFSI]glass transition
-89°C (184 K)
[BMIm][TFSI]
Effect of confinement on DSC
x= 0.5 ⇒⇒⇒⇒ disappearance of crystallization and melting
-0,04
-0,02
0
0,02
0,04
0,06
0,08
0,1
160 180 200 220 240 260 280 300
Temperature (°K)
Heat
flow
(m
W/m
g)
-1,5
-0,5
0,5
160 200 240 280
[BMI][TFSI]
bulk i.l. bulk i.l.
x= 1 ⇒⇒⇒⇒ shift of the crystallization and melting peaks
Chem.Mater. 2006, 18, 3931
x= [BMIm][TFSI] / SiO2 molar ratio
Effect of confinement on 1H NMR
spectra at r.t.
10 8 6 4 2 0δ / ppm
ionogel 3kHz
******ionogel 0.4kHz
Inte
nsity / a
.u.
ionogel 0kHz
[BMI][TFSI]
Monolith ionogels [BMIm][TFSI] / TMOS = 0.5
However complete resolution was not recovered on ↑ spinning rate
⇒ interactions with pore walls
No spinning rate!
Phys. Chem. Chem. Phys., 2007, 9, 5419
Vioux
8
Relaxation time T1 vs Temperature
200 220 240 260 280 300 320 340 360 380 4000
200
400
600
800
1000
1200
1400
IL H2 IL H4-5 IL H3 IL H1a IL H1b IL H1c IL H1d IL H1a-d/2/3/4-5 x=0.5 ionogel
T1 / m
s
T / K
2
1a
1b
1c
1d
45
3
No phase transition near 270 K in the ionogel
Broad minimum near 270 K (for ωL.τc ≈ 1)
9.4 T; 400 MHz
ωL.τc ≈ 1 ⇒ correlation time at 270 K ≈ 0.4 ns
ωL.τc > 1 ⇒ correlation time below 270 K > 0.4 ns
Other confinement effects
Fluorescence of [N(CN)2]-
J Zhang et al. Phys Chem Chem Phys 2010
CO2 desorption profiles
27.8 % loading
Confinement effects: molecular dynamic simulation
Dr Benoit Coasne ICGM (submitted)
[BMIm][TFSI]
Confinement effects: molecular dynamic simulation
Dcation (10-8
cm2/s)
Danion (10-8
cm2/s)
⌠⌠⌠⌠(mS/cm)
25%
loaded IL
1.0 (1) 0.7 (1) 4 (2)
50%
loaded IL
3.5 (1) 3.5 (1) 7 (2)
100%
loaded IL
7.8 (1) 7.7 (1) 14 (2)
Bulk IL 12 (1) 8.7 (1) 17 (3)
Dr Benoit Coasne ICGM (submitted)
[BMIm][TFSI]
Vioux
9
Ionogels, multipurpose materials Lithium batteries
Armand et al. Nature Mater 2009
Lithium batteries
☺☺☺☺More safety
����
Viscosity ↑ on adding Li salt
PVdF-HFP copolymer
Li[(CF3SO2)2N]
PEM for Fuel Cells
Temp. >100°C
Proton conductive ILs
T L Greaves et al. Chem Rev 2008
Conductivity does
not depend on RH
Leaching!
☺☺☺☺
����
Vioux
10
Dye-Sensitized Solar Cells
electrolyte A flexible dye-sensitized solar
cell with a solvent-free ionic
liquid electrolyte
(courtesy G24i Ltd.)
Eutectic melts of 3 solid
imidazolium iodides
M Graetzel et al.
Nature Mater 2008
Elctrochromic displays
P Vidinha et al.
Chem Comm 2008
1
Glass-ITO/ PEDOT/
ionogel/ Prussian
Blue/ ITO-glass
2
[BMIm][Cl]@gelatin
Actuators
c)
d)
Mukai et al, Adv Mater 2009
Catalysis
Volland et al New J. Chem. 2009
Encapsulation of
Pd(OAc)2
The ionogel was put
in a glass basket
and soaked in the
toluene solution
� No leaching of active Pd species
�Trace analysis of Pd in the filtrate ICP-MS : ~1 ppm
�HNEt3 salts trapped in the gel � easier purification
�But no reclycing
Heck-Mizoroki coupling reaction
[BMIm][TFSI]@SiO2
Vioux
11
CF3
O
O
Eu3+
4
N
N
-
Collaboration with Prof K Binnemans, Leuven
[BMIm][TFSI] ionic liquid confined in TMOS/MTMS 1/1 gel
Chem. Mater. 2006, 18, 5711
K Lunstroot’s thesis
Optics : insertion of Ln complexes
5Do→7F2
87%
�Intense photoluminescence at 16 353 cm-1 (612 nm)
�High monochromatic purity
�Average time decays: i.l. 0.55 ms; ionogel 0.52 ms; solid 0.35 ms
18000 15000 12000
600 700 800
Inte
nsity (
a.u
.)
wavenumber (cm-1)
wavelength (nm)
a b
c
d ef g
Synthesis of ionogels containing an API
Si(OR)4 + H2O / HCl
���� molar ratios: Si/ IL = 1 / 0.25
100 0
75 25
50 50
Pre-hydrolysis
COO-
N
N� Hydrolytic sol-gel synthesis
+
� Modulation of matrix hydophobicity
0.70 to 0.87 g Ibuprofen / g SiO2
MCM 41: 0.50 to 0.65 g Ibuprofen / g
Active Pharmaceutical
Ingredient
Viau et al, Chem Comm 2009
Drug release
Temperature : 37°C
Simulated intestinal medium :
KH2PO4 0,05M pH 7,4
Kinetics measured by HPLC
release modulated by
MTMOS/TMOS
Viau et al, Chem Comm 2009
Ionogels, modular tunable materials
Functional devices
Designing the guest IL phase
�choice of the ion pair
�synthesis of task-specific ions
�blending of ILs
�functional solute (metal complex
etc.)
Designing the host support
�nature (inorganic, organic, hybrid)
�structure (cross-linking; porosity)
�control of confinement or
plasticizing effects
Casting, coating
(pellet, film etc.)IL loading %