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UMR 5253 - CNRS, UM2, ENSCM, UM1

André Vioux

Ionogels: Ionic liquid based Ionogels: Ionic liquid based hybrid materialshybrid materials

andre.vioux@univ-montp2.fr

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)

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(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)

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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]

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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

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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

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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)

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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

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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]

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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!

☺☺☺☺

����

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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

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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 %