2010/8/12

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Polymerized Ionic Liquids

Hiroyuki OhnoDepartment of Biotechnology,

Tokyo University of Agriculture and Technology

Tokyo, Japan

Leuven Summer School

27ｔｈ Ａｕｇｕｓｔ ２０１０

Why should ionic liquids be polymerized?

Ionic liquids are very interesting materials

because they are liquid salts!

Why should ionic liquids be polymerized?

What kind of new properties are expected after polymerization?

Why should ionic liquids be polymerized?

They should be charged polymers with very low glass transition

temperature!

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Flexible salt!

Polym e rizable ILs

Polymerization of vinylimidazolium salt

N

N

HC

CH2CH3

CH2

TFSI-

N

N

CH

CH2CH3

CH2

TFSI-

n

H. Ohno and K. Ito, Chem. Lett., 751 (1998)

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Polymerization of ILｓ

• Thin, light weight, and flexible films

• High ionic conductivity

• Controllable permeability

• Thermal stability

• Transparent films

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Ion c onduc t ive

po lym e rs

Ion Conductive Polymers need

high ion concentration and

their fast migration.

These are mainly performed by

high polarity and low glass

transition temperature of the

polymers.

Ion Conductive Polymers

Poly(ethylene oxide) (PEO)

is an excellent polymer

matrix for ion conduction

due to

high polarity and low glass

transition temperature.

Poly(ethylene oxide) (PEO)

is polar enough to dissociate

salts, but ether oxygen is a

strong Lewis base to interact

with cations such as Li+

preferentially.

And therefore it is NOT

suitable for cation conductors.

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Are there any polymer

system except for PEOs?

Polar polymers with no

cation affinity?

-CH2CH

2O- vs. -CH

2CH

2B-

|

“Selective ion transport in organoboron polymer electrolytes bearing

mesitylboron unit” H. Ohno,et al., Macromolecules, 35, 5731 (2002)

Are there any polymer

system except for PEOs?

Polar polymers with low Tg?

How about polymers

derived from ionic liquids?

Polymerized ILs

as ion conductor

Ionic liquids:

liquids composed of only ions!!

Moderate polarity

Thermal/chemical stability

Solubility (affinity) with several

compounds

Low

viscosity

Low melting point

Ion conductive materials

for

Electrochemical devices

Solvents

for

Chemical reactions

Non-volatility

Non-flammability

Variation of ion structure

High ionic

conductivity

Ionic liquids

They may have …

?

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Cation Anion Tm/℃

801Na+

SN

SO

O

CF3O

O

F3C

645

87

38

15

-15

Cs+ Cl-

NO3

-

BF4

-

N N

N N

N N

N N

241(Pr)4N+

Cl-

Cl-

Cl-

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Polymerization of

ionic liquids

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Polymerization of Ionic Liquids

Ionic liquids

Polymer blend

Polycation

Polyanion

N N

R1R2

X-

Zwitterionic-type

polymer

Copolymer

H. Ohno and K. Ito,

Chem. Lett., 751 (1998)

Polymerization of vinylimidazolium salt

-8

-6

-4

-2

3 3.1 3.2 3.3 3.4 3.5 3.6

1000 T-1 / K-1

Ion

ic c

on

du

ctivity lo

g(s

i/

S c

m-1

)

Figure Temperature dependence of the ionic conductivity

for ionic liquid monomer and its polymer.

Polymerization

N

N

HC

CH2CH3

CH2

TFSI-

N

N

CH

CH2CH3

CH2

TFSI-

n

H. Ohno and K. Ito, Chem. Lett., 751 (1998)

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How to minimize the conductivity drop after polymerization?

X- = Br- or TFSI-

X- = Cl- or TFSI-

n = 2 or 8

m = 1.5, 3, or 6

H2C C

C

CH3

OO CH2CH2O CH2CH2 N NEt

X-

H2C CH

C

OO CH2CH2 N NCH2CH3

X-

m

n-1

Use of spacers!

Ionic liquid polymer brush

as flexible salts

Conductive pathIonic liquid

Flexible spacer

Vinyl polymer

M. Yoshizawa and H. Ohno, Chem. Lett., 889 (1999)

M. Yoshizawa and H. Ohno, Electrochim. Acta., 46, 1723 (2001)

-8

-7

-6

-5

-4

-3

-2

3.0 3.1 3.2 3.3 3.4 3.5 3.6

Ionic conductivity of IL polymer brush

1000 T-1 / K-1

Ion

ic c

on

du

ctivity lo

g(s

i/

S c

m-1

)

Figure Temperature dependence of the ionic

conductivity for ionic liquid-type polymer brush.

TFSI-

Cl-

Monomers

Polymers

Effects of spacer length and ether oxygen

-6

-5

-4

-3

0 2 4 6 8

Spacer unit number

log

(si/ S

cm

-1)

at

30

oC

Figure Effect of spacer length on the ionic

conductivity for ionic liquid-polymer brush

CH2CH2 n

CH2CH2 On

N

N

CH CH2

Et

TFSI-

n

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-6

-5

-4

-3

-2

3.0 3.2 3.4 3.6

Polymerized IL film as flexible salts

log

(s

i/

S c

m-1

)

1000 T-1 / K-1

Network-type

Polymer

Monomer

Fig. Temperature dependence of ionic conductivity for

ionic liquid monomer and its polymer

Task sharing

O

O

Spacer Salt

NCF3SO2 SO2CF3

Polymerizablegroup

MIm: R1 = CH3, R2 = H

EIm: R1 = C2H5, R2 = H

E2M: R1 = C2H5, R2 = CH3

BIm: R1 = C4H9, R2 = H

N NR1

R2

N

N

N

R3

MPr

EPy

MP: R3 = CH3

σi / S cm–1 at 30 oC Tg / oC

MIm 1.2 ×10–3 –75

EIm 1.1 ×10–3 –81

E2MIm 6.8 ×10–4 –68

BIm 1.4 ×10–3 –77

MPr 1.2 ×10–3 –75

EPy 9.2 ×10–4 –77

MP 5.5 ×10–4 –66

Table Properties of monomeric ionic liquid

C6

H. Ohno et al., Electrochim. Acta, 51, 2614 (2006)

Effect of cation structure on properties of PILs

Table Properties of polymerized ionic liquids

σi /Scm-1 at 30oC Tg / oC Td /oC State

mim 4.4 ×10–5 –53 371 Film

eim 1.4 ×10–4 –59 381 Sticky solid

e2mim 8.5 ×10–6 –42 389 Film

bim 4.1 ×10–5 –51 382 Film

MPr 2.4 ×10–5 –43 371 Sticky solid

EPy 2.1 ×10–5 –40 372 Sticky solid

MP 6.2 ×10–6 –38 362 Film

Effect of cation structure on properties of PILs

H. Ohno et al., Electrochim. Acta, 51, 2614 (2006)

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Anion species

Polymer

si / S cm−1

at 30 oCTd / oC Tg / oC

BF4 7.8 x 10−6 283 −45

PF6 3.7 x 10−8 319 −21

CF3COO 2.4 x 10−5 165 −63

CF3SO3 1.5 x 10−6 265 −35

TFSI 1.2 x 10−4 381 −59

BETI 6.8 x 10−5 382 −54

TFSI

BETI

Fig. Comparison of Raman spectra of PILs

and 1-ethyl-3-methylimidazolium TFSI in the

710-780 cm−1 region.

Ion pair or AggregateFree ion

Frequency / cm−1

δs(CF3)

CF3SO3

Table Properties of PILs

EMImTFSIN NO

O

Et

n

Effect of anion structure on properties of PILs

-10

-9

-8

-7

-6

-5

3.0 3.1 3.2 3.3 3.4 3.5

Copolymers

Fig. Temperature dependence of the ionic conductivity

for ionic liquid copolymers containing equimolar Li salt.

1000 T-1 / K-1

Ion

ic c

on

du

ctivity lo

g(s

i /

S c

m-1

)

SO3- N

HN

m n

+ LiX

TFSI

BF4

CF3SO3

Effect of spacer

-9

-8

-7

-6

-5

-4

3.0 3.1 3.2 3.3 3.4 3.5 3.6

1000 T-1 / K-1

Ion

ic c

on

du

ctivity lo

g(s

i /

S c

m-1

)

Fig. Temperature dependence of the ionic conductivity

for ionic liquid copolymers containing equimolar Li salt.

m n

m n

Salt concentration dependence

LiTFSI concentration / mol% to imidazolium unit

Figure Effect of salt concentration on the ionic conductivity

for ionic liquid copolymers.

-9

-8

-7

-6

-5

-4

0 50 100 150 200 250 300

log

(si/

S c

m-1

) a

t 3

0 o

C

SO3 N

N

H

m n

N

N

H

m n

O O

SO3

+ x(LiTFSI)

+ x(LiTFSI)

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Amphoteric polyelectrolyte

O N

O

NEt

NCF3SO2 SO2CF3

nO

O

O SO3Li

R

m

O

N,N’-dialkylimidazolium salt type ionic liquid monomer High ionic conductivity Relatively stable with lithium metal

Poly(alkylene oxide)benzensulfonic acid lithium salt type monomer Single ion conductive material

Copolymerization

Li＋

X－

Selective ion conduction in ionic liquid derivatives

Zwitterionic liquid

Li＋X－

Copolymerized Ionic Liquids (CoILs)

Task Sharing!

Polymer Solid

-8

-7

-6

-5

-4

-3

0.0

0.2

0.4

0.6

0.8

1.0

0 20 40 60 80 100

Fig. Ionic conductivity and lithium transference number (tLi+) for A6-B8copolymers with different composition

log

(s

i/ S

cm

-1)

at

30 o

C

t Li+

at

30

oC

B8 concentration / mol%

B8 (Li+) richA6 (TFSI–) richN

CF3SO2 SO2CF3

N N

Et O

SO3Li

8

O

Relation between tLi+ and monomer fraction

H. Ohno et al., Polymer J., 38, 117 (2006)

X－ Li＋

x y

x = y

x > y

X－ Li＋X－

High mobility of carrier ions

Low Li+ concentration

x < y

X－ Li＋ Li＋

High Li+ concentration

Low mobility of carrier ions

Generate lithium ionConstruct

ion conductive pathway

Control of CoIL properties

By changing composition…

Organic/Inorganic

hybrid system

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Proton conductive ILs

Fig. Temperature dependence on the ionic conductivity

of Brønsted Acidic Ionic Liquid.

HTFSI : zwitterion = 2 : 3 (mol/mol)

Non-volatile Brønsted Acid

Td ＞ 300 oC

(HTFSI < zwitterion)

M. Yoshizawa and H. Ohno,

Chem. Commun., 2004, 1828

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Synthesis of

Organic/Inorganic Hybrid systems

HTFSI : zwitterion = 1 : 1 , 2 : 3 , 1 : 2 (mol/mol)

zwitterion : Si(OCH3)4 = 1 : 1 , 2 : 1 (wt/wt)

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Control of physical properties

a b c D

HTFSI

:

zwitterion

(mol / mol)

1 : 1 1 : 1 1 : 2 2 : 3

zwitterion

:

Si(OCH3)4

(wt / wt)

2 : 1 1 : 1 1 : 1 1 : 1

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Thermal stability

TG curve for proton conductive system

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43TG curve of the mixture kept at 200℃

Thermal stability

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Arrhenius plots of ionic conductivity for a series of hybrids

Ionic liquid only

HTFSI/ zwitterion

= 1 : 1 (mol/mol)

HTFSI/ zwitterion

= 1 : 2 (mol/mol)

Ceramic

12%

21%

24%

Use of DNA

Use of DNAs

DNA should be used more

frequently for the

electrochemical fields!

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Electrolyte polymersOrdered structureRigid rodHydrophobic domainStacked base pairsetc

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Td before neutralization.

Tg after neutralization of bases with HTFSI

Bases in DNA are

p-conjugated aromatic rings!

Td(℃) Tg(℃)

Adenine 325 -13.2

Cytosine 330 -30.8

Guanine 320 ー

Thymine 320 ーC・TFSI

Nucleic Acid Bases were Ionic Liquidized by HTFSI!

48Fig. Temperature dependence of ionic conductivity for

bases neutralized with HTFSI.

C・TFSI

Tg:-30.8 C

A・TFSI

Tg:-13.2 C-9.0

-8.0

-7.0

-6.0

-5.0

-4.0

3 3.1 3.2 3.3 3.4 3.5 3.6

log

(siS

/cm

)

1000/T (K-1)

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-9

-8

-7

-6

-5

-4

0 20 40 60 80 100

C・TFSI

log

(s

i S

/cm

)

Added Ionic Liquid Concentration (wt%)

-8

-7

-6

-5

-4

0 20 40 60 80 100

Fig. Effect of added C・TFSI concentration on the ionic conductivity at 50 oC

DNA・BF4

film

50

-8

-6

-4

-2

0 20 40 60 80 100

Added Ionic Liquid Concentration (wt%)

log

(s

i S

/cm

)

Fig. Effect of added EImBF4 concentration on the ionic

conductivity at 50 oC

EImBF4

DNA・BF4

film

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DNA robed with

ionic liquids

Ionic liquidized DNA

53

R1＝C2H5、C4H7、C8H15

R2＝C12H23

OP

O

O-

O

O

P

O

O-

O

Br-Na+

OP

O

OH

O

O

P

O

O-

ON N

R1 + Me

OH-

H2O

NaBr

N NR1 + Me

N NR2 + MeN N

R2 + Me

Preparation

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S.C.Erfurth and W.L.Peticolas,

(1975) Biopolymers, 14, 247

98℃

25℃

1240cm-1

Thymine

1094cm-1

PO2-

Single strand

Double strand

W-helix was maintained!

1300 1200 1100 1000 900

Int.

Raman Shift (cm-1)

Ｒ１＝Ｃ2Ｈ5

Ｃ4Ｈ9

Ｃ8Ｈ17

Ｃ12Ｈ25

NaDNA

PO2-T

Fig. Raman spectra of Im-DNA.

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Alkyl chain length

log

(s

i S

/cm

)

Fig. Effect of alkyl chain length of imidazolium cation on the

ionic conductivity at 100 oC.

Longer alkyl chain length

-8.0

-7.5

-7.0

-6.5

-6.0

-5.5

0 2 4 6 8 10 12 14

56Fig. Effect of added EImBF4 concentration on the ionic

conductivity of EMI-DNA at 50 oC

Added Salt Concentration (wt%)

log

(siS

/cm

)

EImBF4

film

EMI-DNA

-8

-6

-4

-2

0 20 40 60 80 100

film

-

+

+

-

-

+

DNA/IL mixture

H. Ohno et al., J. Electrochem. Soc., 2001, 148, E168-E170.

PEO-modifedDNA

N. Nishimura et al., Polym. Adv. Technol.,2004, 15, 335-339.

-+

+

--

+

PEO/DNA Composite

H. Ohno et al., Chem. Lett.,2000, 642-643.

-

+

+

-

-

+

Ionic Liquidized DNA(inside)

+ -

-

-

+

+

+ -

-

-

+

+

N. Nishimura et al., J. Mater. Chem.,

2002, 12, 2299-2304.

Ionic Liquidized DNA(outside)

++ + + +

++

+

+

+

+

++

+ ++ + + +

++

+

+

+

+

++

+

N.Nishimura et al., Biomaterials, 2005,

26, 5558-5563.

2.79x10-3S/cm 2.91x10-4S/cm

6.43x10-5S/cm

1.8x10-4S/cm

2.17x10-3S/cm

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The answer is “Yes”.

Functional design including polymerization of

the ionic liquids is not so difficult but

generally accompanied by the deterioration of

their characteristics.

They are however very interesting materials

those have never been found before.

Are ionic liquids excellent

materials to prepare

ion conductive polymes?

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MEXT and JSPS (#21225007, 17073005)

21st Century COE Program, TUAT

Acknowledgements