Characterizaton of polyaniline blends with AC impedance measurements

ELSEVIER

Synthetic

Characterization

of polyaniline

‘UNIAX bNeste

Metals

Corp.,

Oy, Chemicals,

69 (1995)

blends

with

237-238

AC impedance

P. Passiniemi%’

and K. V&kipartab

5375

Rd.,Santa

Overpass

Conducting

Polymers,

Barbara,

P.O. Box

measurements

CA93 11, USA

310,

FIN-06101

with

both

Porvoo,

Finland

Abstract Electrical

conductivity

impedance

diagrams

conducting

polymer

high

a parallel

PAN1

has

measured

a very

high

can be attributed

In both

resistor-

has been

salt

The difference

and capacitance.

from

polyaniline

casted

matrices.

conductivity

composed

of protonated

solution

cases

capacitor

to the level

the equivalent

circuit

in series

capacitance circuit,

with

1. INTRODUCTION AC impedance

which

mers

[l].

Recently,

racterization ducting induced which

mechanisms

the method

of pure

polymers

tor circuit.

to be a powerful

reaction

has been

conducting

The

capacitor

double

layers

are separated

can

extended

polymer

can be described

tool in characteriof conducting

into the cha-

samples

with a parallel

be imagined

on the surfaces

of

by non-conducting

poly-

[2,3].

Con-

resistor-capacl-

to be formed conducting

polymer

from

particles

layers.

Someti-

currents.

with

PANI

of the conducting

describes

According

melt fib&

the conduction

to the AC

processed

into

and particles

behaviour

non-

having

of the material,

is

a resistor.

tivity

has proven

electrochemical

and alternating

compared

of distribution

measurtements.

voltage zing

direct

value

wires

was measured analyzer

In

the AC

of the four-probe

se. To avoid

problems

wires,

1 m coaxial

either Both

open

impedance

The

to be in the linear

caused

and

mode.

short

impedance

amplitude

region

by the impedance

cable

or

circuit

were done whenever

16047A

was

of respon-

of the probe

Test

corrections

inner

AC impedance

low frequency

in the average

was checked

the two

were used.

with Hewlett-Packard’s

(HP4192A)

100 mV which

used.

measurements

system

Fixture

were

for the measured

they had significant

effect

(most-

ly at > 5 MHz).

mes, an unexpected inductive etrect has also been found [3]. In this work we will present AC impedance results for pure PANI

salts

blended

as well as for blends

into

a non-conducting

lies on that how other

a pure

where matrix

PANI

conducting polymer.

salt and a blend

PANI Special

dither

salt is

3. RESULTS

from

each

3.1. PAN1 salts

in the AC behaviour.

Films

2. EXPERIMENTAL Protonated

polyaniline

prepared

conducting were

“Neste

delivered

P2H-AT).

salts,

PANI*HCl,,5

as is described complex”

by Neste

The materials

and PANI*DBSA,,

in the literature (Neste-C)

and LDPE

Oy and ABS were

used

by Bayer

as such

(NCPE75 AG

without

18)

(Novodur

f-urther treat-

Extruded miniextruder

samples

were

done

in ca. 4 gm batches

vity measurements

thin films,

xylene Narrow

conductivity

with

a corotating

4 w-O/b solution

(o(4-probe,

small

part up to 3 MHz

capacitive

circuit

from already

with

typical

circuit

Sicm)

(phase

(o(4-probe,

of

from the

only

a very

< 2”) whereas

a

DC) = 50 S/cm)

of a resistor-capacitor

The contact

with

had

angle

part (~~~10

in Fig.1)

strongly

pF/cm,

parallel

related

resistance

to the

of the glued

(ca. 70 % of the total resistan-

the measured

impedance

at higher

Some

3.2. Polymer blends containing PAN1

ca. 100 pm, were pressed films

were

solution

casted

Fig. of blends the complex

measurements

imaginary

paste.

A four-probe

and wires system

were glued

onto them with

was used in the DC conduc-

dance

1 shows with

curve

Neste

correspondence Oy,

101 Porvoo,

0379-6779/95/$09.50

Corporate

should be addressed; Technology, P.O.

permanent Box 310,

is a semi-

0

1995 Elsevier

SSDI 0379-6779(94)02432-X

Science

S.A. All rights

reserved

PANI.

circle

impedance unit,

circuit

as a Nyquist

Z(o)

the real part

describing

AC behaviour

The corresponding

= Re{Z}

AC

(or Argand) + iIm{Z),

is on the x-axis

impe-

plot: from i is the

where

and the imaginary

part on the y-axis. discontinuous ducting

C,

is a double

distribution

medium.

to another.

Finland

an equivalent

protonated

In the circuit address:

behaviour

capacitive

was very high in both cases

ce) interfering

solutions or cold-pressed from PANI-salt powder. strips (width ca. 3 mm) were cut from films for

*) To whom FIN-06

1 w-o/b solution

a high

equivalent wires

the

DC) = 240

solutions

a film cast

twin-screw

(100 ‘pm, 5 min). For conducti-

thickness

at 190 “C and ca. 50 kNicm*.

graphite

pm) cast from xylene

high conductivity:

frequencies.

ment.

from

65-85

had very

showed

[4]. Electrically

(thicknesses

PANI*DBSA,,

film cast were

AND DISCUSSION

interest

R, is a resistance

Rb is the

layer

of conducting

resistivity

capacitance material

caused

from one conducting inside

by a

in a less con-

the conducting

particle particles.

238

P. Passiniemi

K. Viikipatia I Synthetic Metals 69 (1995) 237-238

w/w-%).

Contact

meters

+5-

om=l bulk

resistance

for the mS/cm

equivalent (R,=l97

conductivity

c

only nF/cm

kg)

is

are:

and

in the conductivity

1. Equivalent In Fig.

pressed

2 are

from

Impedance which

circuit

blend.

This

model

in Fig.1.

tits

plotted

readings

were

results

5 and

reases

conductivity

from

ting

“wet” form.

ever

much

detailed

It is possible

In the following

ponding want

intensive

to stress

circuit

in Fig.

100 pm

thick

mixing

ratio.

C,

resistance.

value

well

with

The

achieved the

role of

by increasing

conducRr, how-

estimate

and

values

for C,

and R,,

parameters

20

1 and are not necessarily

50

100

150

200

Reg)/kohm

R, the

4-probe

resis-

o permittivity

are related

0

+

of R and C the corres-

conductivity

??

and

= R,

at the top of the semi-circel, the measured

I

the value

has C,

li(w_R,)

??

40

it also

=

??

We

for the better

and R,

quantities

the

pF),

kR).

??

60

resistances

values

we will use instead

that these

ca.

of the film at 55 “C dec-

We can roughly

R,, a&i, being the frequency diameter of the semi-circle tance.

that

the relationships

(Cd=15

(Rb=O.l

??

??

80

w-%

15 O/b of the overall drying

plot.

the contact

30 to 3 mS/cm

get more

smaller.

Ri, by using

in 20/80

against

can first of all see that vacuum of R,. We cannot

Nyquisi

for a film.

blend

are corrected

between

1 %. The para-

Ill

for a semi-circle

a Neste-CABS

S/cm

near to

100 Figure

~“3

4x2

surprising

for the Neste-CABS b

was in this case circuit

E. We

Figure

3. Nyquist

blend

(30/70

plot

w/w-%).

for a film

pressed

Frequency

from

Neste-C/LDPE

scan is 1 kH.z

10 MHz.

to the equivalent

true materiai

parameters.

PANI*DBSA extend

also

scale

films solution

a semi-circle

cast from xylene

behaviour.

of Fig. 2 or 3 that semicircle

Thus,

casted

work

of conducting

pure

PAN1

films

tibrils

showed

However, would

shrink

are composed

between

to some

if put

into

near

of continuous

which

are

less

the

to origin. net-

conducting

regions. This leads there

us to think

is a self-similarity

but on a different Thus,

?? ??

media

20

40

Re{Z}/kohm Figure

2. Nyquist (20/80

plot

w/w-%).

for

??: after

A: film as such.

a film

Frequency

pressed

scan is from

drying

Neste-CABS

~~~0.9 S/cm

parameters nF/cm

(Cd=6

(R,,=O.l

kn).

w), is a typical PAN1 salt resistance

(related

20 hrs in vacuum

value

powder.

tell whether Another

However, effects

example

ca. 100 pm thick

for DC

for

mS/cm

the

feature

dried

in

kcZ) and a

could

island

[5]).

be characterized

by

are applied

to conducting

of semiconducting

a small

amount

base,

is enough

itself,

model

the question

to this question

approaching

1. G. Sandi

in the resistance

within

this accuracy is plotted

from a Neste-CiLDPE

are: ob=2

a(w+

cold-pressed

in this example

also on the intra-particle

film ressed

film

value,u,=

occurs

of the semi-circle

such

metal

composite

of self-similarities

of PAN1 polymer. for electrical

is multiple

of semi-circles

< 1 9/o

conductivi-

percolation

[S] which

of smaller

and smaller

the origin.

REFERENCES

at 55 “C.

(R,,,=51

conductivity

conductivity

due to drying

particles. water

o&=3

the bulk

A striking

increase

conducting

pF), The

to Fig.1)

models

to view

blends

10 kHZ to 5 MHz. 2. D.

The

fractal

also lead to a series

diameter

from

why

way

as emeraldine

ty. One answer would

blends

[6] as also to impedances

calculated

60

that these

polymer

to the PANI-complex

(cf. segregated

Indeed,

[7]. Another

is to inspect

0

blend

geometry.

polymers

om

’

scale

one may think

fractal

that in the conducting extending

is that the between we cannot

conductivity. in Fig. 3 for a blend

(30170

C.

and P. Vanjsek, Ttivedi

and

Syuth.

S. K.

Met,

Dhawan,

64(1994)1. Polym.

Adv.

Technol,

4(1993)335. 3. Y. Li and R. Quian, 4. Y. Cao,

Synth. Met.,

A. Andreatta,

A.J.

55-57(1993)

Heeger

and

3637.

P. Smith,

Polymer,

30(1989)2305. 5. M. Angelopoulos, 21(1987)

A. Ray

and A.G.

MacDiarmid&rth.

Met.,

21.

6. M. Aldissi,

A&.

7. M. Tomkiewicz, 8. K. Levon, 26(1993)4061.

Muter.,

4(1992)368.

Electrochim.

A. Margolina

and

Actu, A.Z.

38(1993)1923. Patashinsky,

Mucromol,