Morphological study of alkylsubstituted polyaniline

Synthetic Metals, 41-43 (1991) 761-764

761

MORPHOLOGICAL STUDY OF ALKYLSUBSTITUTED POLYANILINE

Sze-Ming Yang and Jyh-Horng Chiang Department of Chemical Engineering, Chung-Li,

Taiwan

National Central University

(R.O.C.)

ABSTRACT The

morphology

ethylaniline) The

morphology

consuming

of polyaniline,

poly(o-toluidine)

synthesized under various of

the

polymer

electric quantity.

quantity is slow,

is

conditions

controlled

by

and were the

When the rate of consuming

poly(2studied. rate

of

electric

fibrous structure was formed. While the rate of

consuming electric quantity is fast , short fibers with amorphous material

or granular

structure were

formed.

Substituents

large effect on the morphology of the polymer. group becomes be obtained,

larger,

have

a

As the substituent

the regular packing of the polymer

can not

the fibrous structure can hardly be formed.

INTRODUCTION Polyaniline

has recently

as a conducting polymer polymers

studied,

switching property

been the subject

of

intensive

[i]. Among the electro-conducting

polyaniline

is u n i q u e

in

its

study

organic

three-stage-

[2]. Substitution on the polymer chain provide

the possibility of fine tuning the switching property and improve the solubility and processibility systematic

morphological

substituted

polyaniline

effects

of the

studies

under

synthetic

[3]. In this study we report a of

various

conditions

polyaniline synthetic and

and

alkyl-

conditions.

substituents

can

The be

investigated. 0379-6779/91/$3.50

© Elsevier Sequoia/Printed in The Netherlands

762 EXPERIMENTAL Polyaniline, were

poly

synthesized

potential density

scan ( 5

synthetic several

(o-toluidine),

under

(i)

(scan rate ~ A / c m 2,

~ A / c m 2,

the

and

and

charge

poly

photograph

polymer

it

on

is

of

taken

the on

a

was

(2)

current

For

each

controlled

at

The s c a n n i n g e l e c t r o n

piece

Hitachi

constant

~A/cm2).

consumed

small

potential,

(3)

i00

levels ranging from 3 mC to 30 mC.

microscopic

(2-ethylaniline)

applied

is 50 mY/s),

30

conditions

and

constant

platinum

S-550

wire

scanning

with

electron

microscope.

RESULTS Polyaniline When

3 mC was

formed

under

consumed

consumed,

constant

there was

potential.

i n c r e a s e d to 7 mC,

a small

When

the

fibers of d i a m e t e r

w i t h some a m o r p h o u s m a t e r i a l were formed. 0.3

~m

diameter

were

amount

formed

and

Above

granular

of

electric

polymer

quantity

0.01 ~ m 12 mC,

together fibers

structure

was

of

also

formed. The scan. grew

fibers When

and

fiber.

of

the

0.i

amorphous

The

~m

electric

fiber

diameter quantity

product

formed

was

under

were

formed

consumed formed

on

potential

under

increased, the

scan

potential more

outside was

fiber

of

longer

the than

those formed under controlled potential. Fibers

of

0.i

q u a n t i t y consumed, -0.4 ~ m

with

~m

diameter

were

formed

with

3

mC

electric

and the diameter of the fiber i n c r e a s e d to 0.2

16 mC consumed,

and change

into g r a n u l a r

structure

w i t h 30 mC c o n s u m e d under constant current d e n s i t y of 30 )/A/cm 2. W h e n the

c o n s u m e d e l e c t r i c q u a n t i t i e was c o n t r o l l e d

spite of the current density,

fiber structure was

at

3 mC,

always

in

formed.

Polv(o-toluidine~ Under

constant

potential

granular

structure

was

formed.

p o l y m e r formed under potential scan shows fibrous structure. fiber formed

grew

as

under

the

electric

constant

quantity

current

density

increased. of

The

30 )/A/cm 2

The More

polymer were

tiny

fibers c o a t e d w i t h amorphous material. As the e l e c t r i c q u a n t i t i e s increased formed was

the

the

fibers

granular

controlled

were

covered

structure.

at 3 mC,

by

When

amorphous the

electric

in spite of the current

c h a n g e in the m o r p h o l o g y was observed.

material

and

quantity

density,

little

763

Fig. I. S E M p h o t o g r a p h s of p o l y a n i l i n e , poly(o-toluidine) , poly(2-ethylaniline) formed under p o t e n t i a l scan w i t h 3 mC, 16 mC and 16 mC e l e c t r i c a l q u a n t i t i e s c o n s u m e d r e s p e c t i v e l y . Poly(2-ethylaniline) Under material

constant were

potential,

formed.

short

Granular

fibers

embedded

structure

was

in

amorphous

formed

under

764 potential

scan

between

-0.i

V

q u a n t i t y c o n s u m e d increases, structure.

The polymer

30 p A / c m 2 observed fibers

shows

under

granular

of d i a m e t e r

synthesized

formed

constant

to

0.9

V.

When

the granule grew. under c o n s t a n t

structure.

current

less than

of

0.1 Nm was

electric

current density

Similar

density

the

into a c o n t i n u o u s

morphology

100

formed

the

Short

polymer

under constant current d e n s i t y of 5}/A/cm 2.

The g r o w t h

of polymer can be separated

into two

steps:

on the

bare Pt e l e c t r o d e and on the p o l y a n i l i n e

coated electrode.

Pt

grown

is

highly

conductive,

the

e l e c t r o d e have dense structure. controlled rate

of

by the rate

consuming scan,

consuming

electric

potential

synthesis,

fibrous

electric

quantity

is slow

structure was

quantity

is fast

short

fibers

conductive

Pt electrode

islands

are

conductive

formed. is

the

Since

bare

The

When

in

the

While

the

in the

with

fast,

quantity. as

formed.

as

case

amorphous

of

Pt

of

rate

of

material

of

, some

polymer

granular

was

is less

is not u n i f o r m

growth the

the

case

constant

coated e l e c t r o d e

and the doping

region

on

The m o r p h o l o g y of the p o l y m e r is

The c o n d u c t i v i t y of p o l y a n i l i n e

than the bare

highly

polymer

of consuming

electric

potential

formed.

was

~ A / c m 2.

for

of

on

the

structure

is

formed. Substituents

have

a

large

effect

on

the

morphology

of

the

polymer.

As shown in figure i, when the s u b s t i t u e n t g r o u p becomes

larger,

the

Polyaniline potential

fibrous and

scan,

structure.

while

Under

polyaniline toluidine)

is

more

show

difficult

fibrous

poly(2-ethylaniline)

constant

always and

structure

poly(o-toluidine)

form

current fibrous

poly(2-ethylaniline)

density structure, form

to

structure show of

form. under

granular

30

~ A / c m 2,

while

poly(o-

granular

or

other

i r r e g u l a r structure.

ACKNOWLEDGEMENT F i n a n c i a l support from NSC, R e p u b l i c of China, u n d e r the grant NSC78-0208-M008-02

is acknowledged.

REFERENCES i. J. C. Chiang and A. G. MacDiarmid, 2. E. W. Paul, (1985)

A. J. Ricco,

Svnth. Met.,, 13

M. S. Wrighton,

J. Phys.

(1986)

193.

Chem.,

89

1441.

3. S. Wang,

F. Wang,

and X. Ge, Synth. Met.,

16 (1986)

99.