Synthesis of polypyrroles in the presence of ferric tetrafluoroborate

Synthetic Metals, 41-43 (1991) 373-376

SYNTHESIS OF POLYPYRROLES

373

IN THE PRESENCE OF FERRIC TETRAFLUORO-

BORATE

YU.A. DUBITSKY

and B.A. ZHUBANOV

Institute of Chemical I06 Krasin Street,

Sciences of the Kazakh

Alma-Ata,

480100,

Academy of Sciences,

(U.S.S.R.)

G.G. MARESCH Max-Planck-Institut Mainz

f~r Polymerforschung,

Postfach 3148,

D-6500

(F.R.G.)

ABSTRACT A new method of the synthesis on chemical

oxidation

based

of corresponding monomers by ferric tetra-

fluoroborate has been devised.

The polymers obtained are black

bulky powders with good ability been shown that polypyrrolee doped by tetrafluoroborate ductivity

of conducting polypyrroles,

for pressing into pellets.

synthesized by this procedure

counterions

It has are

and have an electrical

con-

up to go S/cm.

INTRODUCTION Chemical methods of oxidative polymerization derivatives have been recognized

dizing agents such as persulfates, etc have been used to produce However,

lead dioxide,

so-called

A variety

of oxi-

ferric chloride

"pyrrole black"

[I-~ .

in most cases t h e p o l y m e r s o b t a i n e d had p o o r e l e c t r i c a l

properties.

Preparation

successfully

of polypyrroles

accomplished using

and a r y l s u l p h o n a t e For p r e p a r a t i o n

[6]

by exchange r e a c t i o n sium t e t r a f l u o r o b o r a t e s

with salts

good c o n d u c t i v i t y with

perchlorate

was [5]

anions. agent,

by ou r method we have used a

ferric

between f e r r i c in

Soluble

tetrafluoroborate

chloride

acetone.

t o t h e v e r y poor s o l u b i l i t y solvents.

ferric

of polypyrroles

non-commercial oxidizing

organic

of pyrrole and its

for many years.

This

Fe(BF4) 3

and sodium or p o t a s -

reaction

is

possible

o f sodium and p o t a s s i u m c h l o r i d e s in

acetone,

due in

Fe(BF4) 3 may be r e c r y s t a l -

Abbreviations used: PPy = polypyrrole, PMPy = poly-N-methylpyrrole 0379-6779/91/$3.50

© Elsevier S e q u o i a ~ r i n t e d i n The Netherlands

374 lized

from i s o p r o p a n o l - a c e t o n e m i x t u r e

bright-yellow An o p t i m a l

crystals

(I:I)

and then used w i t h o u t

proportion

for

polymerization

is

in

t h e form o f

further

purification,

2, 2 - 2 . 5 moles o f

Fe(BF4) 3 per I mole o f monomer [ 7 ] . RESULTS

AND DISCUSSION

Synthesis

of polymers

At the first stage of our work we have conducted of pyrrole

and N-methylpyrrole

isopropanol,

acetone

lar reaction

with ferric

organic

and acetonitrile. tosylate

6

these conditions solvents

Thus,

polymerization such as ethanol,

as against

of simi-

of monomers

after oxidizing polymers

All polymers demonstrated

in the range 40 - 70 S/cm

(Table

However,

corresponding

of about 20 - 30%.

being pressed in pillets

ductivities for PMPy

during 3 days,

solvents

polymerization

solvents was gone rather slow.

with low yields

TABLE

in organic

in

under

were formed

obtained

in organic

good electrical

con-

for PPy and 2 - 6xIO "2 S/cm

I).

I

Properties

of polypyrroles

Solvent

synthesized

Reaction time, h

PPy 6,

ethanol isopropanol acetone acetonitrile water water hexane (interphase process)

72.0 72.0 72.0 72.0 0.3

S/cm

3.0

tions hem been also conducted. precipitates

were

~n thin powders

Yield,

90 of pyrrole

formed during

%

6 x I O 2, S/cm

25 25 20 30 80

4 4 3 6 --

80

6

and N-methylpyrrole

In both cases black 20 minutes.

they had very poor ability

which may be attributed

of Fe(BF4) 3 PMPy

60 60 40 70 --

The polymerization

in the presence

%

25 25 I5 30 75

70 in water solu-

unhomogeneous

However,

even if crushing

for pressing

to the low molecular

Yield,

weights

in pillets,

of the polymers

synthesized. The best results of pyrrole

cordance with and monomer solutions two phases

have been obtained

and N-methylpyrrole this procedure

oxidizing

in hexane or petroleum

a thin black

by interphase

in the presence

agent was solved in water

ether.

After mixing

films were instantly

and then polymerization

polymerization

of Fe(BF4) 3. In ac-

formed

of these two

on the board of

was gone very slow.

So,

to produce

375 polypyrroles

by i n t e r p h a s e method with good yields

stirring has been applicated.

an i n t e n s i v e

In that case thin bulky powders were

formed during 3 hours with the yields of about 70 - 80%.

These pow-

ders after drying in vacuum

and p r e s s i n g in pillars d e m o n s t r a t e d

high electrical properties.

Thus,

and of PMPy 6xIO "2 S/cm

conductivity

of PPy was 90 S/cm

(Table I).

Study of polymers Polypyrroles

s y n t h e s i z e d have been studied by elemental

and high resolution mass spectroscopy. all these polymers

analysis

It has been estimated

that

are doped by t e t r a f l u o r o b o r a t e c o u n t e r i o n s

and

their doping level is in the range 0.2 - 0.3. Due to full u n s o l u b i l i t y

of PPy and PMPy the most suitable method

of their study was EPR spectroscopy. BF~ anions is shown on fig.

EPR spectrum of PPy doped by

I.

4OO 300 X

20O IO0 0 -IO0

-

-200

-300 -400

I

I

I

3470

Fig.

I

3480

I

I

I

3490

I

I

3500

3510 G

I. EPR spectrum of PPy doped by BF~,

The cw-EPR p e a k - t o - p e a k

linewidth

Gauss and spins c o n c e n t r a t i o n gram is shown on fig.

~ = 9.78 GHz

for this polymer

is very high.

2. At about

Bpp = 5.7

Time resolved EPR dia-

I30 ns and 330 ns on the scale

there are the remnats of two I6 ns long exiting pulses.

The small

bump at 530 ns is the Hahn echo signal which is very weak. ing the distance ~ between

two pulses,

ple shown on fig. 2 the spin-spin relaxation It is T = 150 ns which is very short. time resolved indication

EPR signal is so weak.

that the spins observed

be attributed

By vary-

which is 200 ns in the examtime T was measured.

This is the reason why the The shortness of T is a strong

are i m m o b i l e species

and may

to the high m o l e c u l a r weight and level of conjugation

of p o l y p y r r o l e s

synthesized

under these conditions.

376 o

150

-

x

IO0

-

50 0

-

-50

-

- I O 0

-

-150

-

l 200

0

Fig.

, 400

2. Time resolved

600

800

EPR diagram

IO00 t, ns of PPy doped

by BF~,

2000 scans

ACKNOWLEDGEMENTS Authors

are very

acknowledged

to Prof.

O.V.

Agashkin

for helpful

discussion. REFERENCES I H. Naarmann, 4,567,250

W. Heckemann,

G. KShler

2 R. Bjorklund

and 1. LundstrSm,

3 R. Sugimoto,

K. Yoshino,

Phys.,

and P. Simak,

U.S.

Pat.

(I984).

24 (Ig85)

4 R. Sugimoto,

J. Electron.

S. Inoue

Mat.,

13 (I984)

and K. Tsukagoshi,

Jpn.

21I.

J. A p p l

L425.

H.B.

Gu, S. Hayashi

and K. Yoshino,

Synth.

Met.,

I8

(1987) 247. 5 P. Audebert and G. Bidan, Synth. Met.,

6 J.A. Walker, Polymer 7 Yu.A.

L.E. Warren

Chem.,

Dubitsky,

Polymers

26 (Ig88) Proc.

Synthesis",

14 (Ig86) 7 I .

and E.F. Witucki,

J. Polymer

Sci:

Part A

1285.

of Int. Alma-Ata,

School

"Non-Traditional

26 Mar.

- 6 Apr.

IggO,

Methods gI.

of