Synthesis, characterization and doping of soluble diblock and triblock copolymers including polyparaphenylene sequences

Synthetic Metals, 41-43 (1991) 955-958

955

SYI~rHESIS,CHARACTERIZATION AND DOPING OF SOLUBLE DIBLOCK AND TRIBLOCK COPOLYMERS INCLUDING POLYPARAPHEN-YLENE SEQUENCES

B.FRANCOIS*

and

X.F.ZHONG

Institut Charles Sadron 6 rue Boussingault

(C.R.M.-E.A.H.P)

- Strasbourg

(CNRS)

(France)-

67083

ABSTRACT Soluble Polystyrene(PS)synthesized precursors. copolymers PPP

PPP diblock and PS-PPP-PS

by aromatization For

a

given

of the corresponding PS

sequence,

the

triblock

PS - poly 1,3

degree

of

copolymers were cyclohexadiene

agregation of these

in solution increases with the length of PPP sequences.

microdomains

characterization

in

the

core

of

these

The sizes of

micelles were determined.

Spectral

of n and p doping of these solutions are presented.

INTRODUCTION The

synthesis

of

different ways: by normally

of soluble

conducting

fixation of a

unsoluble

incorporation

soluble

conducting

of sequences

"classical"

of non

polymers can be developped upon two

number of side polymer

(alkyl

substituted

polymer. A combination

groups on the thiophene

skeleton of a

for exemple)

conducting polymer in the

of these two methods is

or by chain

evidently

also possible. The synthesis of

block copolymers which

well defined block copolymers

is presented here

, having a rod-coil

intends to produce

structure for which organized

phases are expected.

RESULTS a-Synthesis We have reported in preparation 2). These

previous papers some preliminary

of polystrene polymers are

- polyparaphenylene now more

concerning

the

(PS-PPP) diblocks copolymers

results

(i-

precisely characterized

and this

system is

extended to triblock copolymers. The synthetic route presents

0379-6779/91/$3,50

two steps:

© Elsevier Sequoia/Printed in The Netherlands

956 - the synthesis of

PS-poly 1,3 cyclohexadiene

(PS-PCHD) diblock

or eventually PS - PCHD -PS triblock copolymers the aromatization

of the PCHD

sequence to PPP

by dehydrogenation

with p-

chloranil

The

PS-PCHD

copolymers

Butyllithium

in

non

polymerisation

is

are

polar

transfer to

monomer and Nevertheless

prediction

of

the

published

by

The

elsewhere

the

anionic

detailed

(3).

kinetics

leading to

determination

conditions

polymerization

It demonstrates

chain reinitiation

best

copolymers:temperature A systematic

solvent.

reported

homo

PCHD.

synthesized

to

elsewhere.

A

partial

of the 1,3 CHD the existence of

the formation of some

of reaction constants allows the produce

diblock

lower than 5°C, aromatic solvent,

study of the aromatization

with s-

and

triblock

purified initiator.

process was carried out and

copolymer

agregation

occurs

will be

during this

reaction depending of the respective length of PS and PCHD sequences and on the diblock or triblock

structure of copolymers.

This agregation plays

the maximum length of conjugated PPP sequences. the position

of the

maximum of

wavelength of this maximum 339 um

for triblock

these

polymers

during

formation of defects

place essentially

aromatization

the

b- Physicochemical

reaction.

limits the

This

copolymers and

molecular weight

(# 50000).

leads to the hypothesis radical on the

length of conjugated PPP

agregated state.

the

reaction.

accessibility

It can of

be also

cyclohexadiene

that the

chain detected by sequences

,takes

expected that the units

for

the

(Mw= 34000)

and

This point is under investigation.

characterization

of PPP copolymers

A set of dibloek copolymers with the same polystyrene different PCHD sequences has

sequence

been synthesized and aromatized.

Their solutions

in Chloroform or THF have been studied by Gel Permeation Chromatography(GPC) Ligth Scattering The agregated with

a

UV/VIS

(LS) and capillary viscosity and free chains spectrometer

species was recorded.

the

in triblocks could be due to the weaker agregation of

in the

restricts

from

Typically

331 nm for diblock

similar total

(addition of chloranil

chlorine analysis),which

agregation

of

This length was evaluated

absorption band

was found to be

copolymers

This longer PPP sequences

the IIV/Vis

a role in

as

were separated by a a

The fraction of

of peaks detected at 260 run.

detector.

,

. GPC apparatus

equipped

The absorption spectrum of each

free chains is deduced from the

surface

957 The

results

are

reported

increases with the absorption

is located at

preferential

in

table

length of the

l.The

proportion

PPP sequences.

lower wave length for

The

of

agregated chains

position of the

the free chains,

maximum

indicating

The molecular weight of agregates was deduced from LS data after correction the free chain contribution. compact

a

agregation of the longest PPP sequences.

organization

of

The chains

low measured intrinsic viscosities in

these

agregates:

of

support

a

A central core of PPP

surrounded by PS sequences. Assuming a spherical measurements) signal

)

and a

it is

shape for these

possible

to

evaluate the

ranging from 30 to 57 Angstr.

Microphase

micelles

solid state organization

(no light of PPP in

radius of

depolarization the core (no

these PPP

cores. Values

were found for the studied set of copolymers.

separation occurs in concentrated

solutions or in solid state.

TABLE I

Copolymer N °

1

PS-PCHD precursors

:

Mw of PS sequence:

34000

2

3

4

5

Mw of PCHD sequences:

2,350

5,300

7,000

9,300

13,000

Intrinsic viscosity

23.3

25.1

25.9

27.7

31.8

23.3

26

24

23.2

22.3

0.75

0.53

0.39

0.35

0.16

315

320

320

322

(cc/gr

,CHCL3,25"C)

PS-PPP

copolymers

:

Intrinsic viscosity free chains fraction free chains absorption

agregates "

absorption Mol.Weight

(LS measuments

in LS

HR RMN

(rlm) 317

(rim) 333

331.6

331.6

330

328

(106 ) 1.14

1.06

0.91

1.24

1.91

corrected by GPC data)

Mw of PPP per agregate

80,000

138,000

165,000

280,000

539,000

radius of PPP core ( A )

30

36

38

46

57

958 DOPING OF PPP COPOLYMERS

:

The fig i shows the absorption spectra of THF solutions of

PS-PPP copolymer

which were n doped by reaction with K, Na and Li metals. The wavelength of the maximum absorption increases when the size of the decreases.

Such a behaviour is frequently observed in solutions of

cation

ion-radical

or carbanionic salts and is explained by the solvation of cations by the THF. Li doped copolymers films were cast from such solutions glass apparatus.

under vacuum in sealed

Fig 2 and 3 show the influence of a thermal treatment on these

films. The NIR band decreases gradually when the temperature is increased.

In a

first step, the maximum shifts to higher energies and in a second step to lower energies. some

It

days

practically vanishes at

low

temperature

in one this

hour at

band

100°C

grows

accelerated by the addition of traces of THF(d).

, Nevertheless after

again(c). This increase is

It is remarkable that this new

band is located at a greater wavelength than the original one(a). Such a

behaviour can

step,

followed

by

be explained a

dedoping

of

by a

loss of

the

coinserted THF in the first

less conjugated parts of the PPP and

finally by a reversible thermal dedoping of best conjugated PPP microdomains. A p

doping of

the same

copolymer was

carried out in CHCI 3 solution with

FeCI 3 . It is characterized by an absorption band at 1400nm.

U

20°C K o

=i 6

/'l

/"

t,

...... ~

i~i5~i~oo

Fi~ l:Absorption spectra of TNF solution of PS-PPP n doped by Li,Na and K metals

.......5"~'"" i~'"" it~O'""~6bO

Fi£ 2 :effect of heating (i0 min) on films of Li doped PS-PPP

......~ ' " "

i ~ " " i8~'"'~bbo

Fi~ $: reversible dedoping/redoping of Li doped PS-PPP film

REFERENCES:

i- X.F.Zhong

,B.Frangois

Svnt.Met.

2- X.F.Zhong

,B.FranGois

Makrom.Chem.

29 (1989)E35-E40 Rap. Comm. 9,(1988),411

3- X.F.Zhong

,B.Fran~ois

Makrom. Chem.

(2 papers in press)