Thermally Induced Self-Doping of π-Conjugated Polymers Bearing a Pendant Neopentyl Sulfonate Group

Pendant Neopentyl Sulfonate Group

Article

Thermally Induced Self-Doping of π‑Conjugated Polymers Bearing a

Atsunori Mori,* Chihiro Kubota, Keisuke Fujita, Masayasu Hayashi, Tadayuki Ogura, Toyoko Suzuki,

Kentaro Okano, Masahiro Funahashi, and Masaki Horie

Cite This: https://dx.doi.org/10.1021/acs.macromol.9b02554

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sı Supporting Information

ABSTRACT: A regioregular head-to-tail (HT)-type polythio-

phene was synthesized by the deprotonative nickel-catalyzed

cross-coupling polymerization of 2-chlorothiophene bearing a

neopentyl benzenesulfonate group at the 3-position. The obtained

HT-regioregular polymer was found to dissolve in chloroform or

THF, while it became soluble in water upon heating at 185 °C for

0 min by the liberation of the protected neopentyl group. The

thin ﬁlm of the polymer showed a remarkable improvement in

conductivity of ca. 10 times before/after heating, suggesting the

thermally induced intramolecular doping of polythiophene by the formed sulfonic acid at the side chain. The related doping was also

observed in a poly(phenylacetylene) derivative, which was synthesized by rhodium-catalyzed polymerization. Copolymerization of

such thiophene- and acetylene-bearing neopentyl sulfonate with 3-alkylthiophene and phenylacetylene, respectively, produced the

corresponding statistical copolymers, demonstrating the formal self-doping of poly(3-alkylthiophene) and poly(phenylacetylene).

INTRODUCTION

causes synthetic diﬃculties in forming potentially self-doping

conjugated polymers because of the use of a carbanion species

for polymerization, which is in conﬂict with the acidic doping

functionality. Indeed, self-doping polythiophenes bearing such

functionality at the side chain could have only been

synthesized by oxidative polymerization with stoichiometric

■

Polymers of extended π-conjugation have been attracting a lot

of attention in material science as organic electronic materials

showing a wide range of conductivities covering insulative,

−5

semiconductive, and metallic materials. Although most such

conjugated polymers are, in general, much less conductive by

themselves, the external addition of a dopant remarkably

changes their characteristics to make them conductive or

semiconductive. Doping of electron-enriched conjugated

polymers (p-type) has been performed by the addition of

one (radical) or two (cation) electron acceptors to form

polarones/bipolarons on the polymer main chain. For example,

the conductivity of an undoped head-to-tail-type regioregular

or usually much excess FeCl as an oxidant, leading to the

corresponding polymer with uncontrolled regioregular-

−12,16−25

ity.

In contrast, cross-coupling polymerization to

give regioregular polythiophene with the GRIM method

employing metalated thiophene and transition-metal catalyst

would not be tolerable for the doping functionality at the side

chain. Accordingly, the introduction of HT-regioregularity into

self-doping polythiophenes is therefore a signiﬁcant challenge

−5

−7

−1

polythiophene (HT-P3HT) is ca. 10 −10 S cm ; however,

13−15

in materials science

(Figure 1). We considered the

addition of iodine as a dopant improves its conductivity to 10

−

synthesis of a water-soluble HT-regioregular poly-3-substituted

thiophene, which possesses benzenesulfonic acid at the side

chain, employing the deprotonative polymerization of 2-halo-

S cm . Self-doping bearing a dopant moiety in the skeleton

of the conjugated polymer has also been a major concern that

decreases the amount of addition of excess dopants and thus

causes the possible deterioration of the durability to oxidation

or humidity. Introduction of a sulfonic acid moiety into the

side chain of polythiophenes has been performed and several

polymers thus designed have been shown to demonstrate

26−33

3-substituted thiophene as a monomer precursor

since we

have already shown the synthesis of several side-chain-

34,35

functionalized polythiophenes to date.

The acidic moiety

should be protected during the polymerization by employing

an organometallic monomer and/or a transition-metal

−12

improved conductivity.

On the other hand, development

of a practical method for the preparation of π-conjugated

polymers with well-deﬁned structures is an attractive issue in

polymer synthesis, organic synthesis, and organometallic

chemistry, in which organometallic species as well as

transition-metal complexes as polymerization catalysts are

Received: December 3, 2019

Revised: January 23, 2020

,13−15

powerful tools.

However, such a methodology generally

XXXX American Chemical Society

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Article

Figure 1. Self-doping vs thermally induced self-doping.

catalyst. The protected functionality can be removed after

the formation of the polymer thin ﬁlm, wherein the protective

group may be preferably removed without using any additional

chemicals. Accordingly, we focused on the use of neopentyl

sulfonate, which was shown to be removed by thermal

pyridine (DMAP) (95%). Cross-coupling with thiophene-3-

3 43

9−42

boronic acid

catalyzed by Pd-PEPPSI-SIPr gave 3a in

75% yield and subsequent chlorination with NCS gave

monomer 4a in 65% yield.

Polymerization of the thus-obtained chlorothiophenes 4a

was carried out by the reaction with a bulky magnesium amide

TMPMgCl·LiCl (2,2,6,6-teteramethylpiperidine-1-yl chloro-

treatment, leading to the corresponding sulfonic acid.

Herein, we describe that the self-doping of π-conjugated

polymers is induced by heating the thin ﬁlm, whose improved

magnesium: Knochel−Hauser base) to undergo deprotona-

26−35

conductivity is ca. 10 −10 times higher.

tive metallation.

Then, nickel catalyst 5 was added to the

thus-formed thiophene−magnesium species. Smooth polymer-

ization took place at room temperature, as shown in Scheme 2,

RESULTS AND DISCUSSION

■

Preparation and Characterization of Polythiophene

Bearing a Sulfonate Group at the Side Chain. We ﬁrst

studied the introduction of such a side chain into the

thiophene ring. The synthesis of the monomer was carried

out as represented in Scheme 1. The reaction of 4-

bromobenzenesulfonyl chloride (1) with neopentyl alcohol

aﬀorded sulfonate 2, whose synthetic eﬃciency was remarkably

improved by the addition of the catalyst N,N-dimethylamino-

Scheme 2. Nickel-Catalyzed Polymerization of 4a through

the Deprotonation with the Knochel−Hauser Base

Scheme 1. Preparation of Thiophene Monomer 4a Bearing

Benzenesulfonate Group at the 3-Position

to aﬀord the corresponding polythiophene 6a in 66% yield as a

deep orange solid. Measurement of the obtained polymer

revealed a molecular weight of ca. 28 000, which reasonably

corresponded to the monomer/catalyst feed ratio, and the

molecular weight distribution was also found to be narrow

(

M /M = 1.05). The NMR spectra of 6a suggested that the

w n

obtained polymer has a highly regioregular head-to-tail (HT)

orientation. Polymer 6a was found to be soluble in several

organic solvents such as chloroform and THF.

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Thermogravimetric analysis of 6a revealed that a remarkable

mass loss took place at 185 °C, whose amount was consistent

with the thermolysis of neopentyl ester to sulfonic acid.

Indeed, heating of the solid polymer 6a at 180 °C showed an

immediate color change to dark purple and leading to 7a. It

was also remarkable that addition of 7a to neutral water

resulted in dissolution, while it was found to be completely

insoluble in chloroform, despite a highly regioregular HT-type

poly(3-substituted thiophene) of extended π-conjugation.

Figure 2 shows a comparison of the properties of the

obtained polythiophenes before/after thermolysis of the thin-

ﬁlm cast on a quartz substrate. The UV−vis spectrum of

sulfonate 6a was found to show λ value at 440 nm in a

max

chloroform solution (ca. 10⁻M), which was comparable with

that of (poly(3-hexylthiophen-2,5-diyl): P3HT) (λ = 442

max

nm). Measurement of the UV−vis spectrum of the cast ﬁlm of

a revealed the red shift of the absorption edge from 530 to

80 nm, as well as the λ_m_a_xvalue from 440 to 510 nm.

Treatment of the thus-formed cast ﬁlm at 180 °C for 10 min

resulted in a remarkable color change. The UV−vis spectrum

of the ﬁlm of 6a after heating indicated absorption at the range

of a near-infrared region (Figure 2a). Measurement of the

cyclic voltammetry of a chloroform solution of 6a indicated a

reversible wave at 0.93 V vs Ag /Ag standard electrode owing

to one-electron oxidation (Figure 2b) and the UV−vis

spectrum of 6a in the oxidation state exhibited absorption at

ca. 600 nm (Figure 2c). Accordingly, the color change of the

cast ﬁlm of 6a caused by thermolysis leading to 7a could be

attributed to the formation of cation radical species stabilized

by the formed sulfonic anions. Similar oxidation was also

observed in the cast ﬁlm of 6a to indicate the oxidation wave at

.98 V vs Ag /Ag standard electrode accompanied by the

change in the color of the ﬁlm to dark brown, although such a

color change of the ﬁlm was irreversible. It is worth noting that

the change in the doping state was induced by the heating of

the polymer ﬁlm.

These results, based on the characterization of polymer 6a in

the thin-ﬁlm state before/after heating, suggest that the

thermally induced self-doping of the polythiophene main

chain occurred due to the impact of sulfonic acid on the

polythiophene side chain. The ﬁlm thus transformed to 7a

indeed dissolved in water, suggesting the formation of the

sulfonic acid moiety. The doped thin ﬁlm improved the

conductivity when the thus-formed polymer 6a was cast on an

electrode. The polymer 6a was cast to form the thin ﬁlm of 200

nm thickness, and the measurement of the current at a certain

Figure 2. (a) UV−vis absorption spectrum of the chloroform solution

of 6a (green dotted), cast ﬁlm of 6a (black), and cast ﬁlm of 6a after

heating at 180 °C for 10 min (red) (considered to form 7a in the

ﬁlm). (b) Cyclic voltammogram of the chloroform solution of 6a

−

applied voltage showed that the current level was 1 × 10 to 1

−

−5

10 A and thus the calculated conductivities were ca. 10

−

cm . A remarkable increase in the current values was observed

after the thin ﬁlm on the electrode was heated at 190 °C for 20

min, as shown in Figure 3, to result in the conductivity of 1 ×

−

(

black) (1 mM/0.1 M Bu NPF /CHCl , scan rate 0.01 V s ) and the

4 6 3

−

cast ﬁlm (red) (0.1 M Bu NClO /CH CN, scan rate 0.1 V s ). (c)

−

−1 45,46

UV−vis spectrum of 6a in chloroform upon electro-oxidation (0.1 M

S cm .

The results suggested that the conductivity of

Bu NPF ) (red dotted: 0 V; blue: 2.3 V).

the polythiophene thin ﬁlm was improved by ca. 10 times

upon heating. Although several self-doping polythiophenes

bearing sulfonic acid moiety have also been developed to

chemicals due to the liberation of the protected neopentyl

group.

−12

date,

formation of such polymers with a transition-metal-

catalyzed polymerization leading to completely regiocontrolled

polymers cannot be performed due to the inconsistency of the

organometallic thiophene monomer from 4a and the acidic

Synthesis and Characterization of a Polyacetylene

Derivative. It was also found that such a thermally induced

self-doping behavior was observed in a diﬀerent type of

conjugate polymer. Polyacetylenes have also been recognized

as a kind of p-type semiconductive material in which doping

side chain bearing SO H. It should also be pointed out that

such an improved conductivity was observed only upon the

thermal treatment of the thin ﬁlm without external additive

occurs by the addition of acid, iodine, etc. Preparation of

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Figure 3. Electronic properties on current−voltage characteristics of

the as-deposited and thermally treated cast ﬁlm of polythiophene 6a

(

as deposited: black) and after heating at 190 °C for 20 min, leading

to 7a (red).

polyacetylenes can be performed by polymerization of alkynes,

and treatment of a terminal alkyne by rhodium catalyst is

48,49

shown to lead to smooth formation of Z-polyalkynes.

Arylalkyne bearing a neopentyl sulfonate substituent was

synthesized as illustrated in Scheme 3. The Sonogashira

Scheme 3. Preparation and Polymerization of Arylalkyne 8

Bearing a Benzenesulfonate Substituent in the Aromatic

Ring

Figure 4. (a) Absorption spectrum of the thin ﬁlm of polyacetylene 9

and (b) electronic properties on the current−voltage characteristics of

the as-deposited and thermally treated cast ﬁlm of polyacetylene 9

(

as-deposited: black) and after heating at 170 °C for 15 min leading

to 10 (red).

showed little current at the applied voltages in the range 20−

0 V. The conductivity after the treatment of the ﬁlm at 170

C for 15 min was observed to be improved to ca. 0.003−0.005

−1

S cm (20−50 V). The results suggest that the improved

conductivity is at least ca. 10 times higher after the thermal

treatment.

Synthesis and Characterization of Copolymers of

Polyacetylene Derivative and Polythiophene Bearing a

Sulfonate Group at the Side Chain. Such a thermally

induced self-doping protocol is also found to be applicable to

regioregular poly(3-hexylthiophene) HT-(P3HT), which is

shown to be widely available for a broad range of electronic

−5

materials.

P3HT bearing an alkyl group in the side chain

can only be doped by an external additive and is thus incapable

of self-doping. However, incorporation of a partial thiophene

unit bearing a functional group enables thermally induced

doping by copolymerization. As shown in Scheme 4, the

prepared monomer 4a was employed for statistical copoly-

merization with 2-chloro-3-hexylthiophene (11) with a nickel-

coupling of bromobenzenesulfonate 2 with trimethylsilyla-

cetylene followed by the removal of the silyl group aﬀorded the

monomer 8. Subsequent polymerization of 8 was carried out in

26−33

the presence of rhodium(I) catalyst [RhCl(nbd)] (2 mol %)

to aﬀord the corresponding Z-polyacetylene 9 in 95% yield.

(II) catalyst.

Copolymerization of 4a and 11 was carried

out using 1−20 mol % of 4a. A mixture of 4a and 11 was

treated with 1.2 equiv of TMPMgCl·LiCl at room temperature

for 10 min, followed by the addition of nickel catalyst 5 (1.0

mol %) to initiate copolymerization. Table 1 summarizes the

result. Use of diﬀerent ratios of 4a:11 (1/100, 1/50, 1/20, 1/

10, 1/5) was found to result in polymerization to aﬀord

poly(3-hexylthiophene) containing statistical amounts of

The obtained polyacetylene 9 was also subjected to the

formation of the cast thin ﬁlm. Measurement of UV−vis

spectrum of 9 showed the characteristic absorption at 400 nm,

as shown in Figure 4a, suggesting the formation of the

conjugated polyene. Thermal treatment of 9 at 170 °C for 15

min leading to 10 showed the absorption at the NIR region, as

observed for the regioregular polythiophene 7. Figure 4b

shows the change in conductivity before/after the thermal

treatment of the ﬁlm and thus suggests the formation of cation

radicals in the polymer main chain. The ﬁlm of polyene 9

comonomer 4a. The H NMR spectrum revealed reasonable

amount of 4a toward 11 was incorpolated in the copolymer 12,

and the obtained polymers showed M = 20 000−30 000 (M /

M = 1.10−1.44). Analysis of the organic ﬁltrate by H NMR

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Scheme 4. Statistical Copolymerization of Sulfonate-

Containing Thiophene 4a and 2-Chloro-3-hexylthiophene

Scheme 5. Statistical Copolymerization of Arylalkyne 8 and

Phenylacetylene 12

11)

Table 1. Copolymerization of Sulfonate Group-Containing

Chlorothiophene 4a and 2-Chloro-3-hexylthiophene (11)

with the Nickel(II) Catalyst 5

11/

%conv of

M /

(

mmol)

M_n

m/n

2.5

1.3

0.5

100

>99

3.0 × 10

2.9 × 10

2.6 × 10

2.5 × 10

3.1 × 10

1.44

1.18

1.11

1.59

1.17

100

3.7

The reaction was carried out with 2-chloro-3-hexylthiophene (11),

chlorothiophene bearing benzenesulfonate group 4a with TMPMgCl·

LiCl (1.2 equiv) in THF, followed by the addition of NiCl (PPh )IPr

(

5, 1.0 mol %) at room temperature for 1 h. Consumption of

monomer was estimated by the measurement of H NMR of the

ﬁltrate after precipitation of the obtained polymer 12. The molecular

Figure 5. Absorption spectra of the as-deposited (black)/thermally

treated (red) cast ﬁlm of 12 (m = 3.7; n = 1) and those of 14 (m = 65;

n = 35).

weight (M ) and the molecular weight distribution (M /M ) were

measured by SEC analysis. Contents of the monomer unit derived

from 4a and 11 were estimated by the H NMR analysis of the

1.2 × 10⁻to 4.1 × 10⁻²S cm⁻¹(at 50 V) after thermal

polymer.

treatment at 190 °C for 20 min, which is ca. 10 times higher

to detect the remaining monomers showed that both were

almost equally consumed, suggesting little preferential

incorporation of sulfonate comonomer 4a to the P3HT

chain and vice versa.

The related statistical copolymer was also found to be

prepared by the copolymerization of the terminal arylacetylene

than that obtained by thermally induced self-doping. The

related properties of the statistical polyacetylene copolymer 14

are also shown in Figure 5 and Table 2 to observe absorption

at the NIR region and the improved conductivity. It was also

shown that self-doping of the polymer main chain of

polyacetylene was induced by heating, and the improved

conductivity before/after thermal treatment was found to be

and phenylacetylene (13), which was also performed by the

catalysis of rhodium(I) complex in a similar manner to the case

of homopolymerization of 8. The reaction of 8 and 13 in 3:7,

respectively, aﬀorded the copolymer 14 in 67% yield.

ca. 10 times higher. Since both homopolymers poly(3-

alkylthiophene) and poly(arylalkyne) are incapable of self-

doping, the results show formal doping of such polymers.

Worthy of note is a remarkable improvement of the

Measurement of the H NMR spectrum of 14 revealed the

presence of ca. 35% of benzenesulfonate moiety derived from

conductivity of the polymer thin-ﬁlm ca. 10 −10 times

whereas each conductivity is dependent on the conditions of

thin-ﬁlm fabrication.

, and M and M /M values of the copolymer 13 were

n w n

revealed to be 18 000 and 3.0, respectively (Scheme 5).

The obtained copolymers were then subjected to measure-

ments of optoelectronic properties as a thin ﬁlm on quartz or

EXPERIMENTAL SECTION

■

the ITO electrode. As shown in Figure 5, the value of λ_m_a_x

the as-deposited ﬁlm of 12 (m = 3.7; n = 1) was 520 nm, while

the ﬁlm was transparent at the NIR region (>700 nm). When

heated at 190 °C for 20 min, the ﬁlm of 12 showed absorbance

at 700−1000 nm, suggesting that P3HT was formally doped by

the generation of sulfonic acid in the polythiophene side chain.

The conductivity of the copolymer also exhibited a drastic

change, as summarized in Table 2. The as-deposited thin ﬁlm

of 12 (m = 3.7; n = 1) showed an improved conductivity from

Materials and Methods. All of the reactions were carried out

under a nitrogen atmosphere. H NMR (400 MHz) and C{ H}

NMR (100 MHz) spectra were measured on a JEOL ECZ400 NMR

spectrometer with a CDCl solution unless noted. The chemical shifts

were expressed in ppm with CHCl (7.26 ppm for H) or CDCl

77.16 ppm for C) as internal standards. The IR spectra were

(

recorded on a Bruker Alpha with an ATR attachment (Ge). High-

resolution mass spectra (HRMS) were measured by a JEOL JMS-

T100LP AccuTOF LC-Plus (ESI) with a JEOL MS-5414DART

attachment. For thin-layer chromatography (TLC) analyses through-

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Table 2. Thermally Induced Change in Conductivities of Thin Films Obtained by Copolymerization of 11 and 4a

(

Polythiophene) and 8 and 13 (Polyene)

conductivity (S cm⁻¹)^d

as-deposited after heating

copolymer

comonomer

ratio

M_n

1.2 × 10⁻

3.6 × 10⁻

4.1 × 10

1.6 × 10

−2

3.7:1.0

1.0:1.9

31 000

18 000

−3

The measurement of conductivity was carried out with the cast thin ﬁlm of copolymers 12 and 14. The incorporated ratio of 11/4a or 8/13

estimated by H NMR measurement. The molecular weights (M ) were measured by SEC analysis. The conductivity was calculated based on the

current at 100 V (for 12) and 50 V (for 14), respectively.

out this work, Merck precoated TLC plates (silica gel 60 F₂₅₄) were

used. Puriﬁcation by HPLC with a preparative SEC column (JAI-

GEL-1H and JAI-GEL-2H) was performed by JAI LC-9201. SEC

analyses were carried out with a standard HPLC system equipped

combined organic phase was dried over anhydrous sodium sulfate.

Removal of the solvent under reduced pressure left a crude solid,

which was puriﬁed by column chromatography on a silica gel using

CH Cl /hexanes (1/1, v/v) and recrystallization with CH Cl and

with a UV detector at 40 °C using CHCl as eluent with Shodex KF-

hexanes to give 2.04 g of 4a as a colorless solid in 75% yield. H NMR

02HQ and KF-404HQ. Molecular weights and molecular weight

(400 MHz, CDCl ) δ 7.96 (d, J = 8.5 Hz, 2H), 7.76 (d, J = 8.5 Hz,

distributions were estimated based on the calibration curve obtained

by 6 standard polystyrenes. UV−vis−NIR absorption spectra of the

polymer ﬁlms were measured with a Shimadzu UV-3150 UV−vis

spectrophotometer. Cyclic voltammetry was conducted by ALS 600B.

The conductivity of polymer ﬁlms was measured with a digital

electrometer ADCMT8340A. Concerning the solvent for the nickel

and palladium-catalyzed reactions THF (anhydrous grade) was

purchased from Kanto Chemical. Co. Ltd. and passed through

alumina and copper column (Nikko Hansen & Co. Ltd.) or distilled

2H), 7.22 (d, J = 5.7 Hz, 1H), 7.09 (d, J = 5.7 Hz, 1H), 3.74 (s, 2H),

0.93 (s, 9H). C{ H} NMR (100 MHz, CDCl ) δ 139.5, 136.2,

134.8, 129.1, 128.1 × 2, 126.8, 123.7, 79.9, 31.8, 26.1. IR (ATR)

2961, 1598, 1478, 1403, 1353, 1194, 1177, 1100, 1025, 952, 937, 879,

−

846, 824, 757, 741, 727, 721, 671, 641 cm . HRMS (DART−ESI )

calcd for C H ClO S : 345.0386; found m/z 345.0394.

3 2

Poly(3-(4-(2,2-dimethylpropylsulfonylbenzen)-1-yl)thiophene-

2,5-diyl) (6a). To a 20 mL Schlenk tube equipped with a magnetic

stirring bar, 4a (172 mg, 0.5 mmol), THF (5.0 mL), and 1.0 M THF

solution of TMPMgCl·LiCl (0.6 mL, 0.6 mmol) were added at room

temperature. After stirring at room temperature for 10 min,

from sodium dispersion in a mineral oil/benzophenone ketyl prior

to use. The Knochel−Hauser base (TMPMgCl·LiCl) was purchased

from Sigma-Aldrich Co. Ltd. as a 1 M THF solution. NiCl (IPr)-

NiCl (PPh )IPr (5, 4.4 mg, 5.6 μmol) was added to initiate

2 3

54,55

PPh₃

and [RhCl(nbd)]₂were purchased from TCI Co. Ltd.

polymerization. The color of the solution turned to dark orange.

After stirring at room temperature for 3 h, the reaction mixture was

poured into a mixture of hydrochloric acid (1.0 M, 2 mL) and

methanol (10 mL) to form a precipitate, which was ﬁltered oﬀ to

leave an orange solid. After washing with methanol and hexanes

repeatedly, the solid was dried under reduced pressure to aﬀord 101

Other chemicals were purchased and used without further

puriﬁcation.

(2,2-Dimethylpropan-1-yl)4-bromobenzenesulfonate (2). To a

mixture of 4-bromobenzene-1-sulfonyl chloride (4.09 g, 16.0 mmol)

and neopentyl alcohol (1.69 g, 19.2 mmol) in CH Cl (24 mL),

pyridine (2.6 mL, 32.2 mmol) and N,N-dimethyl-4-aminopyridine

DMAP) (0.0972 g, 0.796 mmol) were added. The reaction mixture

mg of 6a (66%). The molecular weight (M

weight distribution (M /M ) were estimated by SEC analysis. M

= 1.05. H NMR (400 MHz, CDCl ) δ 7.89 (d, J =

8.0 Hz, 2H), 7.55 (d, J = 8.0 Hz, 2H), 6.93 (s, 1H), 3.70 (s, 2H), 0.88

) and the molecular

(

was stirred at room temperature for 21 h and diluted with Et O. The

28 000, M

organic layer was washed with 1 M aqueous HCl, water, dried over

anhydrous sodium sulfate, and concentrated in vacuo to aﬀord 4.68 g

(s, 9H). C{ H} NMR (100 MHz, CDCl ) δ 140.6, 137.9, 135.6,

of 2 in 95% yield as a light brown solid, which was directly employed

134.2, 132.7, 130.2, 130.0, 128.4, 80.1, 31.8, 26.1. IR (ATR) 2961,

1598, 1478, 1402, 1361, 1179, 1103, 963, 937, 826, 756, 725, 651,

for the following reaction. H NMR (400 MHz, CDCl ) δ 7.77 (d, J =

−

.2 Hz, 2H), 7.70 (d, J = 9.2 Hz, 2H), 3.69 (s, 2H), 0.91 (s, 9H).

606 cm .

Poly(3-(4-(benzenesulfonic acid)-1-yl)thiophen-2,5-diyl) (7a).

C{ H} NMR (100 MHz, CDCl ) δ 135.2, 132.7, 129.5, 129.0, 80.1,

Polythiophene 6a bearing benzenesulfonate substituent (30 mg)

was taken in a Schlenk tube, which was heated by a heating gun for a

few minutes, to observe the color change from purple to dark purple

1.8, 26.1.

(

2,2-Dimethylpropan-1-yl)4-(thiophen-3-yl)benzenesulfonate

3). To a degassed mixture of 3-thiopheneboronic acid (1.95 g, 15.2

mmol), K CO (6.32 g, 45.7 mmol), (2,2-dimethylpropan-1-yl) 4-

(

solid, which resulted to be dissolved in water. Measurement of the H

bromobenzenesulfonate (2, 4.68 g, 15.2 mmol), and Pd-PEPPSI-SIPr

0.105 g, 0.154 mmol), THF (3.8 mL) and water (7.5 mL) were

NMR spectrum in D O showed broad signals, suggesting low mobility

(

of the organic moiety in an aqueous medium, while the disappearance

of the neopentyl group was conﬁrmed. The TG-DTA proﬁle also

supported the conversion of neopentyl sulfonate into the correspond-

added. The mixture was vigorously stirred at 80 °C for 19 h and then

concentrated in vacuo and passed through a Celite pad. The solvent

was removed under reduced pressure, and the residue was puriﬁed by

recrystallization with CH Cl and hexanes to give 1.13 g of 2 as a

ing sulfonic acid by indicating the mass loss of equivalent to C

H10 at

185 °C.

colorless solid in 75% yield. H NMR (400 MHz, CDCI ) δ 7.92 (d, J

(4-(2,2-Dimethylpropylsulfonyl)-phenyl)ethyne (8). To a 50 mL

Schlenk tube equipped with a magnetic stirring bar, (2,2-

dimethylpropyl)4-bromobenzenesulfonate (2, 1.53 g, 5.0 mmol),

THF (15 mL), trimetylsilylacetylene (1.06 mL, 7.5 mmol), copper(I)

iodide (101 mg, 0.53 mmol), bis(triphenylphosphine)palladium(II)

(175 mg, 0.25 mmol), and trietylamine (7.0 mL, 50 mmol) were

added at room temperature for 21 h. Water (20 mL) was added to the

mixture to quench the reaction. The organic layer was extracted with

8.5 Hz, 2H), 7.76 (d, J = 8.5 Hz, 2H), 7.61 (dd, J = 1.4, 2.7 Hz,

H), 7.49−7.42 (m, 2H), 3.70 (s, 2H), 0.91 (s, 9H). C{ H} NMR

(

100 MHz, CDCl ) δ 140.8, 140.1, 133.9, 128.5, 127.2, 126.8, 126.0,

22.8, 79.7, 31.6, 26.0. IR (ATR) 2967, 1596, 1420, 1357, 1194, 1178,

103, 1016, 955, 938, 870, 851, 840, 819, 783, 759, 729, 722, 640, 628

−

cm . HRMS (DART−ESI ) calcd for C H O S : 311.0776; found

m/z 311.0781.

2,2-Dimethylpropan-1-yl)4-(2-chlorothiophene-3-yl)-

benzensulfonate (4a). To a solution of (2,2-dimethylpropan-1-yl)-4-

2 2

(

O, a water of NH Cl, brine, and water. The combined organic

extracts were dried over Na SO and concentrated in vacuo. The

(

thiophen-3-yl)benzenesulfonate (3, 2.8 g, 9.1 mmol) and NH NO

residue was puriﬁed by column chromatography on silica gel with

hexane/CH Cl (1/1, v/v) as the eluent to aﬀord 1.40 g of (2,2-

36 mg, 0.45 mmol) in DMF (11 mL), N-chlorosuccinimide (NCS)

1.3 g, 9.9 mmol) was added and the mixture was stirred at 60 °C for

dimethylpropyl)4-[2-(trismethylsilyl)ethynyl]benzenesulfonate.

Then, to a solution of (2,2-dimetylpropyl)4-[2-(trismethylsilyl)-

ethynyl]benzenesulfonate (1.28 g, 3.8 mmol) in MeOH/CH Cl

3 h. The reaction mixture was washed with aqueous Na SO and

2 3

NH Cl. The aqueous layer was extracted with CH Cl , and the

Macromolecules XXXX, XXX, XXX−XXX

Macromolecules

The Supporting Information is available free of charge at

Article

(

1/1, v/v, 11.4 mL), K CO (1.06 g, 7.6 mmol) was added and stirred

2 3

2H), 3.65 (s, 2H), 0.90 (s, 16H). Measurement of ¹³C{ H} NMR

at room temperature for 21 h. Water (20 mL) was added to the

mixture to quench the reaction. The organic layer was extracted with

Et O, brine, and water. The combined organic extracts were dried

spectrum (100 MHz, CDCl ) of 14 in CDCl only showed broad

signals: δ 127.9, 127.7, 31.9, 26.1, 1.2. IR (ATR) 2962, 1594, 1481,

−1

1358, 1261, 1177, 1097, 1018, 963, 801, 757 cm .

over Na SO and concentrated in vacuo. The residue was puriﬁed by

column chromatography on a silica gel with hexane/Et O (1/8, v/v)

CONCLUSIONS

■

as the eluent to aﬀord 653 mg of 8 as a colorless solid in 57% yield

In summary, we described the preparations of HT-regioregular

polythiophene and polyacetylene-bearing benzenesulfonic acid

moiety in the side chain by nickel- or rhodium-catalyzed

polymerization, followed by thermolysis of thin ﬁlms to

convert neopentylsulfonate to the corresponding sulfonic

acid. Protected polymers showed high solubility in organic

solvents, while the deprotected ones showed solubilities in the

water despite involving extended π-conjugation. The formation

of the thin ﬁlm of polymers was followed by the thermolysis-

induced self-doping of polythiophene and remarkably

improved conductivity by ca. 10 −10 times. Such behavior

of thermally induced self-doping was also applied to

copolymers of HT-P3HT and poly(phenylacetylene) by

statistical copolymerization with the 3-arenesulfonate-substi-

tuted ones, which also achieved improved conductivity. It

should be pointed out that the self-doping is successful only by

thermal treatment without any additions of external chemicals.

Such behaviors serve as formal self-doping of polymer thin

ﬁlms that bear side-chain functionalities incapable of doping.

The obtained thin ﬁlm would be potentially available for a

wide range of electronic materials.

(

over 2 steps). H NMR (400 MHz, CDCl ) δ 7.86 (d, J = 8.7 Hz,

H), 7.65 (d, J = 8.2 Hz, 2H), 3.69 (s, 2H), 3.29 (s, 1H), 0.90 (s,

H). ¹³C{ H} NMR (100 MHz, CDCl ) δ 135.8, 132.7, 127.8 × 2,

1.7, 81.5, 79.9, 31.6, 25.9.

Poly((4-(2,2-dimethylpropylsulfonyl)phenyl)-ethen)-1,2-diyl) (9).

To a 20 mL Schlenk tube equipped with a magnetic stirring bar,

RhCl(nbd)] (2.6 mg, 5.6 μmol), 8 (76 mg, 0.30 mmol), Et N (8.4

[

μL, 60 μmol), and THF (2 mL) were added at room temperature.

The mixture was further stirred at room temperature for 90 min. The

reaction mixture was poured into a large amount of MeOH (50 mL),

centrifugally separated, and dried under vacuum to aﬀord 72 mg of 9

as an orange solid in 95% yield. The molecular weight (M ) and the

molecular weight distribution (M /M ) were estimated by SEC

analysis. M = 58 000, M = 240 000, and M /M = 4.2. H NMR

(

400 MHz, CDCl ) δ 7.58 (d, J = 8.2 Hz, 2H), 6.87 (d, J = 8.2 Hz,

H), 5.60 (s, 1H), 3.70 (s, 2H), 0.93 (s, 10H). C{ H} NMR (100

MHz, CDCl ) δ 146.2, 139.8, 135.7, 132.1, 128.0 × 2, 80.4, 31.9, 26.1.

IR (ATR) 2962, 1593, 1479, 1402, 1357, 1262, 1176, 1099, 1016,

−

59, 936, 827, 757 cm .

Typical Procedure for the Copolymerization of (2,2-Dimethyl-

propan-1-yl)4-(2-chlorothiophen-3-yl)benzenesulfonate (4a) and

-Chloro-3-hexylthiophene (12). To a 50 mL Schlenk tube equipped

with a magnetic stirring bar, 4a (8.6 mg, 0.025 mmol), 2-chloro-3-

hexylthiophene (11, 506 mg, 2.5 mmol), THF (25 mL), and 1.0 M

THF solution of TMPMgCl·LiCl (3.0 mL, 3.0 mmol) were added at

room temperature. After stirring for 10 min, NiCl (PPh )IPr (19.3

mg, 0.025 mmol) was then added to initiate polymerization. The

color of the solution turned to dark orange. After further stirring at

room temperature for 1 h, the reaction mixture was poured into a

mixture of hydrochloric acid (1.0 M, 2 mL) and methanol (10 mL) to

form a precipitate, which was ﬁltered oﬀ to leave a dark orange solid.

After washing with methanol and hexanes repeatedly, the solid was

dried under reduced pressure to aﬀord 0.38 g of poly[(3-(4-(2,2-

dimethylpropapylsulfonylbenzen)-1-yl)thiophene-2,5-diyl)-stat-(3-

hexylthiopen-2,5-diyl)] (12) (90%). The molecular weight (M ) and

the molecular weight distribution (M /M ) were estimated by SEC

analysis. M = 30 000 and M /M = 1.44. H NMR (400 MHz,

CDCl ): δ 7.93 (br, J = 7.6 Hz, 0.020H), 7.66 (br, J = 7.6 Hz,

ASSOCIATED CONTENT

sı Supporting Information

■

https://pubs.acs.org/doi/10.1021/acs.macromol.9b02554.

Detailed spectroscopic and analytical data (PDF)

AUTHOR INFORMATION

Corresponding Author

■

Atsunori Mori − Department of Chemical Science and

Engineering and Research Center for Membrane and Film

Technology, Kobe University, Kobe 657-8501, Japan;

orcid.org/0000-0002-1163-264X; Email: amori@kobe-

u.ac.jp

.020H), 7.14−6.72 (m, 1.01H), 3.73 (br, 0.020H), 2.98−2.50 (m,

13 1

.0H), 1.91−1.14 (m, 8.0H), 0.91 (br, 3.09H). C{ H} NMR (100

MHz, CDCl ) δ 140.0, 133.8, 130.6, 128.7, 31.9, 30.7, 29.6, 29.4, 22.8,

4.3. IR (ATR) 3054, 2955, 2925, 2856, 1509, 1456, 1377, 1188,

179, 820, 723, 672, 664 cm . Other copolymers were synthesized in

Authors

−

Chihiro Kubota − Department of Chemical Science and

Engineering, Kobe University, Kobe 657-8501, Japan

Keisuke Fujita − Department of Chemical Science and

Engineering, Kobe University, Kobe 657-8501, Japan

Masayasu Hayashi − Department of Chemical Science and

Engineering, Kobe University, Kobe 657-8501, Japan

Tadayuki Ogura − Department of Chemical Science and

Engineering, Kobe University, Kobe 657-8501, Japan

Toyoko Suzuki − Department of Chemical Science and

Engineering, Kobe University, Kobe 657-8501, Japan

Kentaro Okano − Department of Chemical Science and

Engineering, Kobe University, Kobe 657-8501, Japan;

orcid.org/0000-0003-2029-8505

Masahiro Funahashi − Department of Advanced Materials

Science, Kagawa University, Takamatsu, Kagawa 761-0396,

Japan; orcid.org/0000-0002-4259-0657

Masaki Horie − Department of Chemical Engineering, National

Tsing Hua University, Hsinchu 30013, Taiwan; orcid.org/

0000-0002-7734-5694

a similar manner to a ﬀ ord the corresponding statistical copolymers as

summarized in Tables S1 and 1: copolymer 12 with 11 (1.3 mmol)

and 4a (11/4a = 50). Yield 0.21 g (96%); M = 28 500, M /M =

.18 (m/n = 45). Copolymer 12 with 11 (0.5 mmol) and 4a (11/4a =

0): Yield 58 mg (64%); M =26 000; M /M = 1.11, (m/n = 16).

Copolymer 12 with 11 (0.5 mmol) and 4a (11/4a = 10): Yield 81 mg

(

84%); M = 25 000; M /M = 1.59, (m/n = 10). Copolymer 12 with

n w n

1 (0.5 mmol) and 4a (11/4a = 5): Yield 81 mg (84%); M = 31 000;

M /M = 1.17, (m/n = 3.7).

Copolymerization of 8 and 1-Phenylethyne (14). To a 20 mL

Schlenk tube equipped with a magnetic stirring bar, 8 (23 mg, 90

μmol), 1-phenylacetylene (13, 23 μL, 0.21 mmol), THF (2 mL),

Et N (8.4 μL, 60 μmol), and [RhCl(nbd)] (31 mg, 6.7 μmol) were

added at room temperature. After stirring at room temperature for 60

min, the reaction mixture was poured into a large amount of MeOH

(

50 mL), centrifugally separated, and dried under vacuum to aﬀord 30

mg of 14 as an orange solid in 67% yield. The molecular weight (M_n)

and the molecular weight distribution (M /M ) were estimated by

SEC analysis. M = 18 000, M = 54 000, and M /M = 3.0. H NMR

(

400 MHz, CDCl ) δ 7.60 (s, 2H), 7.22−6.25 (br, 12H), 5.84 (s,

Macromolecules XXXX, XXX, XXX−XXX

Macromolecules

Complete contact information is available at:

Article

https://pubs.acs.org/10.1021/acs.macromol.9b02554

Weight and a Low Polydispersity. Macromolecules 2004, 37, 1169−

171.

15) Wang, Q.; Takita, R.; Kikuzaki, Y.; Ozawa, F. Palladium-

Catalyzed Dehydrohalogenative Polycondensation of 2-Bromo-3-

Hexylthiophene: An Efficient Approach to Head-to-Tail Poly(3-

Hexylthiophene). J. Am. Chem. Soc. 2010, 132, 11420−11421.

Notes

The authors declare no competing ﬁnancial interest.

17) Kim, B.; Chen, L.; Gong, J.; Osada, Y.; Kim; Chen, L.; Gong;

16) Patil, A. O.; Ikenoue, Y.; Wudl, F.; Heeger, A. J. Water Soluble

ACKNOWLEDGMENTS

Conducting Polymers. J. Am. Chem. Soc. 1987, 109, 1858−1859.

■

(

This work was partly supported by JSPS Kakenhi B Grant

Numbers JP25288049 and JP19182273 and Cooperative

Research Program of “Network Joint Research Center for

Materials and Devices”. The authors thank Professor Takashi

Nishino and Dr Takuya Matsumoto of Kobe University for

measurements and discussion on thermal analyses and XRD

measurements.

Osada, Y. Titration Behavior and Spectral Transitions of Water-

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