Self-assembled helical conjugated poly(m-phenylene) derivatives that afford whiskers with hexagonal columnar packed structure

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pubs.acs.org/Macromolecules

Self-Assembled Helical Conjugated Poly(m-phenylene) Derivatives

That Afford Whiskers with Hexagonal Columnar Packed Structure

Kiyoshi Suda and Kazuo Akagi*

Department of Polymer Chemistry, Kyoto University, Katsura, Kyoto 615-8510 (Japan)

S Supporting Information

b

ABSTRACT: We have synthesized a series of π-conjugated polymers,

poly(m-phenylene) [PMP] derivatives with chiral or racemic alkyl

groups in side chains. Peculiar liquid crystalline phases or crystalline

structures based on helical conjugated polymer main chains are

elucidated. The PMPs synthesized by polymerizations of chiral and

racemic monomers are found to self-assemble to form whiskers, so far

as the polymers bear secondary alkyl groups with appropriate lengths

in side chains. The whiskers have a hexagonal columnar packed

structure, and the columns are uniaxially aligned parallel to the long

axis of the whisker. The measurements of circular dichroism spectra

and X-ray diﬀractions indicate that the polymers have a one-handed

helical structure consisting of helicene-type conjugated main chains.

The chiral PMPs show not only linearly polarized ﬂuorescence after

the macroscopic alignment but also circularly polarized ﬂuorescence owing to the helical conjugated main chain.

π-conjugation on the main chain despite of the intrachain helical

structure. The m-phenylene fragment is likely a building block

suitable for construction of helicene-like helical structure because

of its ability to form a cis linkage between the 1 and 5 positions of

the phenylene ring. This hypothesis is supported by previous

studies showing that m-phenylethynylene oligomers spontaneously

form helical structures depending on solvent and temperature,¹²

and that the m-deciphenyl compound¹³and poly(m-phenylene)¹⁴

have helical structures where each turn of the helix has ﬁve

aromatic rings.

In this study, we designed and synthesized a series of novel

poly(m-phenylene) [PMP] derivatives with chiral or racemic groups

in the side chains. The PMPs have helicene-like helical structures

through intrachain π-electron overlaps. The PMPs self-assemble

to form whiskers when slowly cooled from the isotropic phase

irrespective of presence of chirality in the side chains. X-ray

diﬀraction (XRD) analyses indicate that the whisker is composed

of a hexagonal columnar packing of the helical main chains. The

formation of the whisker is the ﬁrst example among the helical π-

conjugated polymers reported so far.

1. INTRODUCTION

The whisker of the polymer is a spontaneously formed assem-

bly with a higher-order structure and could be used as a single

ﬁber serving for ampliﬁed intrinsic properties of the polymer.

The whiskers of aromatic polyesters such as poly(p-oxybenzoyl)

and poly(2-oxo-6-naphthoyl) have been intensively investigated,¹

while there have been few reports on the whiskers of conjugated

polymers except poly(3-alkylthiophene).²The whisker of poly-

(3-alkylthiophene) is composed of self-assembled planar conju-

gated chains stacked along the long axis of the polymer, yielding

laminated layers separated by alkyl side chains. However, no

whisker consisting of self-assembled helicene-like helical con-

jugated chains has been put forward until now. When the helical

conjugated polymer giving the whisker structure is designed, the

intrachain and interchain interactions must be balanced by

precisely controlling van der Waals, π-overlap, and electrostatic

interactions.

The helical conjugated polymers have been attracting much

interest because they could provide us with not only unique optical

functions such as circularly polarized luminescence³and nonlinear

second harmonic generation,⁴but also unprecedented physico-

chemical properties such as an induced solenoidal magnetism.⁵

Various kinds of helical conjugated polymers represented by helical

polyacetylenes,⁶amino acid-containing substituted polyacety-

lene derivatives,⁷poly(phenylacetylene) derivatives,⁸and poly-

thiophene derivatives⁹have been reported. These helical conjugated

polymers are constructed with intrachain-spiral, intrachain-twisted

ribbon, or interchain-helically π-stacked structures.¹⁰However,

there are a few reports of the conjugated polymers having a helicene-

like helical structure,^11ꢀ14which is favorable for maintaining

2. SYNTHESES

2.1. Materials. All the reagents were commercially available

and used without further purification. 3,5-Dibromobenzoic acid,

2,2⁰-bipyridine, (()-2-nonanol, diethyl azodicarboxylate (DEAD)

Received: August 12, 2011

Revised:

November 1, 2011

Published: November 21, 2011

r

2011 American Chemical Society

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Scheme 1. Synthetic Routes of Monomers and Polymers^a

^aKey: (a) DCC, DMAP, CH₂Cl₂. (b) DEAD, TPP, THF. (c) Ni(cod)₂, bpy, DMF. DCC: N,N⁰-dicyclohexylcarbodiimide. DMAP: N,N-

dimethylaminopyridine. DEAD: diethylazodicarboxylate. TPP: triphenylphosphine. Ni(cod)₂: bis(1,5-cyclooctadiene)nickel(0). bpy: 2,2⁰-bipyridyl.

(40 wt % solution in toluene), 1-hexanol, 1-octanol, 1-decanol,

1-hexadecanol, 2-hexanol, 2-octanol, 2-nonanol, 2-decanol,

2-undecanol, 2-tridecanol, 3-nonanol, 3-decanol and 3-un-

decanol were purchased from Tokyo Kasei Co. Ltd. (S)-(+)-

2-Nonanol, (R)-(ꢀ)-2-nonanol, and triphenylphosphine (TPP)

were purchased from Wako Co. Ltd. Nickel acetylacetonate was

purchased from Kanto Chemical Co. Ltd. Bis(1,5-cyclooctadiene)-

nickel(0) [Ni(COD)₂] was prepared by the literature procedure.¹⁵

THF and DMF were dried over sodium and potassium hydroxide,

respectively, and distilled prior to use. All experiments were per-

formed under an argon atmosphere.

2.2. Syntheses of polymers. Poly(m-phenylene) derivatives,

whose side chains are composed of various lengths of primary and

secondary racemic alkyl groups, and chiral (R)-(ꢀ)- or (S)-(+)-1-

methyloctyl group, were synthesized by following steps (Scheme 1).

Esteriﬁcation of 3,5-dibromobenzoic acid was carried out in

ethanol in the presence of small amount of sulfuric acid to give a

dibrominated precursor, ethyl 3,5-dibromobenzoate (M1, m =

2). Polymerizations of M1 (m = 2) was carried out in DMF by

dehalogenation polycondensations, where Nickel chloride was

reduced to give nickel(0) complex in the presence of zinc powder

and 2,2⁰-bipyridyl.

were carried out using dicyclohexylcarbodiimide (DCC) and N,

N-dimethylaminopyridine (DMAP), or diethyl azodicarboxylate

(DEAD) and triphenylphosphine (TPP), to give corresponding

dibrominated precursors, M1 (m = 6, 8, 10 and 16), M2 (m = 4,

6, 7, 8, 9 and 11), M3 (m = 8, 9 and 10), and (R)-M2 (m = 7) and

(S)-M2 (m = 7), as yellow to colorless oil in good yields.¹⁶The

stereochemistry of the chiral alcohol of the resulting precursor

changes into the opposite conﬁguration through a Walden’s

inversion in an S_N2 reaction. Polymerizations of the precursors

were carried out at 100 ꢀC in N,N-dimethylformamide using

Ni(COD)₂to give the corresponding poly(m-phenylene) deri-

vatives [P1, P2, P3, (R)-PMP and (S)-PMP] with good yields

(89ꢀ99%).¹⁷Here it should be noted that strictly speaking, (R)-

and (S)-PMP have homochiral side chains and P2 and P3 have

stereochemically random side chains with no optical activity. For

the sake of simplicity, however, (R)- and (S)-PMP are repre-

sented as the polymers having chiral side chains throughout the

manuscript.

3. RESULTS AND DISCUSSION

3.1. Molecular Weights and Thermal Properties. All the

polymers were soluble in common organic solvents such as

THF, CHCl₃and n-hexane, while they were fusible, except for P1

Other esteriﬁcations of 3,5-dibromobenzoic acid with long primary

and secondary alcohols or chiral (R)-(ꢀ)- and (S)-(+)-2-nonanol

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Table 1. Molecular Weights, Dispersion Ratio, and Degrees

of Polymerization Calibrated with Polystyrene Standard

Using THF as an Eluent^a

polymer

m

M_n

M_w

M_w/M_n

D.P. *

P1

2

2100

2300

2800

3700

2100

3000

3500

3100

3000

3600

2800

2000

2100

3500

3700

2900

3000

6200

3700

5400

3200

11 100

6200

4400

12 400

6700

4000

3700

6200

6600

1.3

2.6

1.3

1.5

3.7

1.7

1.4

4.1

1.9

1.4

2.0

1.8

1.7

1.8

14

11

10

11

10

13

14

12

11

12

11

8

6

8

10

16

4

P2

P3

6

7

8

9

11

8

9

10

7

8

(R)-PMP

(S)-PMP

14

15

7

^aM_n: number-average molecular weight. M_w: weight-average molecular

weight. M_w/M_n: degree of dispersion. DP: degree of polymerization.

(m = 2). The molecular weights of the polymers were evaluated

with gel permeation chromatography (GPC) calibrated with

polystyrene standard. As summarized in Table 1, number-

average molecular weights of the polymers were 2000ꢀ3700

and the degrees of polymerizations (DPs) were 8ꢀ15. The DP in

each type of the polymer (P1ꢀP3) tends to gradually decrease

with increasing the alkyl length (m) of side chain. It is probably

due to the steric hindrance of the polymer side chains between

neighbor units. All the polymers allowed us to prepare cast films

by casting the polymer solution onto substrates.

Introduction of a longer aliphatic chain into the side chains

leads to decreases in both melting and clearing points of the

polymers, as already conﬁrmed in several cases of calamitic (rod-

shaped liquid crystalline) compounds.¹⁸Upon slowly cooling the

polymers from the isotropic phases, they showed peculiar optical

textures, as depicted in Figure 1. The thermal behaviors of the

polymers were evaluated by DSC analyses and POM observa-

tions. The phase transition temperatures of the polymers are

summarized in Table 2.

The polymers with primary alkyl side chains, P1 (m = 6ꢀ16),

exhibited mosaic textures characteristic to discotic columnar

phases.¹⁹The domain seems rounded in cases of P1 (m =

6ꢀ10), but squared in a case of P1 (m = 16). It should be noted

that only P1 (m = 16) showed intense DSC peaks at 32 and 29 ꢀC

in the heating and cooling process, respectively, indicating an

occurrence of the second phase transition. The phase transition

temperatures were lowered with an increase of the chain lengths.

This may be due to the fact that the self-assembled polymers in

the meso phase are more ﬂexible and fusible when the alkyl

chains are incorporated to the side chains.²⁰

The phase transition temperatures of P2 with the secondary

alkyl side chains are slightly lower than those of P1 with the

primary alkyl side chains, probably due to smaller interactions

between the branched side chains. The polymers with methyl

branched longer alkyl groups, P2 (m = 6ꢀ8), showed whisker

morphologies when slowly cooled from the isotropic phases.^21,22

Figure 1. Polarized optical micrographs of the poly-m-phenylene

(PMP) polymers.

It seems necessary to have both methyl branched structure and

an appropriate carbon chain length from 7 to 9 for the formation

of the whisker morphology. Actually, P2 (m = 9) showed a bent

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Table 2. Phase Transition Temperatures and Characteriza-

tions of the PMP Polymers^a

phase, as depicted in Figure 2. The whiskers observed for the

present PMPs have 5ꢀ7 μm in diameter and about 100ꢀ200 μm

in length. The size of the whisker depends on not only the

polymer structure including side chains but also the cooling rate

from the isotropic phase. Large area of the POM micrograph is

dark, but the circularly polarized micrograph indicates that the

dark area even contains many whiskers (Figure 2b).

It is useful to remark here that P2 (m = 7) is analogous to the

(R)-PMP and (S)-PMP and that it also forms whiskers whose

morphology is very similar to those of (R)-PMP and (S)-PMP

(see Figure 1 and Figure 2). P2 (m = 7) is synthesized by the

polymerization of racemic monomer, M2 (m = 7), and it can be

regarded as a polymer bearing a stereochemically random side

chains with no optical activity but not as a racemic PMP. This is

because P2 (m = 7) should include (R)-PMP and (S)-PMP and

even the diastereomers having segments mixed with (R) and (S)-

m-phenylene units. Thus, it is worthwhile to note that the

whiskers of PMP might be formed through not only the self-

assembly of the chiral PMPs but also that of the diasteromers of

PMP.

polymer

m

heating (ꢀC)/cooling (ꢀC)

P1

2

b

6

S 158 Col_h250< I

S 130 Col_h250< I

S 152 Col_h250< I

S 126 Col_h250< I

S 131 Col_h209 I

S 106 Col_h182 I

S 26 D_L32 Col_h115 I

S 20 D_L29 Col_h110 I

S 126 Col_h250< I

S 120 Col_h250< I

S 158 Col_h231 I

S 110 Col_h208 I

S 126 Col_h210 I

S 117 Col_h205 I

S 127 Col_h197 I

S 114 Col_h170 I

S 126 Col_h206 I

S 112 Col_h193 I

S 118 Col_h191 I

S 110 Col_h164 I

S 37 Col_h66 I

8

10

16

4

P2

6

7

3.2. X-ray Diffraction Analysis. The structures of the poly-

mers in crystalline phases were investigated by X-ray diffraction

(XRD) measurements. The XRD results and the assignments

of the structures are summarized in Table 3. Schematic repre-

sentation of stacking structures for PMP derivatives is shown

in Figure 3.

8

9

11

8

P1 (m = 2) showed an intense peak corresponding to the

P3

distance of 17.1 Å and weak peaks of 9.5, 8.3, 6.2, and 5.4 Å

√

having the reciprocal Bragg spacing in ratios of 1: 3:2: 7:

S 33 Col_h58 I

√

3: 13:4. These peaks are respectively assigned to Miller indices

of (100), (110), (200), (210), and (300) reﬂections of hexagonal

arrangement with a lattice constant of a = 19.7 Å.^23ꢀ26The result

suggests that P1 (m = 2) is a hexagonal columnar (Col_h) crystal

structure consisting of helical main chains with cisoid linkages. In

addition, the peak of 3.6 Å, that is coincident with the typical

distance for πꢀπ stacking between aromatic rings of the helical

pitches, was also observed in the wide angle region (Figure S2, in

Supporting Information).^21,25,27This means that the lamination

of the aromatic units is ordered along the columnar axis, as

reported for the crystalline phase of triphenylene derivatives.²⁸

Similarly, P1 (m = 6ꢀ10) showed intense peaks around 21ꢀ25 Å

and some diﬀraction peaks based on the Col_hstructure. The

lattice parameters corresponding to the distances between the

columns increase with increasing the alkyl lengths of the side

chains. The broad halos around 4.1ꢀ4.6 Å are related to

disordered alkyl chains.²⁶Since P1 (m = 16) has two phases

in the crystal state, the temperature dependence of XRD proﬁle

of the polymer was examined. At higher temperature, the

polymer showed diﬀractions of 30.3, 17.7, 15.3, 11.2, 10.3, 8.4,

8.2, and 7.9 Å, that correspond to the reciprocal Bragg spacings in

9

S 99 Col_h145 I

S 95 Col_h127 I

S 91 Sm 131 I

10

7

S 86 Sm 114 I

(R)-PMP

(S)-PMP

S 126 Col_h210 I

S 117 Col_h205 I

S 126 Col_h210 I

S 117 Col_h205 I

7

^aS: solid state. Col_h: hexagonal columnar structure. D_L: discotic lamellar

structure. Sm: smectic liquid crystalline phase. I: isotropic phase.

^bInfusible.

whisker, whereas P2 (m = 11) gave no whisker but a fan shaped

texture.

The polymer with ethyl branched octyl group in side chain, P3

(m = 8), showed a homogeneously bright texture at 58 ꢀC on

cooling from the isotropic phase. The polymers with ethyl bran-

ched longer alkyl (noyl and octyl) groups, P3 (m = 9, 10), showed

batonnet textures that resemble to the textures of smectic liquid

crystalline polymers. As seen in Table 3, P3 (m = 8) has relatively

lower phase transition temperatures. This may be due to a larger

steric repulsion between the side chains, which decreases a

thermal stability of the polymers with self-assembled hexagonal

columnar (Col_h) structure. Thus, the morphologies of the PMP

derivatives crucially depend on the bulkiness and lengths of the

side chains.

The PMPs with chiral alkyl groups in the side chains [(R)-

PMP and (S)-PMP] were subsequently synthesized. The aver-

age molecular weights (M_n) of (R)-PMP and (S)-PMP were

3500 and 3700, respectively, and the degrees of polymerizations

(DPs) were 14 and 15, respectively. It is found that these racemic

polymers also form whiskers when slowly cooled from the isotropic

√

√ √

ratios of 1: 3:2: 7:3:2 3: 13:4 of Col_hphase with a lattice

constant of 35.0 Å; At the lower temperature (below 29 ꢀC), the

polymer showed diﬀraction peaks of 33.5, 16.8, 11.3, and 8.3 Å,

that are proportional to the reciprocal ratios of 1:2:3:4. These

peaks are assigned to (001), (002), (003), and (004) of a discotic

lamellar (D_L) phase with a lattice parameter of 33.6 Å.²⁹On the

other hand, the intense peak of 4.2 Å is assigned to a lamellar

structure of the alkyl group. It is understood that the introduction

of the long alkyl groups in the side of PMP leads to a drastic

change from the Col_hto the D_Lstructure.

P2 (m = 4) showed diﬀraction peaks of 19.8, 11.3, 9.7, 6.4, and

5.3 Å, that are respectively assigned to Miller indices of (100),

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Table 3. Crystal Structures and Lattice Parameters of PMP Polymers^a

polymer

m

lattice parameter/Å

diﬀraction distance/Å (Miller indices)

phase

P1

2^b

6

19.7

24.3

26.4

28.3

35.0

33.6

22.5

26.4

27.1

27.2

28.7

28.9

26.8

28.7

24.4

27.5

17.1 (100), 9.5 (110), 8.3 (200), 6.2 (210), 5.4 (300), 3.6

Col_h

D_L

21.4 (100), 12.1 (110), 10.4 (200), 8.0 (210), 7.0 (300), 4.1, 3.7

23.5 (100), 13.2 (110), 11.5 (200), 8.6 (210), 7.6 (300), 4.6, 3.7

25.0 (100), 14.3 (110), 12.0 (200), 9.2 (210), 8.1 (300), 4.5, 3.7

30.3 (100), 17.7 (110), 15.3 (200), 11.2 (210), 10.3 (300), 4.3

33.5 (100), 16.8 (200), 11.3 (300), 8.3 (400), 4.2, 3.7

8

10

16^c

P2

P3

4

6

19.8 (100), 11.3 (110), 9.7 (200), 6.4 (300), 5.3 (310), 4.1, 3.7

23.5 (100), 13.3 (110), 11.3 (200), 8.6 (210), 6.5 (220), 4.1, 3.7

23.8 (100), 11.9 (200), 8.7 (210), 7.8 (300), 6.5 (310), 4.1, 3.7

24.4 (100), 12.2 (200), 9.1 (210), 8.1 (300), 6.7 (310), 4.1, 3.7

24.9 (100), 12.4 (200), 9.3 (210), 8.3 (300), 6.9 (220), 4.1, 3.7

25.0 (100), 12.0 (200), 9.0 (210), 7.9 (300), 4.1, 3.7

Col_h

Sm

7

8

9

11

8

23.2 (100), 13.8 (110), 11.6 (200), 9.4 (210), 7.7 (300), 4.4, 3.7

24.1 (100), 18.4 (110), 12.0 (200), 8.8 (210), 7.9 (300), 4.4, 3.7

24.4 (100), 12.2 (200), 8.2 (300), 6.1 (400), 4.5, 3.7

9

10

7

(R)-PMP

(S)-PMP

23.5 (100), 13.6 (110), 11.8 (200), 8.8 (210), 7.8 (300), 6.7 (310), 5.8 (400), 4.4, 3.7

23.5 (100), 13.8 (110), 11.8 (200), 8.8 (210), 7.7 (300), 6.5 (310), 5.8 (400), 4.4, 3.7

Col_h

7

^aCol_h: hexagonal columnar structure. D_L: discotic lamellar structure. Sm: smectic liquid crystalline phase. ^bInfusible. ^cP1 (m = 16) shows Col_hand D_L

phases at higher and lower temperatures, respectively, between isotropic and solid states.

Figure 2. (a) Polarized optical micrograph and (b) circularly polarized

optical micrograph of (R)-PMP in the solid state.

(110), (200), (300), and (310) of Col_hwith a lattice constant of

a = 22.5 Å. Besides, the peak of 4.1 Å, assigned to the distance

between πꢀπ stacking corresponding to the helical pitch, was

observed in the wide angle region. Similar diﬀraction patterns

were also observed in other P2 (m = 6ꢀ11) polymers having the

whisker textures.

P3 (m = 8 and 9) showed the diﬀraction patterns of Col_hphase

with lattice constants of 26.8 and 28.7 Å, respectively. The

Figure 3. Schematic representation of stacking structures of PMP

polymers: (a) hexagonal columnar (Col_h), (b) discotic lamellar (D_L),

and (c) smectic (Sm) liquid crystalline structures.

diﬀractions with the index of (100) became narrowed with

lengthening of the side chain. The result suggests that the

hexagonal packing is strengthened by the introduction of the

bulky side chains, leading to an enhancement in ordering of

the stacking along the columnar axis. Furthermore, P3 (m = 10)

with the longer side chain showed diﬀractions of 24.4, 12.2, 8.2,

and 6.1 Å in the short angle region where the reciprocal Bragg

spacings are in ratios of 1:2:3:4. Such an integral diﬀraction

pattern seemingly looks like that of the D_Lphase. However,

only a broad halo at 4.5 Å and a shoulder peaks at 3.7 Å were

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Figure 4. X-ray diﬀraction proﬁle and pattern of (R)-PMP at the solid

state. Inset shows the expanded XRD proﬁles in the region of 5ꢀ17ꢀ in

2θ. The assignments for hexagonal columnar (Col_h) crystal are given in

the schematic ﬁgure of self-assembled polymers.

Figure 5. POM photographs of (R)-PMP: (a) solid state of the polymer

on an orientated substrate (orientated direction is vertical one); (b) the

sample is rotated by ꢀ45ꢀ from the position in part a; (c) the sample is

rotated by ꢀ90ꢀ from the position in part a.

observed in the wide angle region, indicating an absence of the

lamellar structure. Hence, this diﬀraction pattern could be

assigned to a smectic phase (Sm) with a layer distance of

24.4 Å.³⁰Note that the side chains of the polymers in the D_L

phase are slightly interdigitated, whereas those in the Sm

phase are not interdigitaed but separated to each other, as

shown in Figure 3.

3.3. Polarizing Optical Micrographs (POMs). To examine

how the columns of the PMP helices are organized to form a

whisker with hexagonal structure, the direction of birefringence

and the refractive index were investigated through POM mea-

surements (Figures 5 and 6). The whiskers were aligned by slowly

cooling the polymer on an oriented substrate from an isotropic to a

solid state, so that the axes of the whiskers were aligned parallel to

the orientation direction of the substrate. The optical texture of the

polymer was well preserved even in the solid state.

When the long axis of the whisker is placed parallel or

perpendicular to the direction of the analyzer, the anisotropic

region darkens because the optical axis of the whisker coincides

with the plane of polarization (Figure 5a). After the sample was

rotated ꢀ45ꢀ from the dark position, a bright area representing a

diagonal position was observed (Figure 5b). Further rotation of

the sample by ꢀ45ꢀ from the bright area produced a dark image

(Figure 5c). The result indicates that the columns of the helices

for the PMPs are uniaxially aligned parallel to the long axes of the

whiskers.²⁴

The refractive indexes of the whisker were next investigated by

examining changes in the interference colors. The changes in the

interference colors were observed with a retardation plate (λ=

530 nm). The aligned sample (the whisker) and the retardation

plate (λ= 530 nm) were set between the polarizer and analyzer.

The interference color was evaluated by changing the relative

angle between the retardation plate and the sample, as shown in

Figure 6. The interference color depends on the retardation (R)

of the light, where the retardation is the product of the thickness

(d) and the diﬀerence (Δn) of refractive index of the sample; R =

dΔn, where Δn = n ꢀ n_^. The retardation plate is arranged

parallel to the sample (see Figure S6 in Supporting Infor-

mation). In this case, when the interference color is blue, the

Δn is negative. This indicates that the refractive index (n )

It is of interest that the polymers with chiral side chains have

XRD results similar to those of the polymers with stereochemi-

cally random side chains. Figure 4 shows the XRD proﬁle and

pattern of (R)-PMP at the solid state. (R)-PMP shows an intense

peak at 23.8 Å and six weak peaks at 13.7, 11.7, 8.7, 7.8, 6.5, and

5.8 Å in the small angle region. A diﬀuse halo is present at 4.4 Å,

and a sharp but small halo is present at 3.7 Å in the wide angle

region. The peaks that represent the reciprocal Bragg spacings

√

with ratios of 1: 3:2: 7:3: 13:4 were assigned to Miller

indices of (100), (110), (200), (210), (300), (310), and (400),

respectively. The reﬂections have a hexagonal arrangement with

a lattice constant of a = 27.5 Å.^27,31The diﬀuse peak in the wide

angle region (4.4 Å) corresponds to the distance of the side

chains.²⁵The periodicity of 3.7 Å corresponds to the distance

between the π-stacks of the phenylene cores.^21,25,27These results

show that the polymer has a helicene-like helical structure with a

helical pith of 3.7 Å.^21,23,24

The XRD proﬁle of (R)-PMP is similar to those of columnar

discotic liquid crystals^21,23,24and helicenes.^25,26In fact, the

molecular mechanics (MM) calculations indicate that the helix

is composed of six repeating units, and the diameter is estimated

to be 25 Å. This estimate is in agreement with the experimental

results (27.5 Å) obtained from the XRD measurements.³²The

aromatic cores are not tilted with respect to the columnar axis.

The order of the whisker remains unchanged even in the solid

state.²⁸Similar XRD results were obtained for (S)-PMP. Hence,

the whisker has a hexagonal columnar (Col_h) structure consisting

of discotically packed helical conjugated polymers, as also illu-

strated in Figure 4.

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Figure 6. Interference colors of the whiskers of (R)-PMP observed on

an oriented substrate. The whiskers are (a) parallel and (c) perpendi-

cular to the inserted direction of ﬁrst-order retardation plate (λ =

530 nm). The relative angle between the whisker and the retardation

plate is (b) 45ꢀ, corresponding to the quenching position. The white

arrow in the photographs indicates the inserted direction of the

retardation plate, and this direction corresponds to the high refractive

index of the retardation plate. The yellow bar indicates the direction of

the whisker axis.

Figure 7. Method for preparation of aligned whisker bundles. (a)

Polymer was cooled from an isotropic to grow whiskers at 210 ꢀC

(ꢀ 0.5 ꢀC/min). (b) Polymer was aligned in the ﬂuid state with drawing.

parallel to the long axis of the sample is smaller than that

(n_^) perpendicular to the long axis of the sample. It also

means that the sample is negatively birefringent. When the

interference color is yellow, the Δn is positive, implying

than n is larger that n_^and hence the sample is positively

birefringent.

Figure 6 depicts the interference colors of the whiskers of (R)-

PMP observed on an oriented substrate. The interference color

changed to a higher order (second-order blue) along the ordinary

ray when the retardation plate was inserted parallel to the long

axis of the whisker (Figure 6a).^24,33The rotation of the sample by

90ꢀ from the previous position changed the color to a lower order

(ﬁrst-order yellow) along the extraordinary ray (Figure 6c). This

result indicates that the long axis of the whisker has a smaller

refractive index, and the short axis (perpendicular to the long

axis) a larger one. In other words, the whisker is negatively

birefringent. It is worthy noting that columnar discotic liquid

crystals have a larger refractive index in the horizontal plane than

in the perpendicular plane.³¹Hence, the planes of the π-stacked

phenylene moieties with a larger refractive index are aligned

perpendicular to the long axis of the whisker.²⁴

It is of interest to note that the polymer whiskers prepared

from polyesters and π-conjugated polythiophenes have struc-

tures in which the polymer main chains self-assemble parallel to

each other owing to van der Waals interactions between inter-

chains, and they are parallel to the direction of the whiskers. On

the other hand, the present whiskers prepared from helical π-

conjugated PMPs have the hexagonal columnar structure in

Figure 8. XRD patterns of the aligned whisker of (R)-PMP. The lower

pattern is an enlargement of the upper one. The arrow in the ﬁgure

shows the extended direction. The halos in XRD patterns are attributed

to π-stack (001), helical correlation (111) and (222), and hexagonal

columnar structure. The corresponding distances are indicated on the

schematically described pictures of the helical polymer and the hexago-

nal columnar structure.

which the polymer main chain is perpendicular to the direction of

the whiskers. This is quite in contrast to the polymer whiskers

reported so far.

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Figure 9. (a) UVꢀvis absorption and (b) ﬂuorescence spectra of (R)-

PMP in chloroform, cast ﬁlm, and annealed ﬁlm. The wavelength of the

excitation light is 274 nm.

3.4. XRD Analysis of Aligned Whiskers. To elucidate the

structure of the whisker in more detail, XRD measurements for

the aligned whisker were carried out on (R)-PMP. The sample

was prepared by drawing the polymer at an isotropic temperature

to obtain the aligned polymer, and then the sample was placed in

a glass capillary, as described in Figure 7. The XRD pattern of the

aligned sample is shown in Figure 8.

Figure 10. CD spectra of (R)-PMP and (S)-PMP in (a) chloroform

and (b) the cast ﬁlms (pink and light blue lines) and the annealed ﬁlms

(red and blue lines).

The diﬀraction peaks at 23.5, 13.6, 11.8, 8.8, 7.8, 6.7, and 5.8 Å

were assigned to Miller indices of (100), (110), (200), (210),

(300), (310) and (400), respectively (see Figure S5 in Support-

ing Information). The diﬀractions of the hexagonal arrangement

were observed perpendicular to the extended direction. The

diﬀraction peak at 3.7 Å (001) represents the distance of the π-

stacked phenylene rings and was observed parallel to the

extended direction (Figure 8). This distance is consistent with

the helical pitch of the polymer. The result implies that both the

helical axis and the stacking order are parallel to the long axis of

the whisker, and the hexagonal packing of the columns is arranged

perpendicular to the long axis of the whisker. The diﬀraction

peaks corresponding to the helical structure were observed at

7.3 Å (111). The XRD shows two pairs of the (111) diﬀraction

intersecting the long axis of the whisker, implying a helical

structure of the polymer chains. The value of 7.3 Å is in good

agreement with the helix diameter (7.0 Å) calculated for the

helical PMP using the molecular mechanics (MM) method.³⁴As

a consequence, it can be remarked that the whiskers are aligned

to form the bundle, and the long axes of the whiskers are parallel

to the aligned direction.

are assigned to πꢀπ* transition of main chain (250 nm) and that

of intrachain π-stacked phenylene moiety of PMP (302 nm).

In the chloroform solution of PMP, two ﬂuorescence bands

were observed at 360 and 420 nm (Figure 9b). These bands are

ascribed to ﬂuorescence of the randomly arranged zigzag main

chain (360 nm) and that of the helical main chain (420 nm). In

the cast ﬁlm, the ﬂuorescence band at 420 nm increased in

intensity, but the band at 360 nm was hardly observed. These

results suggest that PMP in solution forms partly an intrachain

helical π-stacked structure, as well as the nonhelical zigzag

structure. The helical structure may be due to π-stackings

between spatially adjacent phenylene moieties in the folded main

chain.³⁵Similar behavior in ﬂuorescence due to the formation

of a helical structure has been observed in a steady state for

poly(phenylacetylene)s.³⁶

Figure 10 depicts CD spectra of the chiral PMPs in chloro-

form, cast ﬁlm and annealed ﬁlms. The (R)-PMP and (S)-PMP

in chloroform showed bisignate CD bands with negative and

positive signs in Cotton eﬀect, respectively, at the region of

280ꢀ320 nm (Figure 10a). The bisignate CD bands may be

ascribed to the exciton coupling in the intrachain helicene-like

helical π-stacked phenylene moieties of the chiral PMPs. How-

ever, the CD intensities are very small, suggesting that the intrachain

3.5. Optical Properties. The UVꢀvis and fluorescence spec-

tra of (R)-PMP in chloroform, cast film and annealed film are

depicted in Figure 9. Absorption band was observed at 250 nm

and a shoulder at 302 nm in chloroform (Figure 9a). These bands

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Figure 11. Spectra of ﬂuorescence (top), circularly polarized ﬂuores-

cence (CPF) (middle) and dissymmetry factor (g factor) (bottom) for

annealed ﬁlms of (R)-PMP and (S)-PMP. The wavelength of excited

light is 274 nm. The dissymmetry factors (|g_em|) are estimated to be

1.27 ꢁ 10^ꢀ3at λ = 420 nm and 5.0 ꢁ 10^ꢀ3at λ = 550 nm.

helical π-stacked structure is loosely formed in solution, as

implied by the results of UVꢀvis spectra (Figure 9a).

Meanwhile, the cast ﬁlms of (R)-PMP and (S)-PMP showed

CD bands with substantially increased intensities (Figure 10b),

compared with the cases in solution. This implies that the

intrachain helical π-stacking is strengthened by the self-assembly

of the polymers in the cast ﬁlm. However, CD bands in the cast

ﬁlms have opposite signs in Cotton eﬀect to those in solution.

Namely, the positive and negative bisignate Cotton eﬀects are

observed in the cast ﬁlms of (R)-PMP and (S)-PMP, respec-

tively. It remains unclear why the chiral polymer dissolved in

solution and the self-assembled chiral polymers in the form of

ﬁlm exhibit the opposite signs in Cotton eﬀect to each other,

which should be further investigated.

In addition, the annealed ﬁlms of the (R)-PMP and (S)-PMP

show monosignate positive and negative CD bands with remark-

ably increased intensities (Figure 10b). The CD bands in the

annealed ﬁlms have the same signs in Cotton eﬀect as those in the

cast ﬁlms. This indicates that the intrachain helical π-stacking is

further strengthened by the annealing, giving rise to the highly

ampliﬁed helicity in the annealed ﬁlm. It should be noted that the

annealed ﬁlms exhibit long tails extending from 400 nm to over

800 nm, and they may be due to artifacts often observed in CD

spectra for aligned ﬁlms. These tails prohibited from grasping the

intrinsic features of CD bands, especially from the region from

400 nm to longer wavelength. It is worthwhile to emphasize that

the positive Cotton eﬀect of the annealed ﬁlm of (R)-PMP is

consistent with results observed for the chromophores of M-he-

licity in binaphthoxyethoxys and phthalocyanines.^27g,37,38This

supports that the (R)-PMP is stacked within the whisker and is

screwed with respect to the column axis, forming a left-handed

helical structure. Similarly, (S)-PMP with a negative Cotton

eﬀect should have P-helicity, i.e., a right-handed helical structure.

We also examined circularly polarized ﬂuorescence (CPF) for

(R)-PMP and (S)-PMP. Figure 11 depicts the ﬂuorescence

spectra, CPF spectra and dissymmetry factors of the polymers

Figure 12. Linearly polarized optical micrographs of (S)-PMP whis-

kers. The polymer shows a blue ﬂuorescence of 420 nm when excited

with a light of 365 nm. Arrows in the ﬁgures show the direction of the

polarizer.

in annealed ﬁlms. The dissymmetric factor in ﬂuorescence (g_em

)

is deﬁned as g_em= 2(I_Lꢀ I_R)/(I_L+ I_R) = 2ΔI/I, where I_Land I_R

are intensities of left- and right-handed CPFs, respectively.

Although the polymers in chloroform showed no CPF, the

annealed polymer ﬁlms showed CPFs with mirror images for

(R)-PMP and (S)-PMP. The dissymmetry factor evaluated was

|g_em| = 1.27 ꢁ 10^ꢀ3at 420 nm and 5.0 ꢁ 10^ꢀ3at 550 nm, which

is comparable to the values reported for chiral polythiophenes

(|g_em| = 5.0 ꢁ 10^{ꢀ3 1a}

)

and smaller than those of helicenes

(|g_em| = 1.0 ꢁ 10^ꢀ2).^24,39This is probably due to less torsion

between the π-stacked phenylene moieties, because the helical

structure of PMP is composed of coplanar disk-like π-stacked

phenylene moieties.

3.6. Linearly Polarized Luminescence. We investigated linear

polarizations in fluorescence of the PMP whisker (Figure S7 in

Supporting Information). Figure 12 shows the fluorescence of the

annealed film of (R)-PMP when excited with a light of wavelength

365 nm. When the long axis of the whisker was parallel to the plane

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Figure 14. POM photographs of the mixtures of (R)-PMP and (S)-

PMP at 190 ꢀC. The appearance of thinner, shorter and bent whiskers in

the mixing ratios of 70:30 and 30:70 [(R)-PMP:(S)-PMP] implies that a

cancellation in the helical sense between two chiral polymers has

occurred, and the growth of the whisker has decreased in velocity.

It is of keen interest to focus on the changes of the central area

in POM; At the beginning the whole central area was yet dark,

and then the whiskers gradually grew up to form the “whisker

region” in the central area. However, there was still no whisker in

the “dark boundary region” at this stage giving two dark boundary

areas, as seen in Figure 13a. After a while, the whiskers began to

grow in the dark boundary region (Figure 13b). Such changes in

the central area, as well as the appearance of the dark boundary

region, are due to a cancellation in the helical sense of (R)-PMP

and (S)-PMP and a suppressed growing of the whiskers. Namely,

(R)-PMP and (S)-PMP have opposite helical senses to each

other. The whiskers formed in the boundary region consist of an

equimolar mixture of chiral polymers and they are thermally less

stable than those of chiral polymers, (R)-PMP and (S)-PMP.

This is because the whiskers of the equimolar mixture of chiral

polymers are only formed at lower temperature than 204 ꢀC.

Nevertheless, it is important to remark that not only the chiral

PMPs but also the equimolar mixture of chiral PMPs form

whiskers.

It is also intriguing to understand how the whisker formation is

aﬀected when the two polymers with opposite chiral conﬁgura-

tions are mixed in various mixing ratios. The dependence of the

whisker formation on the mixing ratio between (R)-PMP and

(S)-PMP is examined by observing the morphological changes of

the whiskers. The POM photographs of the mixtures of (R)-

PMP and (S)-PMP at 190 ꢀC are depicted in Figure 14.

The mixtures give less condensed whisker morphologies than

the case of neat (R)-PMP or (S)-PMP, implying that the

racemization has partly occurred to decrease the velocity of the

whisker growth in the mixture. In the whisker consisting of the

Figure 13. (a) Contact test between (R)-PMP and (S)-PMP at 204 ꢀC.

The left and right sides of the photo are (R)-PMP and (S)-PMP,

respectively. The central area is the mixture of (R)- and (S)-PMP. The

central area has a whisker region and two dark boundary regions. In the

former (whisker region), the equimolar mixing of (R)- and (S)-PMP

gives thinner and shorter whiskers. In the latter (two dark boundary

region), it seems that nonequimolar mixing of (R)- and (S)-PMP

depresses a grow of whisker, resulting in a dark ﬁeld. (b) After cooling

to 190 ꢀC at the rate of ꢀ1 ꢀC/min, the whiskers began to grow in the

dark boundary.

of polarization of the analyzer (an angle of 0ꢀ), the blue fluorescence

(420 nm) became the brightest color in the analyzer (Figure 12a).

The fluorescence was quenched when the angle between the long

axis and the analyzer was perpendicular (90ꢀ) (Figure 12b). These

results indicate that the fluorescence at 420 nm arising from the

helically π-stacked phenylene moieties is polarized along the long

axis of the whisker, giving the linearly dichroic fluorescence.

3.7. Contact Test of Whiskers. To clarify the helical sense of

the whiskers, we carried out contact tests of the polymers. The

two polymers, (R)-PMP and (S)-PMP, were first heated to isotropic

states and then cooled slowly to the temperature of 204 ꢀC to

grow the whiskers at a rate of 0.2 ꢀC/min. Figure 13a shows a

POM photograph of the contacted region between (R)-PMP at

the left side and (S)-PMP at the right side. The central area in the

photograph has a whisker region and two dark boundary regions.

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5. EXPERIMENTAL SECTION

General Aspects. Proton (¹H) and carbon-13 (¹³C) nuclear

magnetic resonance (NMR) spectra were measured in CDCl₃using

Bruker AVANCE-500 or AVANCE-600 NMR spectrometer. Chemical

shifts are represented in parts per million downfield from tetramethylsi-

lane as an internal standard. Elemental analyses of compounds were

carried out with Perkin-Elmer 2400 CHN Elemental Analyzer. Mole-

cular weights of polymers were determined by gel permeation chroma-

tography (GPC) using a PLgel 5 μm MIXED-D column 300 ꢁ 7.5 mm

(Polymer Laboratories), a JASCO UV-2070 UV detector, and THF as

an eluent at a flow rate of 1.0 mL/min during measurements, where the

instrument was calibrated by polystyrene standard and calculated on a

BORWIN integrator.

The mesomorphic properties of the polymers were evaluated using

polarizing optical microscope (POM), diﬀerential scanning calorimeter

(DSC), and X-ray diﬀraction (XRD) measurements. The polymers for

the POM were sandwiched between two cover glasses. Phase transition

temperatures were determined using a TA Instruments Q-100 diﬀer-

ential scanning calorimeter (DSC) with a constant heating/cooling rate

of 10 ꢀC/min in a ﬂowing N₂atmosphere, while optical textures were

observed under crossed polarizers using a Nikon ECLIPS E 400 POL

polarizing microscope equipped with a Linkam TM 600PM heating and

cooling stage. The texture of the whiskers was further examined with

atomic force microscope (AFM). The samples for AFM was prepared by

casting a chloroform solution of the polymer onto a glass substrate,

followed by slowly cooling (about 1 ꢀC/min) from the isotropic tem-

perature to the solid state.

Speciﬁc rotations of the monomers and polymers were measured at

room temperature in chloroform using JASCO DIP-370. UVꢀvis

absorption spectra were measured at room temperature using a Hitachi

U-2000 spectrometer or a JASCO V-570. Photoluminescence spectra

were recorded using a JASCO FP-750 spectrometer. Circular dichroism

(CD) and circularly polarized ﬂuorescence (CPF) spectra were mea-

sured using a JASCO J-720 and a JASCO CPL-200S spectropolarimeters,

respectively. Dissymmetric factor in ﬂuorescence (g_em) is deﬁned as

g_em= 2(I_Lꢀ I_R)/(I_L+ I_R) = 2ΔI/I, where I_Land I_Rare ﬂuorescence

intensities of left- and right-handed circularly polarized light, respec-

tively. All the spectroscopic measurements, UVꢀvis, CD, ﬂuorescence,

and CPF spectra, were performed at room temperature using a quartz

cell or a quartz substrate. The ﬁlms for UVꢀvis, CD, ﬂuorescence, and

CPF measurements were prepared by casting the chloroform solutions

of the polymers on the quartz glasses. The ﬁlms were heated up to

230 ꢀC and cooled to their mesophase temperatures at a rate of 1 ꢀC/min,

and then cooled further to room temperature, giving annealed ﬁlms. The

measurement for linearly polarized ﬂuorescence was performed with the

microscope by observing the luminescent light of 420 nm through a

dichroic cut ﬁlter (λ = 395 nm) and a polarizer, where the anisotropic

domains were excited using an unpolarized light of 365 nm.

The samples for XRD measurements were prepared on the glass sub-

strates by slowly cooling the polymers (about 1 ꢀC/min) from the isotropic

phases to grow whiskers and then further cooling to the solid states at

room temperature. XRD measurements were performed with Rigaku

ultrax18HB diﬀractometer r using a Cu Kα irradiation (λ = 1.5418 Å), in

which X-ray power was set to 12 kW. The diﬀraction patterns were duplicated

on imaging plates, and recorded with R-AXIS DS3A. The d spacing was

calculated with the Bragg law of nλ = 2d sin θ, where n is an integer, λ is

the wavelength of incident light (1.54 Å) and θ is the diﬀraction angle.

Molecular mechanics (MM) calculations were performed using

CERIUS 2 software (version 2.0; Molecular Simulations Inc., Burling-

ton, MA) running on an Indigo2-Extreme graphics workstation (Silicon

Graphics) with the supplied parameter sets. The polymer model of 10

repeating unit was built by Polymer Builder in CERIUS 2 with the

starting main chain conformation of cis-geometry.

Figure 15. Transition temperature for the mixtures of (R)-PMP and

(S)-PMP. The transition temperatures are determined by the points

where whiskers begin to grow from isotropic phases in cooling process.

mixture of chiral polymers, a part of cancellation in helical sense

between two chiral polymers should have occurred. Interestingly,

the mixtures with mixing ratios of 70:30 and 30:70 [(R)-PMP:-

(S)-PMP] give curious whisker morphologies, where the whis-

kers are relatively thin and short and even bent. This result might

be due to a macroscopic enantioenrichment within the whiskers,

though it needs further investigation for clariﬁcation.

Figure 15 represents the transition temperatures for the

mixtures of (R)-PMP and (S)-PMP. The transition temperatures

are determined by the temperatures at which the whiskers begin

to grow from isotropic phases in cooling process. It is found that

the transition temperatures decrease with decreasing the enan-

tiomer excess (e.e.) under the conditions from 100:0 to 70:30

in the mixting ratio for (R)-PMP:(S)-PMP, and then increase

considerably for the racemate (the mixing ratio of 50:50). The

transition temperatures from 50:50 through 30:70 to 0:100 give

the mirror image of the above-mentioned changes. This result

well explains the phenomena of the contact test between (R)-

PMP and (S)-PMP as shown in Figure 13 and also the peculiar

dependence of the whisker formation on the mixing ratio of the

enantiomers as shown in Figure 14.

4. CONCLUSIONS

We synthesized poly(m-phenylene)s [PMPs] bearing chiral

or achiral alkyl groups in the side chains. The PMPs synthesized

by polymerizations of chiral and racemic monomers self-assem-

ble to form whiskers, so far as the polymers bear secondary alkyl

groups with appropriate lengths in side chains. The formation of

the whisker is the ﬁrst example among the helical π-conjugated

polymers reported so far. The whiskers are composed of hexagonal

columns based on the helicene-type helical π-conjugated poly-

mers, and the columns are uniaxially packed parallel to the long

axis of the whisker. The PMPs have helical structures both in

solution and as solid ﬁlms, and the helical structure is further

enhanced in the annealed ﬁlm. The chiral PMPs show not only

linearly polarized ﬂuorescence after the macroscopic alignment

but also circularly polarized ﬂuorescence owing to the helical

conjugated main chain. The present whiskers have columnar

hyperstructures consisting of self-assembled helical π-conjugated

polymers and could be useful for prototypes of functional single

ﬁbers bearing ampliﬁed helicity.

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Macroscopic alignment of the polymer was carried out by using an

oriented substrate. The sample was annealed above 230 ꢀC on the

substrate which had been rubbed with a polytetraﬂuoroethylene (PTFE)

rod at 170 ꢀC. The refractive indices of the polymers were examined by

observing a color with a retardation plate.

7.9 Hz), 4.32 (t, 2H, 6.7 Hz), 7.84 (t, 1H, 1.8 Hz), 8.09 (d, 2H, 1.8 Hz).

¹³C NMR (150 MHz, CDCl₃): δ 14.14, 22.59, 22.71, 25.95, 28.59,

29.25, 29.38, 29.50, 29.58, 29.65, 29.67, 29.68, 29.71, 31.94, 66.05,

122.97, 131.30, 133.69, 138.10, 164.08. Anal. Calcd for C₂₃H₃₆Br₂O₂: C,

54.77; H, 7.19. Found: C, 54.87; H, 7.16.

Ethyl-3,5-dibromobenzoate (M1, m = 2). To a suspension of 3,5-

dibromobenzoic acid in ethanol (30 mL) was added 0.7 mL of

concentrated H₂SO₄, and the homogenized solution was refluxed for

1 night. Then 20 mL of the solvent was removed under reduced pressure.

The reaction mixture was poured into ice water. The resulting pre-

cipitate was filtered and recrystallized from an ethanol/water solution to

give clear needle crystals (8.48 g, 77.0%). ¹H NMR (600 MHz, CDCl₃):

δ 1.40 (t, 3H, 7.1 Hz), 4.39 (q, 2H, 7.1 Hz), 7.84 (t, 1H, 1.8 Hz), 8.10 (d,

2H, 1.8 Hz). ¹³C NMR (150 MHz, CDCl₃): δ 14.24, 61.86, 122.95,

131.31, 133.63, 137.88, 164.02. Anal. Calcd for C₉H₈Br₂O₂: C, 35.10; H,

2.62; Br, 51.89. Found: C, 35.06; H, 2.80; Br, 51.69.

1-Hexyl-3,5-dibromobenzoate (M1, m = 6). A solution of 1-hexanol

(0.61 g, 5.90 mmol), 3,5-dibromobenzoic acid (1.50 g, 5.36 mmol),

DCC (1.22 g, 5.90 mmol) and DMAP (0.72 g, 5.90 mmol) in

dichloromethane (40 mL) was stirred at room temperature for 1 day.

Then, the precipitate of DCCꢀurea was removed by filtration, and the

solvent was removed under reduced pressure. The resulting product was

purified by column chromatography (silica gel, ethyl acetate/hexane =1/

8 v/v as eluent) to give a clear oil (1.82 g, 93%). ¹H NMR (400 MHz,

CDCl₃): δ 0.91 (t, 3H, 7.2 Hz), 1.34ꢀ1.44 (m, 6H), 1.76 (quint, 2H, 6.8

Hz), 4.32 (t, 2H, 6.8 Hz), 7.83 (t, 1H, 2.0 Hz), 8.08 (d, 2H, 2.0 Hz). ¹³C

NMR (100 MHz, CDCl₃): δ 14.06, 22.58, 25.67, 28.62, 31.47, 66.04,

122.89, 131.21, 133.63, 138.00, 163.93. Anal. Calcd for C₁₃H₁₆Br₂O₂: C,

42.89; H, 4.43. Found: C, 42.57; H, 4.36.

1-Octyl-3,5-dibromobenzoate (M1, m = 8). A solution of 1-octanol

(0.52 g, 3.93 mmol), 3,5-dibromobenzoic acid (1.00 g, 3.57 mmol),

DCC (0.81 g, 3.93 mmol), and DMAP (0.48 g, 3.93 mmol) in

dichloromethane (45 mL) was stirred at room temperature for 1 day.

Then, the precipitate of DCCꢀurea was removed by filtration, and the

solvent was removed under reduced pressure. The resulting product was

purified by column chromatography (silica gel, ethyl acetate/hexane =

1/8 v/v as eluent) to give a clear oil (1.36 g, 97%). ¹H NMR (400 MHz,

CDCl₃): δ 0.89 (t, 3H, 7.2 Hz), 1.29ꢀ1.43 (m, 10H), 1.76ꢀ1.79 (t, 2H,

7.2 Hz), 4.32 (t, 2H, 5.2 Hz), 7.83 (t, 1H, 2.0 Hz), 8.08 (d, 2H, 2.0 Hz).

¹³C NMR (100 MHz, CDCl₃): δ 14.15, 22.68, 26.00, 28.65, 31.47,

66.04, 122.89, 131.21, 133.63, 138.00, 163.93. Anal. Calcd for

C₁₅H₂₀Br₂O₂: C, 45.95; H, 5.14. Found: C, 46.18; H, 5.42.

1-Methylpentyl-3,5-dibromobenzoate (M2, m = 4). A solution of

2-hexanol (0.16 g, 1.58 mmol), 3,5-dibromobenzoic acid (0.40 g, 1.43

mmol), DCC (0.33 g, 1.58 mmol), and DMAP (0.19 g, 1.58 mmol) in

dichloromethane (15 mL) was stirred at room temperature for 1 day.

Then, a precipitate of DCCꢀurea was removed by filtration, and the

solvent was removed under reduced pressure. The resulting product was

purified by column chromatography (silica gel, ethyl acetate/hexane =

1/8 v/v as eluent) to give a clear oil (0.52 g, 99%). ¹H NMR (600 MHz,

CDCl₃): δ 0.91 (t, 3H, 7.1 Hz), 1.31ꢀ1.38 (m, 7H), 1.68 (dm, 2H, 78.8

Hz), 5.13ꢀ5.16 (sext, 1H), 7.84 (t, 1H, 1.8 Hz), 8.09 (d, 2H, 1.8 Hz).

¹³C NMR (150 MHz, CDCl₃): δ 13.98, 20.01, 22.51, 25.62, 27.57,

35.63, 73.00, 122.93, 131.28, 134.10, 137.99, 163.62. Anal. Calcd for

C₁₃H₁₆Br₂O₂: C, 42.89; H, 4.43. Found: C, 43.00; H, 4.52.

1-Methylheptyl-3,5-dibromobenzoate (M2, m = 6). A solution of

2-octanol (0.52 g, 3.93 mmol), 3,5-dibromobenzoic acid (1.00 g, 3.57

mmol), DCC (0.81 g, 3.93 mmol), and DMAP (0.48 g, 3.93 mmol) in

dichloromethane (45 mL) was stirred at room temperature for 1 day.

Then, a precipitate of DCCꢀurea was removed by filtration, and the

solvent was removed under reduced pressure. The resulting product was

purified by column chromatography (silica gel, ethyl acetate/hexane =1/

4 v/v as eluent) to give a clear oil (1.37 g, 98%). ¹H NMR (600 MHz,

CDCl₃): δ 0.88 (t, 3H, 7.1 Hz), 1.24ꢀ1.40 (m, 11H), 1.67 (dm, 2H,

75.2 Hz), 5.15 (sext, 1H), 8.04 (t, 1H, 1.8 Hz), 8.09 (d, 2H, 1.8 Hz). ¹³C

NMR (150 MHz, CDCl₃): δ 14.07, 19.99, 22.46, 25.38, 29.10, 31.69,

35.90, 73.01, 122.69, 131.27, 133.88, 137.97, 163.61. Anal. Calcd for

C₁₅H₂₀Br₂O₂: C, 45.95; H, 5.14. Found: C, 45.98; H, 5.28.

1-Methyloctyl-3,5-dibromobenzoate (M2, m = 7). A solution of

2-nonanol (0.57 g, 3.93 mmol), and 40% toluene solution of DEAD

(1.71 g, 3.93 mmol) in THF (10 mL) was added dropwise to a solution

of 3,5-dibromobenzoic acid (1.00 g, 3.57 mmol) and TPP (1.03 g, 3.93

mmol) in THF (10 mL), and then the reaction mixture was stirred at

room temperature for 48 h. The resulting solution was poured into water

and extracted with dichloromethane. The organic phase was washed

with water, dried over MgSO₄, and filtered. The solvent was removed

under reduced pressure. The resulting product was purified by column

chromatography (silica gel, dichloromethane as eluent) to give yellow oil

1

(1.40 g, 97%). H NMR (600 MHz, CDCl₃): δ 0.88 (t, 3H, 7.0 Hz),

1.22ꢀ1.40 (m, 13H), 1.67 (dm, 2H, 84 Hz), 5.14 (sext, 1H), 7.84 (t, 1H,

1.8 Hz), 8.09 (d, 2H, 1.8 Hz). ¹³C NMR (150 MHz, CDCl₃): δ 14.10,

20.00, 22.64, 25.42, 29.16, 29.38, 31.77, 35.89, 73.03, 122.93, 131.28,

134.09, 137.98, 163.63. Anal. Calcd for C₁₆H₂₂Br₂O₂: C, 47.32; H, 5.46.

Found: C, 47.48; H, 5.47.

1-Decyl-3,5-dibromobenzoate (M1, m = 10). A solution of 1-decan-

ol (0.62 g, 3.93 mmol), 3,5-dibromobenzoic acid (1.00 g, 3.57 mmol),

DCC (0.81 g, 3.93 mmol), and DMAP (0.48 g, 3.93 mmol) in dichlo-

romethane (45 mL) was stirred at room temperature for 1 day. Then, the

precipitate of DCCꢀurea was removed by filtration, and the solvent was

removed under reduced pressure. The resulting product was purified by

column chromatography (silica gel, dichloromethane as eluent) to give a

clear oil (1.46 g, 97%). ¹H NMR (600 MHz, CDCl₃): δ 0.88 (t, 3H, 7.1

Hz), 1.27ꢀ1.44 (m, 14H), 1.76 (quint, 2H, 7.9 Hz), 4.32 (t, 2H, 6.8 Hz),

7.84 (t, 1H, 1.8 Hz), 8.09 (d, 2H, 1.8 Hz). ¹³C NMR (150 MHz,

CDCl₃): δ 14.13, 22.69, 25.95, 28.59, 29.25, 29.30, 29.50, 29.53, 31.89,

66.05, 122.97, 131.30, 133.69, 138.10, 164.08. Anal. Calcd for C₁₇H₂₄-

Br₂O₂: C, 48.59; H, 5.76. Found: C, 48.58; H, 5.78.

1-Hexadecyl-3,5-dibromobenzoate (M1, m = 16). A solution of

1-hexadecanol (0.58 g, 2.36 mmol), 3,5-dibromobenzoic acid (0.60 g,

2.14 mmol), DCC (0.49 g, 2.36 mmol), and DMAP (0.29 g, 2.36 mmol)

in dichloromethane (20 mL) was stirred at room temperature for 1 day.

Then, the precipitate of DCCꢀurea was removed by filtration, and the

solvent was removed under reduced pressure. The resulting product was

purified by column chromatography (silica gel, ethyl acetate/hexane =

1/8 v/v as eluent) to give a clear oil (1.04 g, 97%). ¹H NMR (600 MHz,

CDCl₃): δ 0.88 (t, 3H, 7.1 Hz), 1.25ꢀ1.44 (m, 26H), 1.76 (quint, 2H,

1-Methylnonyl-3,5-dibromobenzoate (M2, m = 8). A solution of

2-decanol (0.63 g, 3.93 mmol), 3,5-dibromobenzoic acid (1.00 g, 3.57

mmol), DCC (0.81 g, 3.93 mmol), and DMAP (0.48 g, 3.93 mmol) in

dichloromethane (45 mL) was stirred at room temperature for 1 day.

Then, a precipitate of DCCꢀurea was removed by filtration, and the

solvent was removed under reduced pressure. The resulting product was

purified by column chromatography (silica gel, ethyl acetate/hexane =

1/8 v/v as eluent) to give a clear oil (1.46 g, 81%). ¹H NMR (400 MHz,

CDCl₃): δ 0.87 (t, 3H, 6.8 Hz), 0.94 (t, 3H, 7.2 Hz), 1.27ꢀ1.32 (m,

10H), 1.63ꢀ1.73 (m, 4H), 5.06 (sext, 1H), 7.83 (t, 1H, 2.0 Hz), 8.08 (d,

2H, 2.0 Hz). ¹³C NMR (100 MHz, CDCl₃): δ 9.73, 14.11, 22.63, 25.36,

27.06, 29.21, 31.73, 33.65, 77.49, 122.87, 131.18, 133.97, 137.88, 163.66;

Anal. Calcd for C₁₇H₂₄Br₂O₂: C, 48.59; H, 5.76; Br, 38.03. Found: C,

48.73; H, 5.84; Br, 37.65.

1-Methyldecyl-3,5-dibromobenzoate (M2, m = 9). A solution of

2-undecanol (0.68 g, 3.93 mmol), 3,5-dibromobenzoic acid (1.00 g, 3.57

mmol), DCC (0.81 g, 3.93 mmol) and DMAP (0.48 g, 3.93 mmol) in

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dichloromethane (45 mL) was stirred at room temperature for 1 day.

Then, a precipitate of DCCꢀurea was removed by filtration, and the

solvent was removed under reduced pressure. The resulting product was

purified by column chromatography (silica gel, ethyl acetate/hexane =

1/4 v/v as eluent) to give a clear oil (1.54 g, 99%). ¹H NMR (600 MHz,

CDCl₃): δ 0.87 (t, 3H, 7.1 Hz), 1.22ꢀ1.40 (m, 17H), 1.67 (dm, 2H,

22.66, 25.33, 27.01, 29.22, 29.45, 31.83, 33.59, 77.50, 122.95, 131.28,

134.03, 137.98, 163.80. Anal. Calcd for C₁₈H₂₈Br₂O₂: C, 49.79; H, 6.04.

Found: C, 50.04; H, 6.18.

Poly[5-ethyl-m-benzoate] (P1, m = 2). To a solution of M1 (m = 2)

(8.00 g, 2.60 mmol) in DMF (25 mL) was added zinc powder (7.33 g,

112 mmol), 2,2⁰-bipyridine (0.41 g, 2.60 mmol), triphenylphosphine

(2.73 g, 10.4 mmol), and nickel chloride (0.37 g, 2.60 mmol). The

reaction mixture was stirred at 85 ꢀC for 48 h, and then poured into 1 L

of HCl solution (concentrated HCl/MeOH, 1/1) and stirred at room

temperature for 6 h. The resulting white precipitate was filtered off,

redissolved in a minimum quantity of chloroform, and poured into 1 L of

MeOH to reprecipitate. After the mix was stirred for 24 h, the precipitate

was filtered off to give a white solid. The precipitate was washed with

disodium dihydrogen ethylenediaminetetraacetate dihydrate aq., water

followed by MeOH. A sequence of the procedure was repeated three

times. Yield: 2.74 g (71%). ¹H NMR (600 MHz, CDCl₃): δ 1.22ꢀ1.57

(br, 3H), 4.22ꢀ4.61 (br, 2H), 5.30ꢀ8.50 (br, 3H). Anal. Calcd for

C₉H₈O₂: C, 72.96; H, 5.44. Found: C, 72.41; H, 5.44.

74.6 Hz), 5.15 (sext, 1H), 7.84 (t, 1H, 1.8 Hz), 8.09 (d, 2H, 1.8 Hz). ¹³

C

NMR (150 MHz, CDCl₃): δ 14.13, 20.00, 22.68, 25.41, 29.29, 29.41,

29.49, 29.51, 31.88, 35.89, 73.02, 122.92, 131.27, 134.09, 137.97, 163.61.

Anal. Calcd for C₁₈H₂₆Br₂O₂: C, 49.79; H, 6.04. Found: C, 50.08;

H, 6.25.

1-Methyldodecyl-3,5-dibromobenzoate (M2, m = 11). A solution of

2-tridecanol (0.87 g, 4.33 mmol), 3,5-dibromobenzoic acid (1.10 g, 3.93

mmol), DCC (0.90 g, 4.33 mmol) and DMAP (0.53 g, 4.33 mmol) in

dichloromethane (60 mL) was stirred at room temperature for 1 day.

Then, a precipitate of DCCꢀurea was removed by filtration, and the

solvent was removed under reduced pressure. The resulting product was

purified by column chromatography (silica gel, ethyl acetate/hexane 1/8

1

v/v as eluent) to give a clear oil (1.59 g, 87%). H NMR (600 MHz,

Poly[5-(1-hexyl)-m-benzoate] (P1, m = 6). To a solution of M1 (m =

6) (0.71 g, 1.94 mmol) in DMF (4 mL) was added 2,2⁰-bipyridine

(0.45 g, 2.91 mmol) and Ni(cod)₂(0.80 g, 2.91 mmol). The reaction

mixture was stirred at 100 ꢀC for 48 h, and then poured into 500 mL of

HCl solution (concentrated HCl/MeOH, 1/9) and stirred at room

temperature for 2 h. The precipitate was filtered off, redissolved in a

minimum quantity of THF, and poured into 500 mL of MeOH to

reprecipitate. After the mix was stirred for 1 night, the precipitate was

filtered to give P1 (m = 6) as a white solid. Yield: 0.30 g (76%). ¹H NMR

(600 MHz, CDCl₃): δ 0.84ꢀ0.98 (m, 3H), 1.22ꢀ1.53 (m, 6H),

1.64ꢀ1.91 (m, 2H), 4.29ꢀ4.67 (m, 2H), 7.86ꢀ8.20 (m, 1H),

8.25ꢀ8.53 (m, 2H). ¹³C NMR (150 MHz, CDCl₃): δ 14.00, 22.50,

25.61, 28.64, 31.40, 65.64, 127.98, 130.65, 132.09, 141.33, 166.17. Anal.

Calcd for C₁₃H₁₆O₂: C, 76.44; H, 7.90. Found: C, 74.45; H, 7.62.

Poly[5-(1-octyl)-m-benzoate] (P1, m = 8). To a solution of M1

(m = 8) (0.65 g, 1.66 mmol) in DMF (3 mL) was added 2,2⁰-bipyridine

(0.39 g, 2.49 mmol) and Ni(cod)₂(0.69 g, 2.49 mmol). The reaction

mixture was stirred at 80 ꢀC for 48 h, and then poured into 500 mL of

HCl solution (concentrated HCl/MeOH, 1/9) and stirred at room

temperature for 2 h. The precipitate was filtered off, redissolved in a

minimum quantity of THF, and poured into 500 mL of MeOH to

reprecipitate. After the mix was stirred for 1 night, the precipitate was

filtered to give P1 (m = 8) as a white solid. Yield: 0.33 g (85%). ¹H NMR

(600 MHz, CDCl₃): δ 0.80ꢀ0.90 (m, 3H), 1.19ꢀ1.64 (m, 10H),

1.76ꢀ1.90 (m, 2H), 4.36ꢀ4.46 (m, 2H), 8.13ꢀ8.17 (m, 1H),

8.31ꢀ8.57 (m, 2H). ¹³C NMR (150 MHz, CDCl₃): δ 14.05, 22.59,

25.94, 28.69, 29.15, 29.20, 31.74, 65.65, 127.98, 130.65, 132.08, 141.33,

166.67. Anal. Calcd for C₁₅H₂₀O₂: C, 77.55; H, 8.68. Found: C, 76.75;

H, 8.37.

Poly[5-(1-decyl)-m-benzoate] (P1, m = 10). To a solution of M1

(m = 10) (0.57 g, 1.36 mmol) in DMF (4 mL) was added 2,2⁰-bipyridine

(0.26 g, 1.64 mmol) and Ni(cod)₂(0.45 g, 1.64 mmol). The reaction

mixture was stirred at 100 ꢀC for 72 h, and then poured into 1000 mL of

HCl solution (concentrated HCl/MeOH, 1/9) and stirred at room

temperature for 2 h. The precipitate was filtered off, redissolved in a

minimum quantity of THF, and poured into 1000 mL of MeOH to

reprecipitate. After the mix was stirred for 1 night, the precipitate was

filtered to give P1 (m = 10) as a brown solid. Yield: 0.42 g (88%). ¹H

NMR (400 MHz, CDCl₃): δ 0.87 (br, 3H), 1.26ꢀ1.43 (m, 14H),

1.80ꢀ1.81 (br, 2H), 4.38 (br, 2H), 7.89ꢀ8.10 (m, 2H), 8.16ꢀ8.52 (m,

2H). Anal. Calcd for C₁₇H₂₆O₂: C, 77.82; H, 9.99. Found: C, 76.52;

H, 8.57.

CDCl₃): δ 0.88 (t, 3H, 7.1 Hz), 1.25ꢀ1.40 (m, 21H), 1.67 (dm, 2H,

74.5 Hz), 5.13ꢀ5.30 (sext, 1H), 7.84 (t, 1H, 1.8 Hz), 8.09 (d, 2H, 1.8

Hz). ¹³C NMR (150 MHz, CDCl₃): δ 14.13, 20.00, 22.69, 25.41, 29.35,

29.42, 29.49, 29.56, 29.62, 29.63, 31.91, 35.90, 73.02, 122.93, 131.28,

134.11, 137.98, 163.62. Anal. Calcd for C₂₀H₃₀Br₂O₂: C, 51.97; H, 6.54.

Found: C, 52.24; H, 6.57.

1-Ethylheptyl-3,5-dibromobenzoate (M3, m = 8). A solution of

3-nonanol (0.81 g, 3.93 mmol), 3,5-dibromobenzoic acid (1.00 g, 3.57

mmol), DCC (0.81 g, 3.93 mmol), and DMAP (0.48 g, 3.93 mmol) in

dichloromethane (45 mL) was stirred at room temperature for 1 day.

Then, a precipitate of DCCꢀurea was removed by filtration, and the

solvent was removed under reduced pressure. The resulting product was

purified by column chromatography (silica gel, ethyl acetate/hexane =

1/8 v/v as eluent) to give a clear oil (1.40 g, 97%). ¹H NMR (400 MHz,

CDCl₃): δ 0.87 (t, 3H, 6.8 Hz), 1.26ꢀ1.37 (m, 13H), 1.65 (dm, 2H,

45.6 Hz), 5.14 (sext, 1H), 7.83 (t, 1H, 2.0 Hz), 8.08 (d, 2H, 2.0 Hz). ¹³C

NMR (100 MHz, CDCl₃): δ 14.16, 20.05, 22.71, 25.46, 29.27, 29.47,

31.88, 35.94, 73.01, 122.85, 131.18, 134.04, 137.88, 163.47. Anal. Calcd

for C₁₆H₂₂Br₂O₂: C, 47.32; H, 5.46, Br, 39.35. Found: C, 47.42; H, 5.55;

Br, 38.32.

1-Ethyloctyl-3,5-dibromobenzoate (M3, m = 9). A solution of

3-decanol (0.63 g, 3.93 mmol), 3,5-dibromobenzoic acid (1.00 g, 3.57

mmol), DCC (0.81 g, 3.93 mmol), and DMAP (0.48 g, 3.93 mmol) in

dichloromethane (45 mL) was stirred at room temperature for 1 day.

Then, a precipitate of DCCꢀurea was removed by filtration, and the

solvent was removed under reduced pressure. The resulting product was

purified by column chromatography (silica gel, ethyl acetate/hexane =

1/8 v/v as eluent) to give a clear oil (1.43 g, 95%). ¹H NMR (600 MHz,

CDCl₃): δ 0.87 (t, 3H, 7.1 Hz), 0.94 (t, 3H, 7.4 Hz), 1.22ꢀ1.35 (m,

10H), 1.60ꢀ1.75 (m, 4H), 5.07 (quint, 1H), 7.84 (t, 1H, 1.8 Hz), 8.10

(d, 2H, 1.8 Hz). ¹³C NMR (150 MHz, CDCl₃): δ9.68, 14.09, 22.63,

25.34, 27.01, 29.16, 29.46, 31.77, 33.60, 77.51, 122.95, 131.28, 134.03,

137.99, 163.82. Anal. Calcd for C₁₇H₂₄Br₂O₂: C, 48.59; H, 5.76. Found:

C, 48.89; H, 5.90.

1-Ethylnonyl-3,5-dibromobenzoate (M3, m = 10). A solution of

3-undecanol (0.68 g, 3.93 mmol), 3,5-dibromobenzoic acid (1.00 g, 3.57

mmol), DCC (0.81 g, 3.93 mmol) and DMAP (0.48 g, 3.93 mmol) in

dichloromethane (45 mL) was stirred at room temperature for 1 day.

Then, a precipitate of DCCꢀurea was removed by filtration, and the

solvent was removed under reduced pressure. The resulting product was

purified by column chromatography (silica gel, ethyl acetate/hexane =

1/4 v/v as eluent) to give a clear oil (1.55 g, 100%). ¹H NMR (600 MHz,

CDCl₃): δ 0.87 (t, 3H, 7.0 Hz), 0.94 (t, 3H, 7.4 Hz), 1.25ꢀ1.34

(m, 12H), 1.59ꢀ1.73 (m, 4H), 5.07 (quint, 1H), 7.84 (t, 1H, 1.8 Hz),

8.10 (d, 2H, 1.8 Hz). ¹³C NMR (150 MHz, CDCl₃): δ 9.68, 14.11,

Poly[5-(1-hexaecyl)-m-benzoate] (P1, m = 16). To a solution of M1

(m = 16) (0.70 g, 1.39 mmol) in DMF (6 mL) was added 2,2⁰-bipyridine

(0.33 g, 2.09 mmol) and Ni(cod)₂(0.58 g, 2.09 mmol). The reaction

mixture was stirred at 80 ꢀC for 72 h, and then poured into 300 mL of

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HCl solution (concentrated HCl/MeOH, 1/9) and stirred at room

temperature for 1 h. The precipitate was filtered off, redissolved in a

minimum quantity of chloroform, and poured into 300 mL of MeOH to

reprecipitate. After the mix was stirred for 1 night, the precipitate was

filtered to give P1 (m = 16) as a brown solid. Yield: 0.21 g (44%). ¹H

NMR (400 MHz, CDCl₃): δ 0.83ꢀ0.86 (m, 3H), 1.21ꢀ1.41 (m, 26H),

1.80 (m, 2H), 4.37ꢀ4.45 (m, 2H), 7.92ꢀ8.13 (m, 1H), 8.30ꢀ8.58 (m,

2H). Anal. Calcd for C₂₃H₃₆O₂: C, 80.18; H, 10.53. Found: C, 78.90;

H, 10.42.

Poly[5-(1-methyhexyl)-m-benzoate] (P2, m = 4). To a solution of

M2 (m = 4) (0.70 g, 1.92 mmol) in DMF (6 mL) was added 2,2⁰-

bipyridine (0.45 g, 2.88 mmol) and Ni(cod)₂(0.80 g, 2.88 mmol). The

reaction mixture was stirred at 60 ꢀC for 72 h, and then poured into

300 mL of HCl solution (concentrated HCl/MeOH, 1/9) and stirred at

room temperature for 2 h. The precipitate was filtered off, redissolved in

a minimum quantity of THF, and poured into 300 mL of MeOH to

reprecipitate. After the mix was stirred for 1 night, the precipitate was

filtered to give P2 (m = 4) as a white solid. Yield: 0.33 g (85%). ¹H NMR

(600 MHz, CDCl₃): δ 0.86ꢀ0.96 (m, 3H), 1.26ꢀ1.46 (m, 7H),

1.61ꢀ1.88 (m, 2H), 5.18ꢀ5.30 (m, 1H), 7.86ꢀ8.13 (m, 1H),

8.28ꢀ8.54 (m, 2H). ¹³C NMR (150 MHz, CDCl₃): δ 14.00, 14.06,

20.13, 20.19, 22.50, 22.58, 27.70, 27.77, 35.67, 72.45, 127.98, 130.70,

132.44, 141.42, 165.75. Anal. Calcd for C₁₃H₁₆O₂: C, 76.44; H, 7.90.

Found: C, 74.31; H, 7.18.

(0.36 g, 2.25 mmol) and Ni(cod)₂(0.62 g, 2.25 mmol). The reaction

mixture was stirred at 100 ꢀC for 48 h and then poured into 500 mL of HCl

solution (concentrated HCl/MeOH, 1/9) and stirred at room temperature

for 2 h. The precipitate was filtered off, redissolved in a minimum quantity of

THF, and poured into 500 mL of MeOH to reprecipitate. After the mix was

stirred for 1 night, the precipitate was filtered to give P2 (m = 9) as a white

solid. Yield: 0.33 g (81%). ¹H NMR (400 MHz, CDCl₃): δ 0.80ꢀ0.85 (m,

3H), 1.19ꢀ1.45 (m, 17H), 1.63ꢀ1.86 (m, 2H), 5.21ꢀ5.31 (m, 1H),

7.88ꢀ8.12 (m, 1H), 8.30ꢀ8.58 (m, 2H). Anal. Calcd for C₁₈H₂₆O₂: C,

78.79; H, 9.55. Found: C, 78.05; H, 9.38.

Poly[5-(1-methyldodecyl)-m-benzoate] (P2, m = 11). To a solution

of M2 (m = 11) (0.70 g, 1.51 mmol) in DMF (6 mL) was added 2,2⁰-

bipyridine (0.36 g, 2.27 mmol) and Ni(cod)₂(0.63 g, 2.27 mmol). The

reaction mixture was stirred at 60 ꢀC for 48 h and then poured into

300 mL of HCl solution (concentrated HCl/MeOH, 1/9) and stirred at

room temperature for 2 h. The precipitate was filtered off, redissolved in

a minimum quantity of THF, and poured into 300 mL of MeOH to

reprecipitate. After the mix was stirred for 1 night, the precipitate was

1

filtered to give P2 (m = 11) as a white solid. Yield: 0.42 g (93%). H

NMR (600 MHz, CDCl₃): δ 0.81ꢀ0.86 (m, 3H), 1.11ꢀ1.45 (m, 21H),

1.60ꢀ1.85 (m, 2H), 5.22ꢀ5.31 (m, 1H), 7.86ꢀ8.22 (m, 1H), 8.31ꢀ

8.53 (m, 2H). ¹³C NMR (150 MHz, CDCl₃): δ 14.10, 20.12, 22.66,

25.58, 29.32, 29.44, 29.53, 29.61, 31.87, 36.00, 72.45, 127.99, 130.67,

132.44, 141.42, 165.73. Anal. Calcd for C₂₀H₃₀O₂: C, 79.42; H, 10.00.

Found: C, 78.02; H, 9.14.

Poly[5-(1-methylheptyl)-m-benzoate] (P2, m = 6). To a solution of

M2 (m = 6) (0.65 g, 1.66 mmol) in DMF (3 mL) was added 2,2⁰-

bipyridine (0.39 g, 2.49 mmol) and Ni(cod)₂(0.69 g, 2.49 mmol). The

reaction mixture was stirred at 100 ꢀC for 48 h, and then poured into

500 mL of HCl solution (concentrated HCl/MeOH, 1/9) and stirred at

room temperature for 2 h. The precipitate was filtered off, redissolved in

a minimum quantity of chloroform, and poured into 500 mL of MeOH

to reprecipitate. After the mix was stirred for 1 night, the precipitate was

filtered to give P7 as a white solid. Yield: 0.35 g (91%). ¹H NMR (400

MHz, CDCl₃): δ 0.79ꢀ0.88 (m, 3H), 1.24ꢀ1.46 (m, 11H), 1.61ꢀ1.79

(m, 2H), 5.20ꢀ5.30 (m, 1H), 7.89ꢀ8.14 (m, 1H), 8.30ꢀ8.59 (m, 2H).

Anal. Calcd for C₁₅H₂₀O₂: C, 77.55; H, 8.68. Found: C, 77.44; H, 8.77.

Poly[5-(1-methyloctyl)-m-benzoate] (P2, m = 7). To a solution of

M2 (m = 7) (1.05 g, 2.59 mmol) in DMF (9 mL) was added 2,2⁰-

bipyridine (0.61 g, 3.89 mmol) and Ni(cod)₂(1.07 g, 3.89 mmol). The

reaction mixture was stirred at 60 ꢀC for 48 h, and then poured into

1000 mL of HCl solution (concentrated HCl/MeOH, 1/9) and stirred

at room temperature for 2 h. The precipitate was filtered off, redissolved

in a minimum quantity of THF, and poured into 1000 mL of MeOH to

reprecipitate. After the mix was stirred for 1 night, the precipitate was

filtered to give P2 (m = 7) as a white solid. Yield: 0.47 g (74%). ¹H NMR

(400 MHz, CDCl₃): δ0.80ꢀ0.86 (m, 3H), 1.24ꢀ1.45 (m, 10H),

1.56ꢀ1.77 (m, 2H), 5.21ꢀ5.22 (m, 1H), 7.92ꢀ8.10 (m, 1H), 8.30ꢀ

8.53 (m, 2H). Anal. Calcd for C₁₆H₂₄O₂: C, 77.38; H, 9.74. Found: C,

77.52; H, 8.83.

Poly[5-(1-methynonyl)-m-benzoate] (P2, m = 8). To a solution of

M2 (m = 8) (0.65 g, 1.60 mmol) in DMF (6 mL) was added 2,2⁰-

bipyridine (0.38 g, 2.40 mmol) and Ni(cod)₂(0.66 g, 2.40 mmol). The

reaction mixture was stirred at 80 ꢀC for 48 h and then poured into

300 mL of HCl solution (concentrated HCl/MeOH, 1/9) and stirred at

room temperature for 2 h. The precipitate was filtered off, redissolved in

a minimum quantity of THF, and poured into 300 mL of MeOH to

reprecipitate. After the mix was stirred for 1 night, the precipitate was

filtered to give P2 (m = 8) as a white solid. Yield: 0.33 g (83%). ¹H NMR

(400 MHz, CDCl₃): δ 0.79ꢀ0.85 (m, 3H), 1.20ꢀ1.45 (m, 15H),

1.58ꢀ1.88 (m, 2H), 5.19ꢀ5.30 (m, 1H), 7.88ꢀ8.11 (m, 1H), 8.30ꢀ

8.58 (m, 2H). Anal. Calcd for C₁₇H₂₄O₂: C, 78.42; H, 9.29. Found: C,

77.52; H, 9.10.

Poly[5-(1-ethylheptyl)-m-benzoate] (P3, m = 8). To a solution of M3

(m = 8) (0.65 g, 1.60 mmol) in DMF (6 mL) was added 2,2⁰-bipyridine

(0.38 g, 2.40 mmol) and Ni(cod)₂(0.66 g, 2.40 mmol). The reaction

mixture was stirred at 80 ꢀC for 48 h and then poured into 300 mL of

HCl solution (concentrated HCl/MeOH, 1/9) and stirred at room

temperature for 1 h. The precipitate was filtered off, redissolved in a

minimum quantity of chloroform, and poured into 300 mL of MeOH to

reprecipitate. After the mix was stirred for 1 night, the precipitate was

filtered to give P3 (m = 8) as a white solid. Yield: 0.32 g (79%). ¹H NMR

(400 MHz, CDCl₃): δ 0.79ꢀ0.87 (m, 3H), 0.94ꢀ1.06 (m, 3H),

1.23ꢀ1.31 (m, 8H), 1.64ꢀ1.83 (m, 4H), 5.12ꢀ5.23 (m, 1H), 7.90ꢀ

8.15 (m, 1H), 8.32ꢀ8.60 (m, 2H). Anal. Calcd for C₁₆H₂₂O₂: C, 78.01;

H, 9.00. Found: C, 77.23; H, 9.05.

Poly[5-(1-ethyloctyl)-m-benzoate] (P3, m = 9). To a solution of M3

(m = 9) (0.65 g, 1.55 mmol) in DMF (6 mL) was added 2,2⁰-bipyridine

(0.37 g, 2.33 mmol) and Ni(cod)₂(0.64 g, 2.33 mmol). The reaction

mixture was stirred at 100 ꢀC for 48 h and then poured into 500 mL of

HCl solution (concentrated HCl/MeOH, 1/9) and stirred at room

temperature for 2 h. The precipitate was filtered off, redissolved in a

minimum quantity of chloroform, and poured into 500 mL of MeOH to

reprecipitate. After the mix was stirred for 1 night, the precipitate was

filtered to give P3 (m = 9) as a white solid. Yield: 0.32 g (78%). ¹H NMR

(400 MHz, CDCl₃): δ 0.78ꢀ0.87 (m, 3H), 0.94ꢀ1.06 (m, 3H), 1.20ꢀ

1.47 (m, 10H), 1.64ꢀ1.83 (m, 4H), 5.12ꢀ5.23 (m, 1H), 7.90ꢀ8.14 (m,

1H), 8.32ꢀ8.60 (m, 2H). Anal. Calcd for C₁₇H₂₄O₂: C, 78.42; H, 9.29.

Found: C, 77.95; H, 9.18.

Poly[5-(1-ethynonyl)-m-benzoate] (P3, m = 10). To a solution of

M3 (m = 10) (0.65 g, 1.50 mmol) in DMF (6 mL) was added 2,2⁰-

bipyridine (0.36 g, 2.25 mmol) and Ni(cod)₂(0.62 g, 2.25 mmol). The

reaction mixture was stirred at 100 ꢀC for 48 h and then poured into

500 mL of HCl solution (concentrated HCl/MeOH, 1/9) and stirred at

room temperature for 2 h. The precipitate was filtered off, redissolved in

a minimum quantity of chloroform, and poured into 500 mL of MeOH

to reprecipitate. After the mix was stirred for 1 night, the precipitate was

1

filtered to give P3 (m = 10) as a white solid. Yield: 0.41 g (99%). H

NMR (400 MHz, CDCl₃): δ0.79ꢀ0.85 (m, 3H), 0.94ꢀ1.06 (m, 3H),

1.25ꢀ1.46 (m, 12H), 1.62ꢀ1.84 (m, 4H), 5.13ꢀ5.23 (m, 1H), 7.93ꢀ

8.14 (m, 1H), 8.32ꢀ8.60 (m, 2H). Anal. Calcd for C₁₈H₂₆O₂: C, 78.79;

H, 9.55. Found: C, 78.88; H, 9.64.

Poly[5-(1-methyldecyl)-m-benzoate] (P2, m = 9). To a solution of M2

(m = 9) (0.65 g, 1.50 mmol) in DMF (6 mL) was added 2,2⁰-bipyridine

9486

dx.doi.org/10.1021/ma201846m |Macromolecules 2011, 44, 9473–9488

Macromolecules

ARTICLE

(R)-(ꢀ)-1-Methyloctyl-3,5-dibromobenzoate [(R)-M2, m = 7].

(S)-(+)-2-Nonanol (4.10 g, 29.0 mmol) and DEAD (5.00 g, 40 wt %

in toluene, 29.0 mmol) dissolved in THF (10 mL) was added dropwise

to a solution of 3,5-dibromobenzoic acid (8.00 g, 29.0 mmol) and TPP

(7.50 g, 29.0 mmol) in THF (20 mL). The mixture was stirred for 48 h at

60 ꢀC under an argon atmosphere. The solution was poured into water

and extracted with dichloromethane. The organic phase was washed

with water, dried over MgSO₄, and filtered. The solvent was removed

under reduced pressure, and the residue was purified by column chro-

matography (silica gel, dichloromethane as eluent) to give yellow oil

’ AUTHOR INFORMATION

Corresponding Author

*E-mail: akagi@fps.polym.kyoto-u.ac.jp.

’ ACKNOWLEDGMENT

We thank Mr. Jun Yoshida for his helpful cooperation in

polarized optical microscope measurements.

This work is supported by a Grant-in-Aid for Science Research

(S) (No. 20225007) from the Ministry of Education, Culture,

Sports, Science and Technology, Japan.

1

(8.6 g, 74%). H NMR (600 MHz, CDCl₃): δ 0.88 (t, 3H, 7 Hz),

1.36ꢀ1.25 (m, 12H), 1.66 (d, 3H, 53 Hz), 5.14 (sext, 1H, 6 Hz), 7.83

(s, 1H), 8.08 (s, 2H). ¹³C NMR (150 MHz, CDCl₃) δ 14.1, 20.0, 22.6,

25.4, 29.2, 29.4, 31.8, 35.9, 73.0, 122.9, 131.3, 134.1, 138.0, 163.6; Anal.

22

’ REFERENCES

Calcd for C₂₃H₂₉NO₂: C, 47.3; H, 5.46. Found: C, 47.0; H 5.53. [α]_D

ꢀ25.9ꢀ (c = 1.0 in chloroform).

=

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(S)-(+)-1-Methyloctyl-3,5-dibromobenzoate [(S)-M2, m = 7]. The

titled compound was prepared from 2-nonanol (5.7 g, 40 mmol), DEAD

(17 g, 40 mmol), 3,5-dibromobenzoic acid (11 g, 40 mmol), and TPP

(10 g, 40 mmol) in THF (40 mL), using the same procedure as that for

(R)-(ꢀ)-1-methyloctyl-3,5-dibromobenzoate. Yield: 12 g (74%). ¹H

NMR (600 MHz, CDCl₃): δ 0.90 (t, 3H, 7 Hz,), 1.39ꢀ1.29 (m, 12H),

1.70 (d, 3H, 68 Hz), 5.17 (sext, 1H, 6 Hz), 7.86 (s, 1H), 8.11 (s, 2H). ¹³C

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73.0, 122.9, 131.3, 134.1, 138.0, 163.6. Anal. Calcd for C₂₃H₂₉NO₂: C,

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Poly{5-[(R)-(ꢀ)-1-methyloctyl]-m-benzoate} [(R)-PMP, m = 7]. A

mixture of DMF (5 mL) and 2,2⁰-bipyridine, bpy (0.94 g, 6.02 mmol),

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solved in 5 mL of DMF was added to it. The mixture was stirred at

100 ꢀC for 48 h. The reaction mixture was cooled to room temperature,

poured into a large amount of a mixture of 12 M hydrochloric acid and

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filtrate was reprecipitated in methanol (1000 mL). After stirring for 24 h,

the resulting precipitate was collected by filtration. (R)-PMP was

obtained as a brown solid (1.28 g, 99%). ¹H NMR (600, MHz, CDCl₃):

δ 0.81 (t, 3H, 7 Hz), 1.37ꢀ1.13 (m, 12H), 1.71 (d, 3H, 80 Hz), 5.22

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Poly{5-[(S)-(+)-1-methyloctyl]-m-benzoate} [(S)-PMP, m = 7]. The

titled polymer was prepared from (S)-(+)-1-methyloctyl-3,5-dibromo-

benzoate (2.10 g, 51.7 mmol), 2,2⁰-bipyridine (0.94 g, 6.02 mmol), and

Ni(cod)₂(1.65 g, 6.00 mmol) in DMF (10 mL), with the same

procedure as that for poly{5-[(R)-(ꢀ)-1-methyloctyl]-m-phenylbenzoate}.

Yield: 1.25 g (97%). ¹H NMR (600 MHz, CDCl₃): δ 0.81 (t, 3H, 7 Hz),

8.35 (s, 2H), 1.37ꢀ1.13 (m, 12H), 1.71 (d, 3H, 78 Hz), 5.22 (sext, 1H, 6

Hz), 8.11 (s, 1H), 8.35 (s, 2H). ¹³C NMR (125 MHz, CDCl₃): δ 14.4,

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’ ASSOCIATED CONTENT

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Self-assembled helical conjugated poly(m-phenylene) derivatives that afford whiskers with hexagonal columnar packed structure

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