固相における置換ポリアセチレンの外部刺激によるへリックス転移メタデータ

言語: Japanese
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公開日: 2014-06-26
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キーワード (En):作成者: 元茂, 朝日
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URL

https://doi.org/10.15118/00005113

Doctoral Thesis

Helix Rearrangement of Substituted Polyacetylenes
Induced byExternal Stimulus in the Solid Phase

ASAHI MOTOSHIGE

Department of Chemical and Materials Engineering
Muroran Institute of Technology

博 士 学 位 論 文

	
  題	
  目

固相における置換ポリアセチレンの	 外部刺激によるヘリックス転移	
 

氏	
  名	
  	
 	
  	
  元茂	
  朝日	
 

室蘭工業大学	  大学院工学研究科
博士後期課程	  物質工学専攻

Contents

Introduction .................................................................................................................. 1

Chapter 1. 	
  Irreversible Helix Rearrangement from Cis-transoid to Cis-cisoid in
Poly (p-n-hexyloxyphenylacetylene) Induced by Heat-treatment in Solid Phase ........ 11

Chapter 2. 	
  Contracted Helix to Stretched Helix Rearrangement of an Aromatic	 Polyacetylene Prepared in n-Hexane with [Rh(norbornadiene)Cl]2-triethylamine
Catalyst ......................................................................................................................... 40

Chapter 3. 	
  Synthesis and Solid State Helix to Helix Rearrangement ofPoly(phenylacetylene) Bearing n-Octyl Alkyl Side Chains ......................................... 68

Summary of this thesis ............................................................................................. 100

List of publications ................................................................................................... 104

Acknowledgments ..................................................................................................... 106	 Introduction1π-Conjugated Polymers
	  π-Conjugated polymers consist of alternative double-bonds and single-bonds, andthey have been synthesized using various catalysts.1,2 Furthermore, at present theirchemical and physical properties are also studying extensively.1 There are two types of
π-conjugation polymers. The first is linear π-conjugated polymers such aspoly(acetylene)s,3 poly(phenylene)s,4 poly(thiophene)s,5 and another is poly(aromatichydrocarbon)s such as graphite hexa-peri-hexabenzocoronenes.6
	  These polymers have fairly long π-conjugation lengths which affect the various
properties, e.g., colors such as yellow, red, and black.7,8 These phenomena were causedby the degree of the π-conjugation system. The differences or changes of polymer
colors are correlated with the absorption band depending on conformation of the
π-conjugated main-chains or phenyl-rings.

Figure 1. Various of π-conjugated polymers and materials.

2

Polyacetylenes
Polyacetylene is one of typical π-conjugated polymers which have alternative single
bond and double bond. In 1958, Natta and coworkers prepared the poly(acetylene)s forthe first time by using a Ti-based catalyst.9 This polyacetylene is known to have atrans-transoid structure among four theoretically possible conformers, e.g., cis-transoid,
cis-cisoid, trans-cisoid, and trans-transoid.10
Films of the non-substituted polyacetylene were synthesized by Shirakawa and hiscolleagues. Then, they found that the electrical conductivity is highly increased byhalogen doping.11 This is a very important finding in the field of chemistry. Because
this is a first discover, i.e., the polyacetylene polymers have high industrial potential as
indicated by high conductivity as metals.

Moreover, this work provided the Nobel

Prize award in Chemistry for Prof. ALAN J. HEEGER, Prof. ALAN G.
MACDIARMID, and Prof. HIDEKI SHIRAKAWA in 2000. Although thisnon-substituted polyacetylene has important and interest properties but this polymer has
also disadvantages, e.g., insoluble in organic solvents. On the other hands, many
substituted polyacetylenes have displayed interesting properties, such as oxygen
permeability,12 semi conductivities,13 humidity sensitivity,14 nonlinear optical properties(NLO),15 amino acid permselective properties,16 external stimulus responsibility,17anti-ferromagnetic properties accompanying with the time memory effect,18 andradiation sensitive properties.19 The substituted polyacetylenes having many kind of
substitutes as the side-chain have been synthesized by using various type of catalysts
such

as

Ziegler-Nattacatalyst,

Fe(acac)3-AlH(i-Bu)2,20
3

Luttinger

catalyst,

(n-Bu3P)2NiCl2-NaBH4,21 Co(NO2)2-NaBH4,22 RhCl3-LiBH4,20 Wilkinson catalyst,
RhCl(PPh3)3,20 Pt or Ni complex catalysts,23,34 metathesis catalysts such as WCl6 or
MoCl5,24,25 Rh complex catalyst like [Rh(nbd)Cl]2-cocatalyst (nbd=norbornadiene),26
and zwitterionic Rh catalyst.27 Especially, metathesis catalysts have been developed bysome groups.24,25 It is well known that the transition metal chloride-based catalysts are
effective in metathesis polymerization of substituted acetylenes, but the molecularweight is up to around 5000. In 1974, Masuda group found that transition metal
chlorides, i.e., WCl6 and MoCl5, are quite active for the polymerization of substituted
acetylene.28 However, the molecular weight of the polymers is less than 10000.
Additionally, these polymers had different structures, e.g., cis-rich or trans-rich whose
structures are depended on polymerization conditions or catalysts, and these weresoluble and mainly amorphous.29

Figure 2. Synthesis of substituted polyacetylene with a Rh complex catalyst.

The [Rh(nbd)Cl]2 catalyst was revealed to induce the polymerization of thesubstituted acetylenes under quite mild conditions by Tabata group.26 And also, the Rh

4complex catalyst afford the highly stereoregular substituted polyacetylenes with ahelical cis-transoid main-chain which generates a molecular assemble in the solid phase,i.e., pseudohexagonal crystal structure called columnar which has a long-range
positional order along the molecular axis.30 Tabata group also revealed thattriethylamine or alcohol causes the dissociation of the binuclear complex, [Rh(nbd)Cl]2
into the monomeric species which may, in turn, function as an important initiation
species for this polymerization. There are marked structural and physicochemicaldifferences between π−conjugated polymers prepared using Rh complex and metathesis
catalysts as evidenced by NMR, ESR, and laser Raman spectroscopies.26,30

Diameter: D

D

	
 

(110)
(100)

(200)

Figure 3. Pseudohexagonal crystal structure called columnar.

Helical Polyacetylenes
Deoxyribonucleic acid (DNA) has a stable helical conformation. Many helical5

polymers as DNA have been synthesized. Recently, helical polymers including
substituted polyacetylenes with one-handed helical conformation have received muchattention because the chiral structure are expected to enhance unique properties andproperties.31 For example, Aoki’s group have reported helix-sense-selective
polymerization of achiral phenlacetylene monomers having two hydroxyl groups.32
Yashima’s group has been reported the helix inversions of various helicalpolyacetylenes proposed based on CD spectral data.31,33
On the other hands, Tabata’s group reported that poly(phenylacetylene)s preparedusing the Rh complex catalyst showed various colors, e.g., red, yellow, and black.17
These colors in difference are related to different π-conjugated system. Accordingly, it
is considered that the main-chain of these polymers have different pitches, loose helix
or tight helix.

Purposes of this Thesis	  The substituted polyacetylenes display many interesting properties which are related
to the geometrical structure and higher-order structure of the helical main-chain.
However, the helical pitch width, its diameter, and the crystal structures of substitutedpolyacetylenes which were stereoregularly prepared with the Rh complex catalyst,[Rh(norbornadiene)Cl]2-triethylamine have not yet been investigated in detail.
Therefore, we have investigated whether the geometrical and helical structures of thesubstituted polyacetylenes can be controlled through molecular design and/or external
stimuli.
6Reference
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Am. Chem. Soc. 1998, 120, 8895-8896. (e) E. Yashima, T. Matsushima, Y.
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8

17. Y. Mawatari, M. Tabata, J. Jpn. Soc. Colour Mater 2009, 82, 204-209.
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Synth. Met. 2003, 139, 99-107. (c) M. Tabata, Y. Nozaki, W. Yang, K. Yokota, Y.
Tazuke, Proc. Jpn. Acad. 1995, 71, 219-224. (d) K. H. Fisher, J. A. Herz, Spinglass; Cambridge University Press: 1991, 30. (e) J. J. Pregjean, J. Souletie, J. Phys.
1980, 41, 1335-1352. (f) L. Floch, F. Hammann, J, Ocio, M. Vincent, Euro. Phys.
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M. Tabata, Jpn. J. Appl. Phys. Part 2 Lett. 2004, 43, 300-302.
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10Chapter 1
Irreversible Helix Rearrangement from Cis-transoid toCis-cisoid in Poly(p-n-hexyloxyphenylacetylene)
Induced by Heat-treatment in Solid Phase11

Abstract
Polymerizationof

p-n-hexyloxyphenylacetylene(pHPA)

by

using

a

[Rh(norbornadine)Cl]2-triethylamine catalyst was carried out at room temperature toafford stereoregular helical poly(p-n-hexyloxyphenylacetylene)s (PpHPAs). Whenethanol and n-hexane were used as polymerization solvents, a bright yellow PpHPAs,
poly(Y) with Mn = 8.5 x 104 and its purple red polymer, poly(R) with Mn = 5.3 x 104
were obtained in 95% yields and 84% yields, respectively. Diffuse reflective UV-vis
spectra of poly(Y) and poly(R) in solid phase showed different broad absorption peaks
at 445 and 575 nm, respectively. X-Ray diffraction patterns of poly(Y) and poly(R)showed typical columnar structures assignable to cis-transoid and cis-cisoid structures,
respectively, which were also supported by molecule mechanics calculation. Poly(Y)was irreversibly transformed to a reddish-black polymer, poly(Y→B), which columnar
diameter was nearly the same as that of poly(R). Further, poly(Y) showed an
exothermic peak in the differential scanning calorimetry trace at 80 ℃ for 1 h in N2
gas. Thus, these findings suggest a thermally irreversible rearrangement from an
unstable cis-transoid form, poly(Y) with a stretched cis-transoid helix to a stablecis-cisoid form, poly(R), with a contracted cis-cisoid helix in the solid phase to givepoly(Y→B) with the cis-cisoid form.

12

Introduction
Polyacetylenes (PAs) and mono-substituted PAs (SPAs), which are one of the typicalconjugated polymers, have been prepared by using various types of catalysts, such as
Ziegler–Nattacatalyst,(n-Bu3P)2NiCl2-NaBH4,2Fe(acac)3-AlH(i-Bu)2,1

Co(NO2)2-NaBH4,3

Luttinger

RhCl3-LiBH4,1

Wilkinson

catalyst,
catalyst,

RhCl(PPh3)3,1 Pt or Ni complex catalysts,4,5 metathesis catalysts such as WCl6 or
MoCl5,6 Rh-diene catalyst, [Rh(nbd)Cl]2-cocatalyst (norbornadiene, nbd),7 andzwitterionic mono-Rh complex catalyst.8 Among them, the Rh catalyst was revealed toinduce the polymerization of the substituted acetylenes (SAs) and afford the highly
stereoregular SPAs with a helical cis-transoid main-chain which generates a molecularassemble based on the hexagonal crystal structure called a columnar.7,9 The SPAs
displayinterestingsolid-phase

properties,

such

as

oxygenpermeability,10

semiconductivities,11 humidity sensitivity,12 nonlinear optical properties,13 amino acidpermselective properties,14 external stimulus responsibility,15 antiferromagnetic
properties accompanying with the time memory effect,16 and radiation sensitive
properties.17 To the best of our knowledge, the cis-cisoid helix with contracted pitches
has been considered as an interesting one among four theoretically possible conformers,for example, cis-transoid, cis-cisoid, trans-cisoid, and trans-transoid for a longtime.18,19 Further it seems that an important question regarding whether the cis-cisoid
helix is really generated in solution and/or in solid phase has remained still unsolved.18
Because detailed physicochemical properties regarding the cis-transoid and cis-cisoid
helices in the solid and/or solution phases are not enough understood. In this report, we
13

describe the formation of the two poly(p-n-hexyloxyphenylacetylene)s (PpHPAs), that
is, a bright yellow poly(Y) consisting of cis-transoid helix with stretched pitches andpurple red poly(R) consisting of cis-cisoid helix with contracted pitches. A Rh-dienecatalyst, [Rh(nbd)Cl]2 and triethylamine(NEt3) as cocatalyst in ethanol (EtOH) or
n-hexane (Hex) were used for the polymerization at 25 ℃. Furthermore, the thermallyinduced rearrangement of the stretched cis-transoid helical form to the contracted
cis-cisoid form at about 80 ℃ was studied, and such helical structures for poly(Y) andpoly(R) were characterized in details by 1H NMR, wide angle X-ray diffraction (XRD),
solution and diffuse reflective UV–vis (DRUV–vis) spectra, resonance laser Raman
spectra in solid phase using an Ar+ laser and molecular mechanics (MM) calculation(MMFF94 force field).

14Experimental Section
Materials
Absolute ethanol, n-hexane, and triethylamine were distilled before use.
[Rh(nbd)Cl]2 (nbd = norbornadiene) was purchased from Aldrich and used without
further purification.

Monomer Synthesis
The monomer, p-n-hexyloxyphenylacetylene pHPA, was prepared according to aliterature20 and purified by distillation under reduce pressure before use.
99 °C/22 Pa.

1B. p.:H NMR (500 MHz, CDCl3, ppm): 7.41 (Ph-H, d, J = 8.9 Hz, 2H),

6.83 (Ph-H, d, J = 8.9 Hz, 2H), 3.95 (PhOCH2, t, J = 6.7 Hz, 2H), 2.99 (C≡CH, s, 1H),
1.82-1.72 (OCH2CH2, m, 2H), 1.49-1.41 (OCH2CH2CH2, m, 2H), 1.38-1.29(OCH2CH2CH2CH2CH2, m, 4H), 0.90 (CH2CH3, t, J = 7.1 Hz, 3H).

13

C NMR (125MHz, CDCl3, ppm): 159.51, 133.53, 114.41, 113.80, 83.75, 75.63, 68.03, 31.54, 29.10,
25.66, 22.58, 14.02.

Anal. Calcd for C14H18O: C, 83.12; H, 8.97. Found: C, 83.08; H,

9.10.

Polymerization
Poly(p-n-hexyloxyphenylacetylene)s (PpHPA) were prepared by polymerization of
pHPA using [Rh(nbd)Cl]2 as catalyst and NEt3 as cocatalyst in EtOH or Hex.

In atypical procedure, 700 mg (3.5 mmol) of pHPA and 16 mg (3.5 x 10-2 mmol) of[Rh(nbd)Cl]2, and 0.48 ml of NEt3 (3.5 mmol) were dissolved in 17.3 mL of Hex or
15

EtOH in a specially designed U-shaped flask.7

The polymerization was continued at

25 °C for 0.5 h, and quenched by adding 300 mL of methanol.

The polymer obtained

was filtered off, washed with methanol, followed by dynamic vacuum drying at 4 x 10-2
torr for 24 h.
Poly(Y) was obtained as a bright yellow powder (95%) by polymerization in EtOH:
1

H NMR (500 MHz, CDCl3, ppm): 6.59 (br., 2H), 6.43 (br., 2H), 5.75 (br., 1H), 3.67

(br., 2H), 1.65 (br., 2H), 1.5-1.2 (br., 6H), 0.89 (br., 3H). 13C NMR (125 MHz, CDCl3,ppm): 158.15, 138.62, 135.69, 130.14, 128.73, 113.58, 67.86, 31.73, 29.40, 25.86,
22.63, 14.08. Anal. Calcd. for C14H18O: C, 83.12; H, 8.97. Found: C, 82.72; H, 9.07.
Poly(R) was obtained as a purple red powder (84%) by polymerization in Hex: 1H
NMR (500 MHz, CDCl3, ppm): 6.59 (br., 2H), 6.43 (br., 2H), 5.75 (br., 1H), 3.67 (br.,2H), 1.65 (br., 2H), 1.5-1.2 (br., 6H), 0.89 (br., 3H).

13

C NMR (125 MHz, CDCl3,ppm): 158.15, 138.63, 135.69, 130.18, 128.74, 113.59, 67.87, 31.74, 29.40, 25.86, 22.64,
14.08.

Anal. Calcd. for C14H18O: C, 83.12; H, 8.97. Found: C, 82.22; H, 9.07.

Thermal Treatment
Poly(Y) placed at the bottom of a test tube was immersed in a pre-heated oil bath at
80 °C for 1 h under N2.

The color of poly(Y) was gradually changed from brightyellow to reddish black (poly(Y→B)).

Measurements
Number- and weight average molecular weights (Mn and Mw) of the polymers were16

measured using JASCO GPC 900-1 equipped with two Shodex K-806L columns and RI
detector.

Chloroform was used as eluent at 40 ºC, and polystyrene standards (Mn =800−1,090,000) were employed for calibration.

1

H (500 MHz) NMR and 13C (125MHz) NMR spectra were measured on a JEOL ECA-500 in CDCl3 at room temperature.
Solution and diffuse reflective UV-Vis (DRUV-Vis) spectra of the polymers wererecorded on a JASCO V570 spectrophotometer equipped with an ISV-470 integrating
sphere accessory.

Wide angle X-ray diffraction (XRD) patterns of the polymers wererecorded on a RIGAKU RINT2200 Ultima with CuKα as a radiation source equippedwith a heater with a programmable temperature controller (PTC-30).

Differential

scanning calorimetry (DSC) was performed on a SHIMADZU DSC-60 and traces wererun in an atmosphere of N2 at heating rate of 1 or 10 °C/min.

Laser Raman spectra

were measured on JASCO NR-1800S using laser light at 532 nm

using samples

obtained after mixing 3 mg of each polymer and 200 mg of KBr with a mortar andpestle.

Molecular Mechanics Calculation
Energetically optimal conformation of 20-mer of pHPA was deduced by molecularmechanics calculation using MMFF94 force field (Wavefunction, Inc., Spartan ’04
Windows version 1.0.3).21

17

Results and Discussion
Polymerization
Polymerization of the monomer, pHPA, in a catalytic system of[Rh(nbd)Cl]2/NEt3

in EtOH or Hex was carried out at 25 °C to afford the corresponding PpHPAs as shownin Scheme 1.

The yield with number average molecular weights (Mn), its distributions(Mw/Mn), and the ratio of cis carbon-carbon double bonds are listed in Table 1.
Poly(Y) was obtained in EtOH in 95% yield, and poly(R) was obtained in Hex in 84%
yield, respectively.

Their cis%s were carefully calculated based on the integration

ratio of vinyl proton and methyl or methylene protons observed in the 1H NMR
spectra.26,27 Previously, we have reported that an organic solvent such as EtOH or
NEt3 with lone pair electrons induces the dissociation of the dimeric Rh complex
catalyst to give a substantial monomeric species, which is stabilized with the solventand causes a good polymerization.18a,c,26

In contract, Hex has not been used as thepolymerization solvent, and its solvent effect has not been known, up to date to the bestof our knowledge.

18

Scheme 1. Synthesis of poly(p-n-hexyloxyphenylacetylene)s having a stretched
cis-transoid helix and a contracted cis-cisoid helix using a [Rh(nbd)Cl]2-NEt3 catalyst
in ethanol or n-hexane.

Table 1.
polymer

Polymerization of pHPA with a [Rh(nbd)Cl]2- NEt3 Catalyst.asolventb

yieldd Mne
(%)

x10-4

Mw/Mne

cisf

color

(%)

λmaxg

dobsh

(nm)

(Å)

poly(Y)

EtOH

95

8.5

2.6

91

bright yellow

445

24.9

poly(R)n-hexane 84

5.3

2.3

92

purple red

575

30.0

4.2

2.7

91

reddish black

570

29.3

poly(Y→B) -ca-

Polymerization conditions: 25 °C, 0.5 h, [M]0 = 0.20 M, [M]0/[Rh cat.] = 100,

[NEt3]/[Rh cat.] = 100. b Polymerization solvent used. c Prepared by thermal treatmentof poly(Y) at 80 °C for 1 h under N2. d MeOH insoluble part. e Estimated by GPC
analysis (PSt, CHCl3). f Determined by 1H NMR analysis (CDCl3). g Measured by
DRUV-Vis method. h Diameters of columnar determined by XRD analysis.

19Solid Phase DRUV-Vis Spectra
The DRUV-Vis spectra of poly(Y) and poly(R) were shown in Figure 1.

Theabsorption maximum, λmax, of poly(Y) was observed at 445 nm, which was notably
shorter compared to 575 nm of poly(R).
for PnHPAs.

A similar color change has not been reported

It has been reported that poly(phenylacetylene) (PPA) prepared in aFe(acac)3-AlH(i-Bu)2 catalytic

system

was

a

red

insoluble

polymer,1andpoly(p-methylphenylacetylene) (PMPA) prepared with the Rh complex catalyst was a
red solid powder which was insoluble to ordinary organic solvents.24

The spectrum ofpoly(R) appears to hide an absorption peak in a shoulder around at 360−445 nm in an
addition to a peak at 575 nm, suggesting that poly(R) is composed from two kinds ofconjugated systems. On the other hand, λmax of poly(Y) was observed at 445 nm in a
fairly narrower absorption peak compared to that of poly(R).

Previously cis and transpolyacetylenes with no substituent prepared by the Ziegler-Natta catalyst,
Et3Al-Ti(On-Bu)4, have been reported to show two λmaxs at 570 nm and 675 nm,
respectively.25

It seems that the λmax of poly(R) is quite similar to that of the so-called

Shirakawa polyacetylene with cis conjugation sequences.25

20

Figure 1.

DRUV–vis spectra of poly(Y), poly(R), and poly(Y→ B) observed onalumina powder.

The solution UV spectra of poly(Y) and poly(R) measured in chloroform at room
temperature showed similar absorption maxima at 290, 340, and 410 nms without asignificant difference, as shown in Figure 2.

Their absorptions may be assigned to theabsorptions due to the monomer unit moiety involving one cis C=C, relatively shorthelical sequences, and/or helical main-chain conjugation comprising a few monomer
unit moieties.

These UV-vis spectra seems that at least the color difference is not

related to the degree of the polymer concentration difference between poly(Y) andpoly(R) because the same concentration solutions were used.

Alternatively, thedifference of polymer color in solid phase may be ascribable to that of morphology

21and/or helical structures as mentioned below.
Figure 3 shows the resonance laser Raman spectra of poly(Y) and poly(R) measured
in solid phase using an Ar+ laser using samples obtained after mixing 3 mg of eachpolymer and 200 mg of KBr with a mortar and pestle.

The absorption bands at 1530,

1335, and 965 cm-1 were assigned to those of cis C=C bond and/or phenyl ring, cis C-C
bond and/or C-C bond between the main-chain and phenyl ring, and cis C-H bond,respectively, as reported before.22,26

Figure 2.

Solution UV–vis spectra of poly(Y), poly(R), and poly(Y→B) observed inchloroform at room temperature.

We found that there are fairly large differences, especially in the peak corresponding
to the cis C=C bond over-rapped with the phenyl ring at around 1530 cm-1 between

22them.

The Raman spectrum of poly(Y) appeared in fairly broader band compared tothat of poly(R).
The broad peak suggests that poly(Y) takes rather disordered and/or disturbed
structures in thermodynamically more unstable form compared to that of poly(R).

It isalso noteworthy that the peaks due to trans C=C bond, e.g., 1500 cm-1 and 1210 cm-1
were never observed in the present polymers,23,27 though the trans ratio for poly(R) andfor poly(Y) were estimated to be 8% and 9%, respectively, using 1H NMR spectra ofthem. It is noteworthy that their Raman spectra of poly(R) and poly(Y) together with
their DRUV-Vis spectra observed in solid phase have never been reported up to date to
the best of our knowledge.

Figure 3.

Laser Raman spectra of poly(Y), poly(R), and poly(Y→B) observed on KBr

powder.

23

1

H NMR Spectra
As shown in Figure 4, the 1H NMR spectra of poly(Y) and poly(R) were measured in

CDCl3 solution at room temperature. In both spectra, the peaks observed at 6.60 and
6.43, 5.75, 3.67, 1.66, 1.39-1.13, and 0.89 ppm were assigned to those of phenyl,
H-C=C, OCH2, OCH2CH2, (CH2)3, and CH3, respectively. There are basically no large
difference in chemical shift, line shape and line width, irrespective of notably large
color difference between them in solid phase, though the 1H NMR spectrum of poly(R)is not shown. This suggests that the color of the solid polymers is never distinguished in
the solution, though the color of the both polymers never faded even in EtOH.
Therefore, the origin of the color difference	  may be ascribed to the morphologicaland/or conformational	  difference. In other words, to explain difference in	  colorbetween poly(Y) and poly(R), an existence of some	  stretched and contracted pitch
polymers corresponding to	  cis-transoid and cis-cisoid helices may be considered,though	  the structural differences are unable to be detected in the	  solution.18(a,c)

24

Figure 4.

1

H NMR spectra of poly(Y) observed in CDCl3 solution.

Because the exchange speed between them	  may be too fast to be differentiated eachother judging from	  the time scale of the present 1H NMR spectrometer at room	 temperature.

X-ray Diffraction
Figures 5 and 6 show the XRD patterns of poly(Y) and poly(R) measured in thetemperature range form 30 °C to 140 °C in air.

From the pattern denoted with a dottedline measured at 30 °C the formation of psuedohexagonal crystal called a columnar isdeduced and its crystal is composed from a polymer assemble due to the helical
cis-transoid main-chain.7d,15,24,27 The reflection peaks at 2θ = 4.2° and 20° wereassigned to those of the (100) and amorphous halo superposed with an intramolecularhexyloxy chain distance as the side chain of poly(Y), as reported before.27
25

Furthermore, the diameter of poly(Y) having the helical cis-transoid structure wasdetermined to be 24.9 Å. The XRD pattern of poly(R) having the helical cis-cisoidmain-chain was also analyzed.

The formation of a similar columnar was assumed, andthe diameter of poly(R) was determined to be 30.0 Å. The diameter of poly(Y) is thus
found to be smaller by 5.1 Å than that of poly(R). Further a fairly small peak was
observed at around 2θ = 26°, i.e., d = 3.4 Å in each polymer whose intensity is much
lower in poly(Y) compared to that of poly(R), as shown in Figures 5 and 6. This factsuggests that the intramolecular distance between the neighbouring benzene rings
and/or C=C bonds is 3.4 Å, and this fairly narrow distance is approximately the same asthat of a typical layer compound such as graphite.28 This implies that an intramolecularπ-conjugation, that is, the so-called π-stacking takes place between the neighbor phenyl
rings and/or the cis C=C bonds each other along to the axis of the helical polymer
chains and the degree of the π-stacking conjugation in poly(R) is much stronger thanthat of poly(Y). Consequently, it is said that the stronger π-stacking created in poly(R)caused the larger red-shift of poly(R) compared to that of poly(Y) in their solid phase
UV spectra.

26

Figure 5.

Temperature dependences of the XRD patterns of poly(Y).

30
60
100
(100)
110
26.1 Å
120

b: poly(R)

130

30

4.2 Å

120110 100

60

3.4 Å

130

Temp.
30 °C
60 °C
100 °C
110 °C
120 °C
130 °C

0

5

10

15

20

25

30

35

2θ (°)

Figure 6.

Temperature dependences of the XRD patterns of poly(R).

Fig. 6.

27

Thermally Induced Helical Rearrangement from Cis-transoid to Cis-cisoid
We found that the reflection peak intensity of poly(Y) was decreased with increasing
the observed temperature, as shown in Figure 5. Especially the speed of decreasing
intensity was fairly rapid at 70−80 °C, as shown in Figure 5. Furthermore, a new peak
was gradually created at 2θ = 3.4°, Bragg distance d = 25.5 Å as a new (100) reflection,and decayed completely at around 140 °C. These pattern changes may correspond to theso-called cis-to-trans isomerization,9a,18a,19 and be explained in terms of the phasetransition to thermodynamically more stable form, such as from the cis-transoid helix to
cis-cisoid helix. This thought is strongly supported by the fact that the newly appeared
peak at d = 25.5 Å is approximately comparable to that of the diameter, 26.1 Å ofpoly(R) having a cis-cisoid helix, which is composed from a fairly narrow contracted
pitch, i.e., 3.4 Å as mentioned above. This distance corresponds to that of a typical layercompound such as graphite where the p-stacking takes place along the molecular axis
which is correlated to the electrical conductivity.28 However, we could not find thereverse thermally induced pattern change of poly(R), and the reflection intensity was
simply decreased with increasing the temperature, as shown in Figure 6. This also
supports that poly(R) in solid phase is thermodynamically more stable helix comparedto that of poly(Y), Therefore, based on these XRD pattern changes it is concluded thatpoly(Y) having a helical cis-transoid pitch can rearrange to the thermodynamicallymore stable poly(R) having a narrower helical pitch in the cis-cisoid helix.

Thethermally rearranged polymer, poly(Y→B), showed a reddish black color (Scheme 2).
The DRUV-Vis absorption maximum observed after the heat-treatment of poly(Y) is
28

almost coincided to that, 575 nm of the pristine poly(R), though a small peak was newly
generated at around 290 nm as shown in Figure 1.

Scheme 2.

Structural rearrangement from poly(Y) to poly(Y → B) induced byheat-treatment at 80 ℃ for 1 h accompanied with a color change.

Molecular Mechanics Calculation
The energetically most stable conformations of both poly(Y) and poly(R) were
simulated using 20-mer of pHPA as a model polymer molecule by a molecularmechanics (MM) calculation using a MMFF94 force field,21 as shown in Figure 7. The
MMFF94 calculation undoubtedly revealed that the energetically favored polymer
structures for poly(Y) and poly(R) have a stretched cis-transoid helix with its columnar
diameter of 24.7 Å and the contacted cis-cisoid helix with its columnar diameter of 29.1
Å, respectively.

29

Figure 7. Cis-transoid and cis-cisiod helices and dihedral angles, θ°, calculated by
MMFF94 force field.

Figure 8.

Strain energy dependences of dihedral angle around C-C single bond in the

C-C-C=C sequence in the main chain.
30

Thus, the observed and calculated diameters are well agreed each other within 0.2-0.9 Å,
indicating a reliability of our analysis. It shows that the thermal treatment of poly(Y) at
80 ℃ expanded its helix diameter by ~ 3.8 Å, which value was observed in the XRD
pattern (Fig. 5). Figure 8 shows a relation between the dihedral angle θ° connecting two
C=C bonds in the cis-transoid configuration making a C=C-C=C bond in the
main-chain and strain energy (kJ/(unit mol)). This result clearly shows that the strainenergy of the dihedral angle becomes minimum at 70° which is also substantiallyagreed to that of the angle, about 70° calculated by the XRD studies. The layer distancecorresponding to the helical pitch in 20-mer used as the model of poly(R) was also
calculated to be 3.4 Å. This indicates that the observed layer distance can be exactly
reproduced through the MM calculation.

Column Diameters
The temperature dependence of the columnar diameters of poly(Y) and poly(R) at thetemperature from 30 °C to 130 °C under N2 was observed by the XRD method, as
shown in Figure 9.

The diameter of poly(Y) was notably changed from 24.9 Å to 29.3

Å at 80 °C, but poly(R) did not.

This clearly indicates that the thermal rearrangement

took place leading to the structure isomerization from the stretched cis-transoid helix tothe contracted cis-cisoid helix.

31

Figure 9. Temperature dependences of the columnar diameters of poly(Y) and poly(R)measured by XRD method.

DSC Studies
Figure 10 shows the DSC traces of poly(Y) and poly(R) measured at the heating rateof 1 or 10 °C/min. in the temperature range from 30 °C to 200 °C in an atmosphere ofnitrogen.

Poly(Y) showed two exothermic peaks at ca. 80 °C and 140 °C, respectively,

which correspond to the rearrangement temperatures from the cis-transoid helix to thecis-cisoid helix and the thermal cis-to-trans isomerization, as mentioned above.
It is essentially noteworthy that the thermal treatment of poly(Y) at 80 °C for 1 h
under N2 atmosphere did not decrease the cis% because the cis-to-trans isomerization
temperature is much higher, i.e., approximately 130 °C than that of the thermal
treatment temperature. No such an exothermic peak in poly(R) was observed except for32

an isomerization peak at around 140 °C and melting points due to a n-hexyloxy side
chain which is shown in both polymers were observed at 61−67 °C when the heating
rate was increased from 1 to 10 °C/min., as shown in Figure 10b. The enthalpy oftransition, DH(kJ/(unit mol), corresponding to the thermally induced rearrangement ofpoly(Y) to poly(Y→B) was estimated to be 1.6 kJ/(unit mol), which is approximately
1/5 of the calculated value, 7.8 kJ/(unit mol) obtained by the MMFF94 method asshown in Figure 8. This inconsistency may be explained in terms of the columnar
structure of poly(Y) which is assemble of the cis-transoid helix main-chain. A fairly
large energy may be necessary to generate the cis-cisoid helix polymer, poly(Y→B)
from poly(Y) in solid phase because the columnar of cis-cisoid helix polymer is newly
reconstructed. Therefore, the thermally induced rearrangement may not proceedsmoothly or quantitatively, in other words, at least around less than 1/2 of the helix
component in poly(Y) may only rearrange to the cis-cisoid helix jugging from the
DRUV-Vis spectra (see Figure 1).

This also suggests that a half of poly(Y) remains

unchanged as it is when poly(Y) was heated even at 80 °C. Consequently the boundary
sequences between the unchanged poly(Y) and the changed poly(Y→B) which is arelatively short and distorted sequences and show a small absorption at around 290 nm
as shown in Figure 1. Thus, this inconsistency is reasonably explained if the solid phasestructural rearrangement between the cis-transoid helix and cis-cisoid helix is notproceeded easily.

33

Figure 10.

DSC traces of poly(Y) and poly(R) observed under N2 atmosphere.

Conclusion
The stereospecific polymerization of p-n-hexyloxyphenyacetylene, pHPA, wassuccessfully performed using a Rh catalyst, [Rh(nbd)Cl]2-NEt3 in EtOH or Hex at 25 °C
to afford poly(Y) with a bright yellow color and poly(R) with a purple red color as
powders selectively in fairly high yields. The structures and colors of the polymers were
investigated not only in solution but also in solid phase using 1H NMR, DRUV-Vis,
UV-Vis, and resonance Raman spectra, XRD, and MM calculation, together with DSC
method. Poly(Y) and poly(R) showed an absorption maximum, λmax, at 445 nm or 575
nm in solid phase, respectively. In chloroform, no significant difference was observed
between the both polymers. The line width of Raman spectrum for poly(Y) was wider
than that of poly(R). This suggested that the polymer structure of poly(Y) is a more34

disordered than that of poly(R). The former is therefore considered to be
thermodynamically less stable.
The XRD patterns suggested columnar structures comprising of the helical chains forboth polymers, and their diameters were found to be 24.9 Å for poly(Y) and 30.0 Å forpoly(R), respectively. A small peak at d = ca. 3.4 Å was assigned to the layer distant,which was corresponding to an average helical pitch. The pitch of poly(R) is narrower
than that of poly(Y). Interestingly a thermally induced rearrangement of the yellow
poly(Y) to a reddish black polymer, poly(Y→B) took place at 80 °C. Such structuraland helical changes associated with a drastic color change have never been reported
before to the best our knowledge. Poly(Y→B) showed a λmax at 570 nm accompanying
with a very wide absorption peak from 300 nm to 900 nm which may give a dark redcolor in this polymer. The observed helix diameter, 30.0 Å in columnar of poly(R) is
near to that, 29.3 Å of the diameter of poly(Y→B) (Figures 5 and 6). This means thatpoly(Y) is thermodynamically less stable helix compared to that of poly(R). The
thermal instability of poly(Y) was proven by the fact that its exothermic transition
temperature was observed at 80 °C. Thus, these data clearly indicate that the stretchedhelix polymer, poly(Y), was changed to the contracted helix polymer, poly(Y→B),
when heated at 80 °C under N2.

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39

Chapter 2
Contracted Helix to Stretched Helix Rearrangement of
an Aromatic	
  Polyacetylene Prepared in n-Hexanewith [Rh(norbornadiene)Cl]2-triethylamine Catalyst

40

Abstractp-n-Heptylphenylacetylene (pHepPA) was stereoregularly polymerized in n-hexaneat 25 °C using [Rh(nbd)Cl]2 catalyst and NEt3, affording the purple-red Poly(R) in 97 %yield. A 80 °C heat treatment transformed Poly(R) to the black Poly(B). The Poly(R)XRD pattern revealed a hexagonal crystal structure comprising contracted cis-cisoid
helices (HexaPoly(R)CC). The 80 °C heat treatment generated two tetragonal crystals:
Tetra

Poly(B)CC containing contracted cis-cisoid helices and TetraPoly(B)CT containing

stretched cis-transoid helices. The helical diameters before and after heat treatment
were estimated using XRD and were consistent with MMFF 94 calculations. Whenheated at 80 °C in the solid phase, the λmax in the diffuse reflective UV-vis spectra of
Hexa

Poly(R)CC shifted from 482 nm to 560 nm. Additionally, an endothermic transition

occurred in the HexaPoly(R)CC DSC trace at approximately 80 °C. Therefore, these data
corroborated the assertion that HexaPoly(R)CC thermally converted to TetraPoly(B)CC andTetra

Poly(B)CT.

41

Introduction
During

the

past

two

decades,bidentaterhodium

complexes,e.g.,[Rh(nbd)Cl]2-cocatalysts (nbd: norbornadiene),1 zwitterionic Rh complexes,2 andcationic Rh+BF3 complexes,3 have become important stereoselective polymerization−

catalysts for the creation of helical substituted polyacetylenes (SPAs) with cis-transoid
geometrical structures from various substituted acetylene (SA) monomers. A
monodentate Rh complex has been reported as the active catalyst, and this species isgenerated in situ when triethylamine (TEA), alcohols, or aqueous alcohols are used as
cocatalyst or solvent.4 SPAs having helical cis-transoid structures are associated withchiroptical properties5,6 and are driven by van der Waals forces to produce columns ofpseudohexagonal crystals in the solid state.7 The helical pitch of an alkoxy-substitutedpoly(phenylacetylene) can be controlled using external stimuli. For example, thermal
treatment of the solids or exposure to solvent vapor converts the stretched cis-transoid
helices to contracted cis-cisoid helices, and this transformation is accompanied by a
drastic color change from bright yellow to dark red.8 However, the morphology of thesepolymers and the mechanism of their solid phase transformations have not beenthoroughly investigated despite the polymers’ many interesting physicochemical
properties: oxygen permeability,9 nonlinear optical behavior,10 electrical conductivity,11time and temperature memory effects,12 enantioselectivity, and responsiveness toexternal stimuli.13
Recently, the chiral-side-chain-induced formation of predominantly one-handed SPA
helices was explained by CD spectral data, and CD spectral data were also used to42

explain their dynamical helix inversions.14,5 PPAs prepared using Ziegler-Natta15 andmetathesis catalysts16 have interfered with the polymers’ own geometrical and spatial
structure analysis by 1H and 13C NMR. These interferences occurred because gels, large
quantities of irregular sequences, e.g., head-to-head or tail-to-tail bond units, or
unpaired electrons were present in the polymers. The unpaired electrons were generated
through the rotational scission of cis C=C bonds by thermal cis-to-trans isomerization,17
compression,8(b) and the polymerization itself.17(c),18
In Chapter 1, we found that p-n-hexyloxyphenyacetylene afforded poly(Y) with abright yellow color and poly(R) with a purple red color which are dependent on
different of polymerization solvent used. In this report, we changed the structure ofmonomer from p-n-hexyloxyphenyacetylene to p-n-heptylphenylacetylene in order todetermine whether the helical pitch can be controlled.
In this report, p-n-heptylphenylacetylene (pHepPA) was polymerized in n-hexane atroom temperature using a Rh-complex catalyst and TEA cocatalyst, affording the
purple-red poly(pHepPA) (Poly(R)) with a contracted cis-cisoid helical structure.
Moreover, we report a solid state helix rearrangement from contracted to stretched thatwas induced by heating from 30 °C to 80 °C, in contrast with the previous case. To thebest of our knowledge, such an irreversible rearrangement of crystal form associatedwith the color change has not been reported,19 although the static and dynamical
behaviors of these helices are significant features of these p-conjugated polymers.20
Furthermore, determining whether the contracted cis-cisoid helix (contracted helixCC)
is generated as a stable structure is important. The SPA contracted helixCC was
43

considered a missing helix for a long time and was only recently identified in solution21
and solid phases.8(a) Recently, we reported that the helical backbones of achiral andchiral aliphatic polyacetylene esters exhibit an interesting “accordion-like oscillation of
the helical (HELIOS) main chain” in solution. Morphology before and after thePoly(R) thermal treatment was evaluated using 1H and 13C NMR spectroscopy,
wide-angle X-ray diffraction (XRD), differential scanning calorimetry (DSC), solid
phase UV-vis spectroscopy, and molecular mechanics calculations (MMFF94 force
field method).

44

Experimental Section
Materials
MeOH, n-hexane (nHex), and triethylamine (TEA) (JUNSEI Chemical Co.) weredistilled before use. [Rh(nbd)Cl]2 (nbd = norbornadiene) was purchased from Aldrichand used without further purification.

Monomer Synthesis
The monomer, p-n-heptylphenylacetylene (pHepPA) was prepared according to aliterature procedure22 and purified by silica gel column chromatography using n-hexane
as eluent. 1H NMR (500 MHz, CDCl3, ppm): 7.40 (Ph-H, d, J = 8.3 Hz, 2H), 7.12
(Ph-H, d, J = 8.0 Hz, 2H), 3.02 (C≡CH, s, 1H), 2.59 (Ph-CH2, t, J = 15.5 Hz, 2H),
1.61-1.57 (CH2CH2, m, 2H), 1.30-1.25 (CH2CH2CH2CH2CH2, m, 8H), 0.87 (CH2CH3, t,
J = 14.2 Hz, 3H). 13C NMR (125 MHz, CDCl3, ppm): 144.10, 132.12, 128.51, 119.25,
83.97, 76.52, 35.99, 31.88, 31.34, 29.29, 29.24, 22.75, 14.20.

Polymerization
p-n-Heptylphenylacetylene (pHepPA) was stereoselectively polymerized in nHex
using [Rh(nbd)Cl]2 as catalyst and NEt3 as cocatalyst, affording purple-redpoly(pHepPA) (Poly(R)). In a typical procedure, 600 mg pHepPA (3.0 mmol), 14 mg[Rh(nbd)Cl]2 (3.0 x 10-2 mmol), and 0.42 mL NEt3 (3.0 mmol) were dissolved in 15.0
mL nHex in a specially designed U-shaped flask.1,4 The polymerization was performed
at 25 °C. After 0.5 h, the reaction was quenched with 300 mL MeOH. The polymer was45isolated by filtration, washed with MeOH, and then dried for 24 h at 4 x 10-2 torr in a
dynamic vacuum.
Poly(R) 1H NMR (500 MHz, CDCl3, ppm): 6.67 (br., 2H), 6.52 (br., 2H), 5.78 (br., 1H),
2.36 (br., 2H), 1.45 (br., 2H), 1.25 (br., 8H), 0.87 (br., 3H). 13C NMR (125 MHz, CDCl3,ppm): 141.11, 140.67, 138.86, 131.27, 127.66, 35.85, 32.07, 31.88, 29.84, 29.45, 22.85,
14.25. Anal. Calcd. for C14H18O: C, 89.94; H, 10.06. Found: C, 89.56; H, 10.07.

Heat Treatment of Poly(R) at 80 °C
A Poly(R) sample was transferred to the bottom of a test tube. While under N2, thetube was immersed in an 80 °C pre-heated oil bath for 1 h. During the heat treatment,
the purple-red Poly(R) gradually changed to the black polymer, Poly(B).

Measurements
Number and weight average molecular weights (Mn and Mw, respectively) of thepolymers were measured at 40 °C using a JASCO GPC 900-1 equipped with two
Shodex K-806L columns and a RI detector. Chloroform was used as the eluent, andpolystyrene standards (Mn = 800−1,090,000) were employed for calibration. 1H (500MHz) and 13C (125 MHz) NMR spectra were acquired on a JEOL ECA-500 in CDCl3 atroom temperature. Diffuse reflective UV-vis (DRUV-vis) spectra of the polymers wereobtained using a JASCO V570 spectrophotometer equipped with an ISN-470
integrating sphere accessory. Wide-angle X-ray diffraction (XRD) patterns of thepolymers were recorded on a RIGAKU RINT 2200 Ultima equipped with a heater and a46

PTC-30 programmable temperature controller. CuKα radiation was used as the X-ray
source. Differential scanning calorimetry (DSC) was performed on a SHIMADZU
DSC-60, and samples were run in a N2 atmosphere using a 10 °C/min heating rate. The
thermodynamically favored conformation of pHepPA 20-mer was deduced by amolecular mechanics (MM) calculation using the MMFF94 force field (Wavefunction,Inc., Spartan ’10 Windows version 1.1.0).23

47

Results and Discussion
Polymerization
The polymerization of pHepPA using the Rh complex-NEt3 catalyst affordedpoly(pHepPA) (Poly(R)) as a purple-red powder in 97 % yield (Scheme 1). The yield,
number average molecular weight (Mn), polydispersity (Mw/Mn), and the percentage ofcis carbon-carbon double bonds are listed in Table 1. The cis % of the polymer was
carefully determined using 1H NMR spectra.1 Previously, we reported that polar, donororganic solvents such as EtOH and NEt3 induce the dissociation of the Rh catalyst
dimer into its catalytically active, solvent-stabilized monomeric species.1,24 However, tothe best of our knowledge, a nonpolar, aprotic, nondonor solvent such as nHex has
never been used in this type of polymerization. The decrease of the molecular weight ofPoly(B) observed after the thermal treatment at 80 °C is substantially correlated to sucha stiffness of p-conjugated polymer which induces the main-chain scission.8(a)Scheme 1.

Synthesis of poly(p-n-heptyphenylacetylene) having contracted cis-cisoid

helices, using [Rh(nbd)Cl]2-NEt3 catalyst in n-hexane.
48

Table 1.

Polymerization of para-n-heptylphenylacetylene (pHepPA)with a [Rh(nbd)Cl]2-NEt3 catalyst.a

Polymera

Solvent

Yieldc

Mn d

(%)

x10-4

Mw/Mnd

Cise

Color

(%)

Poly(R)n-hexaneb

97

15.1

3.6

87

purple redPoly(B)

HTf

-

7.1

3.1

85

black

Polymerization conditions: 25 °C, 30 min, [M]0 = 0.20 M, [M]0/[Rh cat.] = 100,

[NEt3]/[Rh cat.] = 100. b Polymerization solvent used. c MeOH insoluble part. d
Estimated by GPC analysis (PSt, CHCl3). e MeOH insoluble part. Determined by 1H
NMR analysis (CDCl3, r.t.). f Prepared by heat treatment (HT) of poly(R) at 80 °C for 1
h under N2 atmosphere.

Structure of Poly(R) in Solution Detected 1H NMR
The 1H NMR spectrum of the purple-red Poly(R) was obtained in CDCl3 at room
temperature (Fig. 1) to determine its molecular geometry. The peaks observed at 6.67,
6.52, 5.78, 2.36, 1.45, 1.25, and 0.87 ppm were assigned to the meta protons in a phenyl
rings, the ortho protons in the phenyl rings, the H-C=C vinyl protons, Ph-C1H2, C2H2,(C3~6)H8, and C7H3, respectively. The 1H NMR spectrum of the black Poly(B) was
almost identical to the spectrum of Poly(R) (see Fig. S1). Therefore, no significant
differences in chemical shift, line shape, and line width between two polymers weredetected in solution phase, despite the large color difference between the solids. Notably,
the color of neither polymer faded when the solid chemicals were exposed to air for an49

extended time at room temperature. The Poly(R) and Poly(B) color difference was thus
ascribed to morphological or conformational differences, such as in helical structure,
although SPAs in solution have been considered to take cis-transoid structures such as
the stretched helix (Stretched helixCT).8(a)Figure 1.

1

H NMR spectra of the purple-red Poly(R), observed at room temperature in

CDCl3.

Crystal Structure Changes Detected by XRD
To explain the color difference, Poly(R) XRD patterns were obtained from room
temperature to 140 °C to evaluate temperature dependence (see Fig. 2). At room
temperature, two primary reflection peaks were observed: one at a low angle side
(Bragg distance (d)=24.5 Å) and one at higher angle side (d=4.6 Å). A small peak wasalso observed at d=3.4 Å. This pattern was analyzed assuming pseudohexagonal
crystals with contracted cis-cisoid helices (contracted helicesCC) (Fig. 3a). The peak at50

d=24.5 Å was attributed to the (100) reflection of the hexagonal crystal. In contrast tothestretched

cis-transoid

helicesinthehexagonal

crystalsofpoly(p-n-hexoxylphenylacetylene) (PpHexPA) resulting from using ethanol as thepolymerization solvent,8(a) this (100) reflection peak indicated that the column
diameter (D) of the 	  π-conjugated helical column was approximately 28.3 Å(=24.5/sin60°). The large, broad peak at 4.6 Å was attributed to a halo peaksuperposed on the intramolecular n-heptyl alkyl chain distance, as reported
previously.8(a) The relatively small peak at d = 3.4 Å was attributed to theaverage intramolecular distance between the helical main chain rings andneighboring benzene rings. These results indicated that the contracted helicesCC werestabilized in the solid phase.

51

Figure 2.	
  Temperature dependence of the Poly(R) XRD patterns.

Additionally, the results indicated that intramolecular	  π-conjugation, i.e., π-stacking
occurred between neighboring phenyl rings or the C=C bonds of the helical backbone.
The Poly(R) peak at d= 24.5 gradually split into two reflection peaks at d=28.2 Å and19.8 Å when the sample was heated to approximately 80 °C. The half width of thed=28.2 Å peak was small compared with the half width of the d=19.8 Å peak. Thisdifference clearly indicated that the two peaks arose from different crystal structures.
The d=28.2 Å peak was ascribed to tetragonal crystals Tet1 containing cis-cisoid helices,whereas the d=19.8 Å peak was ascribed to tetragonal crystals Tet2 containing
cis-transoid helices. Therefore, a solid phase cis-transoid helices. Therefore, a solid52phase transformation occurred. The Tet1 peak at d=28.2 Å corresponded to an estimatedhelical diameter of 28.2 Å (Fig. 3b), and the Tet2 peak at d=19.8 Å (Tet2 crystals
typically contain stretched helicesCT) corresponded to an estimated helical diameter of
19.8 Å (Fig. 3c).

Figure 3. Thermally induced crystal changes accompanied by helical structure changes.

The three peaks decayed completely at approximately 140 °C (Fig. 2). These peak
disappearances indicated melting of the polymer. The XRD pattern at approximately
80 °C was consistent with the XRD pattern of Poly(B), which was obtained by heating
Poly(R) to approximately 80 °C under N2. These results indicated that Poly(B) wascomposed of two tetragonal crystals in which different helices, i.e., contracted
helicesCC and stretched helicesCT, are packed in the solid columnar phase. Formation of53

the D=28.2 Å tetragonal crystal resulted in the 3.4 Å peak remaining until 120 °C.

Table 2.

Column diameters determined by XRD spectra and molecularmechanics calculations.
Polymer

Temp.

Lattice

(°C)

a

d100a

Dobs.

Dcalc.c

(Å)

(Å)

(Å)

Poly(R)

r.t.

Hexagonal

24.5

28.3b

28.3

Poly(B)

90

Tetragonal

28.2

28.2

28.3

Poly(B)

90

Tetragonal

19.8

19.8

20.1

Determined by XRD analysis. b d100/sin60°. c Determined by molecularmechanics (MM) calculations used a MMFF 94 force field program.

Moreover, the relatively broad reflection peak at d=19.8 Å was attributed to the (100)reflection of the Tet2 crystal, which contained stretched helicesCT. For tetragonal
crystals, the helical diameter corresponds to the length derived from the (100) reflection
peak (Figs. 2 and 3); therefore, the helical diameter for Tet2 was calculated as
approximately 19.8 Å. This assignment was supported by the small peak at d=5.6 Å
because this peak was consistent with a (400) reflection of Tet2 crystals containing
D=19.8 Å stretched helicesCT. The change in XRD pattern with temperature indicatedthat the pristine HexaPoly(R)CC (hexagonal crystals comprising cis-cisoid helices) was
thermodynamically unstable relative to TetraPoly(B)CC (tetragonal crystals comprisingcis-cisoid helices) andTetra

Poly(B)CT (tetragonal crystals comprising cis-transoid

helices).
54

Figure 4.

Top and side views of cis-cisoid and cis-transoid helices calculated using

the MMFF94 force field.

In summary, heating induces an important solid phase rearrangement from pristine
hexagonal crystals to two types of tetragonal crystals: Tet1 and Tet2. Tet1 contains
identical cis-cisoid helices to the pristine hexagonal crystal, and Tet2 contains
cis-transoid helices (Figs. 3 and 4).8(a)Molecular Mechanics Calculation
The most stable helical conformations of
Tetra

Hexa

Poly(R)CC,

Tetra

Poly(B)CC, andPoly(B)CT were simulated using the pHepPA 20-mer as a model. The molecularmechanics (MM) calculations used a MMFF 94 force field program.23 The MMFF 94
calculations were performed by rotating the dihedral angles (θ) about the C-C single

55

bonds in the C=C-C=C moieties. These calculations afforded the relationship between θ(°) and the strain energy (kJ/(unit mol)) (Figs. 4 and 5). These results clearly
demonstrated that the strain energy was minimized (119.0 kJ/(unit mol)) atapproximately θ = 110°, in agreement with the angle calculated using the helical
diameter D=20.1 Å and assuming a hexagonal helix (see Fig. 4). Moreover, the dihedral
angle θ=70° corresponded to the strain energy of the cis-cisoid helix, and the helical
diameter calculated from that dihedral angle was consistent with the helical diameter(28.3 Å) obtained from XRD data. These data support the assertion that the unstablecis-cisoid helix is easily produced in n-hexane but partly transformed to theconsiderably more stable cis-transoid helix upon heating to 80 °C. The π-stacking
distance corresponded to the helical pitch in the 20-mer model polymers of
Hexa

Poly(R)CC and TetraPoly(B)CC, and the MMFF 94 calculation of approximately 3.4 Å

was consistent with XRD results. Additionally, the lengths of the cis-cisoid helices,which were experimentally deduced using XRD peak widths, were at least 100 Å, i.e., arelatively large value.

56

Figure 5.

Strain energy dependence on the C=C-C=C dihedral angles as calculated by

the MMFF94 force field program.

DSC Studies
Fig. 6 shows the DSC trace of HexaPoly(R)CC measured under nitrogen from 30 to
200 °C at the heating rate of 10 °C/min. The trace exhibited three endothermic peaks at
approximately 40, 75, and 85 °C and a large exothermic peak at approximately 150 °C.
The third endothermic peak at approximately 85 °C was attributed to the solid phasetransition from pristine hexagonal crystals comprising cis-cisoid helices to Tet1
tetragonal crystals comprising cis-cisoid helices and Tet2 tetragonal crystals comprising
stretched helicesCT having the cis-transoid helix. The small endotherms at
approximately 40 and 75 °C (Fig. 6b) were attributed to the melt or reorientation of then-heptyl alkyl side chains. Notably, the thermal treatment of Poly(B) under N2 for 1 h at57

temperatures higher than 140 °C rapidly decreased the cis % because of isomerization,
as evinced by the DSC trace (Fig. 6). The enthalpy of transition energy (DH≈0.89
kJ/(unit mol)) corresponded to the thermally induced rearrangement of HexaPoly(R)CC to
Tetra

Poly(B)CC and TetraPoly(B)CT, although the enthalpy from the small endothermic

peak at 70 °C is included in this value. This enthalpy value was approximately 1/5 ofthe calculated 4.0 kJ/(unit mol) obtained from the MMFF 94 method (Fig. 5).

This

inconsistency was rationalized in terms of column structure. Because both the rotational
angles about the main-chain and the positioning of the long alkyl chains requirechanging, i.e., the solid phase transition of HexaPoly(R)CC to TetraPoly(B)CC andTetra

Poly(B)CT requires a large amount of energy. Therefore, the thermally induced

rearrangement did not proceed smoothly. In other words, less than 1/5 of the helicalcomponents in HexaPoly(R)CC rearranged to TetraPoly(B)CC and TetraPoly(B)CT in the solid
phase.

58

Figure 6.

DSC traces of TetraPoly(R)CC from 30 °C to 200 °C under N2 .

Solid Phase DRUV-Vis Spectra
The DRUV-Vis spectra of HexaPoly(R)CC were obtained before and after the heat
treatment (Figs. 7a and b). The absorption spectrum of HexaPoly(R)CC exhibited two
maxima (λmax) at 292 and 482 nm and an extremely long absorption tail until
approximately 1100 nm. The absorption at approximately 482 nm was attributed to thecis-cisoid helices within HexaPoly(R)CC.8(a) Previously, cis and trans polyacetylenes withno substituents were prepared using the Ziegler-Natta catalyst Et3Al-Ti(On-Bu)4 andhad λmax at 570 and 675 nm with small shoulders at approximately 500 and 600 nm,
respectively.25 The λmax at 482 nm in HexaPoly(R)CC shifted to 560 nm when heated at59

approximately 80 °C for 1 h. This observation indicated that the helical pitch shortenedto accommodate ordered π-stacking along the helical backbone. The large absorption at
294 nm with a relatively narrow width was also attributed to shorter cis-cisoid helices or
distorted cis-cisoid helices that were generated during the original polymerization inn-hexane. Therefore, polymerization in n-hexane produced helices with both long andshort pitches. To the best of our knowledge, however, the long absorption tail extending
into the near infrared region, i.e., more than 1100 nm is neither explained by π-stacking
nor reported in other π-conjugated polymers.26 Poly(phenylacetylene) (PPA) preparedusing the Ziegler–Natta catalyst Fe(acac)3-AlH(i-Bu)2 was red and insoluble.

Figure 7.

DRUV-vis spectra of Poly(R) and Poly(B) observed on alumina powder.
60

Poly(p-methylphenylacetylene) (PMPA) prepared with a Rh catalyst was also red andinsoluble.8(c) Therefore, the physical properties of those previous PPAs interfered withdetailed structural analyses.

Importance of PPA Including PpHepPA with a Contracted Helical Pitch
SPAs, including the present PPA, are some of the stiffest helical polymers because
they are composed of alternating C-C and C=C conjugated bonds and possess additional
p-conjugation from π-stacking in the direction of the molecular backbone.8 The
calculated helical pitch of HexaPoly(R)CC and TetraPoly(B)CC was approximately 3.4 Å(Table 2) and was comparable to the layer distance of electrically conductive graphite,
3.35 Å and graphene.27 For poly(ethyl propiolate) (PEP), the vertical electric current ofa single helix was measured as approximately 10-8 A without doping, and it was thesmallest semi-conductor using such a helical polymer.28

Conclusion
p-n-Heptylphenylacetylene (pHepPA) was stereoregularly polymerized at 25 °C
using [Rh(nbd)Cl]2 and NEt3 in n-hexane, affording the purple-red polymer Poly(R) in
high yield. Poly(R) transformed into the black polymer Poly(B) upon heating to 80 °C.
Both polymers were analyzed by XRD, MMFF 94 calculations, DSC, and DRUV-vis.
In solid-phase DRUV-vis, Poly(R) and Poly(B) exhibited absorption maxima (lmax) at
482 and 560 nm, respectively. No significant differences were observed in 1H NMR
when the spectra were obtained in chloroform. The XRD patterns of Poly(R) revealed61that it had a hexagonal crystal structure (HexaPoly(R)) comprising cis-cisoid helices (i.e.,
contracted helices called HexaPoly(R)CC). Furthermore, heating Poly(R) up to 120 °C
induced the solid phase transformation of HexaPoly(R)CC to two tetragonal crystal
phases: one containing large-diameter cis-cisoid helices and the other containing
small-diameter stretched helices. Moreover, the thermally induced rearrangement of
Hexa

Poly(R)CC to the black polymers TetraPoly(B)CC and TetraPoly(B)CT occurred at

approximately 80 °C. To the best of our knowledge, a solid phase rearrangement
resulting from a contracted helixCC to a stretched helixCT transformation andaccompanied by a drastic color change has never been reported. The thermal instabilityof HexaPoly(R)CC was proven by the DSC endotherm at approximately 80 °C. These dataclearly corroborated that the pristine HexaPoly(R)CC crystals thermally converted into thetwo tetragonal crystals containing contracted helicesCC and stretched helicesCT atapproximately 80 °C. The origin of the color changes observed before and after the heat
treatment is attributed to the helical pitch width and the increment of intramolecularπ-stack order i.e., the degree of π-conjugation in the vertical direction of the main chainof the contracted helix packed in the tetragonal crystal 1 as indicated by the large red
shift of the lmax from 482 nm to 560nm in the DRUV-vis spectrum.

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Furusho and K. Nagai, Chem. Rev. 2009, 109, 6102–6211.
15. R. J. Kern, J. Polym. Sci., Polym. Chem. Ed. 1969, 7, 621-631.
16. T. Masuda, T. Higashimura, Adv. Polym. Sci. 1986, 81, 121.
65

17. (a) T. Sone, R. Amato, Y. Mawatari, M. Tabata, A. Furlani, M. V. Russo, J.
Polym. Sci. Part A: Polym. Chem. 2004, 42, 2365-2376. (b) C. I. Shimionescu,
V. Percec, S. Dumitrescu, J. Polym. Sci: Polym. Chem. Ed. 1977, 2497-2509. (c)R. D’Amato, T. Sone, M. Tabata, Y. Sadahiro, M. V. Russo, A. Furlani,
Macromolecules 1998, 31, 8660-8665.
18. (a) T. Sone, R. Asako, T. Masuda, M. Tabata, T. Wada, H. Sasabe,
Macromolecules 2001, 34, 1586-1592. (b) A. Miyasaka, M. Nakamura, Y.
Mawatari, K.

Orito, M. Tabata, Macromol. Symp. 2006, 239, 13-20. (c) E.

Sato, Y. Mawatari, Y.

Sadahiro, B. Yamada, M. Tabata, Y. Kashiwaya,

Polymer 2008, 49, 1620-1628.
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W. Cho, S. K. V. Balagurusamy, A. P. Heiney, J. Am. Chem. Soc. 2005, 127,
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Yoshida, Y. Mawatari, A. Motoshige, R. Motoshige, T. Hiraoki, M. Tabata,
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Nanotechnology 2009, 20, 105201.

67

Chapter 3
Synthesis and Solid State Helix to Helix
Rearrangement of Poly(phenylacetylene) Bearing
n-Octyl Alkyl Side Chains

68Abstract
Highly stereoregular polymerisations of p-n-octyphenylacetylene (pOcPA) were
performed using a [Rh(norbornadine)Cl]2-triethylamine catalyst in ethanol at -20 and 25°C to afford yellow and orange polymers, Poly(Y) and Poly(O), in yields of 64 and 99%,
respectively. The XRD patterns of Poly(Y) showed a hexagonal columnar liquid crystal
with a contracted cis-cisoid helix, HexaPoly(Y)CC. The XRD pattern of Poly(O) matchedthat of Poly(Y) heated to 80 °C. The heat treatment of HexaPoly(Y)CC at 100 °C
generated two tetragonal crystals: Tetra1Poly(R)CC, containing contracted cis-cisoid
helices and Tetra2Poly(R)CT, containing stretched cis-transoid helices. The helical
diameters of HexaPoly(Y)CC before and after heat treatment were estimated using XRD
and were consistent with the results of MMFF 94 calculations, although the n-octyl
alkyl chains of HexaPoly(Y)CC and Tetra2Poly(R)CT did not have a linear alkyl chains; abent in the chains was confirmed by 13C CP-MAS NMR. When HexaPoly(Y)CC washeated to 100 °C in the solid phase, the λmax in the diffuse reflective UV-vis spectra
shifted from 448 nm to 565 nm. Furthermore, the endothermic transition for
Hexa

Poly(Y)CC occurred at 100 °C in the DSC trace. Therefore, these data corroborated

the assertion that
Tetra2Hexa

Poly(Y)CC thermally converted toPoly(R)CT.

69

Tetra1

Poly(R)CC andIntroduction
Polyacetylenes (PA)s and mono-substituted polyacetylenes (SPA)s typical for
conjugated polymers have been prepared using various catalysts, such as theZiegler-Natta(n-Bu3P)2NiCl2-NaBH42;
metathesis

Fe(acac)3-AlH(i-Bu)21;

catalyst,

catalysts,

RhCl3-LiBH41;
such

as

the

Luttinger

theWilkinson

catalyst,

or

MoCl53;bidentate

WCl6

catalyst,

RhCl(PPh3)31;
Rh

catalysts,[Rh(nbd)Cl]2-cocatalyst (nbd=norbornadiene)4; and zwitterionic mono Rh complex
catalysts.5 Among them, the Rh bidentate catalyst has become an important catalyst forthe synthesis of helical SPAs with cis-transoid geometrical structures from various
mono-substituted acetylene (SA) monomers. A monodentate Rh complex has beenreported as the active catalyst, and this species is generated in situ from the Rh bidentate
catalyst when triethylamine (TEA), alcohol, or aqueous alcohols are used as the
cocatalyst or solvent.4a-4e The cis-transoid helices are driven by van der Waals forces to
produce a columnar liquid crystal called a hexagonal columnar crystals as the assemblyof the helical main chain in the solid phase.6,7
The helical pitch of an alkoxy substituted poly(phenylacetylene) was controlled using
external stimuli.8 For example, thermal treatment of the solid converts the stretched
cis-transoid helices to contracted cis-cisoid helices, and this transformation isaccompanied by a drastic colour change from bright yellow to dark red.8a However, themorphology of these polymers and the mechanism of the solid phase transformation
have not been thoroughly investigated despite the many interesting physicochemical
properties of the polymer, including oxygen permeability,6b,9 nonlinear optical70

behaviour,10

electricalconductivity,11

time

and

temperature

memory,12enantioselectivity,13 and response to external stimuli.14
Recently, the chiral side-chain induced formation of predominantly one-handed SPA
helices was explained by CD spectral data, which were also used to explain the dynamic
helix inversions.15,16 Poly(phenylacetylene)s (PPAs) prepared using the Ziegler-Natta1
and metathesis catalysts3 have interfered with the geometrical and spatial structure of
the polymers. These interferences occurred because of the presence of gels, large
quantities of irregular sequences, (i.e., head-to-head and/or tail-to-tail bond units), or
unpaired electrons present in the polymers. The unpaired electrons were generated
through the rotational scission of cis C=C bonds17 by thermal cis-to-transisomerisation,17(b) and compression,17(c) and even during polymerisation.17(d,e)
In Chapter 2, we found that poly(p-n-heptylphenylacetylene) transformed fromcontracted helix to stretched helix by the heat-treatment. Moreover, we showed that thecolumnar structure changed from hexagonal crystal to tetragonal crystal. In this Chapter,
we used p-n-octylphenyacetylene as an another monomer. We found an important
experimental conditions to change such helical pitch and crystal structure.
In this report, p-n-octylphenylacetylene (pOcPA) was polymerised in ethanol at -20°C using the Rh complex catalyst with TEA as the cocatalyst affording the brightyellow poly(pOcPA), HexaPoly(Y)CC, which was a hexagonal columnar crystal with
contracted cis-cisoid helices. Moreover, we report a solid state helix to helix
rearrangement from HexaPoly(Y)CC to two tetragonal crystals when heated from 30 °C
to 100 °C: Tetra1 with contracted cis-cisoid helices, Tetra1Poly(R)CC, and Tetra2 with71

stretched cis-transoid helices,
Hexa

Tetra2

Poly(R)CT. The n-octyl alkyl chains ofPoly(Y)CC and Tetra2Poly(R)CT do not have extended alkyl chains but have bent

chains. Furthermore, determining if the contracted cis-cisoid helices (contracted
helixCC) generated are energetically stable structures is important. Because thecontracted helixCC was considered to be a missing helix for a long time and was only
recently identified in the solid phase and in solution, in which an interesting
Accordion-like Helix Oscillation (HELIOS) of achiral and chiral aliphatic
polyacetylene is shown.18 Therefore, the morphologies and geometric structures ofPoly(Y) before and after thermal treatment were carefully determined using 1H and 13C
NMR spectroscopies, wide angle X-ray diffraction (XRD), differential scanningcalorimetry (DSC), solid phase UV-vis spectroscopy, molecular mechanics calculations(MMFF 94 force field), and solid state 13C CP-MAS NMR methods.

72Experimental Section
Materials
Ethanol (EtOH), and triethylamine (TEA) (JUNSEI Chemical Co.) were distilled
before use. [Rh(nbd)Cl]2 (nbd = norbornadiene) was purchased from Aldrich and usedwithout further purification.

Monomer Synthesis
The [Rh(nbd)Cl]2 (nbd = norbornadiene) catalyst was purchased from Aldrich andused without further purification.

The monomer, p-n-octylphenylacetylene (pOcPA),

was prepared according to a literature procedure19 and purified by silica gel column
chromatography using n-hexane as an eluent. 1H NMR (500 MHz, CDCl3, ppm): 6.67
(Ph-H, d, J = 8.2 Hz, 2H), 6.51 (Ph-H, d, J = 8.3 Hz, 2H), 3.03 (H-C≡C, s, 1H), 2.59
(Ph-CH2, t, J = 15.6 Hz, 2H), 1.60-1.57 (CH2CH2, m, 2H), 1.29-1.26(CH2CH2CH2CH2CH2, m, 10H), 0.88 (CH2CH3, t, J = 14.1 Hz, 3H). 13C NMR (125MHz, CDCl3, ppm): 144.13, 132.18, 128.55, 119.35, 84.03, 76.56, 36.05, 32.02, 31.38,
29.59, 29.39, 29.39, 22.82, 14.25.

Polymerisation
pOcPA was polymerised in EtOH using [Rh(nbd)Cl]2 as the catalyst and TEA as the
cocatalyst to afford bright yellow poly(pOcPA), (Poly(Y)). In a typical procedure, 500
mg of pOcPA (2.3 mmol), 10 mg of [Rh(nbd)Cl]2 (2.3 x 10-2 mmol), and 0.32 mL of
TEA (2.3 mmol) were dissolved in 11.7 mL of EtOH in a specially designed U-shaped73flask.4a-4e The polymerisations were performed at -20°C and 25 °C. After 0.5 h, thereaction was quenched with 300 mL of MeOH. The polymers were isolated by filtration,
washed with MeOH and then dried for 24 h at 4 x10-2 torr in a dynamic vacuum. The
polymerisations at -20 °C and 25 °C afforded a bright yellow polymer, Poly(Y), and anorange polymer, Poly(O), as powders with yields of 64 % and 99 %, respectively: 1H
NMR (500 MHz, CDCl3, ppm): 6.67 (br., 2H), 6.51 (br., 2H), 5.78 (br., 1H), 2.36 (br.,2H), 1.45 (br., 2H), 1.25 (br., 10H), 0.88 (br., 3H). 13C NMR (125 MHz, CDCl3, ppm):
141.16, 140.74, 138.95, 131.32, 127.71, 127.71, 35.92, 32.16, 31.93, 29.98, 29.81,
29.62, 22.89, 14.28. Anal. Calcd. for C16H22: C, 89.65; H, 10.35. Found: C, 89.32; H,
10.35.

Heat Treatment of Poly(Y) at 80 and 100 °C
A sample of Poly(Y) was placed at the bottom of a test tube and the tube was
immersed in a pre-heated oil bath for 1 h under N2. At ~80 °C, Poly(Y) graduallychanged to an orange polymer, Poly(O). Furthermore, Poly(O) gradually changed to a
red colour polymer, Poly(R) when heated at 100 °C.

Measurements
The number and weight average molecular weights (Mn and Mw) of Poly(Y), Poly(O),and Poly(R) were measured using a JASCO GPC 900-1 equipped with two Shodex
K-806L columns and an RI detector. Chloroform was used as an eluent at 40 ºC, andpoly(styrene) standards (Mn = 800−1,090,000 Da) were employed for calibration. The
74

1

H and 13C NMR spectra in solution were measured on a JEOL JNM-ECA500 in CDCl3

at room temperature. Solid state 13C CP-MAS NMR (125 MHz) spectra were measured
on the same spectrometer using adamantine as a standard and 2 millisec as the contact
time at room temperature. Diffuse reflective UV-vis spectra, DRUV-vis, of thepolymers in the solid phase were recorded on a JASCO V570 spectrophotometerequipped with an ISV-470 integrating sphere accessory. Differential scanningcalorimetry (DSC) was performed on a SHIMADZU DSC-60, and the traces were runin an atmosphere of N2 at a heating rate of 10 °C/min. Wide-angle X-ray diffraction(XRD) patterns of the polymers were recorded on a RIGAKU RINT 2200 Ultima
equipped with a heater and a PTC-30 programmable temperature controller. CuKα
radiation was used as the X-ray source. The thermodynamically favoured conformationof the pOcPA 20-mer was determined by a molecular mechanics (MM) calculation
using the MMFF 94 force field (Wavefunction, Inc., Spartan ’10 Windows version
1.1.0).

75

Results and Discussion
Polymerisation
The polymerisations of pOcPA using the Rh complex catalyst and TEA cocatalyst in
EtOH at -20 °C and 25 °C afforded Poly(Y) and Poly(O) in yields of 64 % and 99 %,respectively. Their number average molecular weights (Mn), polydispersities (Mw/Mn),
and the cis percentages are listed in Table 1. The polymerisability of pOcPA was
reduced at temperatures of less than -20 °C, and the cis ratio and the polydispersity weremaintained. The cis % of the polymers was determined using 1H NMR.8,17 Previously,
we reported that polar organic solvents such as EtOH and TEA induced the dissociationof the Rh catalyst into its catalytically active, solvent-stabilised monomeric species.4 A
bright orange polymer, Poly(O) with a cis ratio of 96 % was obtained in a yield of 99 %when the polymerisation was performed at 25 °C (Scheme 1 and Table 1). The cis %remained the same as that when the polymerisation was carried out at -20 °C. However,the Mn was fairly decreased from 37.1x104 to 26.9x104 at 25 °C compared to -20 °C.

76

Scheme 1. Synthesis of poly(p-n-octylphenylacetylene) having contracted cis-cisoid
helices using a [Rh(nbd)Cl]2-TEA catalyst in EtOH at 25 °C.

This suggests that when the polymerisation is performed at 25 °C, the polymer
decomposed and the Mn decreased. This is supported by the fact that the polydispersity
increases from 2.0 at -20 °C to 4.4 at 25 °C. The decrease in molecular weight is
attributed to the fairly stiff main chain, which is an important feature of helical
π-conjugated polymers.

77

Table 1.

Polymerisation of pOcPA with a [Rh(nbd)Cl]2-NEt3 catalysta

PolymerSolventb

Yielddtemp. (°C)(%)

Mne ×10-4

Mw/MneCisf

Colour(%)

Poly(Y)

EtOH

-20

64

37.1

2.0

98

Yellow

Poly(O)

EtOH

25

99

26.9

4.4

96

Orange

-

-

23.4

3.2

90

Red

Poly(R) HTc(EtOH)
aPolymn.

Polymerisation conditions: 30 min, [M]0 = 0.20 M, [M]0/[Rh cat.] = 100, [NEt3]/[Rhcat.] = 100. b Polymerization solvent used. c Prepared by heat treatment(HT) at 100 °C
for 1 h under N2 atmosphere. d MeOH insoluble part. e Estimated by GPC analysis (PSt,
CHCl3). f Determined by 1H NMR analysis (CDCl3).

Structural Characterisation by 1H NMR
The 1H NMR spectrum of Poly(Y) was measured in CDCl3 at room temperature (Fig.
1) to determine its geometrical structure. The peaks observed at 6.67 and 6.51, 5.78,
2.36, 1.45, 1.25, and 0.88 ppm were assigned to the meta protons and the ortho protons
in the phenyl rings; the vinyl protons in Hα-C=C; Ph-C1H2; C2H2; (C3~7)H10; and C8H3
protons in the side alkyl chains, respectively. However, the 1H NMR spectra of Poly(O)and Poly(R) were almost identical to the spectrum of Poly(Y). No significant differencein the chemical shifts, line shapes, or line widths among the polymers was detected in
the solution phase, despite the large colour differences in the solid phase. Notably, thecolours of the three polymers faded or were unchanged when the solid polymers were
held at room temperature for a long time in the solid phase. Therefore, the colour
78differences among Poly(Y), Poly(O), and Poly(R) were ascribed to morphologicaland/or conformational differences, such as the presence of helical structures, although
SPAs in solution generally have been considered to have a cis-transoid structure calleda Stretched helixCT.8(a)Figure 1.

1

H NMR spectrum of Poly(Y) observed at 25 °C in CDCl3 solution.

Heat treatment of Poly(Y)To determine the origin of the colour difference among the polymers, the pristine
Poly(Y) powders were heated to 80 °C for 1 h using a test tube evacuated to 10-3 torr,
and the cis ratio did not change (Table 1).8a While heating, Poly(Y) gradually changed
to an orange polymer, Poly(O). Furthermore, the colour of Poly(O) changed to a red
when heated to ca. 100 °C. Therefore, the origin of the colour difference in the solid
79

phase can be attributed to the morphological and/or conformational differences,including the presence of helical structures and/or crystal structure transitions.8,20

Figure 2.

Temperature dependence of the XRD patterns of Poly(Y) measured from

30 °C to 130 °C under N2 gas: (a) a full scale and (b) an expanded

pattern from 2θ =2° to 7°.

Crystal Structure Changes Detected by XRD
To explain the morphology and conformational differences, the XRD patterns ofPoly(Y) were measured from 30 °C to 130 °C (Fig. 2). At 30 °C, two primary reflection
peaks were observed: one at the low angle side, with a Bragg distance of d=25.6 Å, and80

one at the higher angle side, with d=4.5 Å. This pattern was analysed under theassumption that the structure was a hexagonal columnar crystal with contracted
cis-cisoid helices (=contracted helixCC) (Fig. 3a). The peak at d=25.6 Å was attributed
to the (100) reflection of the hexagonal columnar crystal. This assignment was
supported by the appearance of peaks at 15.4 Å and 6.5 Å, which were attributed to the(110) and (400) reflections, respectively. In contrast to the stretched cis-transoid helices(=stretched helicesCT), were obtained as the hexagonal columnar crystals in the case ofpoly(p-n-hexoxyphenylacetylene) (PpHexOPA) prepared in EtOH at 25 °C.8(a)Therefore, the (100) reflection indicates that the column diameter, Dobs., of the
π-conjugated helical columnar was approximately 29.6 Å (=25.6/sin60°). The large
broad peak at 4.5 Å was attributed to a halo peak superimposed with an intramolecularn-octyl alkyl chain distance in the side chain of Poly(Y), as previously reported.8 The
relatively small peak at d = 3.4 Å observed when heated to ca. 70-100 °C was attributed
to the average intramolecular distance between the helical main chain rings and theneighbouring phenyl rings. These results indicate that the contracted helixCC wasstabilised in the solid phase. Additionally, these results also indicate that the
intramolecular π-conjugation, i.e., π-stacking, occurred between neighbouring phenyl
rings and/or the C=C alkene bonds of the helical backbone (Fig. 4). The Poly(Y) peakat d=25.6 Å gradually split into two reflection peaks at d=30.4 Å and 20.3 Å,
respectively, when heated to ca. 100 °C. The half width of the peak at d=30.4 Å wassmall compared to the peak at d=20.3 Å. This difference clearly indicates that the two
peaks arose from different crystal structures.
81

Figure 3.

Helix to Helix rearrangement from (a) a hexagonal columnar crystal having

contracted cis-cisoid helices, to (b) tetragonal crystal1 having contracted cis-cisoid
helices, and (c) tetragonal crystal2 having stretched cis-transoid helices.

In other words, the peak at d=30.4 Å was attributed to a tetragonal crystal (Tetra1)
containing cis-cisoid helices, whereas the d=20.3 Å peak was attributed to an anothertetragonal crystal (Tetra2) containing cis-transoid helices, which are distinct from thepristine hexagonal columnar crystal structure (see Figs. 3a, b and c). Therefore, a solid
phase transformation was corroborated to be surely induced by the heat treatment. The
Tetra1 peak at d=30.4 Å corresponded to an estimated helical diameter of 30.4 Å (Fig.
3b), and the Tetra2 peak at 20.3 Å corresponded to an estimated helical diameter of 20.3
Å (Figs. 3c). The small peaks at 7.5 Å and 5.3 Å were also attributed to the (400)reflections of Tetra1Poly(R)CC and Tetra2Poly(R)CT, respectively. These peaks decayed at82

approximately 130 °C, together with the π-stacking peak at 3.4 Å, as shown in Figs. 2aand b. This disappearance shows the melt of this polymer, as mentioned below. XRD
patterns observed at approximately 80 °C agreed with the patterns of the Poly(O) thatwas prepared at 25 °C. This finding indicates that the polymerisation temperature iscorrelated to the resulting helical crystal and main chain structures. Therefore, theseresults allow us to conclude that Poly(O) and Poly(R) were composed from two
tetragonal crystals in which two types of helices, the contracted helixCC and stretchedhelixCT, are packed in the solid columnar phase. The thermal changes of the XRD
patterns indicate that pristine HexaPoly(Y)CC is a thermodynamically unstable helix
compared to Tetra1Poly(R)CC and Tetra2Poly(R)CT.21 Moreover, these findings were
supported by the calculation of a model polymer, a 20-mer of pOcPA, using the MMFF
94 calculation method, as mentioned below. Thus, the diameter for HexaPoly(Y)CC isfairly fine with a magnitude of 9.3−10.1 Å compared to the contracted helices of
Tetra2

Poly(R)CT and Tetra1Poly(R)CC. This allows us to conclude that HexaPoly(Y)CC iscomposed of contracted helices (Fig. 3).

83

Figure 4.

Calculated helical backbone, (a) a contracted helix with a bent n-octyl

phenyl ring, (b) a contracted helix with an extended alkyl phenyl ring, and (c) astretched helix with a bent n-octyl phenyl ring.

Energetically Stable Structures Calculated by MMFF 94
The most stable helical conformations of
Tetra2Hexa

Poly(Y)CC,

Tetra1

Poly(R)CC, andPoly(R)CT were simulated using the pOcPA 20-mer as a model molecule. The

molecular mechanics (MM) calculations used the MMFF 94 force field program.8a The
MMFF 94 calculations were performed by rotating the dihedral angles, θ (°) along thecentre C-C single bonds in the C=C-C=C moieties. These calculations were assumed
that the alkyl chains have a bent structure at the C6 carbon in HexaPoly(Y)CC (see Fig. 4a),an extended alkyl chain in Tetra1Poly(R)CC (Fig. 4b), and the same bent structure in
Tetra2

Poly(R)CT(Fig. 4c). Moreover, the bent angles, θ, between the benzene ring and thealkyl chain were assumed to take θ1=112° and θ2=90°, respectively, and the bond angle
84between the C4-C5 and C6-C7 carbons was also assumed to be approximately θ3=66°.
Thus, the stable conformation of the alkyl benzene ring was optimised in advance using
the MMFF 94 program. These calculations afforded the relationship between θ and thestrain energy (kJ/unit mol) (Fig. 6). These results clearly demonstrated that the strainenergy was minimised, (122.5 kJ/unit mol) at approximately θ=110° in the case of theextended alkyl chain (see Fig. 4c). This indicated that the model polymer having such abent alkyl chain can exist as two stable conformations at θ=70° and 110°, respectively(see Fig. 6). When the dihedral angle is 70°, the contracted and stretched helices takebent alkyl chain and zig-zag straight chain, respectively. Therefore, the final
conformations between the two contracted helices having the bent alkyl chain and thestraight alkyl chain are different each other, irrespective of the same dihedral angles. In
other words, the dihedral angles in HexaPoly(Y)CC and Tetra2Poly(R)CT take θ=70° and
110°, respectively, and have contracted cis-cisoid and stretched cis-transoid helices,
respectively. Thereby, the diameters of

Hexa

Poly(Y)CC andTetra2

Poly(R)CT were

determined to be Dcalc.=29.6 Å and 20.4 Å, respectively, which are in agreement withthe diameters obtained by XRD, Dobs.=29.6 Å and 20.3 Å. On the other hand, in the caseof the helical main chain having such an extended alkyl chain the minimum energy
reached to ca. 114.5 kJ/unit mol at θ=70°. This indicates that Tetra1Poly(R)CC has acalculated diameter of Dcalc.=30.8 Å, while the diameter determined by XRD isDobs.=30.4 Å (see Figs. 3b and 5b). Thus, the MMFF 94 calculations agreed with thedetermined diameters, indicating high calculation reliability.

85

Figure 5.

Observed and calculated helix diameters of Poly(Y) obtained before andafter heat treatment at 100 °C for 1 h: (a) a hexagonal columnar crystal having
contracted cis-cisoid helices, (b) a tetragonal crystal having contracted cis-cisoid
helices, (c) a tetragonal crystal having stretched cis-transoid helices.

Furthermore, the calculations for the model polymer of Tetra1Poly(R)CC indicate thatthe distances between every helical pitch width, i.e., p-stacking of the phenyl rings withextended alkyl chains is approximately 3.4 Å, which was observed at approximately

8670-100 °C in the XRD patterns. Thus, the calculated helical pitch width agrees wellwith the observed helical pitch. However, notably the possibility regarding formation ofrectangular crystal instead of the two tetragonal crystals is not always excluded asreported by Percec et al.14d

Figure 6.

Strain energy dependences of dihedral angles θ° around the C-C single bondin the C=C-C=C bond in (a) an extended alkyl chain and (b) a bent alkyl chain.

π-Conjugation Length in the Solid Phase
The DRUV-vis spectra of Poly(Y), Poly(O), and Poly(R) are shown in Fig. 7. The
absorption maximum, λmax, of Poly(Y) was observed at 448 nm with a shoulder at 565
nm. The absorption at 448 nm was attributed to contracted cis-cisoid helices in
Hexa

Poly(Y)CC.8(a)87Figure 7.

DRUV-vis spectra of (a) Poly(Y), (b) Poly(O), and (c) Poly(R) observed onalumina powders.

Previously, cis and trans polyacetylenes with no substituents prepared using theZiegler-Natta catalyst Et3Al-Ti(On-Bu)4 showed λmax at 570 and 675 nm with small
shoulders at approximately 500 and 600 nm, respectively.22 The λmax at 448 nm in
Hexa

Poly(Y)CC shifted to 565 nm when heated to 100 °C for 1 h. This observation

indicated that the helical pitch was shortened to accommodate ordered π-stacking along
the helical backbone. Therefore, the λmax at 565 nm was attributed to the Tetra1Poly(R)CC,
although the absorption of Tetra2Poly(R)CT is superimposed on this peak to some extent.
The DRUV-vis spectrum of Poly(O) was attributed to be an intermediate between the
spectra of Poly(Y) and Poly(R).

88Bent n-Octyl Alkyl Chains Detected by Solid State 13C CP-MAS NMR
Solid state 13C CP-MAS NMR was used to determine whether the n-octyl side chainsof HexaPoly(Y)CC and Tetra2Poly(R)CT hold a linear or a bent structure in the solid phase,in addition to the position of the bend. Because the XRD data and MMFF 94
calculations indicated that the two polymers have a bent alkyl chain (see Figs. 4a, c, 5a,and c).

Figure 8.

Solid state 13C CP-MAS NMR spectra from 0 to 45 ppm of Poly(Y) at room

temperature.	
 Fig. 8 shows only the alkyl carbon chemical shift region from 0 to 45 ppm. The peaks at
36.5, 32.8, 30.6, 24.3, 23.6, and 14.8 ppm were attributed to the C1H2, C2~6H2, C7H2,
C7’H2, and C8H3 carbons, respectively. This assignment was confirmed by the solution
89

13

C NMR spectrum (see Figs. S1 and S2).† Interestingly, the peak due to C7 at thesecond position from the terminal methyl moiety was found to be splitted into two
peaks at 23.6 and 24.3 ppm, respectively, having a ratio of 5:6 (Fig. 8). It is necessary tonote that the intensity of the 13C peaks is not related to the formation ratio of theextended and bent carbon chains but is related to the contact time used. The peaks at
23.6 and 24.3 ppm were assigned to the normal zigzag extended C7 methylene carbons
and the bent carbons at C7, respectively,23 although the position of the bend is at the C6
carbon. Thus, we corroborated that the bend position within the alkyl chain structure isat the C6 carbon using the solid state 13C CP-MAS NMR method, although such a bent
alkyl chain structure in the columnar has never been reported to the best of ourknowledge.

DSC Studies
Fig. 9 shows the DSC trace of Poly(Y) measured under nitrogen from 50 to 180 °C at
a heating rate of 10 °C/min. The trace exhibited three endothermic peaks at
approximately 82, 105, and 145 °C, respectively. The second peak at ca. 105 °C was
attributed to the solid phase transition from the hexagonal structure having thecontracted helixCC with cis-cisoid helices to the tetragonal crystal, Tetra1, with
contracted cis-cisoid helices and tetragonal crystals, Tetra2, with stretched helicesCT.
The small endotherm at ca. 82°C was attributed to the melt or reorientation of then-octyl alkyl side chains. Such small reorientation peaks are often observed before aphase transition.24 Notably, the thermal treatment of Poly(Y) under N2 for 1 h at a90

temperature greater than 140 °C rapidly decreased the cis % because of the cis-to-transisomerisation as evidenced by the DSC trace.8(a) The enthalpy of the transition energy(ΔH2= ca. 0.61 kJ/unit mol) corresponded to the thermally induced rearrangement of
Hexa

Poly(Y)CC to

Tetra1

Poly(R)CC andTetra2

Poly(R)CT. This enthalpy value wasapproximately 1/10 of the calculated transition energy (6.0 kJ/unit mol) obtained from
the MMFF 94 method (Fig. 6). This inconsistency was rationalised in terms ofcolumnar structure. Because both the rotational angles around the primary alkyl chain
and the position of the long alkyl chain require to be changed during the solid phasetransition of

Hexa

Poly(Y)CC to

Tetra1

Poly(R)CC andTetra2

Poly(R)CT. Therefore, thethermally induced rearrangement did not proceed to completion. In other words, lessthan 1/10 of the helical components in HexaPoly(Y)CC rearrange to Tetra1Poly(R)CC andTetra2

Poly(R)CT in the solid phase. Furthermore, it is noteworthy that the thermal

treatment of HexaPoly(Y)CC at ca. 100 °C did not appreciably decrease the cis %. This
indicates that the cis-to-trans isomerisation reaction was not significantly induced evenduring this heat treatment in the solid phase. This also suggests that half of the Poly(O)remains unchanged when heated to 80 °C. Consequently, the boundary sequences
between the unchanged Poly(O) and the changed Poly(R) are relatively short andproduce distorted sequences. This distortion is the reason why a small absorption at~320 nm is created when heated to 100 °C, as shown in Fig. 9.

91

Figure 9.

Fig. S1

13

DSC thermogram of Poly(Y) observed from 50 to 180 °C.

C NMR spectrum of poly(p-n-octyphenylacetylene) observed at 25 °C

in CDCl3 solution.

92

Fig. S2 Solid state 13C CP-MAS NMR spectra of Poly(Y) at room temperature.

Conclusions
p-n-Octylphenyacetylene (pOcPA) was stereoregularly polymerised at -20 °C and 25°C using [Rh(nbd)Cl]2 and a TEA cocatalyst in EtOH to afford yellow and orange
polymers, Poly(Y) and Poly(O), in high yields of 64 and 99 %, respectively. Poly(Y)transformed into red polymer, Poly(R), upon heating to 100 °C. The three polymers
were analysed by XRD, MMFF 94 calculations, DSC, DRUV-vis, and solid state 13C
CP-MAS NMR. Poly(Y) and Poly(R) exhibited absorption maximums, λmax, at 448 and565 nm, respectively. No significant differences were observed in the 1H NMR spectra
obtained in chloroform. The XRD patterns of Poly(Y) revealed that it has a hexagonal
columnar crystal structure comprising cis-cisoid helices, i.e., contracted helices, called

93

Hexa

Poly(Y)CC. Furthermore, heating HexaPoly(Y)CC up to 100 °C induced a solid phasetransformation to the red polymers, Tetra1Poly(R)CC and Tetra2Poly(R)CT. The XRD
pattern of Poly(O) agreed with the pattern of Poly(Y) that was heated to ca. 90 °C. To
the best of our knowledge, such solid phase rearrangements resulting from a contracted
helixCC to a stretched helixCT accompanied by a drastic colour change have never beenreported. The thermal instability of HexaPoly(Y)CC was proven by the DSC endotherm at
ca. 105 °C. Moreover, the XRD and MMFF 94 data of the n-octyl chains of
Hexa

Poly(Y)CC and Tetra2Poly(R)CT showed that the octyl side chain in the phenyl rings

bend at the third carbon from the terminal methyl group, i.e., C6. Therefore, these dataclearly corroborated that HexaPoly(Y)CC crystals are thermally converted to the twotetragonal crystals containing contracted helicesCC and stretched helicesCT at 100 °C.

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99

Summary of this Thesis

100

The polymerization of p-n-alkoxyphenylacetylene and p-n-alkylphenylacetylene wascarried out by using a [Rh(norbornadine)Cl]2-triethylamine catalyst to afford
stereoregularhelicalpoly(p-n-alkoxyphenylacetylene)sandpoly(p-n-alkylphenylacetylene)s in the presence of solvent. We could show that thehelical polyacetylenes have stretched helix, cis-transoid main-chain structure andcis-cisoid main-chain structure, contracted helix, respectively. Futhermore, we foundthat their polymer colors are related to the geometric structures and/or higher-order
structures of the resulting polymers in solid phase.

The helical pitches and colors of

their polymers were changed by the heat-treatment accompanied with thetransformation of the crystal structures in solid phase.

Chapter 1, The stereospecific polymerization of p-n-hexyloxyphenyacetylene was
successfully performed using a [Rh(norbornadine)Cl]2-triethylamine catalyst in ethanolor hexane at 25 °C to afford poly(Y) with a bright yellow color and poly(R) with apurple red color as powders, selectively, in fairly high yields. The XRD patterns ofpoly(Y) showed columnar structures comprising of the helical chains for both polymers,
and the pitch of poly(R) is narrower than that of poly(Y). Interestingly a thermallyinduced rearrangement from the yellow poly(Y) to a reddish black polymer,
poly(Y→B) took place at 80 °C. Poly(Y→B) showed that the helix diameter is near topoly(R). This means that poly(Y) is thermodynamically less stable helix compared tothat of poly(R). The thermal instability of poly(Y) was proven by the fact that its
exothermic transition temperature was observed at 80 °C. Thus, these data clearly101

indicated that the stretched helix polymer, poly(Y), was changed to the contracted helix
polymer, poly(Y→B), when heated at 80 °C under N2.

Chapter 2, p-n-heptylphenylacetylene was stereoregularly polymerized using[Rh(norbornadiene)Cl]2 and triethylamine in n-hexane, to afford the purple-red polymer
Poly(R) in high yield. Poly(R) transformed into the black polymer Poly(B) uponheating to 80 °C. The XRD patterns of Poly(R) revealed that it had a hexagonal crystal
structure (HexaPoly(R)) comprising cis-cisoid helices (i.e., contracted helices called
Hexa

Poly(R)CC).

Furthermore, heating Poly(R) up to 120 °C induced the solid phasetransformation of HexaPoly(R)CC to two tetragonal crystal phases: one containing
large-diameter cis-cisoid helices and the other containing small-diameter stretchedhelices. The thermal instability of HexaPoly(R)CC was proven by the DSC endotherm atapproximately 80 °C.

These data clearly corroborated that the pristine HexaPoly(R)CC

crystals thermally converted into the two tetragonal crystals containing contracted
helicesCC and stretched helicesCT at approximately 80 °C, respectively. The origin of thecolor changes observed before and after the heat treatment was attributed to the helicalpitch width and the increment of intramolecular π-stack order in the polymer chain.

Chapter 3, Para-n-octylphenyacetylene was stereoregularly polymerised using[Rh(norbornadiene)Cl]2 in ethanol at -20 °C and 25 °C to afford yellow and orange
polymers, Poly(Y) and Poly(O), respectively, in high yields.
red polymer, Poly(R), upon heating to 100 °C.
102

Poly(Y) transformed into

The XRD patterns of Poly(Y) revealedthat it has a hexagonal columnar crystal structure comprising cis-cisoid helices, i.e.,
contracted helices, called HexaPoly(Y)CC.

Furthermore, heating HexaPoly(Y)CC up to

100 °C induced a solid phase transformation to the red polymers, Tetra1Poly(R)CC andTetra2

Poly(R)CT, respectively.

Moreover, we revealed that the HexaPoly(Y)CC andTetra2

Poly(R)CT have a bend n-octyl side chains using the solid state 13C CP-MAS NMR

method.

This study described new helical polyacetylenes which are composed from stretchedhelix and/or contracted helix. The color of the polyacetylenes was attributed to thegeometrical structure and higher order structure, i.e., helical pitch width and theincrement of intramolecular π-stack order in the polymer chain. Furthermore, we
revealed that the columnar polymers comprising of the helical chains have two crystals
phase, i.e., hexagonal crystal and tetragonal crystal. And we also revealed that thehelical pitch and crystal structure could can be controlled by the heat-treatment. Thus,
this study described important chemical and physical features of a helical π-conjugatedpolymer, that will be developed as a new class of advanced materials and /or molecularmaterials near future.

List of Publications
1.

Asahi MOTOSHIGE, Yasuteru MAWATARI, Yoshiaki YOSHIDA, Chigusa SEKI,

103

HaruoMATSUYAMA,

Rearrangement

and

from

Masayoshi

TABATA, 「 Irreversible

Cis-transoidtoCis-cisoid

Helix
in

Poly(p-n-hexyloxyphenylacetylene) Induced by Heat-treatment in Solid Phase」, J.
Polym. Sci., Part A: Polym. Chem., 2012, 50, 3008-3015.

2.

Asahi MOTOSHIGE, Yasuteru MAWATARI, Ranko MOTOSHIGE, Yoshiaki
YOSHIDA, and Masayoshi TABATA, 「 Contracted Helix to Stretched Helix
Rearrangement of an Aromatic Polyacetylene Prepared in n-Hexane with[Rh(norbornadiene)Cl]2-trietylamine Catalyst」, J. Polym. Sci., Part A: Polym.
Chem., 2013, 51, 5177-5183.

3.

Asahi MOTOSHIGE, Yasuteru MAWATARI, Yoshiaki YOSHIDA, Ranko
MOTOSHIGE, and Masayoshi TABATA, 「Synthesis and Solid State Helix to
Helix Rearrangement of Poly(phenylacetylene) Bearing n-Octyl Alkyl Side Chains」,
Polym. Chem., 2014, 5, 971-978.

4.

Yoshiaki YOSHIDA, Yasuteru MAWATARI, Asahi MOTOSHIGE, Ranko
MOTOSHIGE, Toshifumi HIRAOKI, Manfred WAGNER, Klaus MÜLLEN, andMasayoshi TABATA, 「Accordion-like Osillation of Contracted and Stretched
Helices of Polyacetylenes Synchronized with the Restricted Rotation of Side
Chains」, J. Am. Chem. Soc., 2013, 135, 4110-4116.

5.

Yoshiaki YOSHIDA, Yasuteru MAWATARI, Asahi MOTOSHIGE, Ranko
104

MOTOSHIGE, Toshifumi HIRAOKI, and Masayoshi TABATA, 「 Helix
Oscillation of Polyacetylene Esters Detected by Dynamic 1H NMR, IR, and UV-vis
Methods in Solution」, Polym. Chem., 2013, 4, 2982-2988.

6.

Ranko MOTOSHIGE, Yasuteru MAWATARI, Asahi MOTOSHIGE, Yoshiaki
YOSHIDA, Takahiro SASAKI, Hiroaki YOSHIMIZU, Tomoyuki SUZUKI,
Yoshiharu TSUJITA, Masayoshi TABATA, 「 Mutual Conversion between
Stretched and Contracted Helices Accompanied by a Drastic Change in Color andSpatial Structure of Poly(phenylacetylene) Prepared with a [Rh(nbd)Cl]2-Amine
Catalyst」, J. Polym. Sci., Part A: Polym. Chem., 2014, 52, 752–759.

Acknowledgements

This thesis presents the studies which the author has carried out from 2009 to 2013 at

105

Department of Chemical and Materials Engineering, Muroran Institute of Technology.
The author would like to express my gratitude to Professor Masayoshi Tabata for his
continuous guidance and critical suggestions throughout this study.
The author is also grateful to Professor Haruo Matsuyama and Professor Hiroto
Nakano for their helpful advices. The author is deeply grateful to Dr. Yasuteru
Mawatari for his constant guidance, interesting discussion and encouragement.
The author is grateful to Professor Toshifumi Hiraoki (Hokkaido University) for
NMR measurements and advice, Mr. Yoshikazu Sadahiro for X-ray diffraction
measurement and discussion.
The author is grateful to Professor Klaus Müllen and his Lab. members (Max-Planck
Institute for Polymer Research in Germany) and Professor Roberto Lazzaroni and hisLab. members (University of Mons in Belgium) for giving me to useful opportunities
and interesting discussion.
The author thankful to member of Tabata Lab. members; Dr. Yoshiaki Yoshida, Dr.
Takahiro Sasaki Ms. Ranko Motoshige and Matsuyama Lab. members for spending me
useful and enjoyable research activities.
Finally, the author is deeply grateful to my family for everything.

March 2014
Asahi Motoshige

106