Lyotropic chiral nematic liquid crystalline aliphatic conjugated polymers based on disubstituted polyacetylene derivatives that exhibit high dissymmetry factors in circularly polarized luminescence

Article abstract of DOI:10.1021/ja3086565

We synthesized disubstituted liquid crystalline polyacetylene (diLCPA) derivatives bearing 4-nonyloxy phenyl groups with lyotropic and thermotropic LC behavior. The poly(diphenylacetylene) main chain structure of the diLCPAs and the chirality induced with either chiral moieties or chiral dopants allow the formation of a highly ordered lyotropic N*-LC phase. Circular dichroism (CD) spectra of the diLCPAs imply that one-handed intrachain helical structures are formed in solution, while interchain helical π-stacking between the polymer main chains are formed in cast film and in the N*-LC state. Absorption dissymmetry factors (g_abs) in the N*-LC state show values on the order of 10^-1. The N*-LC state facilitates the formation of helically π-stacked structures with a high degree of helical ordering of the diLCPA and is indispensable for the generation of circularly polarized luminescence (CPL) with high emission dissymmetry factors (g _em) on the order of 10^-1. To the best of our knowledge, this is the highest reported value of CPL achieved for aliphatic, conjugated polymers. As an alternative to the thermotropic N*-LC phase, we have found that the lyotropic N*-LC phase of diLCPA could be promising materials possessing CPL functionality for use in next-generation π-conjugated organic optoelectronic devices, displays, and sensors.

Full text of DOI:10.1021/ja3086565

Article
pubs.acs.org/JACS
Lyotropic Chiral Nematic Liquid Crystalline Aliphatic Conjugated
Polymers Based on Disubstituted Polyacetylene Derivatives That
Exhibit High Dissymmetry Factors in Circularly Polarized
Luminescence
Benedict A. San Jose, Satoshi Matsushita, and Kazuo Akagi*
Department of Polymer Chemistry, Kyoto University, Katsura, Kyoto 615-8510, Japan
S
* Supporting Information
ABSTRACT: We synthesized disubstituted liquid crystalline
polyacetylene (diLCPA) derivatives bearing 4-nonyloxy phenyl
groups with lyotropic and thermotropic LC behavior. The
poly(diphenylacetylene) main chain structure of the diLCPAs
and the chirality induced with either chiral moieties or chiral
dopants allow the formation of a highly ordered lyotropic N*-
LC phase. Circular dichroism (CD) spectra of the diLCPAs
imply that one-handed intrachain helical structures are formed
in solution, while interchain helical π-stacking between the
polymer main chains are formed in cast film and in the N*-LC
state. Absorption dissymmetry factors (gabs) in the N*-LC state show values on the order of 10−1. The N*-LC state facilitates the
formation of helically π-stacked structures with a high degree of helical ordering of the diLCPA and is indispensable for the
generation of circularly polarized luminescence (CPL) with high emission dissymmetry factors (gem) on the order of 10−1. To the
best of our knowledge, this is the highest reported value of CPL achieved for aliphatic, conjugated polymers. As an alternative to
the thermotropic N*-LC phase, we have found that the lyotropic N*-LC phase of diLCPA could be promising materials
possessing CPL functionality for use in next-generation π-conjugated organic optoelectronic devices, displays, and sensors.
combination of well-defined chiral packing of the liquid
crystalline PF as well as chiral interchain interactions is the
key for the increase in gem values of the PF-based CPEL device.
Subsequently, CPL in other aromatic conjugated polymers has
also been reported.5,6
Meanwhile, research concerning the generation of CPL from
chiral nematic liquid crystal (N*-LC) materials has been
pursued. Liquid crystals (LCs) are anisotropic fluids of
supramolecular assemblies that exist as an intermediate phase
between isotropic fluid and solid crystal phases. LCs can be
classified as either thermotropic or lyotropic.7 N*-LC materials
exhibit optical activity, circular dichroism (CD), and even
selective reflection at specific wavelengths of circularly polarized
light of a certain handedness.8
1. INTRODUCTION
Circularly polarized luminescence (CPL) of organic and
polymeric materials has attracted considerable interest in
photonic devices, such as light-emitting diodes, optical
amplifiers, and optical information storage.1,2 CPL can also
be used to illuminate liquid crystal displays (LCDs). As a
specific example, LCDs using a CPL backlight have been shown
to exhibit several advantages, including steeper transmission-
voltage characteristics and higher brightness, compared with
LCDs using linearly polarized luminescence (LPL) illumina-
tion.1 Hence, considerable effort has been devoted to the
generation of CPL emission using various materials and
methods.
CPL from conjugated polymer systems was first reported
using polythiophene (PT) having a chiral side chain with
emission dissymmetry factors (gem) values of up to 5.0 × 10−3.3
Subsequently, circularly polarized electroluminescence
(CPEL)2 was reported using an EL cell with poly(p-
phenylenevinylene) (PPV) bearing a chiral side chain as an
emissive layer. The CPEL device has reported values of gem up
to −1.7 × 10−3. In chiral substituted conjugated polymers, the
chiroptical properties are assumed to evolve mainly from
interchain interactions within chiral aggregates. There has been
a CPEL device described that is constructed with a
thermotropic liquid crystalline polyfluorene (PF) bearing chiral
side chains with gem values of up to −2.5 × 10−1.4 The
The first approach to produce CPL with high gem involved
using a fluorescent dye embedded in a N*-LC host.9 Recently,
this research was expanded to include CPL generated within
the selective reflection band of the N*-LC10 and wavelength-
tunable CPL.8 Furthermore, N*-LCs are used as platforms for
the generation of low-threshold lasing,11,12 and CPL lasers.12
These developments demonstrate that the supramolecular
helical ordering of the N*-LC phase can be utilized to generate
CPL with high gem values.
Received: August 31, 2012
Published: November 14, 2012
© 2012 American Chemical Society
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One-handed helical conjugated polymers can be excellent
N*-LC materials for the generation of CPL, due to their
fluorescence and their ability to exhibit LC functionalities.
Many approaches to synthesize helical conjugated polymers
have been proposed. Helical polyacetylene (H-PA) films,
having helical chains and fibrils, have been synthesized through
the polymerization of acetylene in an asymmetric reaction field
constructed with N*-LC and Ziegler−Natta catalyst.13 The
introduction of chiral moieties as side chains is widely used to
induce helicity to the main chain of conjugated polymers.4,5 It
was also shown that when chiral dopants are added to the N-
LC phase of poly-p-phenylene (PPP) with LC side chains, the
resulting film exhibits chiroptical activity.14
2. RESULTS AND DISCUSSION
2.1. Synthesis and Characterization of Polymers.
Various disubstituted LCPA derivatives and chiral dopants
were synthesized (Scheme 1). The three diLCPA derivatives
Scheme 1. Structures of the Disubstituted LCPA Derivatives
and Chiral Dopants
Thermotropic N*-LC systems in conjugated polymers have
been widely used for generating CPL.4,5a,b,e,f,14 On the other
hand, it would be appealing to investigate lyotropic N*-LC
systems as alternative circularly polarized optical materials for
use in optoelectronic devices and displays. The effects of the
solvent, solution concentration, and chiral dopant employed on
the lyotropic N*-LC system would be of particular interest
especially in relation to the helical structure of the LC phase
and its chiroptical properties.
Various helical polymers with lyotropic LC behavior such as
polyisocyanate,15a cellulose derivatives,15b deoxyribonucleic
acid (DNA),15c−e and tobacco mosaic virus (TMV)15f,g have
been extensively studied. The substitution of two bulky side
chains directly into the main chain of polyacetylene leads to
disubstituted polyacetylene (diPA) exhibiting fluorescence.16,18
It was reported that fluorescent diPA adopting a poly-
(diphenylacetylene) (PDPA) structure with alkyl side chains
exhibits lyotropic LC behavior.17,18 The PDPA structure, with
phenyl moieties directly attached to the main chain, has a stiff
main chain that acts as a LC mesogen, which will self-assemble
into a lyotropic LC phase above a critical concentration.
Investigations on the lyotropic LC behavior of PDPAs have
been published; however, there are only a small number of
reports of PDPAs exhibiting the lyotropic N*-LC phase.17c
Therefore, examining the lyotropic N*-LC of diPA is
worthwhile because it has been shown that N*-LC materials
demonstrate supramolecular helical ordering that leads to CPL
with high gem and that lyotropic liquid crystallinity has excellent
potential for use in CPL devices. For these reasons, we aim to
synthesize disubstituted liquid crystalline polyacetylene (diLC-
PA) having a lyotropic N*-LC phase to generate CPL with high
gem.
In this research, various diLCPA derivatives having either a
poly(alkylphenylacetylene) (PAPA) structure or a PDPA main
chain structure were synthesized. Chirality in diLCPA was
induced by means of substitution of chiral moieties to the side
chains or with the use of chiral dopants. The structural effects
on the functionalities of the diLCPA derivatives were examined.
We focused on the thermotropic and lyotropic LC of the
diLCPAs, as well as their photoluminescent (PL), chiroptical,
and CPL properties.
In this study, we demonstrate that chiral diLCPA derivatives
form a lyotropic N*-LC film, and they exhibit CPL having a
high gem value. To the best of our knowledge, the gem values on
the order of 10−1 are the highest values of CPL achieved in the
aliphatic conjugated polymers. In this work, we have found that
the highly ordered lyotropic N*-LC phase is essential for the
generation of CPL with high gem values.
have a 4-nonyloxy phenyl groups with either racemic (rac)-,
(R)-, or (S)- handedness. PA1 has a poly(alkylphenylacetylene)
(PAPA) structure, while PA2 and PA3 have a poly-
(diphenylacetylene) (PDPA) structure that is responsible for
both green fluorescence and lyotropic liquid crystallinity.
Axially chiral dopants were synthesized as described in a
previous report.13 (R)-/(S)-2,2′-PCH506-Binaphthyl, abbre-
viated as (R)-/(S)-D1, have phenylcyclohexyl (PCH) LC
moieties that are substituted at the 2,2′ position of the
binaphthyl rings. The substituted PCH LC moieties of (R)-/
(S)-D1 improve the miscibility between the polymer and the
chiral dopant and also give rise to the chiral induction between
them.
The synthesis routes for the monomers and polymers are
shown in Scheme 2. The monomers of the diLCPA derivatives
and the chiral dopants were synthesized using chemical
reactions, such as Sonogashira−Hagihara coupling,19a,b Mitsu-
nobu reaction,19c and Williamson etherification reaction.19d
The monomers were polymerized via a metathesis reaction
using tungsten hexachloride (WCl6) as a catalyst with
tetraphenyltin (Ph4Sn) as a co-catalyst. The polymerization
reaction was conducted at 80 °C under an argon atmosphere
using toluene as a solvent. The polymerization proceeded for
24 h followed by washing of the polymer in methanol (MeOH)
under constant stirring for 24 h. The precipitated polymers
were subsequently dried under a vacuum.
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a
Scheme 2. Synthesis Routes for the Monomers and Disubstituted LCPA Derivatives
a
Reagents and conditions: PA1: (a) 1-octyne, PdCl2(TPP)2, CuI, NH3 (aq), THF, r.t., 24 h; (b,c,d) 1, (rac)/(S)/(R)-2-nonanol, DEAD, TPP, THF,
r.t., 24 h; (e,f,g) (rac)-M1, (R)-M1, (S)-M1, WCl6, Ph4Sn, toluene, 80 °C, 24 h; PA2: (h) phenylacetylene, PdCl2(TPP)2, CuI, Et3N, THF, 65 °C,
24 h; (i,j,k) 2, (rac)/(S)/(R)-2-nonanol, DEAD, TPP, THF, r.t., 24 h; (l,m,n) (rac)-M2, (R)-M2, (S)-M2, WCl6, Ph4Sn, toluene, 80 °C, 24 h; PA3:
(o,p,q) (rac)/(S)/(R)-2-nonanol, DEAD, TPP, THF, r.t., 24 h; (r,s,t) 3, 4, 5, trimethylsilylacetylene, PdCl2(TPP)2, CuI, Et3N, THF, 65 °C, 24 h;
(u,v,w) 6, 7, 8, K2CO3, MeOH, THF, r.t., 24 h; (x,y,z) 9, 10, 11, 4-iodophenol, PdCl2(TPP)2, CuI, Et3N, THF, 65 °C, 24 h; (aa,ab,ac) 12, 13, 14,
(rac)/(S)/(R)-2-nonanol, DEAD, TPP, THF, r.t., 24 h; (ad,ae,af) (rac)-M3, (R)-M3, (S)-M3, WCl6, Ph4Sn, toluene, 80 °C, 24 h.
The number-average molecular weight (Mn) and the
polydispersity (Mw/Mn) of the polymers were measured using
gel permeation chromatography (GPC) and calibrated using a
polystyrene (PS) standard. The GPC results showed that the
polymers have Mn values ranging from 12 700 to 48 300 and
Mw/Mn values ranging from 1.7 to 2.8 (Table 1).
2.2. Liquid Crystallinity. The diLCPAs exhibited lyotropic
and thermotropic liquid crystallinity. PA1 exhibited thermo-
tropic LC behavior having a smectic A (SA) LC phase (see
Supporting Information, Figure S1), while PA2 and PA3
showed main chain type lyotropic LC behavior. In the case of
the PA1, the alternating phenyl moieties attached at the
polymer main chain act as LC mesogens, and PA1 shows side
chain type liquid crystallinity arranged in a layered SA phase.
Even with the presence of chiral moieties in the side chain of
(R)-/(S)-PA1, the side chain type liquid crystalline behavior of
PA1 aligns the main chain into a layered SA LC phase.
Previously, we observed main chain type lyotropic LC
behavior in diLCPAs having a PDPA structure, which showed a
lyotropic nematic LC (N-LC) phase.18 The main chains of PA2
and PA3 have a stiff polymer structure because their side chains
are composed of phenyl moieties directly attached to the main
chain forming a stilbene fragment enforced by π-conjugation. A
polymer exhibiting this elevated level of stiffness should be
infusible upon the heating, resulting in an LC with no
thermotropic behavior. Instead, by virtue of the nonyloxy
group substituted at the phenyl moiety, PA2 and PA3 are
soluble in organic solvents, such as a toluene, and show
lyotropic LC behavior. Note that PA1 is also soluble in organic
solvents, but it shows no lyotropic LC. This finding is probably
due to its higher solubility, which might depress the formation
of spontaneously aligned self-assemblies that is a prerequisite to
the formation of domains of lyotropic LC. In other words,
polymers with high solubility are freely dissolved in a solvent
with randomly oriented conformation and form neither a
regularly stacked nor an associated structure. This situation is
Table 1. Weight-Average (Mw) and Number-Average (Mn)
Molecular Weights, Dispersion Degree (Mw/Mn), and
Degree of Polymerization (DP) of the Disubstituted LCPAs
Mw
Mn
Mw/Mn
DP
(rac)-PA1
(R)-PA1
(S)-PA1
(rac)-PA2
(R)-PA2
(S)-PA2
(rac)-PA3
(R)-PA3
(S)-PA3
100 000
46 400
73 500
53 000
53 000
56 000
27 100
21 000
33 000
48 300
26 700
44 400
22 000
23 000
25 000
13 400
12 700
14 000
2.1
1.7
1.7
2.4
2.1
2.3
2.0
2.8
2.3
151
83
139
70
72
77
29
16
30
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far from what is necessary for the formation of the lyotropic
LC. In the case of the PDPA structure of PA2 and PA3, the
stilbene fragment might be suitable for the formation of an
interchain π-electron overlapped association through van der
Waals interactions, which enables the polymers to exhibit the
lyotropic LC.
In the lyotropic LC phase of (S)-PA2, the polymer main
chains act as LC mesogens, which spontaneously align to form
a helically twisted structure in a N*-LC phase. Polarizing
optical microscopy (POM) analysis reveals a lyotropic N*-LC
phase prepared from 10 wt% solution using toluene as solvent
(Figure 1a). Figure 1a shows a double-spiraled texture
(rac)-PA2 and N*-LC film of (S)-D1/(rac)-PA2 (Figure S2)
showed XRD profiles similar to (S)-PA2 (Figure 1b).21
Table 2 summarizes the LC phases of the diLCPAs. PA1,
having a PAPA structure, exhibited a thermotropic SA phase.
PA2 and PA3 demonstrate lyotropic liquid crystallinity at a
critical concentration range from 5 to 10 wt% in toluene.
Analogous to thermotropic LCs which show an isotropic phase
above a critical temperature, lyotropic LCs become isotropic
liquids below 5 wt% concentration in toluene, where the
polymer main chains (which act as LC mesogens) are dispersed
randomly without any ordering. At the lyotropic LC
concentration range, there are weak π-interactions between
the aromatic stilbene structure and toluene. In such a situation,
the toluene enhances the attraction between polymer main
chains for spontaneous self-assembly to occur and also provide
enough fluidity in the system for liquid crystallinity to take
place.
(rac)-PA2 and (rac)-PA3 displayed a lyotropic N-LC phase,
while (R)-/(S)-PA2 (Figure 1a) and (R)-/(S)-PA3 (Figure
S3a) exhibited a lyotropic N*-LC phase. D1-doped (rac)-PA2
(Figure 2b) and D1-doped (rac)-PA3 (Figure S3b) also
exhibited a N*-LC phase through chiral induction. Thus, by
introducing chirality to diLCPA, either with a chiral moiety on
the side chain or with the addition of a chiral dopant, a
lyotropic N*-LC phase was formed in diLCPA, as long as the
PDPA structure is adopted in the polymer main chain.
2.3. Absorption and Photoluminescence. In the case of
polymer solutions in a good solvent such as chloroform
(CHCl3), the high solubility of the polymer main chains in the
solvent depresses the spontaneous self-assembly required for
liquid crystallinity to occur. To investigate the optical
properties of the diLCPAs in an isotropic state, we prepared
the diLCPA solutions using CHCl3 in a concentration of 1.2 ×
10−4 M. We examined the UV−vis, PL, absolute fluorescence
quantum yield (Φ), and specific rotation ([α]D) of the
diLCPAs in isotropic solution (CHCl3) and as cast films
(Table 3).
PA1 exhibits a main chain absorption band measuring ∼340
nm and a blue-colored emission measuring ∼450 nm in both
solution and film (Figure 3a). Conversely, PA2 and PA3 show
a main chain absorption band of ∼440 nm and a trans-stilbene
moiety-based absorption band measuring ∼380 nm. PA2 and
PA3 display a green colored emission of ∼500 nm in both
solution and film (Figure 3b,c). Previously, we elucidated the
origin of emission of substituted PAs and investigated the
fluorescent trends of diLCPA.18 In that earlier work, we
observed that diLCPAs with PAPA and PDPA structures
generally exhibit blue and green emissions, respectively. The
green emission color of the latter is associated with the PDPA
structure in which two bulky phenyl rings are directly attached
to the polyene main chain. Specifically, the two bulky side
chains contribute to lower the 1Bu excited state and later to
decrease the band gap,23 resulting in a bathochromic shift of the
PA2 and PA3 emission bands. Generally, the PAs show small
emission shifts between the solution and cast film, which is
advantageous for applications of diLCPAs as fluorescent
materials in EL devices. Absolute fluorescence quantum yields
(Φ) of the diLCPAs in solution and in cast film were measured
using the integrating-sphere method. The quantum yields of
the diLCPAs in solution range from 21 to 34%, while those in
cast film from 10 to 14%. Specific rotation ([α]D) measure-
ments showed that (R)-/(S)-PA3 (∼ 2100°) have values an
Figure 1. (a) POM image of the N*-LC phase of (S)-PA2 in 10 wt%
lyotropic LC solution in toluene showing a double-spiraled texture.
Inset shows a fingerprint texture with a half helical pitch of 1.5 μm. (b)
XRD pattern of (S)-PA2 shows a reflection at 15.0 Å (5.9° in 2θ)
describing the polymer interchain distance within a N*-LC domain.
Inset shows the Laue pattern of (S)-PA2. (c) Schematic representation
of the N*-LC phase of (S)-PA2. (d) Top view of a N*-LC domain
describing the polymer interchain distance.
characteristic of the N*-LC phase.20 The inset of Figure 1a
shows a fingerprint texture with a distance of 1.5 μm between
striae, which corresponds to the half helical pitch of the N*-LC
phase. We performed X-ray diffraction (XRD) on the N*-LC
film of (S)-PA2. The XRD profile of the (S)-PA2 N*-LC film
(Figure 1b) shows a peak corresponding to a distance of 15.0 Å,
which is assigned as the polymer interchain distance within a
N*-LC domain (Figure 1d).21 The XRD pattern also shows a
broad scattering signal in the wide angle range from 15 to 25°
(4−6 Å) due to the distance between side chains and/or π-
stacking of phenyl rings in the side chain, similar to previous
reports of PDPA showing lyotropic LC.17a,b Figure 1c shows a
schematic representation of the N*-LC phase of (S)-PA2.
In Figure 2, the chiral induction of (rac)-PA2 forming a N*-
LC phase is illustrated. The POM image of (rac)-PA2 shows a
Schlieren texture characteristic of lyotropic N-LC phase20
prepared from 10 wt% toluene solution (Figure 2a). Upon
addition of chiral dopant (S)-D1 at 10 wt%, the N-LC phase of
(rac)-PA2 changes into a N*-LC phase (Figure 2b). The POM
image of (S)-D1/(rac)-PA2 reveals a fingerprint texture with a
half helical pitch of 2.0 μm.22 XRD analysis on the N-LC film of
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Figure 2. Schematic model of the chiral induction of (rac)-PA2 into a N*-LC phase. Upon the addition of the chiral dopant (S)-D1 at 10 wt% into
the N-LC phase of (rac)-PA2 (left), a N*-LC phase is induced (right). (a) POM image of the N-LC phase of (rac)-PA2 10 wt% lyotropic LC
solution in toluene showing a Schlieren texture. (b) POM image of the N*-LC phase of (S)-D1/(rac)-PA2 in 10 wt% lyotropic LC solution in
toluene showing a fingerprint texture. Inset shows the half helical pitch of 2.0 μm.
2.4. Circular Dichroism. With the aim to investigate the
helical conformation and arrangement of the polymer chains in
an isotropic, aggregate, and liquid crystalline self-assembled
state, we measured the circular dichroism (CD) spectra of the
diLCPA derivatives in CHCl3 solution, cast film, and N*-LC
film.
Table 2. Thermotropic and Lyotropic Liquid Crystallinity of
the Disubstituted LCPAs
a
Solutions of the diLCPAs were prepared using CHCl3 (c =
1.2 × 10−4 M) as solvent. The cast film samples were prepared
by dissolving the diLCPAs in CHCl3, and later casting the
solution onto a quartz plate. The N*-LC film samples were
prepared by dissolving the diLCPAs or the diLCPAs with chiral
dopant24 in toluene (5−10 wt%) to form a lyotropic LC state.
The LC solution was subsequently cast onto a quartz plate,
which was later exposed under toluene vapor for one hour and
was dried slowly at room temperature. Toluene vapor exposure
of the N*-LC film was performed to increase the domain size
of the N*-LC phase.
a
Red, heating process; blue, cooling process; G, glassy state; N,
nematic; N*, chiral nematic; SA, smectic A.
order of magnitude higher than (R)-/(S)-PA1 (∼ 240°) and
(R)-/(S)-PA2 (∼ 220°).
The CD spectra of the diLCPAs in CHCl3 solution showed
monosignate Cotton effects at the absorption region of the
Table 3. Spectroscopic Data for Absorption (λmax), Fluorescence (Em,max), Excitation (Ex,max), Quantum Yield (Φ), and Specific
Rotation ([α]D) of the Disubstituted LCPAs in CHCl3 and Film
a
b
λmax (nm)
in CHCl3
Em,max (nm)
in CHCl3
Ex,max (nm)
in CHCl3
Φ (%)
in CHCl3
[α]D (deg)
film
film
film
film
in CHCl3
(rac)-PA1
(R)-PA1
(S)-PA1
(rac)-PA2
(R)-PA2
(S)-PA2
(rac)-PA3
(R)-PA3
(S)-PA3
340
338
344
430
430
432
438
440
436
340
338
341
428
430
428
438
444
438
454
452
452
501
502
501
501
501
498
444
444
445
502
500
501
494
493
493
337
338
336
361
376
365
372
372
372
340
338
341
374
378
374
365
365
365
26
21
22
29
24
28
34
29
33
12
10
11
11
14
13
13
12
13
N/A
−241
+247
N/A
+229
−226
N/A
+2080
−2158
a
b
Absolute quantum yield measured using integrating-sphere method. Specific rotation measured at room temperature in chloroform.
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Figure 3. UV−vis and PL spectra of (a) (R)-PA1, (b) (R)-PA2, (c) (R)-PA3 in CHCl3 solution (c = 1.2 × 10−4 M) and in cast film. Insets: PLs in
CHCl3 solution (left) and in cast film (right).
Figure 4. UV−vis (upper) and CD spectra (lower) in CHCl3 solution (c = 1.2 × 10−4 M) of (a) (R)-/(S)-PA1, (b) (R)-/(S)-PA2, and (c) (R)-/
(S)-PA3.
polymer main chains (Figure 4a−c).25 These results imply that
the diLCPAs have a one-handed helical excess conformation.
The monosignate Cotton effects of the CD spectra of the
diLCPAs suggest intrachain helicity of the polyene main chains.
The degree of CD was evaluated using absorption dissymmetry
factor, gabs. This factor is defined by the following equation: gabs
= (εL − εR)/[(εL + εR)/2] = Δε/ε, where |gabs| < 2. The εL and
εR are defined as the absorption coefficients of left- and right-
handed polarized light, respectively. The CD spectra of (R)-/
(S)-PA1 and (R)-/(S)-PA2 in solution showed gabs values on
the order of 10−4, while (R)-/(S)-PA3 showed gabs values on
the order of 10−3 (Table 4), which suggest that (R)-/(S)-PA3
in solution may have a more strongly twisted main chain helical
conformation compared to (R)-/(S)-PA1 and (R)-/(S)-PA2.
The two chiral nonyloxy moieties in (R)-/(S)-PA3 induce a
stronger helical conformation to the main chain, as quantified
by Δε and gabs values observed in the CD spectra in solution.
The measured specific rotation values of the diLCPAs in
solution (Table 3) also support the CD results, where (R)-PA3
(+2,080°) and (S)-PA3 (−2,158°) showed values an order
higher than (R)-PA1 (−241°), (S)-PA1 (+247°), (R)-PA2
(+229°), and (S)-PA2 (−226°).
Cast films of (R)-/(S)-PA1 showed monosignate Cotton
effects in the absorption region of the polymer main chain
(Figure 5a). For the other samples, the CD spectra of (R)-/
(S)-PA2 and (R)-/(S)-PA3 in cast film and in N*-LC film
exhibited bisignate Cotton effects in the absorption region of
the polymer main chain.26 Using the exciton coupling theory,27
we can deduce that (R)-/(S)-PA2 and (R)-/(S)-PA3 have
interchain helical π-stacking between the polymer main chains.
(R)-PA2, which has a positive and negative Cotton effect at
longer wavelengths and shorter wavelengths, respectively, can
be assigned as having P-helicity with a right-handed (clockwise)
π-stacked structure, while (S)-PA2 can be assigned as having
M-helicity with a left-handed (counterclockwise) π-stacked
structure (Figure 5b). From the CD spectra, (R)-PA3 and (S)-
PA3 are assigned as having M-helicity and P-helicity,
respectively (Figure 5c). The cast films of (R)-/(S)-PA2 and
(R)-/(S)-PA3 exhibited similar CD spectra and handedness to
the PA2 and PA3 N*-LC samples (Figure S5a,b). It should be
noted that the CD spectra of (R)-/(S)-PA1 in cast film form
showed no bisignate CD signal in the polymer main chain
absorption region. These results suggest that the PDPA
Table 4. Absorption Dissymmetry Factors (gabs) of the
Disubstituted LCPAs in CHCl3 Solution, Cast Film, and N*-
LC Film
a
gabs (wavelength/nm)
CHCl3
cast film/N*-LC film
b
(R)-PA1
−8.3 × 10−4 (325)
4.9 × 10−4 (320)
1.5 × 10−4 (378)
−2.6 × 10−4 (378)
4.8 × 10−3 (388)
−7.3 × 10−3 (385)
−6.8 × 10−4 (326)
b
(S)-PA1
5.9 × 10−4 (326)
c
(R)-PA2
1.7 × 10−1 (455)
c
(S)-PA2
−1.3 × 10−1 (445)
c
(R)-PA3
−2.9 × 10−2 (453)
c
(S)-PA3
5.4 × 10−2 (451)
c
(R)-D1/(rac)-PA2
(S)-D1/(rac)-PA2
N/A
−4.2 × 10−2 (449)
c
N/A
6.1 × 10−2 (459)
a
b
c
Wavelength at which gabs was evaluated. In cast film. In N*-LC film.
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Figure 5. UV−vis (upper) and CD spectra (lower) of (a) (R)-/(S)-PA1 cast film, and (b) (R)-/(S)-PA2 N*-LC film, (c) (R)-/(S)-PA3 N*-LC
film, (d) (R)-/(S)-D1 doped (rac)-PA2 (10 wt%) N*-LC film.
structure of (R)-/(S)-PA2 and (R)-/(S)-PA3 facilitates helical
π-stacking in cast film and N*-LC state.
(rac)-PA2 originated from the chiral induction of the (rac)-
PA2. Moreover, D1-doped (rac)-PA3 in N*-LC film also
showed a bisignate CD spectra (Figure S5c).
It should be noted that (R)-PA2 and (R)-PA3, having the
same configuration of chiral moieties, exhibit the same
intrachain helical sense in solution (Figure 4b,c, Table 4).
However, in cast films and N*-LC films, (R)-PA2 and (R)-PA3
exhibit opposite bisignate Cotton effects with P- and M-
helicity, respectively (Figure 5b,c, Table 4). Such behavior may
be related to the chiral organization of the polymer main chains
during self-assembly from a disordered (solution) state to a
helical π-stacked structure in cast film and N*-LC states. The
degree of the attractive interchain π-stacking interactions during
self-assembly would be quite different for (R)-PA2 and (R)-
PA3 because the latter has a more twisted helical main chain
conformation induced by its two chiral nonyloxy moieties. Such
a difference in attractive π-stacking interactions would be
sufficient to favor a different helical sense during the self-
assembly of (R)-PA2 and (R)-PA3.
It is also interesting that (R)-PA2 and (R)-D1/(rac)-PA2
N*-LC films showed bisignate Cotton effects with P- and M-
helicity, respectively (Figure 5b,d, Table 4). The chiral
organization of these two N*-LC films during self-assembly
would be quite different because the chirality of (R)-PA2 and
(R)-D1 exhibits central chirality and axial chirality, respectively.
Similarly, differences in the type of chirality would be sufficient
to favor a different helical sense during the self-assembly of (R)-
PA2 and (R)-D1/(rac)-PA2 N*-LC films. (R)-PA3 (Figure
5c) and (R)-D1/(rac)-PA3 (Figure S5c) films also exhibit
opposite helical sense in helical π-stacking.
(R)-/(S)-PA1 in cast film form showed gabs values on the
order of 10−4, and (R)-/(S)-PA3 and D1-doped (rac)-PA2
N*-LC films showed gabs values on the order of 10−2, while
(R)-/(S)-PA2 N*-LC films showed gabs values up to 10−1
(Table 4).28 It can be observed that the gabs values of the (R)-/
(S)-PA2 and (R)-/(S)-PA3 cast films are an order smaller than
those of (R)-/(S)-PA2 and (R)-/(S)-PA3 N*-LC films (Table
S1).
D1-doped (rac)-PA2 N*-LC films exhibited bisignate
Cotton effects at the polymer main chain region. It was
observed that (R)-D1/(rac)-PA2 N*-LC film showed M-
helicity, while (S)-D1/(rac)-PA2 N*-LC film showed P-
helicity (Figure 5d). The CD spectra of (rac)-PA2 displayed
no optical handedness; therefore, the chirality of D1-doped
The CD spectra of the diLCPAs indicate that one-handed
intrachain helical structure is formed in solution, while the
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Figure 6. PL (upper), CPL spectra (middle), and gem (lower) spectra of (a) (R)-/(S)-PA2 N*-LC film, and (b) (R)-/(S)-D1-doped (rac)-PA2 (10
wt%) N*-LC film. The measurements were performed with excitation using unpolarized light at 367 nm.
interchain helical π-stacking between the polymer main chains
is formed in cast films and in N*-LC films. The diLCPAs in
solution showed gabs values up to the orders of 10−3, while
diLCPAs in N*-LC film are in orders of up to 10−1. These
results indicate that an increase in interchain interactions from
solution to cast film and a subsequently further increase in N*-
LC film, leading to a higher degree of helical π-stacked
ordering.
2.5. Circularly Polarized Luminescence. We investigated
the potential of circularly polarized luminescence (CPL) of the
diLCPAs. Even though the diLCPAs in solution and in cast film
showed Cotton effects in their CD spectra, they exhibited no
CPL.
However, (R)-/(S)-PA2 in N*-LC film showed bisignate
CPL bands centered around the PL emission band (Figure 6a).
(R)-PA2 bearing P-helicity in the π-stacked structure exhibited
positive and negative CPL bands at wavelengths shorter and
longer than 530 nm, respectively. (S)-PA2, which has M-
helicity in the π-stacked structure, exhibited CPL bands with
handedness opposite to (R)-PA2. The degree of CPL was
evaluated by the emission dissymmetry factor, gem. The
emission dissymmetry factor is defined as gem = (IL − IR)/
[(IL + IR)/2] = ΔI/I, where |gem| < 2. The IL and IR are defined
as the intensities of left- and right-handed polarized light,
respectively. The CPL spectra of (R)-/(S)-PA2 in N*-LC film
showed gem values up to orders of 10−1 (Table 5).28 These high
gem values suggest the formation of higher ordered helical π-
stacked structures in the N*-LC film of (R)-/(S)-PA2. The gem
values on the order of 10−1 are the highest values of CPL
achieved in the aliphatic conjugated polymers to the best of our
knowledge.
The N*-LC film of D1-doped (rac)-PA2 exhibited CPL
similar to that of (R)-/(S)-PA2 (Figure 6b). The CPL spectra
of D1-doped PA2 films show handedness opposite to their
counterparts in (R)-/(S)-PA2 with gem values up to orders of
10−1. The CPL spectrum of (rac)-PA2 showed no CPL;
therefore, the CPL of D1-doped (rac)-PA2 originated from the
chiral induction of the (rac)-PA2. (R)-/(S)-PA3 and D1-doped
(rac)-PA3 N*-LC films also exhibited CPL (Figure S6, Table
S2).
It should be noted that (R)-PA2 and (R)-D1/(rac)-PA2 N*-
LC films, which showed P- and M- helicity, respectively, in their
helical π-stacked structure, also exhibited gem values with
opposite signs. The same trend of opposite signs in the gabs and
gem values was also observed in (R)-PA2 and (R)-PA3. This
finding suggests that the chiral organization of the helically π-
stacked structures influences the CPL behavior of the diLCPAs.
In contrast to PA2 and PA3, (R)-/(S)-PA1, bearing a PAPA
main chain structure, exhibited no CPL in cast films. These
results, along with the CD data, suggest that the PDPA main
chain structure is much more suitable for the helical π-stacking
necessary for CPL in diLCPA. Furthermore, the lyotropic LC
properties of the PDPA main chain enables the formation of a
higher-ordered helical arrangement through the N*-LC phase
that is essential for the emergence of CPL with high values of
gem.
2.6. Relationships between Helical Arrangement,
Interchain Interaction, and g-Factors of diLCPAs. At
this stage, it is helpful to summarize the relationships between
helical arrangement, interchain interaction and g-factors of
diLCPAs, as represented by (R)-PA2, depicted in Table 6. The
relationship between the degree of helical arrangement and the
magnitude of interchain interactions of the diLCPAs can be
elucidated by comparing the measured g-factors in CD and
CPL at different states. In the case of (R)-PA2 in CHCl3
solution, we observed intrachain helicity with weak interchain
interactions. The CD spectrum of (R)-PA2 in solution revealed
monosignate Cotton effects with gabs values on the order of
10−4. On the other hand, in the cast film of (R)-PA2, the
interchain interactions are large enough to give interchain
helical π-stacking. The emergence of a bisignate Cotton effect
in CD spectra with gabs values up to orders of 10−2 indicates
that the helical π-stacking between polymer main chains is
Table 5. Emission Dissymmetry Factors (gem) of the
Disubstituted LCPAs in N*-LC Films
a
gem(wavelength/nm)
(R)-PA2
1.8 × 10−1 (466)
−2.3 × 10−1 (471)
−1.2 × 10−1 (478)
5.9 × 10−2 (473)
(S)-PA2
(R)-D1/(rac)-PA2
(S)-D1/(rac)-PA2
a
Wavelength at which gem was evaluated.
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Table 6. Summary of the Relationship between Helical Arrangement, Interchain Interaction, and g-Factors of (R)-PA2 at
Various States
in solution
in cast film
in N*-LC film
helical arrangement
intrachain helicity
weak
1.5 × 10−4 (378)
interchain π-stacking
large
3.7 × 10−2 (445)
higher ordered helical arrangement
very large
interchain interaction
gabs of (R)-PA2 (λ, nm)
a
1.7 × 10−1 (455)
a
gem of (R)-PA2 (λ, nm)
1.8 × 10−1 (466)
a
Wavelength at which gabs and gem were evaluated.
3, MT-5 and MT-6), JSL JM-10, Mitsubishi chemical analytech AQF-
100 and Dionex ICS-1500.
formed through polymer interchain chiral aggregation. While in
the N*-LC state, very large interchain interactions are present,
resulting in a highly ordered interchain helical arrangement.
The CD and CPL spectra of (R)-PA2 in the N*-LC state show
high gabs and gem values of up to orders of 10−1, respectively.
This trend in the CD and CPL results of the diLCPAs leads us
to believe that the use of the N*-LC phase facilitates a high
degree of supramolecular helical ordering and is indispensable
for the emergence of CPL with high g-factors.
As a consequence, when one designs polyacetylene
derivatives with CPL having a high gem, it is essential to
adopt a PDPA main chain structure, to introduce helicity to the
main chain, and to utilize the lyotropic LC behavior of PDPA
to form a higher-ordered helical structure through the N*-LC
phase.
The microscope observation was carried out under crossed nicols
using a Carl Zeiss Axio Imager M1m polarizing microscope equipped
with a Carl Zeiss AxioCam MRc5 digital camera and a Linkam
TH600PM and L600 heating and cooling stage with temperature
control. The samples for observations with POM were sandwiched
between two cover glasses.
Optical absorption spectra were measured using a JASCO V-570
UV/VIS/NIR spectrophotometer, and fluorescence spectra were
measured using JASCO FP-750 spectrometer with quartz cell (for
solution) and quartz plate (for cast film). Absolute fluorescence
quantum yield of the polymers was measured using integrating-sphere
method at the JASCO FP-6500 spectrometer. Optical purity of the
chiral compounds and polymers were evaluated with specific rotation
measured by JASCO P2300 polarimeter. Circular dichroism spectra
were measured using JASCO J-820 spectropolarimeter. Circularly
polarized luminescence was measured using JASCO CPL-200S
spectrometer.
3. CONCLUSION
The molecular weights of the polymers were determined by gel
permeation chromatography (GPC) using a PLgel 5 μm MIXED-D
(Polymer Laboratories), a JASCO MD915 UV detector and THF as
an eluent at a flow rate of 1.0 mL/min during measurements, where
the instrument was calibrated using polystyrene (PS) standard, and
were calculated on an 807-IT integrator.
We synthesized chiral diLCPA derivatives that show a highly
ordered lyotropic N*-LC phase, thereby giving rise to a high
degree of circular polarization. The PDPA main chain structure
of the diLCPAs, along with chirality induced with either chiral
nonyloxy phenyl moieties or chiral dopants, allows the
formation of a highly ordered lyotropic N*-LC phase. We
found that the highly ordered lyotropic N*-LC phase is
indispensable for the generation of CPL with high gem values. In
addition to having the highest values of CPL in aliphatic
conjugated polymers, our approach represents an attractive
alternative to thermotropic LC systems for the development of
LC-based optoelectronic devices and future applications that
utilize circularly polarized optical materials.
XRD diffraction (XRD) measurements of the polymers were
performed with a Rigaku ultra X18 diffractometer (X-ray Cu Kα
radiation: 40 kV/300 mA, λ = 0.154 nm; camera length: 100 mm) and
a Rigaku Nanoviewer Micromax-007HF diffractometer (X-ray Cu Kα
radiation: 40 kV/30 mA, λ = 0.154 nm; camera length: 120 mm). XRD
patterns were recorded with an X-ray generator with Nickel filtered Cu
Kα radiation and a flat plate camera (RINT2500, Rigaku). The
polymers were heated up to isotropic state, and then slowly cooled to
room temperature via LC states, yielding XRD samples. Lyotropic LC
samples for XRD measurements were prepared by first dissolving the
polymer in toluene (5−10 wt% solution) to form a lyotropic LC
phase. The lyotropic LC solution is then pulled up a XRD capillary
tube (Hilgenberg Mark-tube glass no. 10, 0.01 mm wall thickness) and
allowed to dry, yielding XRD samples. The diffraction pattern was
recorded on an imaging plate and scanned by a R-AXIS DS3A imaging
plate reader at 100 μm resolution.
4.3. Syntheses of Monomers and Polymers. The synthesis
routes for precursor compounds 1 to 14 are detailed in the Supporting
Information. The syntheses of the diLCPA monomers (rac)-/(R)-/
(S)-M1−M3, the diLCPAs (rac)-/(R)-/(S)-PA1−PA3 are written
below. Synthesis of the chiral dopants (R)-/(S)-D1 were synthesized
as described in a previous report.13
(rac)-Monomer 1 ((rac)-M1). (rac)-M1 was synthesized as follows.
Into a 100 mL three-necked flask were added compound 1 (0.81 g,
5.69 mmol) and TPP (1.37 g, 5.22 mmol) under argon gas and
dissolved in THF (30 mL). In the addition funnel, a mixture of DEAD
(2.64 g, 40 wt% in toluene, 5.22 mmol), 2-nonanol (0.68 g, 4.74
mmol), and 30 mL THF were prepared. After dissolving the reagents
under constant stirring, the flask was placed in an ice bath and the
THF solution in the addition funnel was added dropwise to the
solution in the flask. The solution was left overnight at room
temperature. Thin layer chromatography (TLC) indicated completion
of the reaction. After evaporation of the solvent, the residue was
washed with water and extracted with CHCl3 (3×). The residue was
4. EXPERIMENTAL SECTION
4.1. Materials. The chemical reagents we purchased from
commercially available sources and were used as received. trans-
Dichlorobis(triphenylphosphine)palladium(II) (PdCl2(TPP)2) was
purchased from Aldrich Co. Ltd. Diethylazodicarboxylate (DEAD),
tetraphenyltin (Ph4Sn), 1-octyne, 4-iodophenol, trimethylsilylacety-
lene, and 2-nonanol were purchased from Tokyo Kasei Co. Ltd.
Tungsten(VI) hexachloride (WCl6), and copper(I) iodide (CuI) were
purchased from Kanto Chemical Co. Ltd. Triphenylphosphine (TPP),
(R)-(−)-2-nonanol, (S)-(+)-2-nonanol, and 25% ammonia (NH3)
solution were purchased from Wako Co. Ltd. Phenylacetylene,
potassium carbonate (K2CO3), sodium sulfate (Na2SO4), triethyl
amine (Et3N), tetrahydrofuran (THF), toluene, methanol (MeOH),
hexane (n-C6H14), ethyl acetate, and chloroform (CHCl3) were
purchased from Nacalai Tesque Co. Ltd. All experiments were
performed under argon (>99.9995% purity) atmosphere. THF, Et3N,
and toluene used were distilled from sodium as a drying agent under
argon gas before use.
4.2. Methods. Proton (1H) and carbon (13C) nuclear magnetic
resonance (NMR) spectra were measured in chloroform-d using either
JEOL JNM EX400 400 MHz or JEOL AL-400 400 MHz NMR
spectrometer. Chemical shifts are represented in parts per million
downfield from tetramethylsilane (TMS) as an internal standard.
Elemental analysis was measured using a Yanako CHN Corders (MT-
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dried over anhydrous Na2SO4 and the crude product was then purified
by open column chromatography using CHCl3 as eluent. The product
was evaporated and dried under vacuum to give 0.78 g (2.37 mmol) of
(rac)-M1 as a light yellow oil. Yield = 50%.
lized from ethanol and dried under vacuum to give 0.37 g (1.14 mmol)
of (rac)-M2 as a white crystal. Yield = 67%.
Anal. Calcd for (C23H281O)n (320.47)n: C, 86.20; H, 8.81; O, 4.99.
Found: C 86.15, H 8.85. H NMR (400 MHz, CDCl3): δ = 0.88 (t,
3H, J = 6.8 Hz, −CH3), 1.19−1.50 (m, 13H, Ar−O−CH(CH3)
CH2(CH2)5CH3), 1.52−1.68 (m, 2H, Ar−O−CH(CH3)
CH2(CH2)5CH3), 4.29−4.46 (m, 1H, Ar−O−CH(CH3)-
CH2(CH2)5CH3), 6.84 (d, 2H, J = 8.8 Hz, Ar−H ortho to −O−
CH(CH3)(CH2)6CH3), 7.40−7.47 (m, 3H, Ar−H meta and para to
−O−CH(CH3)(CH2)6CH3), 7.49−7.55 (m, 4H, Ar−H ortho to
−CC−). 13C NMR (400 MHz, CDCl3): δ = 14.1, 19.7, 22.6, 25.5,
29.2, 29.5, 31.8, 36.4, 73.9, 87.8, 89.4, 114.8, 115.6, 127.7, 128.1, 131.3,
132.9, 158.2. HRMS (APCI) calcd for C23H28O [M + H+]: 321.2213.
Found: 321.2211.
(R)-Monomer 2 ((R)-M2). (R)-M2 was synthesized in a similar way
as (rac)-M2. Into a 200 mL three-necked flask were added compound
2 (1.61 g, 8.29 mmol) and TPP (2.39 g, 9.12 mmol) under argon gas
and dissolved in THF (60 mL). In the addition funnel, a mixture of
DEAD (3.97 g, 40 wt% in toluene, 9.12 mmol), (S)-(+)-2-nonanol
(1.20 g, 8.29 mmol), and 20 mL THF was prepared. The reagents
were then stirred overnight at room temperature. The reaction yielded
a white crystal with a yield of 82% (2.17 g, 6.80 mmol).
Anal. Calcd for (C23H36O)n (328.53)n: C, 84.09; H, 11.04; O, 4.87,
1
Found: C 83.84, H 10.98. H NMR (400 MHz, CDCl3): δ = 0.79−
0.98 (m, 6H, −CH3), 1.21−1.48 (m, 18H, Ar−O−CH(CH3)
(CH2)6CH3, −CC−(CH2)2(CH2)3CH3), 1.49−1.78 (m, 5H, Ar−
O−CH(CH3)(CH2)6CH3, −CC−CH2CH2(CH2)3CH3), 2.38 (t,
2H, J = 7.2 Hz, −CC−CH2(CH2)4CH3), 4.28−4.39 (m, 1H, Ar−
O−CH(CH3)(CH2)6CH3), 6.78 (d, 2H, J = 8.8 Hz, Ar−H meta to
C6H13−CC−), 7.30 (d, 2H, J = 9.2 Hz, Ar−H ortho to C6H13−C
C−). 13C NMR (400 MHz, CDCl3): δ = 14.1, 19.1, 21.9, 22.0, 24.9,
28.0, 28.2, 28.6, 28.9, 30.8, 31.2, 35.8, 73.3, 79.6, 87.9, 114.9, 115.2,
132.1, 156.9. HRMS (DART) calcd for C23H36O [M + H+]: 329.2839.
Found: 329.2829.
(R)-Monomer 1 ((R)-M1). (R)-M1 was synthesized in a similar way
as (rac)-M1. Into a 100 mL three-necked flask were added compound
1 (1.05 g, 5.19 mmol) and TPP (1.25 g, 4.76 mmol) under argon gas
and dissolved in THF (30 mL). In the addition funnel, a mixture of
DEAD (2.41 g, 40 wt% in toluene, 4.75 mmol), (S)-(+)-2-nonanol
(0.62 g, 4.32 mmol), and 30 mL THF was prepared. The reagents
were then stirred overnight at room temperature. The reaction yielded
a light yellow oil with a yield of 66% (0.93 g, 2.84 mmol).
Anal. Calcd for (C23H281O)n (320.47)n: C, 86.20; H, 8.81; O, 4.99.
Found: C 86.26, H 8.83. H NMR (400 MHz, CDCl3): δ = 0.89 (t,
3H, J = 7.0 Hz, −CH3), 1.29−1.53 (m, 13H, Ar−O−CH(CH3)
CH2(CH2)5CH3), 1.54−1.59 (m, 2H, Ar−O−CH(CH3)
CH2(CH2)5CH3), 4.35−4.37 (m, 1H, Ar−O−CH(CH3)-
CH2(CH2)5CH3), 6.86 (d, 2H, J = 8.6 Hz, Ar−H ortho to −O−
CH(CH3)(CH2)6CH3), 7.24−7.34 (m, 3H, Ar−H meta and para to
−O−CH(CH3)(CH2)6CH3), 7.43−7.50 (m, 4H, Ar−H ortho to
−CC−). 13C NMR (400 MHz, CDCl3): δ = 14.1, 19.6, 22.6, 25.5,
29.5, 31.8, 36.4, 73.9, 87.7, 89.6, 115.0, 115.6, 123.7, 127.7, 128.1,
131.3, 132.9, 158.2. HRMS (APCI) calcd for C23H28O [M + H+]:
Anal. Calcd for (C23H36O)n (328.53)n: C, 84.09; H, 11.04; O, 4.87.
Found: C 82.52, H 9.90. 1H NMR (400 MHz, CDCl3): δ = 0.81−0.95
(m, 6H, −CH3), 1.18−1.46 (m, 18H, Ar−O−CH(CH3)(CH2)6CH3,
−CC−(CH2)2(CH2)3CH3), 1.48−1.80 (m, 5H, Ar−O−CH(CH3)
(CH2)6CH3, −CC−CH2CH2(CH2)3CH3), 2.38 (t, 2H, J = 7.2 Hz,
−CC−CH2(CH2)4CH3), 4.21−4.39 (m, 1H, Ar−O−CH(CH3)-
(CH2)6CH3), 6.65−6.78 (m, 2H, Ar−H meta to C6H13−CC−),
7.28−7.53 (m, 2H, Ar−H ortho to C6H13−CC−). 13C NMR (400
MHz, CDCl3): δ = 14.1, 19.6, 22.5, 22.6, 25.5, 28.6, 29.2, 29.5, 29.8,
31.4, 31.8, 36.3, 74.1, 82.1, 88.5, 115.5, 118.1, 132.7, 158.0. HRMS
(DART) calcd for C23H36O [M + H+]: 329.2839. Found: 329.2828.
321.2213. Found: 321.2213. [α]25 +4.73° (c 1.0, CHCl3).
D
(S)-Monomer 2 ((S)-M2). (S)-M2 was synthesized in a similar way
as (rac)-M2. Into a 200 mL three-necked flask were added compound
2 (0.65 g, 3.35 mmol) and TPP (0.97 g, 3.68 mmol) under argon gas
and dissolved in THF (30 mL). In the addition funnel, a mixture of
DEAD (1.88 g, 40 wt% in toluene, 3.68 mmol), (R)-(−)-2-nonanol
(0.58 g, 4.02 mmol), and 20 mL THF was prepared. The reagents
were then stirred overnight at room temperature. The reaction yielded
a white crystal with a yield of 72% (0.77 g, 2.41 mmol).
[α]25 −2.95° (c 1.0, CHCl3).
D
(S)-Monomer 1 ((S)-M1). (S)-M1 was synthesized in a similar way
as (rac)-M1. Into a 100 mL three-necked flask were added compound
1 (1.05 g, 5.19 mmol) and TPP (1.25 g, 4.76 mmol) under argon gas
and dissolved in THF (30 mL). In the addition funnel, a mixture of
DEAD (2.41 g, 40 wt% in toluene, 4.75 mmol), (R)-(−)-2-nonanol
(0.62 g, 4.32 mmol), and 30 mL THF was prepared. The reagents
were then stirred overnight at room temperature. The reaction yielded
a light yellow oil with a yield of 82% (1.17 g, 3.55 mmol).
Anal. Calcd for (C23H281O)n (320.47)n: C, 86.20; H, 8.81; O, 4.99.
Found: C 86.28, H 8.81. H NMR (400 MHz, CDCl3): δ = 0.88 (t,
3H, J = 7.2 Hz, −CH3), 1.29−1.51 (m, 13H, Ar−O−CH(CH3)
CH2(CH2)5CH3), 1.53−1.57 (m, 2H, Ar−O−CH(CH3)
CH2(CH2)5CH3), 4.35−4.38 (m, 1H, Ar−O−CH(CH3)-
CH2(CH2)5CH3), 6.84 (d, 2H, J = 8.8 Hz, Ar−H ortho to −O−
CH(CH3)(CH2)6CH3), 7.26−7.35 (m, 3H, Ar−H meta and para to
−O−CH(CH3)(CH2)6CH3), 7.43−7.52 (m, 4H, Ar−H ortho to
−CC−). 13C NMR (400 MHz, CDCl3): δ = 14.1, 19.7, 22.6, 25.5,
29.2, 31.8, 36.4, 73.9, 89.4, 91.6, 114.8, 115.6, 123.5, 127.7, 128.1,
131.3, 132.9, 156.9. HRMS (APCI) calcd for C23H28O [M + H+]:
Anal. Calcd for (C23H36O)n (328.53)n: C, 84.09; H, 11.04; O, 4.87.
Found: C 82.91, H 9.97. 1H NMR (400 MHz, CDCl3): δ = 0.80−1.00
(m, 6H, −CH3), 1.20−1.51 (m, 18H, Ar−O−CH(CH3)(CH2)6CH3,
−CC−(CH2)2(CH2)3CH3), 1.52−1.79 (m, 5H, Ar−O−CH(CH3)
(CH2)6CH3, −CC−CH2CH2(CH2)3CH3), 2.38 (t, 2H, J = 6.8 Hz,
−CC−CH2(CH2)4CH3), 4.27−4.34 (m, 1H, Ar−O−CH(CH3)-
(CH2)6CH3), 6.66−6.79 (m, 2H, Ar−H meta to C6H13−CC−),
7.26−7.52 (m, 2H, Ar−H ortho to C6H13−CC−). 13C NMR (400
MHz, CDCl3): δ = 14.1, 19.7, 22.5, 22.6, 25.5, 28.6, 29.2, 29.5, 29.5,
31.4, 31.8, 36.3, 73.9, 82.1, 88.5, 115.5, 118.1, 132.7, 157.5. HRMS
(DART) calcd for C23H36O [M + H+]: 329.2839. Found: 329.2824.
321.2213. Found: 321.2213. [α]25 −4.95° (c 1.0, CHCl3).
D
(rac)-Monomer 3 ((rac)-M3). (rac)-M3 was synthesized as follows.
Into a 100 mL three-necked flask were added compound 12 (1.10 g,
3.27 mmol) and TPP (0.94 g, 3.60 mmol) under argon gas and
dissolved in THF (30 mL). In the addition funnel, a mixture of DEAD
(1.82 g, 40 wt% in toluene, 3.60 mmol), 2-nonanol (0.61 g, 4.25
mmol), and 30 mL THF were prepared. After dissolving the reagents
under constant stirring, the flask was placed in an ice bath and the
THF solution in the addition funnel was added dropwise to the
solution in the flask. The solution was left overnight at room
temperature. TLC indicated completion of the reaction. After
evaporation of the solvent, the residue was washed with water and
extracted with CHCl3 (3×). The residue was dried over anhydrous
Na2SO4 and the crude product was then purified by open column
chromatography using CHCl3 as eluent. The product was evaporated
and dried under vacuum to give compound (rac)-M3 (0.95 g, 2.06
mmol) as a yellow oil. Yield = 63%.
[α]25 +3.00° (c 1.0, CHCl3).
D
(rac)-Monomer 2 ((rac)-M2). (rac)-M2 was synthesized as follows.
Into a 100 mL three-necked flask were added compound 2 (330 mg,
1.70 mmol) and TPP (491 mg, 1.87 mmol) under argon gas and
dissolved in THF (30 mL). In the addition funnel, a mixture of DEAD
(816 mg, 40 wt% in toluene, 1.87 mmol), 2-nonanol (246 mg, 1.70
mmol), and 20 mL THF were prepared. After dissolving the reagents
under constant stirring, the flask was placed in an ice bath and the
THF solution in the addition funnel was added dropwise to the
solution in the flask. The solution was left overnight at room
temperature. TLC indicated completion of the reaction. After
evaporation of the solvent, the residue was washed with water and
extracted with CHCl3 (3×). The residue was dried over anhydrous
Na2SO4, and the crude product was then purified by open column
chromatography using CHCl3 as eluent. The product was recrystal-
19804
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Article
Anal. Calcd for (C32H46O2)n (462.71)n: C, 83.06; H, 10.02; O, 6.92.
Found: C 82.30, H 10.38. H NMR (400 MHz, CDCl3): δ = 0.83−
19.1, 21.5, 22.6, 23.9, 29.3, 30.7, 31.8, 73.0, 80.0, 100.5, 114.0, 133.2,
155.1.
1
(R)-PA1. (R)-PA1 was synthesized in a similar way as (rac)-PA1.
Polymerization of (R)-M1 (0.35 g, 1.06 mmol) yielded a yellowish
solid with a yield of 41% (0.15 g, 0.44 mmol). Mw = 26 700; Mw/Mn =
1.7 (GPC, PS calibration).
0.94 (m, 6H, −CH3), 1.22−1.48 (m, 26H, Ar−O−CH(CH3)
CH2(CH2)5CH3), 1.51−1.79 (m, 4H, Ar−O−CH(CH3)
CH2(CH2)5CH3), 4.32−4.41 (m, 2H, Ar−O−CH(CH3)-
CH2(CH2)5CH3), 6.79−6.87 (d, 4H, J = 8.8 Hz, Ar−H ortho to
−O−CH(CH3)(CH2)6CH3), 7.37−7.45 (d, 4H, J = 8.4 Hz, Ar−H
meta to −O−CH(CH3)(CH2)6CH3). 13C NMR (400 MHz, CDCl3):
δ = 14.1, 19.6, 22.6, 25.5, 29.2, 29.5, 31.8, 36.4, 73.8, 87.8, 115.3, 115.6,
132.7, 157.9. HRMS (APCI) calcd for C32H46O2 [M + H+]: 463.3571.
Found: 463.3570.
(R)-Monomer 3 ((R)-M3). (R)-M3 was synthesized in a similar way
as (rac)-M3. Into a 100 mL three-necked flask were added compound
13 (1.30 g, 3.86 mmol) and TPP (1.11 g, 4.25 mmol) under argon gas
and dissolved in THF (30 mL). In the addition funnel, a mixture of
DEAD (2.15 g, 40 wt% in toluene, 4.25 mmol), (S)-(+)-2-nonanol
(0.72 g, 5.02 mmol), and 30 mL THF was prepared. The reagents
were then stirred overnight at room temperature. The product was
evaporated and dried under vacuum to give compound (R)-M3 (1.25
g, 2.69 mmol) as a yellow oil. Yield = 70%.
Anal. Calcd for (C23H28O)n (328.53)n: C, 84.09; H, 11.04; O, 4.87.
1
Found: C, 83.33; H, 11.65. H NMR (400 MHz, CDCl3): δ = 0.55−
0.98 (br, 6H, −CH3), 1.00−1.81 (br, 25H, Ar−O−CH(CH3)
(CH2)6CH3, −CC−(CH2)2(CH2)3CH3, Ar−O−CH(CH3)
(CH2 )6 CH3 , −CC−CH2 CH2 (CH2 )3 CH3 , −CC−
CH2(CH2)4CH3), 3.80−4.47 (br, 1H, Ar−O−CH(CH3)(CH2)6CH3),
7.19−7.31 (br, 4H, Ar−H). 13C NMR (400 MHz, CDCl3): δ = 14.0,
19.6, 22.1, 22.6, 23.1, 29.3, 29.7, 32.0, 71.2, 80.7, 102.7, 114.1, 134.5,
157.3. [α]25 −241° (c 1.0, CHCl3).
D
(S)-PA1. (S)-PA1 was synthesized in a similar way as (rac)-PA1.
Polymerization of (S)-M1 (0.35 g, 1.06 mmol) yielded a yellowish
solid with a yield of 5.9% (20.8 mg, 0.06 mmol). Mw = 44 400; Mw/Mn
= 1.7 (GPC, PS calibration).
Anal. Calcd for (C23H28O)n (328.53)n: C, 84.09; H, 11.04; O, 4.87.
1
Found: C 79.09, H 11.24. H NMR (400 MHz, CDCl3): δ = 0.55−
Anal. Calcd for (C32H46O2)n (462.71)n: C, 83.06; H, 10.02; O, 6.92.
Found: C 81.83, H 9.78. 1H NMR (400 MHz, CDCl3): δ = 0.81−0.92
(m, 6H, −CH3), 1.19−1.48 (m, 26H, Ar−O−CH(CH3)
CH2(CH2)5CH3), 1.50−1.79 (m, 4H, Ar−O−CH(CH3)
CH2(CH2)5CH3), 4.31−4.41 (m, 2H, Ar−O−CH(CH3)-
CH2(CH2)5CH3), 6.79−6.87 (d, 4H, J = 8.8 Hz, Ar−H ortho to
−O−CH(CH3)(CH2)6CH3), 7.38−7.46 (d, 4H, J = 8.0 Hz, Ar−H
meta to −O−CH(CH3)(CH2)6CH3). 13C NMR (400 MHz, CDCl3):
δ = 14.1, 19.7, 22.6, 25.5, 29.2, 29.5, 31.8, 36.4, 73.9, 87.8, 115.3, 115.6,
132.7, 157.9. HRMS (APCI) calcd for C32H46O2 [M + H+]: 463.3571.
0.99 (br, 6H, −CH3), 1.10−1.85 (br, 25H, Ar−O−CH(CH3)
(CH2)6CH3, −CC−(CH2)2(CH2)3CH3, Ar−O−CH(CH3)
(CH2 )6 CH3 , −CC−CH2 CH2 (CH2 )3 CH3 , −CC−
CH2(CH2)4CH3), 3.79−4.51 (br, 1H, Ar−O−CH(CH3)(CH2)6CH3),
7.15−7.32 (br, 4H, Ar−H). 13C NMR (400 MHz, CDCl3): δ = 14.1,
18.5, 22.3, 22.5, 23.2, 29.1, 30.2, 31.8, 73.6, 82.4, 101.3, 113.7, 130.7,
157.7. [α]25 +247° (c 1.0, CHCl3).
D
(rac)-PA2. (rac)-PA2 was synthesized in a similar way as (rac)-PA1.
Polymerization of (rac)-M2 (0.28 g, 0.86 mmol) yielded a greenish
powder with a yield of 45% (0.12 g, 0.39 mmol). Mw = 22 000; Mw/Mn
= 2.4 (GPC, PS calibration).
Anal. Calcd for (C23H28O)n (320.47)n: C, 86.20; H, 8.81; O, 4.99.
Found: C 83.96, H 8.65. 1H NMR (400 MHz, CDCl3): δ = 0.81−0.95
(br, 3H, −CH3), 1.20−1.61 (br, 15H, Ar−O−CH(CH3)
CH2(CH2)5CH3, and Ar−O−CH(CH3)CH2(CH2)5CH3), 3.96−4.21
(br, 1H, Ar−O−CH(CH3)CH2(CH2)5CH3), 6.91−7.61 (br, 9H, Ar−
H). 13C NMR (400 MHz, CDCl3): δ = 14.1, 19.5, 23.5, 25.4, 31.0,
33.7, 85.5, 114.9, 122.5, 124.7, 131.5, 151.6.
Found: 463.3571. [α]25 +7.87° (c 1.0, CHCl3).
D
(S)-Monomer 3 ((S)-M3). (S)-M3 was synthesized in a similar way
as (rac)-M3. Into a 100 mL three-necked flask were added compound
14 (488 mg, 1.33 mmol) and TPP (384 g, 1.46 mmol) under argon
gas and dissolved in THF (20 mL). In the addition funnel, a mixture of
DEAD (637 mg, 40 wt% in toluene, 1.46 mmol), (R)-(−)-2-nonanol
(192 mg, 1.33 mmol), and 20 mL THF was prepared. The reagents
were then stirred overnight at room temperature. The product was
evaporated and dried under vacuum to give compound (S)-M3 (0.38
g, 0.81 mmol) as a yellow oil. Yield = 61%.
(R)-PA2. (R)-PA2 was synthesized synthesized in a similar way as
(rac)-PA1. Polymerization of (R)-M2 (0.30 g, 0.9 mmol) yielded a
greenish powder with a yield of 6% (16.7 mg, 0.06 mmol). Mw = 23
000; Mw/Mn = 2.1 (GPC, PS calibration).
Anal. Calcd for (C32H46O2)n (462.71)n: C, 83.06; H, 10.02; O, 6.92.
1
Found: C 82.16, H 10.52. H NMR (400 MHz, CDCl3): δ = 0.81−
0.96 (m, 6H, −CH3), 1.19−1.50 (m, 26H, Ar−O−CH(CH3)
CH2(CH2)5CH3), 1.52−1.79 (m, 4H, Ar−O−CH(CH3)
CH2(CH2)5CH3), 4.25−4.45 (m, 2H, Ar−O−CH(CH3)-
CH2(CH2)5CH3), 6.77−6.96 (d, 4H, J = 8.8 Hz, Ar−H ortho to
−O−CH(CH3)(CH2)6CH3), 7.36−7.48 (d, 4H, J = 8.8 Hz, Ar−H
meta to −O−CH(CH3)(CH2)6CH3). 13C NMR (400 MHz, CDCl3):
δ = 14.1, 19.7, 22.6, 25.5, 29.2, 29.6, 31.8, 36.4, 73.9, 87.8, 115.3, 115.6,
132.7, 157.9. HRMS (APCI) calcd for C32H46O2 [M + H+]: 463.3571.
Anal. Calcd for (C23H28O)n (320.47)n: C, 86.20; H, 8.81; O, 4.99.
Found: C 81.56, H 9.57. 1H NMR (400 MHz, CDCl3): δ = 0.80−1.00
(br, 3H, −CH3), 1.05−1.80 (br, 15H, Ar−O−CH(CH3)
CH2(CH2)5CH3, and Ar−O−CH(CH3)CH2(CH2)5CH3), 3.95−4.18
(br, 1H, Ar−O−CH(CH3)CH2(CH2)5CH3), 6.92−7.52 (br, 9H, Ar−
H). 13C NMR (400 MHz, CDCl3): δ = 14.1, 19.6, 22.7, 25.4, 29.5,
32.0, 85.1, 114.9, 122.6, 124.7, 139.8, 156.6. [α]25 +229° (c 1.0,
D
CHCl3).
Found: 463.3571. [α]25 −7.26° (c 1.0, CHCl3).
D
(S)-PA2. (S)-PA2 was synthesized in a similar way as (rac)-PA1.
Polymerization of (S)-M2 (0.30 g, 0.94 mmol) yielded a greenish
powder with a yield of 80% (0.24 g, 0.75 mmol). Mw = 25 000 Mw/Mn
= 2.3 (GPC, PS calibration).
(rac)-PA1. (rac)-PA1 was synthesized as follows. Toluene (1.0 mL),
WCl6 (17.1 mg, 0.04 mmol), and n-Ph4Sn (36.8 mg, 0.08 mmol) were
added under argon into a Schlenk flask. The catalyst mixture was
stirred at 80 °C for 30 min, and then (rac)-M1 (0.28 g, 0.86 mmol)
was dissolved in 1 mL toluene and was then added to the reaction
mixture. The reaction mixture was stirred at 80 °C for 24 h. The
mixture was cooled to room temperature and was added dropwise to
800 mL of methanol under stirring. The polymer precipitate was
stirred for 24 h, which was then filtered and dried in vacuo. A yellowish
solid was obtained with a yield of 8.6% (23.3 mg, 0.08 mmol). Mw =
48 300; Mw/Mn = 2.1 (GPC, PS calibration).
Anal. Calcd for (C23H28O)n (320.47)n: C, 86.20; H, 8.81; O, 4.99.
Found: C 83.00, H 8.87. 1H NMR (400 MHz, CDCl3): δ = 0.82−0.98
(br, 3H, −CH3), 1.03−1.78 (br, 15H, Ar−O−CH(CH3)
CH2(CH2)5CH3, and Ar−O−CH(CH3)CH2(CH2)5CH3), 3.90−4.15
(br, 1H, Ar−O−CH(CH3)CH2(CH2)5CH3), 6.95−7.50 (br, 9H, Ar−
H). 13C NMR (400 MHz, CDCl3): δ = 14.1, 19.6, 22.7, 25.4, 29.5,
83.1, 114.2, 122.0, 139.8, 152.8. [α]25 −226° (c 1.0, CHCl3).
D
(rac)-PA3. (rac)-PA3 was synthesized in a similar way as (rac)-PA1.
Polymerization of (rac)-M3 (0.30 g, 0.65 mmol) yielded a greenish
powder with a yield of 7% (21.7 mg, 0.05 mmol). Mw = 13 400; Mw/
Mn = 2.0 (GPC, PS calibration).
Anal. Calcd for (C23H28O)n (328.53)n: C, 84.09; H, 11.04; O, 4.87.
1
Found: C 81.23, H 10.34. H NMR (400 MHz, CDCl3): δ = 0.50−
0.95 (br, 6H, −CH3), 0.97−1.84 (br, 25H, Ar−O−CH(CH3)
(CH2)6CH3, −CC−(CH2)2(CH2)3CH3, Ar−O−CH(CH3)
(CH2 )6 CH3 , −CC−CH2 CH2 (CH2 )3 CH3 , −CC−
CH2(CH2)4CH3), 3.81−4.49 (br, 1H, Ar−O−CH(CH3)(CH2)6CH3),
7.21−7.39 (br, 4H, Ar−H). 13C NMR (400 MHz, CDCl3): δ = 14.0,
Anal. Calcd for (C32H46O2)n (462.71)n: C, 83.06; H, 10.02; O, 6.92.
Found: C 79.40, H 8.91. 1H NMR (400 MHz, CDCl3): δ = 0.72−0.96
(br, 6H, −CH3), 0.98−1.80 (br, 30H, Ar−O−CH(CH3)
CH2(CH2)5CH3, Ar−O−CH(CH3)CH2(CH2)5CH3), 3.95−4.20 (br,
19805
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Journal of the American Chemical Society
Article
2H, Ar−O−CH(CH3)CH2(CH2)5CH3), 5.90−6.20 (br, 4H, Ar−H
ortho to −O−CH(CH3)CH2(CH2)5CH3), 7.08−7.40 (br, 4H, Ar−H
meta to −O−CH(CH3)CH2(CH2)5CH3). 13C NMR (400 MHz,
CDCl3): δ = 14.1, 20.4, 22.5, 27.3, 30.0, 32.2, 36.1, 74.3, 87.4, 123.4,
132.3, 157.8.
(R)-PA3. (R)-PA3 was synthesized in a similar way as (rac)-PA1.
Polymerization of (R)-M3 (0.30 g, 0.65 mmol) yielded a greenish
powder with a yield of 11% (32.6 mg, 0.07 mmol). Mw = 12 700; Mw/
Mn = 2.8 (GPC, PS calibration).
(3) Langeveld-Voss, B. M. W.; Janssen, R. A. J.; Christiaans, M. P. T.;
Meskers, S. C. J.; Dekkers, H. P. J. M.; Meijer, E. W. J. Am. Chem. Soc.
1996, 118, 4908−4909.
(4) Oda, M.; Nothofer, H. G.; Lieser; Scherf, U.; Meskers, S. C. J.;
Neher, D. Adv. Mater. 2000, 12, 362−365.
(5) (a) Chen, S. H.; Conger, B. M.; Mastrangelo, J. C.; Kende, A. S.;
Kim, D. U. Macromolecules 1998, 31, 8051−8057. (b) Wilson, J.;
Steffen, W.; McKenzie, T. G.; Lieser, G.; Oda, M.; Neher, D.; Bunz, U.
H. F. J. Am. Chem. Soc. 2002, 124, 6830−6831. (c) Oda, M.; Nothofer,
H. G.; Scherf, U.; Sunjic, V.; Richter, D.; Regenstein, W.; Neher, D.
Macromolecules 2002, 35, 6792−6798. (d) Satrijo, A.; Meskers, S. C. J.;
Swager, T. M. J. Am. Chem. Soc. 2006, 128, 9030−9031. (e) Watanabe,
K.; Osaka, I.; Yorozuya, S.; Akagi, K. Chem. Mater. 2012, 24, 1011−
1024. (f) Watanabe, K.; Iida, H.; Akagi, K. Adv. Mater. 2012,
DOI: 10.1002/adma.201203155.
Anal. Calcd for (C32H46O2)n (462.71)n: C, 83.06; H, 10.02; O, 6.92.
Found: C 78.17, H 9.58. 1H NMR (400 MHz, CDCl3): δ = 0.79−0.98
(br, 6H, −CH3), 0.99−1.71 (br, 30H, Ar−O−CH(CH3)
CH2(CH2)5CH3, Ar−O−CH(CH3)CH2(CH2)5CH3), 4.00−4.20 (br,
2H, Ar−O−CH(CH3)CH2(CH2)5CH3), 5.91−6.22 (br, 4H, Ar−H
ortho to −O−CH(CH3)CH2(CH2)5CH3), 7.18−7.40 (br, 4H, Ar−H
meta to −O−CH(CH3)CH2(CH2)5CH3). 13C NMR (400 MHz,
CDCl3): δ = 14.1, 20.7, 22.7, 27.4, 29.9, 31.1, 36.2, 74.9, 85.4, 122.4,
(6) (a) Goto, H. Macromolecules 2007, 40, 1377−1385. (b) Har-
aguchi, S.; Numata, M.; Li, C.; Nakano, Y.; Fujiki, M.; Shinkai, S.
Chem. Lett. 2009, 38, 254−255.
131.4, 158.1. [α]25 +2080° (c 1.0, CHCl3).
D
(S)-PA3. (S)-PA3 was synthesized in a similar way as (rac)-PA1.
Polymerization of (S)-M3 (0.30 g, 0.65 mmol) yielded a greenish
powder with a yield of 30% (90.1 mg, 0.19 mmol). Mw = 14 000; Mw/
Mn = 2.3 (GPC, PS calibration).
(7) Thermotropic LCs exhibit phase transitions as a function of
temperature, while lyotropic LCs exhibit phase transitions as a
function of concentration of the LC molecules in a solvent. The
nematic LC (N-LC) has a mesophase where the LC molecules have
no positional ordering but align along one direction. The N*-LC has
an orientation ordering similar to the N-LC, but the director of each
domain rotates along a helical axis resulting in a right-handed
(clockwise) or left-handed (counter-clockwise) screw structure.
(8) Bobrovsky, A. Y.; Boiko, N. I.; Shibaev, V. P.; Wendorff, J. H. Adv.
Mater. 2003, 15, 282−287.
Anal. Calcd for (C32H46O2)n (462.71)n: C, 83.06; H, 10.02; O, 6.92.
1
Found: C 82.91, H 10.58. H NMR (400 MHz, CDCl3): δ = 0.75−
0.98 (br, 6H, −CH3), 1.00−1.69 (br, 30H, Ar−O−CH(CH3)
CH2(CH2)5CH3, Ar−O−CH(CH3)CH2(CH2)5CH3), 3.96−4.19 (br,
2H, Ar−O−CH(CH3)CH2(CH2)5CH3), 5.94−6.22 (br, 4H, Ar−H
ortho to −O−CH(CH3)CH2(CH2)5CH3), 7.19−7.38 (br, 4H, Ar−H
meta to −O−CH(CH3)CH2(CH2)5CH3). 13C NMR (400 MHz,
CDCl3): δ = 14.1, 21.4, 22.7, 27.7, 29.3, 32.0, 36.5, 74.1, 82.2, 119.4,
(9) Pollmann, P.; Mainusch, K. J.; Stegemeyer, H. Z. Phys. Chem.
(Leipzig) 1976, 103, 295−309.
131.4, 157.9. [α]25 −2158° (c 1.0, CHCl3).
D
(10) (a) Chen, S. H.; Katsis, D.; Schmid, A. W.; Mastrangelo, J. C.;
Tsutsui, T.; Blanton, T. N. Nature 1999, 397, 506−508. (b) Grell, M.;
Oda, M.; Whitehead, K. S.; Asimakis, A.; Neher, D.; Bradley, D. D. C.
Adv. Mater. 2001, 13, 577−580.
ASSOCIATED CONTENT
■
S
* Supporting Information
Synthetic routes of the precursor compounds, representative
results of X-ray diffraction (XRD), polarizing optical micro-
scope (POM), and chiroptical properties (CD and CPL). This
material is available free of charge via the Internet at http://
pubs.acs.org.
(11) Il’chishin, I. P.; Tikhonov, E. A.; Tishchenko, V. G.; Shpak, M.
T. JETP Lett. 1981, 32, 24−27.
(12) Furumi, S. Chem. Rec. 2010, 10, 394−408.
(13) (a) Akagi, K.; Piao, G.; Kaneko, S.; Sakamaki, K.; Shirakawa, H.;
Kyotani, M. Science 1998, 282, 1683−1686. (b) Akagi, K.; Piao, G.;
Kaneko, S.; Higuchi, I.; Shirakawa, H.; Kyotani, M. Synth. Met. 1999,
102, 1406−1409. (c) Akagi, K.; Guo, S.; Mori, T.; Goh, M.; Piao, G.;
Kyotani, M. J. Am. Chem. Soc. 2005, 127, 14647−14654. (d) Akagi, K.
Polym. Int. 2007, 56, 1192−1199.
AUTHOR INFORMATION
■
Corresponding Author
akagi@fps.polym.kyoto-u.ac.jp
(14) Iida, H.; Nakamura, A.; Inoue, Y.; Akagi, K. Synth. Met. 2003,
135, 91−92.
Notes
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The authors declare no competing financial interest.
ACKNOWLEDGMENTS
■
The authors thank Prof. Kenji Saijo (Kyoto University) for the
XRD measurements of the polymers. This work was supported
by a Grant-in-Aid for Science Research (S) (No. 20225007)
from the Ministry of Education, Culture, Sports, Science and
Technology, Japan.
(16) (a) Lam, J. W. Y.; Tang, B. Z. J. Polym. Sci., Part A: Polym. Chem.
2003, 41, 2607−2629. (b) Liu, J.; Lam, J. W. Y.; Tang, B. Z. Chem. Rev.
2009, 109, 5799−5867.
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(21) The length of the PA2 nonyloxy phenyl side chain was
calculated using molecular mechanics calculations. The side chain with
the nonyloxy phenyl moiety has a length (L1) computed as 15 Å. The
XRD peak distance of 15 Å observed in the (S)-PA2 N*-LC film can
be assigned as the average polymer interchain distance approximate to
that of the side chain length, d ≈ L1, within the N*-LC domain. XRD
analysis on the N-LC film of (rac)-PA2 and N*-LC film of (S)-D1/
(rac)-PA2 showed similar XRD profiles (Figure S2), which suggest
that the measured distances of 15−17 Å can be correlated to the
polymer interchain distance−regardless of the LC phase. The observed
XRD patterns are similar to the XRD profiles of other reports of
PDPA showing lyotropic liquid crystallinity.17a,b
(22) It was observed that the N*-LC phase of (S)-PA2 and (S)-D1/
(rac)-PA2, have different helical half-pitches of 1.5 and 2.0 μm,
respectively (Figures 1a and 2b). This shows that the N*-LC phase of
(S)-PA2 has a more twisted helical ordering on a microscopic level,
given the same lyotropic LC concentration. This difference can be
attributed to the type of the chiral dopant used. In the N*-LC phase of
(S)-PA2, the chiral dopant is the chiral nonyloxy moiety with an
asymmetric type chirality. On the other hand, for the N*-LC phase of
(S)-D1/(rac)-PA2 the chiral dopant (S)-D1 has an axial type chirality.
In the N*-LC phase of (S)-D1/(rac)-PA2, the chiral dopant is in
between the nematic LC layers where it directs the layers into a helical
arrangement.
(23) (a) Shukla, A.; Mazumdar, S. Phy. Rev. Lett. 1999, 19, 3944−
3947. (b) Hidayat, R.; Fujii, A.; Ozaki, M.; Teraguchi, M.; Masuda, T.;
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H.; Mazumdar, S. Synth. Met. 2001, 116, 87−90. (d) Ghosh, H.;
Shukla, A.; Mazumdar, S. Phys. Rev. B. 2000, 19, 12763−12774.
(e) Vardeny, Z. V., Korovyanko, O. In Handbook of Conducting
Polymers, Conjugated Polymers, 3rd ed.; Skotheim, T. A., Reynolds, J.
R., Eds.; CRC Press: New York, 2007; pp 22-1−22-74.
(24) For the preparation of D1-doped (rac)-PA2 and (rac)-PA3 N*-
LC films, the (R)-/(S)-D1 chiral dopant at 10 wt%, was added to the
polymers and then the solution was dissolved in toluene (5−10 wt%)
to form a lyotropic LC state. The lyotropic LC solution was cast onto
a quartz plate, which was then exposed under toluene vapor and
allowed to dry slowly at room temperature.
(25) It is expected that in low concentration solutions of PDPA in
toluene, the polymer main chains will lose the cooperative ordering of
the LC phase and will behave like an isotropic liquid. To verify this we
measured the UV−vis and CD spectra of (rac)-/(R)-/(S)-PA2 in low
concentration solution (1.2 × 10−4 M) in toluene. The spectra on
Figure S4 reveals monosignate Cotton effects that reflect the
intrachain helicity of PA2, similar to PA2 in chloroform solution
(Figure 4b).
(26) CD measurements in cast films and N*-LC films were taken on
all the four possible orientations (horizontal and vertical) of the quartz
plates and the results were compared. This procedure was performed
to check for sample orientation dependence of the CD measurements.
CD results of the samples showed no sample orientation dependence.
(27) (a) Harada, N.; Nakanishi, K.Circular Dichroic Spectroscopy:
Exciton Coupling in Organic Steroechemistry; University Science Books:
Sausalito, CA, 1983. (b) Berova, N.; Nakanishi, K. In Circular
Dichroism: Principles and Applications, 2nd ed.; Berova, N., Nakanishi,
K., Woody, R., Eds.; John Wiley and Sons, Inc.: New York, 2000;
Chap. 12, pp 337−382.
(28) For all cast films and N*-LC films, the linear dichroism was
much less than 0.01, which discounts that the large g-values are due to
measurement artifacts. In addition, measurements were taken on all
the four possible orientations (horizontal and vertical), and no
orientation dependence was apparent.
19807
dx.doi.org/10.1021/ja3086565 | J. Am. Chem. Soc. 2012, 134, 19795−19807