One-dimensional ion-conductive polymer films: Alignment and fixation of ionic channels formed by self-organization of polymerizable columnar liquid crystals

Article abstract of DOI:10.1021/ja0606935

We have prepared two types of one-dimensional ion-conductive polymer films containing ion nanochannels that are both perpendicular and parallel to the film surface. These films have been obtained by photopolymerization of aligned columnar liquid crystals

Full text of DOI:10.1021/ja0606935

Published on Web 03/31/2006
One-Dimensional Ion-Conductive Polymer Films: Alignment
and Fixation of Ionic Channels Formed by Self-Organization
of Polymerizable Columnar Liquid Crystals
Masafumi Yoshio,† Takayoshi Kagata,† Koji Hoshino,† Tomohiro Mukai,‡
Hiroyuki Ohno,‡ and Takashi Kato*,†
Contribution from the Department of Chemistry and Biotechnology, School of Engineering,
The UniVersity of Tokyo, Hongo, Bunkyo-ku, Tokyo 113-8656, Japan, and Department of
Biotechnology, Tokyo UniVersity of Agriculture and Technology,
Nakacho, Koganei, Tokyo 184-8588, Japan
Received January 30, 2006; E-mail: kato@chiral.t.u-tokyo.ac.jp
Abstract: We have prepared two types of one-dimensional ion-conductive polymer films containing ion
nanochannels that are both perpendicular and parallel to the film surface. These films have been obtained
by photopolymerization of aligned columnar liquid crystals of a fan-shaped imidazolium salt having acrylate
groups at the periphery. In the columnar structure, the ionic part self-assembles into the inner part of the
column. The column is oriented macroscopically in two directions by different methods: orientation
perpendicular to the modified surfaces of glass and indium tin oxide with 3-(aminopropyl)triethoxysilane
and orientation parallel to a glass surface by mechanical shearing. Ionic conductivities have been measured
for the films with columnar orientation vertical and parallel to the surface. Anisotropic ionic conductivities
are observed for the oriented films fixed by photopolymerization. The ionic conductivities parallel to the
columnar axis are higher than those perpendicular to the columnar axis because the lipophilic part functions
as an ion-insulating part. The film with the columns oriented vertically to the surface shows an anisotropy
of ionic conductivities higher than that of the film with the columns aligned parallel to the surface.
key in the design and development of these materials.1
Intermolecular interactions, such as hydrogen bonding,5 ionic
Introduction
The use of self-organized structures, such as liquid crystals,
is a promising approach for the preparation of low-dimensional
(anisotropic) functional materials.1 For example, ion,2,3 electron,4
and hole4 transport materials have been prepared by using liquid
crystalline (LC) molecular order. These materials have potential
applications, such as electrolytes in lithium ion batteries and
conducting paths in electronic devices. Control of intermolecular
interactions and formation of phase-segregated structures are
interactions,6 ion-dipolar interactions,7 π-π interactions,8 and
charge-transfer interactions,9 can be used for the construction
of functional and ordered supramolecular structures. Block
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Ujiie, S.; Ohno, H.; Kato, T. Macromol. Chem. Phys. 2002, 203, 1547-
1555. (d) Kishimoto, K.; Yoshio, M.; Mukai, T.; Yoshizawa, M.; Ohno,
H.; Kato, T. J. Am. Chem. Soc. 2003, 125, 3196-3197. (e) Kishimoto, K.;
Suzawa, T.; Yokota, T.; Mukai, T.; Ohno, H.; Kato, T. J. Am. Chem. Soc.
2005, 127, 15618-15623. (f) Percec, V.; Johansson, G.; Heck, J.; Ungar,
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2002, 428-429. (g) Kitamura, T.; Nakaso, S.; Mizoshita, N.; Tochigi, Y.;
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† The University of Tokyo.
‡ Tokyo University of Agriculture and Technology.
(1) (a) Demus, D.; Goodby, J. W.; Gray, G. W.; Spiess, H.-W.; Hill, V.
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9
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J. AM. CHEM. SOC. 2006, 128, 5570-5577
10.1021/ja0606935 CCC: $33.50 © 2006 American Chemical Society

One-Dimensional Ion-Conductive Polymer Films
A R T I C L E S
molecules consisting of immiscible parts1b,c,10 and molecular
mixtures consisting of partially miscible components2b-e can
form phase-segregated structures from micro- to nanometer scale
that induce function.
Recently, anisotropic ion conduction has been achieved in
aligned LC materials based on imidazolium salts2 and oligo-
(ethylene oxide)s.3a-e For example, aligned columnar LC phases
of fan-shaped imidazolium tetrafluoroborate salts containing tris-
(alkoxy)phenyl groups lead to the induction of one-dimensional
(1D) ion conduction.2a Imidazolium and pyridinium salts
coordinating perfluorinated anions are representative ionic
liquids showing nonvolatility and high ionic conductivity. Ionic
liquids have received great interests as electrolytes for batteries11
and reaction solvents for organic syntheses.12 We designed ionic
liquids having block molecular structures of ionic and nonionic
moieties to exhibit LC properties.2a The ionic moieties self-
assembled into the inner part of columnar structures through
nanosegregation and electrostatic interactions. These nanoseg-
regated columnar structures were macroscopically oriented only
in the direction in which columns are parallel to the surface. If
we could also succeed in columnar orientation perpendicular
to the film surface, the applicability of the anisotropically
conductive materials will be increased. Moreover, these LC
materials exhibit fluidity, which might decrease applicability
as materials. If these LC nanostructures could be preserved in
macroscopically ordered polymeric films, the materials can be
more easily incorporated into solid devices.
Figure 1. Polymerizable fan-shaped imidazolium salts 1 and 2.
Table 1. Thermal Properties of Compounds 1 and 2
compound
phase transition behaviora
1
2
Cr
Cr
20 (44.2)
13 (43.7)
Colh
50 (0.30)
I
I
a Transition temperatures (°C) and enthalpies of transition (kJ mol-1, in
parentheses). Colh: hexagonal columnar; Cr: crystalline; I: isotropic.
fixation of such oriented columns by polymerization could
enhance the anisotropy due to the decrease of thermal fluctuation
of the columns in solid polymer matrices. We previously
prepared 2D ion-conductive films by photopolymerization of
smectic LC methacrylate monomers containing imidazolium
salts2f and oligo(ethylene oxide)3d,e moieties. These monomers
that homeotropically aligned on the glass surface were polym-
erized in the smectic A phases. However, it is not easy to fix
aligned 1D ionic channels because columnar orientation cannot
be controlled easily.
We considered that if functional moieties capable of interact-
ing with the ionic molecules are introduced into the surface of
substrates vertical orientation of the 1D columns to the substrates
could be induced spontaneously. We also expected that the
Here we report on the development of anisotropically ion-
conductive films that have ionic channels aligned vertical and
parallel to the film surface. We have successfully designed and
prepared 1D ion-conductive polymeric materials by orientation
control of their self-assembled nanosegregated structures and
subsequent photopolymerization of a columnar ionic liquid
crystal based on an imidazolium salt.
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Results and Discussion
Synthesis and Liquid Crystalline Properties. We have
designed and synthesized molecules 1 and 2 shown in Figure
1. These compounds have imidazolium and tris(alkoxy)phenyl
moieties containing acrylate polymerizable groups at their
periphery. For these molecules, the nonionic (aliphatic and
aromatic) and the imidazolium (ionic) moieties are connected
through an ethyleneoxy carbonyl group. They were obtained
by an esterification reaction of a hydroxy-functionalized imi-
dazolium salt13 and etherified gallic acid derivatives having two
or three acrylate polymerizable groups at their periphery.
The phase transition behavior of compounds 1 and 2 is
summarized in Table 1. Compound 1 forms a hexagonal
columnar LC (Colh) phase between 20 and 50 °C on heating,
while no mesomorphic behavior is observed for 2. The three
bulky acrylate groups of 2 may disturb its columnar packing.
Analogous benzylimidazolium salts, which have no ester groups,
having two and three acrylate groups exhibit no liquid crystal-
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A R T I C L E S
Yoshio et al.
Figure 2. Schematic illustration of the strategy for preparation of one-dimensional ion-conductive polymeric films: self-assembly and subsequent
photopolymerization of columnar liquid crystalline imidazolium salt 1 with two different columnar orientations. (a) Vertical orientation of unpolymerized
columns on 3-(aminopropyl)triethoxysilane (APS)-modified surface of substrates; (b) parallel orientation of the unpolymerized columns by shearing;
(c) polymer film with vertical columnar orientation to the film surface (Film-V); (d) polymer film with parallel columnar orientation to the film surface
(Film-P).
linity (see Supporting Information). The dipole-dipole interac-
tions between the ester groups for 1 should be important to
stabilize the columnar packing.
X-ray Diffraction Study. The X-ray diffraction pattern of
compound 1 at 25 °C presents three peaks with the ratio of
1:1/x3:1/2 (d100 ) 36.2 Å at 2θ ) 2.44°, d110 ) 20.8 Å at 2θ
) 4.24°, d200 ) 18.1 Å at 2θ ) 4.88°). This indicates the
formation of a hexagonal columnar structure. The intercolumnar
distance (a) is calculated to be 4.2 nm with the following
macroscopically oriented nanostructured films (Film-V (Verti-
cal) and Film-P (Parallel)). Film-V and Film-P can transport
ions in two directions: perpendicular and parallel to the film
surface, respectively. These different structures of the Film-V
and Film-P have been obtained by using different liquid crystal/
surface interactions.
Compound 1 does not spontaneously form a single domain
on glass and indium tin oxide (ITO) substrates. Polarizing optical
micrographs shown in Figure 3a,b show that the polydomains
of 1 are formed when its isotropic melt is cooled to the
temperature range of the columnar phase on these substrates.
For anisotropic 1D ion conduction in the direction perpendicular
to the film surface, uniaxially vertical macroscopic orientation
of the columns that function as ion-conductive paths is needed.
We have used a modified surface for the alignment control of
the columnar structure of 1. Surface modification of the oxidized
substrates such as silica and metal oxides with silane coupling
agents is an effective approach for the orientation of LC
materials.16,17 In the present study, we have achieved vertical
alignment of the columns to the surface (homeotropic orienta-
tion) by using chemically modified glass and ITO substrates
with 3-(aminopropyl)triethoxysilane18 (APS) as shown in Figure
3c and 3d. This alignment has been confirmed by the conoscopic
equation: a ) 2 <d100>/x3, <d100> ) (d100 + x3d110
+
2d200)/3. The number (n) of molecules per unit cell in a
hexagonal lattice is estimated to be 4.7 from n ) x3NAa2hF/
2M,14 where NA is Avogadro’s number (6.02 × 1023 mol-1), h
is the layer thickness (4.4 Å), and M is molecular weight (983.07
g mol-1). The density (F) of the material is 1.13 g cm-3, which
has been determined by a flotation method in D-(+)-sucrose/
H2O at 20 °C. The value of h has been taken from the halo of
X-ray at 2θ ) 20.3° due to disordered aliphatic chains and
benzene ring in the direction of the column axis.15
Alignment of a Monomer. Our approach to the preparation
for macroscopically oriented 1D ion-conductive polymeric films
is schematically shown in Figure 2. Molecular self-assembly,
macroscopic orientation, and subsequent photopolymerization
of columnar LC imidazolium salt 1 has given two types of
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One-Dimensional Ion-Conductive Polymer Films
A R T I C L E S
Figure 3. Polarizing optical micrographs of monomer 1 in the Colh state at 25 °C: (a) on the nonmodified surface of a glass substrate with comb-shaped
gold electrodes; (b) on the nonmodified surface of an ITO substrate; (c) on the surface of the 3-(aminopropyl)triethoxysilane (APS)-modified glass substrate;
(d) on the surface of the APS-modified ITO substrate. The scale bar is 100 µm.
observation on a polarized microscope. A cross-shaped pattern
is observed as shown in the inset of Figure 3d. This homeotropic
alignment can be attributed to the interactions between the
imidazolium moiety of 1 and the APS-modified surface. Self-
assembly and orientation of columnar liquid crystals on a variety
of substrates, including graphite, mica, and self-assembled
monolayers, have been studied by several groups.19-24 The
observed orientations of the columns have been interpreted in
terms of interactions and affinity between the columnar liquid
crystals and substrate surfaces and the flatness of substrates.
The macroscopic 1D orientation of the columns parallel to
Figure 4. Polarizing optical micrograph of the monomer oriented by
shearing in the Colh state at 25 °C on the nonmodified surface of a glass
substrate.
the surface has been induced by mechanical shearing of the
polydomain sample of 1. The columnar LC sample cooled from
the isotropic temperature range has been sheared with two
glasses sandwiching the sample. Figure 4 shows a polarizing
optical micrograph of 1 in the columnar phase after shearing.
The direction of the long axis of columns corresponds to the
shearing direction, which is confirmed by the periodic change
in the pattern with the sample’s rotation for the polarizing
microscopic observation. No birefringence is observed when
the shearing direction is along the polarizer or analyzer axis.
The highest brightness is seen when the oriented material is at
a 45° angle.
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Fixation of Columnar Structures by Photopolymerization.
The macroscopic vertical and parallel alignment of the columns
to the substrate surfaces has been successfully fixed by
photopolymerization. These oriented columnar liquid crystals
at 30 °C were irradiated by a UV lamp (365 nm, 30 mW cm-2
,
for 1 h) in the presence of 1.0 wt % of 2,2-dimethoxy-2-
phenylacetophenone as a photoinitiator. For example, after
polymerization of 1 with vertical orientation of the columns on
9
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A R T I C L E S
Yoshio et al.
Figure 5. Photograph of a free-standing film (5 mm × 5 mm) obtained
by photopolymerization of 1 with vertical orientation of the columns on
the APS-modified glass substrate at 30 °C. The illustration of this film is
shown as Film-V in Figure 2c.
Figure 7. Anisotropic ionic conductivities of Film-V and the corresponding
monomer whose columnar axes are aligned perpendicular to the surface of
the APS-modified glass and ITO substrates: (b) parallel and (9) perpen-
dicular to the columnar axis for the Film-V; (O) parallel and (0)
perpendicular to the columnar axis for the monomer.
selective filtration properties31 by using polymerizable lyotropic
columnar liquid crystals in the presence of water. By using a
thermotropic columnar liquid crystal with polymerizable groups,
our present study is the first example of 1D ion-conductive
polymer films consisting of anisotropic ionic channels with
controlled directions.
Figure 6. FE-SEM images of the macroscopically oriented polymer Film-
P: (a) over view; (b) high magnified view of the image in (a).
Anisotropic Ionic Conductivities. Anisotropic ionic con-
ductivities of the Film-V comprised of polymer 1 as well as
those of an unpolymerized sample of monomer 1 with columnar
orientation vertical to the surface of substrates have been
successfully measured using two different types of electrodes,
APS-modified ITO and comb-shaped gold electrodes with APS-
modified glass substrates (see Supporting Information). To
measure the ionic conductivities along the direction parallel to
the columns (σ|), a pair of APS-modified ITO electrodes filled
with the Film-V or corresponding monomer 1 was used. The
distance between the two electrodes was fixed by a Teflon spacer
of thickness 10 µm. The ionic conductivities perpendicular to
the columnar axis (σ ) were measured using an APS-modified
glass cell with comb-shaped gold electrodes. The Film-V or
monomer 1 was filled between the gold electrodes for σ .
Figure 7 shows the anisotropic ionic conductivities of the
Film-V and its monomer as a function of temperature. The ionic
conductivities parallel to the columnar axis (σ|) are higher than
those perpendicular to the columnar axis (σ ). The magnitude
of anisotropy (σ|/σ ) for the Film-V is 2.6 × 102 at 50 °C and
1.4 × 103 at 150 °C. These values are 10-100 times higher
than those obtained for the unpolymerized sample of 1. These
results show that the fixation of the oriented nanostructure for
the monomer by in situ photopolymerization enhances the
the APS-modified glass substrate, a transparent free-standing
film has been obtained (Figure 5). In the infrared spectrum of
the photopolymerized sample, the acrylate bands at 1637 and
811 cm-1 disappear, although all reacted polymerizable groups
might not be completely consumed during polymerization. This
resultant film is thermally stable, and no peaks of phase
transitions are detected up to 250 °C in DSC measurements.
The film is also mechanically stable and insoluble in water and
conventional organic solvents, such as methanol and chloroform.
The density of the polymer film (Film-V) has been determined
to be 1.11 g cm-3 by the same flotation method as that for the
monomer. This value is smaller than that of the monomer. These
results suggest that cross-linked network structures are formed
in the films. Before and after polymerization, no changes of
the optical properties have been observed under the polarized
microscope.
The X-ray diffraction patterns of the polymer films (Film-V
and Film-P in Figure 2) exhibit the fixation of the hexagonal
columnar structures in the film, and the size of the polymerized
columns slightly increases upon polymerization (see Supporting
Information). The intercolumnar distance is 4.3 nm.
The Film-P obtained by polymerization of 1 has been
observed by scanning electron microscopy, as shown in Figure
6. Oriented grooves along the direction of shearing are formed
in the photopolymerized film. This observation also supports
the macroscopic alignment of the columnar nanostructures.
(27) (a) O’Brien, D. F.; Armitage, B.; Benedicto, A.; Bennett, D. E.; Lamparski,
H. G.; Lee, Y.-S.; Srisiri, W.; Sisson, T. M. Acc. Chem. Res. 1998, 31,
861-868. (b) Mueller, A.; O’Brien, D. F. Chem. ReV. 2002, 102, 727-
757.
(28) Oriol, L.; Serrano, J. L. Angew. Chem., Int. Ed. 2005, 44, 6618-6621.
(29) Penterman, R.; Klink, S. I.; de Koning, H.; Nisato, G.; Broer, D. J. Nature
2002, 417, 55-58.
(30) (a) Miller, S. A.; Ding, J. H.; Gin, D. L. Curr. Opin. Colloid Interface Sci.
1999, 4, 338-347. (b) Gin, D. L.; Xu, Y.; Gu, W.; Zhou, M.; Kidd, T. J.;
Sentman, A. C. Trans. Mater. Res. Soc. Jpn. 2004, 29, 3113-3118. (c)
Gin, D. L.; Gu, W. AdV. Mater. 2001, 13, 1407-1410. (d) Ding, J. H.;
Gin, D. L. Chem. Mater. 2000, 12, 22-24. (e) Gu, W.; Zhou, W.-J.; Gin,
D. L. Chem. Mater. 2001, 13, 1949-1951. (f) Pecinovsky, C. S.;
Nicodemus, G. D.; Gin, D. L. Chem. Mater. 2005, 17, 4889-4891.
(31) Zhou, M.; Kidd, T. J.; Noble, R. D.; Gin, D. L. AdV. Mater. 2005, 17,
1850-1853.
Functional nanostructured polymeric materials were prepared
by photopolymerization of LC monomers.1f,2f,3d,e,25-31 For
example, Gin and co-workers developed nanoporous polymer
materials exhibiting catalytic properties1f,30 and molecular-size-
(25) (a) Broer, D. J.; Finkelmann, H.; Kondo, K. Makromol. Chem. 1988, 189,
185-194. (b) Broer, D. J.; Mol, G. N.; Challa, G. Makromol. Chem. 1989,
190, 19-30. (c) Heynderickx, I.; Broer, D. J.; Tervoort-Engelen, Y. J.
Mater. Sci. 1992, 27, 4107-4114.
(26) Hikmet, R. A. M. J. Mater. Chem. 1999, 9, 1921-1932.
9
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One-Dimensional Ion-Conductive Polymer Films
A R T I C L E S
Figure 8. Molecular alignment and ionic conductivities of polymer films prepared by photopolymerization of monomer 1. Polarizing optical microscopic
images of polymer films with four different molecular orientations: (a) Film-P with parallel orientation of the columnar axis (|) to the direction of electric
field; (b) Film-P with perpendicular orientation of the columnar axis ( ) to the direction of electric field; (c) Film-R comprised of randomly oriented
columns; (d) Film-I of the disordered amorphous (isotropic) state. Directions of A: analyzer; P: polarizer; S: shearing of unpolymerized columns of
monomer; E: electric field. The scale bar is 100 µm. Ionic conductivities of polymer films as a function of temperature (e): (b) parallel and (9) perpendicular
to the columnar axis for Film-P; (2) for Film-R; (1) for Film-I.
anisotropy of the conductivities. It seems that ion conduction
perpendicular to the columnar axis may be effectively disturbed
in the solid polymer film due to the low mobility of the cross-
linked alkyl chains. It is an advantage of the polymer film that
anisotropy of the ionic conductivities is maintained for the
Film-V up to 200 °C, while no anisotropy of the conductivities
is observed for the monomer above the isotropization temper-
ature.
We have also measured the anisotropic ionic conductivities
of the Film-P with columnar orientation parallel to the surface
of the glass substrate using nontreated comb-shaped gold
electrodes (see Supporting Information). To measure anisotropic
conductivities, the columns have been aligned in two directions
by shearing parallel (Figure 8a, Film-P (σ|)) and perpendicular
(Figure 8b, Film-P (σ )) to the direction of the electric field
between Au electrodes, and their alignments have been fixed
by photoirradiation. To examine the effects of molecular
alignment on the ionic conductivities, nonaligned films have
been obtained: the polymer film consisting of a nonoriented
columnar polydomain (Figure 8c, Film-R (Random)) and the
polymer film of a disordered amorphous state (Figure 8d, Film-I
(Isotropic)). Film-R was prepared by photopolymerization of
monomer 1 in the nonoriented columnar phase at 30 °C. Film-I
was obtained by photopolymerization of 1 in the isotropic phase
at 70 °C.
Figure 8e shows the ionic conductivities for these polymer
films. The ionic conductivities parallel (σ|) to the columnar axis
are higher than those perpendicular (σ ) to the columnar axis.
For example, the Film-P exhibits conductivities of 1.6 × 10-3
S cm-1 (σ|), 1.4 × 10-5 S cm-1 (σ ), and a σ|/σ of 1.2 × 102
at 150 °C. The magnitude of anisotropy of Film-P is lower than
that of Film-V with columnar orientation perpendicular to the
film surface. For the polydomain columnar film (Film-R) (2),
the value of 1.1 × 10-5 S cm-1 at 100 °C is between the values
of σ| (3.1 × 10-4 S cm-1) and σ (2.2 × 10-6 S cm-1) for the
homogeneously oriented films (Film-P). These results are
attributable to the random formation of ion-conduction paths
in the polydomain film. As for the isotropic film (Film-I) (1),
the value of 3.7 × 10-5 S cm-1 at 100 °C is lower than that of
σ
||
for the oriented film (Film-P) at the same temperature.
Furthermore, the ionic conductivities of the amorphous film
(Film-I) is higher than those of the polydomain film (Film-R).
The results obtained for Films-V, P, R, and I indicate that the
introduction of only oriented nanostructures can enhance the
conductivity of the polymer film. The highest ion conduction
for the polymer 1 has been achieved by the formation of the
anisotropic nanosegregated structure and the macroscopic
orientation.
Conclusion
Two types of 1D ion-conductive polymeric films that
transport ions both perpendicular and parallel to the film surface
have been prepared by using liquid crystal self-assembly of a
polymerizable fan-shaped imidazolium salt and that have been
aligned by different techniques. We have demonstrated that
macroscopic alignment of the nanostructures of the columnar
liquid crystals in the polymeric films enhances the ion-
conductive properties. Ionic channels shielded by the ion-
insulating alkyloxyphenyl part are spontaneously formed through
nanophase segregation of nonionic and ionic parts. They have
been fixed by photopolymerization. The anisotropically oriented
nanochannels can transport ions most effectively. Furthermore,
the films show distinct anisotropy of ionic conductivities. These
results show the approach presented here is useful for the
preparation of new low-dimensionally functional solid materials.
Experimental Section
General. 1H NMR and 13C NMR spectra were obtained using a
JEOL JNM-LA400 at 400 and 100 MHz in CDCl3, respectively.
1
Chemical shifts of H and 13C NMR signals were quoted to (CH3)4Si
9
J. AM. CHEM. SOC. VOL. 128, NO. 16, 2006 5575

A R T I C L E S
Yoshio et al.
(δ ) 0.00) and CDCl3 (δ ) 77.0) as internal standards, respectively,
and expressed by chemical shifts in parts per million (δ), multiplicity,
coupling constant (hertz), and relative intensity. Recycling preparative
GPC was carried out with a Japan Analytical Industry LC-908
chromatograph. Matrix-associated laser desorption ionization-time-of-
flight mass spectra (MALDI-TOF MS) were taken on a PerSeptive
Biosystems Voyager-DE STR spectrometer using dithranol as the
matrix. Elemental analyses were carried out on a Perkin-Elmer CHNS/O
2400 apparatus. IR measurements were conducted on a JASCO FT/
IR-660 Plus spectrometer. Phase transition behavior of the materials
was examined by a differential scanning calorimetry (DSC) using a
Netzsch DSC204 Phoenix. The heating and cooling rates were 5 °C
min-1. Transition temperatures were taken at the maximum of the
transition peaks. A polarizing optical microscope Olympus BX51
equipped with a Mettler FP82HT hot stage was used for visual
observation. X-ray diffraction measurements were carried out on a
Rigaku RINT 2500 diffractometer using monochromated Cu KR
radiation. UV irradiation was carried out using a high-pressure mercury
lamp (Ushio, 500 W) with appropriate glass filter (Asahi Technoglass
UV-35 and UVD-36C) as an irradiation source. FE-SEM measurements
were performed on a HITACHI S-900 at an accelerating voltage of 10
kV for the free-standing oriented polymer films, whose cross-section
was shaded with platinum.
980, 831, 784 cm-1. MS (MALDI-TOF): calcd for [M + H]+, 595.21;
found, 595.56.
Synthesis of Ethyl 3,5-Dihydroxy-4-dodecyloxybenzoate (5). A
1.0 M solution of tetrabutylammonium fluoride (TBAF) in tetrahydro-
furan (50 mL, 50 mmol) was added dropwise to a solution of 4 (13.2
g, 22.2 mmol) in dichloromethane (40 mL) at 0 °C. The mixture was
stirred for 10 h at room temperature. The solution was poured into
water and extracted with chloroform three times. The combined organic
phase was washed with brine, dried over anhydrous MgSO4, filtered
through a pad of Celite, and concentrated with a rotary evaporator.
The residue was purified by flash column chromatography on silica
gel (eluent: chloroform) to afford 5 (8.12 g, 22.1 mmol, 100%) as a
1
white solid. H NMR (400 MHz, CDCl3): δ ) 7.30 (s, 2H), 6.29 (s,
2H), 4.34 (q, J ) 6.8 Hz, 2H), 4.16 (t, J ) 6.8 Hz, 2H), 1.77 (t, J )
7.6 Hz, 3H), 1.26 (s, 20H), 0.88 (t, J ) 7.2 Hz, 3H). 13C NMR (100
MHz, CDCl3): δ ) 166.85, 148.87, 137.75, 125.57, 109.64, 73.80,
61.33, 31.87, 30.10, 29.60, 29.59, 29.53, 29.49, 29.34, 29.31, 25.81,
22.65, 14.15, 14.08. IR (KBr): ν ) 3403, 2917, 2850, 1696, 1601,
1520, 1471, 1448, 1397, 1350, 1240, 1190, 1099, 1054, 1029, 877,
768 cm-1. MS (MALDI-TOF): calcd for [M + Na]+, 389.23; found,
389.33.
Synthesis of 3,5-Bis(11-hydroxyundecyloxy)-4-dodecyloxybenzoic
acid (6). A DMF (50 mL) suspension of 5 (1.44 g, 3.92 mmol), 11-
bromoundecane-1-ol (2.36 g, 9.41 mmol), and K2CO3 (1.38 g, 10.0
mmol) was vigorously stirred for 6 h at 70 °C. After the resulting brown
mixture was cooled to room temperature, the mixture was poured into
a saturated NH4Cl aqueous solution and extracted with EtOAc three
times. The combined organic extracts were washed with brine. The
resulting organic phase was dried over anhydrous MgSO4, filtered
through a pad of Celite, and concentrated under reduced pressure. The
residue was dissolved in a mixture of ethanol/water (99:1 v/v, 100 mL)
containing KOH (1.0 g, 18 mmol). After stirring for 3 h under a refluxed
condition, the solution was neutralized with a 1.0 M HCl aqueous
solution and extracted with EtOAc twice. The combined organic phase
was dried over anhydrous MgSO4, filtered, and concentrated. The
residue was recrystallized from ethanol to yield 6 (1.86 g, 2.74 mmol,
70%) as a white solid. 1H NMR (400 MHz, CDCl3): δ ) 7.31 (s, 2H),
4.03 (t, J ) 6.8 Hz, 6H), 3.66 (t, J ) 6.8 Hz, 2H), 1.84-1.70 (m, 4H),
1.70-1.63 (m, 4H), 1.51-1.44 (m, 6H), 1.44-1.20 (m, 42H), 0.88 (t,
J ) 6.8 Hz, 3H). 13C NMR (100 MHz, CDCl3): δ ) 170.83, 152.75,
142.92, 123.94, 108.50, 73.51, 69.10, 63.02, 32.66, 31.92, 30.28, 29.72,
29.69, 29.67, 29.61, 29.56, 29.54, 29.49, 29.44, 29.38, 29.23, 29.16,
26.01, 25.93, 25.70, 22.68, 14.12. IR (KBr): ν ) 3349, 2920, 2850,
1687, 1588, 1506, 1468, 1433, 1386, 1335, 1278, 1227, 1129, 1058,
993, 862, 768 cm-1. MS (MALDI-TOF): calcd for [M + Na]+, 701.53;
found, 701.90.
Materials. All chemical reagents and solvents were obtained from
commercial sources and used without purification. All reactions were
carried out under an argon atmosphere in anhydrous solvents.
Synthesis of Ethyl 3,5-Bis[(tert-butyldimethylsilyl)oxy]-4-hydrox-
ybenzoate (3). A solution of tert-butyldimethylsilyl chloride (TBSCl)
(15.4 g, 102.2 mmol) in N,N-dimethylformamide (DMF) (20 mL) was
added dropwise to a solution of ethyl gallate (ethyl 3,4,5-trihydroxy-
benzoate) (10.1 g, 50.1 mmol) and imidazole (10.5 g, 154.4 mmol) in
DMF (50 mL) at 0 °C. The reaction mixture was warmed to room
temperature and stirred for a further 12 h. Then water and ethyl acetate
(EtOAc) were added, and the organic layer was separated and washed
with a saturated NH4Cl aqueous solution. The resulting organic phase
was dried over anhydrous MgSO4, filtered through a pad of Celite,
and concentrated under vacuum. The residue was purified by flash
column chromatography on silica gel (eluent: hexane/chloroform )
1
2/1) to give 3 (14.9 g, 34.9 mmol, 70%) as a white solid. H NMR
(400 MHz, CDCl3): δ ) 7.22 (s, 2H), 5.65 (s, 1H), 4.31 (q, J ) 6.8
Hz, 2H), 1.36 (t, J ) 7.0 Hz, 3H), 1.00 (s, 18H), 0.24 (s, 12H). 13C
NMR (100 MHz, CDCl3): δ ) 166.29, 143.46, 142.77, 120.98, 114.68,
60.71, 25.67, 18.25, 14.29, -4.37. IR (KBr): ν ) 3422, 2956, 2931,
2860, 1717, 1603, 1506, 1472, 1435, 1394, 1372, 1338, 1260, 1224,
1073, 1029, 841, 785 cm-1. MS (MALDI-TOF): calcd for [M + H]+,
427.23; found, 427.28.
Synthesis of 3,5-Bis(11-acryloyloxyundecyloxy)-4-dodecyloxy-
benzoic acid (7). To a solution of 6 (1.84 g, 2.71 mmol) and N,N-
diethylaniline (1.21 g, 8.13 mmol) in 1,4-dioxane (100 mL) was added
dropwise acryloyl chloride (0.74 g, 8.13 mmol) at 70 °C in a light
resistant container, and the reaction mixture was stirred for 3 h at 60
°C. After an excess amount of acryloyl chloride was inactivated by
the addition of methanol (10 mL), the mixture was concentrated by
using a rotary evaporator. The residue as a viscous liquid was dissolved
in a mixture of pyridine (5 mL) and water (5 mL). The mixture was
stirred for 1 h at 80 °C to cleave the benzoic acryloyl anhydride. Then,
the mixture was acidified with a HCl aqueous solution (5%) and
extracted with EtOAc. The organic phase was washed with a NaHCO3
aqueous solution (5%) and dried over anhydrous MgSO4. The solvent
was removed under reduced pressured. The crude product was purified
by flash column chromatography on silica gel (eluent: chloroform/
methanol ) 10/1) and then recrystallized from EtOAc to give 7 (1.52
g, 1.93 mmol, 71%) as a white solid. 1H NMR (400 MHz, CDCl3): δ
) 7.32 (s, 2H), 6.40 (dd, J ) 17, 1.4 Hz, 2H), 6.12 (dd, J ) 17, 10
Hz, 2H), 5.82 (dd, J ) 11, 1.4 Hz, 2H), 4.15 (t, J ) 6.8 Hz, 4H), 4.04
(t, J ) 6.8 Hz, 6H), 1.84-1.70 (m, 4H), 1.70-1.63 (m, 4H), 1.51-
Synthesis of Ethyl 3,5-Bis[(tert-butyldimethylsilyl)oxy]-4-dode-
cyloxybenzoate (4). To a solution of triphenylphosphine (6.11 g, 23.3
mmol), 1-dodecanol (6.12 g, 32.9 mmol), and 3 (10.0 g, 23.5 mmol)
in toluene (50 mL) was added dropwise diethyl azodicarboxylate
(DEAD) (3.8 mL, 24.1 mmol) with stirring at room temperature. After
stirring for 10 h at room temperature, the resulting mixture was poured
into a mixture of water and EtOAc. The organic phase was separated
and washed with a saturated aqueous NaCl solution. The resulting
organic phase was dried over anhydrous MgSO4, filtered through a
pad of Celite, and concentrated in vacuo. The residue was purified by
silica gel column chromatography (eluent: hexane/chloroform ) 2/1)
to give 4 (13.2 g, 22.2 mmol, 94%) as a viscous liquid. 1H NMR (400
MHz, CDCl3): δ ) 7.19 (s, 2H), 4.32 (q, J ) 6.8 Hz, 2H), 3.94 (t, J
) 6.8 Hz, 2H), 1.73 (t, J ) 7.2 Hz, 3H), 1.26 (s, 20H), 1.00 (s, 18H),
0.88 (t, J ) 7.2 Hz, 3H), 0.20 (s, 12H). 13C NMR (100 MHz, CDCl3):
δ ) 166.20, 149.59, 146.57, 124.84, 115.82, 72.92, 60.78, 31.91, 30.11,
29.64, 29.63, 29.57, 29.54, 29.35, 26.06, 25.87, 25.76, 22.68, 18.32,
14.29, 14.13, -4.48. IR (KBr): ν ) 2956, 2929, 2857, 1721, 1577,
1490, 1472, 1428, 1391, 1369, 1346, 1254, 1215, 1094, 1032, 1006,
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5576 J. AM. CHEM. SOC. VOL. 128, NO. 16, 2006

One-Dimensional Ion-Conductive Polymer Films
A R T I C L E S
1.44 (m, 6H), 1.44-1.20 (m, 42H), 0.88 (t, J ) 6.8 Hz, 3H). 13C NMR
(100 MHz, CDCl3): δ ) 171.54, 166.37, 152.80, 143.02, 130.46,
128.59, 123.61, 108.45, 73.50, 69.11, 64.71, 38.17, 31.91, 30.28, 29.72,
29.70, 29.68, 29.66, 29.55, 29.52, 29.49, 29.36, 29.34, 29.25, 29.22,
28.57, 26.02, 26.00, 25.90, 22.67, 14.11. IR (KBr): ν ) 2920, 2851,
1726, 1683, 1635, 1586, 1505, 1472, 1432, 1410, 1386, 1335, 1295,
1275, 1228, 1200, 1122, 1058, 987, 966, 811, 723 cm-1. MS (MALDI-
TOF): calcd for [M + Na]+, 809.55; found, 810.07. Elemental analysis
calcd (%) for C47H78O9: C, 71.72; H, 9.99. Found: C, 71.40; H, 10.15.
Synthesis of 3-{3,5-Bis(11-acryloyloxyundecyloxy)-4-dodecyloxy-
benzoyloxyethyl}-1-methylimidazolium tetrafluoroborate (1). To a
mixture of 7 (1.00 g, 1.27 mmol), 1-(2-hydroxyethyl)-3-methylimida-
zolium tetrafluoroborate13 (0.278 g, 1.30 mmol), and 4-(N,N-dimethy-
lamino)pyridine (DMAP) (1.6 mg, 0.012 mmol) in a mixture of
dichloromethane/acetonitrile (1:1, v/v, 30 mL) was added N,N-
dicyclohexylcarbodiimide (DCC) (0.262 g, 1.27 mmol). The reaction
mixture was stirred for 13 h at room temperature. After filtration of
insoluble materials, the organic phase was concentrated under vacuum.
The residue was purified by flash column chromatography on silica
gel (eluent: CHCl3/MeOH ) 10/1) followed by GPC to yield 1 (0.691
g, 0.703 mmol, 55%). 1H NMR (400 MHz, CDCl3): δ ) 8.90 (s, 1H),
7.35 (s, 1H), 7.26 (s, 1H), 7.19 (s, 2H), 6.39 (dd, J ) 17, 1.8 Hz, 2H),
6.12 (dd, J ) 18, 10 Hz, 2H), 5.82 (dd, J ) 10, 1.4 Hz, 2H), 4.67-
4.64 (m, 4H), 4.14 (t, J ) 7.0 Hz, 4H), 4.03-3.98 (m, 6H), 3.95 (s,
3H), 1.84-1.70 (m, 4H), 1.70-1.63 (m, 4H), 1.51-1.44 (m, 6H), 1.44-
1.20 (m, 42H), 0.88 (t, J ) 6.8, 3H). 13C NMR (100 MHz, CDCl3): δ
) 166.32, 165.77, 152.96, 142.94, 137.34, 130.43, 128.58, 123.27,
123.23, 122.66, 107.99, 73.52, 69.26, 64.66, 62.73, 49.00, 36.44, 31.89,
30.30, 29.71, 29.68, 29.65, 29.56, 29.53, 29.50, 29.49, 29.39, 29.35,
29.28, 29.23, 28.56, 26.08, 26.01, 25.89, 22.66, 14.09. IR (KBr): ν )
3155, 3091, 2921, 2851, 1726, 1699, 1635, 1587, 1505, 1469, 1432,
1410, 1387, 1338, 1298, 1271, 1200, 1130, 1063, 984, 855, 810, 723
cm-1. MS (MALDI-TOF): calcd for [M - BF4]+, 895.64; found,
895.76. Elemental analysis calcd (%) for C53H87BF4N2O9: C, 64.75;
H, 8.92; N, 2.85. Found: C, 64.15; H, 8.92; N, 2.85.
1432, 1410, 1386, 1335, 1295, 1275, 1228, 1200, 1122, 1058, 987,
966, 811, 723 cm-1. MS (MALDI-TOF): calcd for [M - BF4]+, 951.63;
found, 952.20. Elemental analysis calcd (%) for C55H87BF4N2O11: C,
63.57; H, 8.44; N, 2.70. Found: C, 63.05; H, 8.71; N, 2.79.
Preparation of APS-Modified Glass and ITO Substrates. Glass
substrates with comb-shaped gold electrodes (25 × 10 mm) and ITO-
coated glass substrates (15 × 10 mm) were immersed in piranha solution
(3:7 by volume of 30% H2O2 and H2SO4) for 5 min at room temperature
to generate hydroxyl groups as well as to clean the surfaces. These
substrates were washed with H2O, acetone, and MeOH, and dried. The
cleaned substrates were immersed in a 5% toluene solution of
3-(aminopropyl)triethoxysilane (APS) for 1 h at 25 °C. Then, the APS-
modified substrates were rinsed with toluene and MeOH and dried at
120 °C for 30 min under an argon atmosphere.
Sample Preparation for Photopolymerization. The photopoly-
merizable sample was prepared by mixing monomer 1 and 2,2-
dimethoxy-2-phenylacetophenone (5 wt % to the monomer) as the
photoinitiator. The mixture was sandwiched between two glass
substrates, two ITO substrates, or the APS-modified substrates, heated
to an isotropic state at 70 °C, and then cooled to room temperature at
a cooling rate of 1 °C min-1. Photopolymerization of columnar liquid
crystals was carried out at 30 °C for 60 min under the exposure to UV
light (365 nm, 22 mW/cm2).
Measurements of Ionic Conductivities. Ionic conductivities were
measured by the alternating current impedance method using a
Schlumberger Solartron 1260 impedance analyzer (frequency range )
10 Hz-10 MHz, applied voltage ) 0.3 V) and a temperature
controller.2a,3a,32 The heating rate of the measurements was fixed to 3
°C min-1 from 30 to 200 °C. Ionic conductivities were calibrated with
aqueous KCl solution (1.00 mmol L-1) as a standard conductive
solution.
Acknowledgment. This study was partially supported by
Grant-in-Aid for Creative Scientific Research of “Invention of
Conjugated Electronic Structures and Novel Functions” (No.
16GS0209) (T.K.) and Grant-in-Aid for Scientific Research (B)
(No. 17350065) (T.K.) from the Japan Society for the Promotion
of Science (JSPS), and Grant-in-Aid for The 21st Century COE
Program for Frontiers in Fundamental Chemistry (T.K.) from
the Ministry of Education, Culture, Sports, Science, and
Technology.
3-{3,4,5-Tris(11-acryloyloxyundecyloxy)benzoyloxyethyl}-1-me-
thylimidazolium tetrafluoroborate (2). To a mixture of 3,4,5-tris-
(11-acryloyloxyundecyloxy benzoic acid4d (1.00 g, 1.19 mmol), 1-(2-
hydroxyethyl)-3-methylimidazolium tetrafluoroborate13 (0.278 g, 1.30
mmol), and DMAP (1.6 mg, 0.012 mmol) in a mixture of dry CH2-
Cl2/acetonitrile (1:1, v/v, 30 mL) was added DCC (0.268 g, 1.30 mmol).
The reaction mixture was stirred for 13 h at room temperature. After
filtration of insoluble materials, the organic phase was concentrated
under vacuum. The residue was purified by flash column chromatog-
raphy on silica gel (eluent: CHCl3/MeOH ) 10/1) followed by GPC
Supporting Information Available: X-ray diffraction spectra
of 1 in the columnar LC phase before and after photopolym-
erization, illustrations of the cells for anisotropic ionic conduc-
tivity measurements, and synthesis and phase transition behavior
of non-LC benzylimidazolium salts having two and three
acrylate groups. This material is available free of charge via
the Internet at http://pubs.acs.org.
1
to give 2 (0.473 g, 0.455 mmol, 38%). H NMR (400 MHz, CDCl3):
δ ) 8.90 (s, 1H), 7.35 (s, 1H), 7.26 (s, 1H), 7.19 (s, 2H), 6.39 (dd, J
) 17, 1.8 Hz, 2H), 6.12 (dd, J ) 18, 10 Hz, 2H), 5.82 (dd, J ) 10, 1.4
Hz, 2H), 4.67-4.64 (m, 4H), 4.14 (t, J ) 7.0 Hz, 4H), 4.03-3.98 (m,
6H), 3.95 (s, 3H), 1.84-1.70 (m, 4H), 1.70-1.63 (m, 4H), 1.51-1.44
(m, 6H), 1.44-1.20 (m, 42H), 0.88 (t, J ) 6.8, 3H). 13C NMR (100
MHz, CDCl3): δ ) 166.32, 165.77, 152.96, 142.94, 137.34, 130.43,
128.58, 123.27, 123.23, 122.66, 107.99, 73.52, 69.26, 64.66, 62.73,
49.00, 36.44, 31.89, 30.30, 29.71, 29.68, 29.65, 29.56, 29.53, 29.50,
29.49, 29.39, 29.35, 29.28, 29.23, 28.56, 26.08, 26.01, 25.89, 22.66,
14.09. IR (KBr): ν ) 2920, 2851, 1726, 1683, 1620, 1586, 1505, 1472,
JA0606935
(32) (a) Macdonald, J. R. Impedance Spectroscopy Emphasizing Solid Materials
and Systems; John Wiley & Sons: New York, 1987. (b) Mukai, T.; Yoshio,
M.; Kato, T.; Yoshizawa, M.; Ohno, H. Chem. Commun. 2005, 1333-
1335.
9
J. AM. CHEM. SOC. VOL. 128, NO. 16, 2006 5577