Acoustic alignment of a supramolecular nanofiber in harmony with the sound of music

Article abstract of DOI:10.1002/cplu.201300400

Audible sound with a low-frequency vibration brings about hydrodynamic alignment of a supramolecular nanofiber in solution. Design of the nanoscale molecules and molecular assemblies, which can sense a wide range of frequencies of the audible sound wave with high sensitivity, develops sound-driven molecular machines and sound-responsive nanomaterials, and is also interesting for investigation of unknown physical interactions between the molecules and audible sound vibrations. In this study, it was found that a supramolecular nanofiber, composed of an anthracene derivative AN, in an n-hexane solution aligned upon exposure to an audible sound wave at frequencies up to 1000 Hz, with quick responses to the sound and silence, and to amplitude and frequency changes of the sound wave. These properties are of great advantage to sense dynamic changes of fluid flows, such as those induced by the sound of music. Music is composed of multiple complex sounds and silence, which characteristically change in the course of its playing time. When classical music was playing, the AN nanofiber aligned itself in harmony with the sound of the music. Time course linear dichroism spectroscopy revealed the dynamic acoustic alignments of the AN nanofiber in the solution upon playing the music. The sound vibrations of music, which generate acoustic streaming flows in liquid media, allowed shear-induced alignments of the nanofiber. Sound effects: A supramolecular nanofiber, composed of an anthracene derivative having benzamide substituents bearing long chiral alkyl chains, aligns in solution upon exposure to an audible sound wave with frequency up to 1000 Hz (see figure). When classical music is playing, the nanofiber aligns in harmony with the sound. Copyright

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DOI: 10.1002/cplu.201300400
Acoustic Alignment of a Supramolecular Nanofiber in
Harmony with the Sound of Music
Ryosuke Miura,[a] Yasunari Ando,[a] Yasuhisa Hotta,[a] Yoshiki Nagatani,*[b] and
Akihiko Tsuda*[a]
Audible sound with a low-frequency vibration brings about hy-
drodynamic alignment of a supramolecular nanofiber in solu-
tion. Design of the nanoscale molecules and molecular assem-
blies, which can sense a wide range of frequencies of the audi-
ble sound wave with high sensitivity, develops sound-driven
molecular machines and sound-responsive nanomaterials, and
is also interesting for investigation of unknown physical inter-
actions between the molecules and audible sound vibrations.
In this study, it was found that a supramolecular nanofiber,
composed of an anthracene derivative AN, in an n-hexane so-
lution aligned upon exposure to an audible sound wave at fre-
quencies up to 1000 Hz, with quick responses to the sound
and silence, and to amplitude and frequency changes of the
sound wave. These properties are of great advantage to sense
dynamic changes of fluid flows, such as those induced by the
sound of music. Music is composed of multiple complex
sounds and silence, which characteristically change in the
course of its playing time. When classical music was playing,
the AN nanofiber aligned itself in harmony with the sound of
the music. Time course linear dichroism spectroscopy revealed
the dynamic acoustic alignments of the AN nanofiber in the
solution upon playing the music. The sound vibrations of
music, which generate acoustic streaming flows in liquid
media, allowed shear-induced alignments of the nanofiber.
Introduction
Sound is vibration of matter, having a frequency,[1] in which
physical interactions occur between acoustically vibrating
media and solute molecules or molecular assemblies. Control
of dynamic molecular orientation in solution with sound waves
has been an important research subject in sonochemistry, ma-
terials science, and nanotechnology.[2–10] It is known that solu-
tions containing anisotropic macroscopic objects, such as poly-
mers and colloidal particles, provide ultrasonically induced bi-
refringence.[7–10] The timescale of ultrasonic vibrations with
>1 MHz frequency allows the formation of a microscopic ve-
locity gradient or radiation pressure for the macromolecules in
solution, which induces them to become aligned. However, it
is difficult to see such a phenomenon with audible sound
having a lower frequency in the range of 20–20000 Hz, at
which the wavelength is substantially longer than molecular
length scales.[11] In line with this we recently reported that a de-
signed supramolecular nanofiber,
composed of a zinc porphyrin de-
rivative in solution, showed linear
dichroism (LD) upon exposure to
an audible sound wave with si-
nusoidal frequency.[12] The nano-
fibers align in the solution along
the direction of the sound wave.
Although the detailed mechanism
of the observed acoustic align-
ment has not been clarified, the
velocity gradient generated in the
acoustically vibrating medium
COVER
may allow shear-induced align-
ment of the nanofiber.[13–16] With
the added advantage of using audible sound for controlling
the orientation of the nanofiber, we had the idea of develop-
ing a supramolecular nanofiber capable of sensing the sound
of music in its acoustic alignment. Music is an art form consist-
ing of sound and silence expressed through time, and charac-
terized by rhythm, harmony, and melody.[17] The question of
whether music can cause any kind of molecular or macromo-
lecular event is controversial,[18,19] and the physical interaction
between the molecules and the sound of music has never
been reported. Herein, we show that our designed supra-
molecular nanofiber in solution, when classical music was play-
ing, brought about dynamic alignments in harmony with the
sound of the music.
[a] R. Miura,+ Y. Ando,+ Y. Hotta, Prof. Dr. A. Tsuda
Department of Chemistry, Graduate School of Science
Kobe University
1-1 Rokkodai-cho, Nada-ku, Kobe 657-8501 (Japan)
Fax: (+81)78-803-5671
E-mail: tsuda@harbor.kobe-u.ac.jp
[b] Prof. Dr. Y. Nagatani++
Department of Electronics
Kobe City College of Technology
8-3 Gakuen-Higashi-machi, Nishi-ku, Kobe 651-2194 (Japan)
E-mail: nagatani@ultrasonics.jp
[+] These authors contributed equally to this work.
++] Carried out acoustic measurements and characterizations of music.
[
To design a supramolecular nanofiber that can dynamically
align in response to the sound of music, we conceived the fol-
Supporting information for this article is available on the WWW under
http://dx.doi.org/10.1002/cplu.201300400.
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lowing requirements: 1) a molecular structure that senses
weak fluid motions of audible sounds leading to certain molec-
ular actions beyond Brownian motions of solvent mole-
cules;[20–23] 2) capability of sensing and screening the complex
sound mixtures of music over a wide range of audible frequen-
cies; and 3) showing quick responses to dynamic changes of
the sound waves. The previous zinc porphyrin nanofiber was,
however, inadequate for requirement (2), because it could only
sense the lower-frequency sounds below 300 Hz, which covers
only a limited range of the audible sound used in music. Fur-
thermore, the solutions containing the nanofibers, which have
large needle-shaped structures, scatter light and give notable
noise in spectral measurements (Figure S1 in the Supporting
Information). The hydrodynamic behavior of nanofibers may
be modified by the length, thickness, and stiffness of the
formed nanofibers, as well as their affinity with solvent mole-
cules.[24,25] Herein, we found that a supramolecular nanofiber,
composed of an anthracene derivative AN having benzamide
substituents bearing long chiral alkyl chains (Figure 1), can
align by sensing higher-frequency sounds up to 1000 Hz with
quick responses, and further, the solution dramatically reduces
the light scattering property.
Figure 2. Scanning electron micrographs of an air-dried sample of AN nano-
fibers prepared from n-hexane solutions of [AN]=a) 4.2ꢁ10ꢀ5 and
b) 8.3ꢁ10ꢀ5 m deposited on a specimen grid covered with a thin carbon
support film.
with approximate length distribution of 10–1000 nm (Fig-
ure 2a). They have, however, an almost uniform diameter of
approximately 8 nm, which may form through bundling of
a couple of single nanofibers with a diameter of approximately
3 nm (Figure 1b). The nanofibers prepared at double the con-
centration of AN (8.3ꢁ10ꢀ5 m) showed elongations of the
linear structures without notable change of their diameter,
with some entanglements (Figure 2b). The attached chiral alkyl
chains of AN at the 3-, 4-, and 5-positions of the phenyl
groups may allow formation of such shape-consistent supra-
molecular polymers, because an AN analogue with achiral do-
decyl chains, AN_C12, provided larger nanofibers with nonuni-
form diameters, which were hardly soluble in n-hexane solvent
(Figure S4). Van der Waals interactions as well as steric repul-
sions between the attached alkyl chains affect significantly the
bundling of the single supramolecular polymers.
Figure 1. a) Anthracene derivatives having benzamide substituents bearing
optically active alkyl chains AN or dodecyl chains AN_C12. b) Schematic illus-
tration of the self-assembly of AN molecules, and a helical bundle of the
single fibers.
Results and Discussion
Acoustic alignment of the AN nanofiber with sinusoidal au-
dible sound waves
Formation of supramolecular AN nanofiber
Synthesis of AN nanofiber with hydrodynamic behavior in
vortex flows has been reported previously by our group.[23] The
AN molecules in n-hexane self-assemble by hydrogen bonding
and p–p stacking interactions to form linear supramolecular
polymers, which can further assemble to form one-handedly
twisted helical bundles (Figure 1b and Figures S2 and S3).[26–28]
In this study, the sample n-hexane solutions were prepared by
dilution of a CHCl3 solution of AN, allowing it to stand at 258C
for 2 hours, and then stirring for 1 hour. Scanning electron mi-
croscopy (SEM) of the sample prepared from a solution with
a concentration of [AN]=4.2ꢁ10ꢀ5 m shows that nanofibers
formed under these conditions have linear fibrous structures,
The orientations of AN nanofibers in solution can be character-
ized by LD spectroscopy.[29–31] The LD spectrometer in this
study was equipped with a 12ꢁ12ꢁ44 mm quartz optical cuv-
ette with a f10ꢁ10 mm cylindrical neck (outer diameter), com-
posed of 1 mm-thick quartz glass, which was filled with an
n-hexane solution of AN (Figure 3a). An n-hexane solution con-
taining AN nanofibers with a concentration of 4.2ꢁ10ꢀ5 m at
258C displayed no LD response without irradiation by audible
sound. Strong LD responses were obtained upon irradiation
with sound in the frequency range of 100–1000 Hz (Figure 3b).
On exposure of the solution to 120 Hz sound with a sound
pressure level of 31.6 Pa, intense LD bands were observed in
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analogous LD pattern (Figure S5), the nanofibers may also ver-
tically align dominantly in the solution. However, no LD re-
sponses were observed after attachment of a glass cap at the
top of the cuvette, which prevents sound transmission into the
solution, or if using a CHCl3 solution of AN, in which AN mole-
cules cannot form self-assemblies. Further, the observed LD in-
tensity decreased nonlinearly with increasing distance between
the sound speaker and the optical cuvette (Figure S6). The LD
intensity was also highly dependent on the frequency and am-
plitude of the sound (Figure 3c). The frequency up to 1000 Hz
allowed LD induction; the maximum Do.d. of ꢀ0.013 was ach-
ieved at 100 Hz (30 Pa).[34] Upon monitoring the LD response
of the sample solution at 403 nm, and turning the sound on
and off, the nanofibers quickly responded to the rise and fall
of the fluid flows with an induction time of 8 seconds, includ-
ing a leading time of 6 seconds (see below) and a relaxation
time with a half-life of 10 seconds (Figure 3d, blue curve). In
this experiment, the induction time is defined as the time
needed to reach the maximum LD intensity at the plateau of
the LD profile, after turning the sound on. With the higher
concentration of AN (8.3ꢁ10ꢀ5 m), which allows formation of
longer fibers (Figure 2b), both the induction and relaxation
times for the acoustic alignment of the nanofibers increased to
15 seconds, including the leading time of 7–8 seconds, and
32 seconds, respectively (Figure 3d, red curve). The LD intensi-
ty is increased monotonically with increasing sound pressure
level in the low concentration of AN, and this property allows
quantitative evaluation of the sound intensity (Figure S9). In
control experiments, no acoustic LD responses were observed
for solutions of conjugated polymers, such as polystyrene and
polycarbonate, which allow ultrasonically induced birefrin-
gence.[10] The observed alignments of the supramolecular
nanofibers with audible sound may, thus, occur through
a mechanism different from those observed in the ultrasonic
wave.
Mechanism of the acoustic alignment
The wavelength of an audible sound with frequency of 120 Hz
in n-hexane is 9.0 meters at 258C.[35] There is a significant size
mismatch between the sound wave and nanoscale objects, so
direct physical interaction, as observed in the ultrasonic wave
and the polymers,[10] is hardly expected for nanoscale objects
and the audible sound waves. From this and the above experi-
mental result of the LD induction for sound irradiation, which
showed a leading time of 6–8 seconds after turning the sound
on (Figure 3d, inset), we might assume that the nanofiber in-
teracts predominantly with an acoustic streaming owing to the
sound vibration. The acoustic streaming is known as a secon-
dary steady flow generated from the primary oscillatory
flow.[36,37] Nonzero time averages of fluid mass transport occur
because of attenuation and nonlinearity of the fundamental
equations. We actually found that the diffusion rate of ink
dropped into the solution was accelerated under exposure to
audible sound (Figure 4 and Movies S1 and S2). In the case
without sound irradiation, a little downward dispersion of the
ink deposited on the surface of the solution was observed.
Figure 3. LD spectroscopic visualization of acoustic alignment of AN nano-
fiber induced by a sinusoidal sound wave. a) Schematic illustration of the
sample solution upon exposure to the sound and acoustic alignment of
supramolecular nanofibers in the solution. b) LD spectra of AN in n-hexane
(4.2ꢁ10ꢀ5 m) at 208C with and without 120 Hz sound irradiation (blue and
black curves, respectively). The sound pressure level at 120 Hz was measured
as 31.6 Pa at the top of the cuvette. c) Changes in LD intensity at 403 nm in
response to different sound frequencies, in which the obtained LD intensi-
ties were averaged for 100 s. d) Changes in LD intensity at 403 nm in re-
sponse to an ON–OFF sequence of 120 Hz sound irradiation at
[AN]=4.2ꢁ10ꢀ5 m (blue curve) and 8.3ꢁ10ꢀ5 m (red curve). Inset: a magnified
profile in the range of 0–20 s.
the characteristic vibronic absorption bands of anthracene
[402 (Do.d.=ꢀ0.011; o.d. represents LD intensity), 380
(ꢀ0.007), and 362 nm (ꢀ0.004)], which originated mainly from
1
1La, Lb transitions and polarization along the shorter in-plane
axis.[32,33] As the dip-coated thin film, in which nanofibers are
oriented preferentially along the vertical direction, showed an
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Figure 4. Snapshot of the dispersion of red ink from the top of the cuvette
(12ꢁ12ꢁ54 mm) to the bottom seen inside the liquid medium: a) without
and b) with 120 Hz sound (31.6 Pa). The photo in (b) at 20 s shows the rever-
sal of flow. Ink: 5,10,15,20-tetrakis(3,5-di-tert-butylphenyl)porphyrin. Liquid:
CHCl3.
However, in the case with sound irradiation, the ink, under ex-
posure to a 120 Hz sound wave, flowed rapidly toward the
bottom of the cuvette through the center of the sample solu-
tion, and then it reversed flowing upward along the wall side
of the cuvette. The overall flow in the glass cuvette was more
accurately visualized by using a suspension containing small
solid particles, in which both the downward and upward flows
occurred synchronously at the center and the wall of the cuv-
ette (Movie S3).
Figure 5. LD responses in dynamic alignment of the supramolecular nanofib-
ers to the sound irradiation. Time course LD intensity profiles of an n-hexane
solution of AN nanofibers upon exposure to 120 Hz sound wave (31.6 Pa)
for a) 1.0, 3.0, or 5.0 s, and b) 3.0 (sound)+3.0 (silent)+3.0 (sound) s. The LD
intensity was monitored at 403 nm at 208C. [AN]=4.2ꢁ10ꢀ5 m.
Hence, the observed leading time in the LD induction after
turning the sound on, described above, may be the time
before a strong acoustic streaming generates at the light pass
of the LD spectroscopy. As the acoustic streaming occurs
toward the sound propagation direction, and the flows dimin-
ish slowly after turning the sound off, we then investigated
the induction response of LD against the acoustic streaming of
the fluid by generating short irradiation of the sinusoidal
sound wave to the sample solution (Figure 5). When a sample
solution with a concentration of 4.2ꢁ10ꢀ5 m was exposed to
120 Hz sound for 1.0, 3.0, or 5.0 seconds, the LD response oc-
curred with induction times of 11.9, 10.8, or 8.9 seconds with
LD intensities of ꢀ0.008, ꢀ0.009, or ꢀ0.018, respectively (Fig-
ure 5a). The observed induction time was shortened with in-
creased LD intensity by longer sound irradiation, which most
likely accelerates the generation of the acoustic streaming.
These results indicate that the observed acoustic streaming,
owing to sound vibration, can bring about alignment of the
supramolecular nanofiber. As lower-frequency sound, which
causes larger vibration, could generate stronger acoustic
streaming than higher-frequency sound in this system
(Movie S4), the nanofiber might provide a higher LD response
to lower-frequency sound. Here, the nanofiber aligns by sens-
ing velocity gradients of the medium occurring in the crossing
of the downward and upward streaming flows, and by the
laminar flows generated around the glass surfaces of the
vessel as a result of the acoustic streaming (Figure 6). In sup-
port of this proposed mechanism, a larger LD intensity was ac-
tually observed in pointwise LD spectroscopy around the wall
side of the cuvette, including both the glass-surface boundary
layer and the crossing area of the downward and upward
flows (Figure S10). Further, no LD response was observed for
acoustic LD spectroscopy with a larger 32ꢁ32ꢁ45 mm (outer
diameter) quartz optical cuvette, which allows generation of
more complex fluid mixtures in the solution under exposure to
the audible sound. With this proposed mechanism, the notable
changes in increase and decrease of the induced LD intensity
while the sample solution was exposed to the sinusoidal
sound wave, as observed in Figure 3d, can be explained by
complex fluid fluctuations owing to mixing of the local acous-
tic streaming flows that occurred through the continuous
sound irradiation of the sample solution (Figure 4b and
Movie S2).
We further found that AN nanofiber can respond to dynamic
changes of the acoustic streaming, caused by alternate switch-
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first theme of the exposition was played, and the LD signal
became silent at around 60–75 seconds in the quiet part of
the second theme. As the symphony continued, LD induction
also occurred in response to the sound of music with the char-
acteristic LD profile. The intense changes of LD intensity in the
coda reflected the liveliest part of the music at around 390–
500 seconds. To clarify the mechanism of the observed phe-
nomenon, the temporal waveform of the music was trans-
formed into a band-filtered short-time root-mean-square (RMS)
value corresponding to the acoustic power. The values were
calculated in the frequency range of 100–1000 Hz with a mean
running time of 1.0 seconds, and plotted with respect to the
playing time of the music (Figure 7a, red curve).[39] Quite inter-
estingly, this profile fitted well with the observed LD profile,
thus indicating that AN nanofibers in the solution clearly align
and relax dynamically in response to the sound of the music.
Some deviations of the peaks and gradient in the LD profile
from the RMS profile were observed, but may be explained by
such factors as induction and relaxation times of the LD re-
sponses for the dynamically changing complex sound waves.
The higher concentration of the AN molecule allows formation
of the longer nanofibers, which have slower responses of
rising and relaxation in their alignment in solution (Figure 3d),
and brought about a broadening of the observed peaks giving
low-resolution LD profiles (Figure 7a and Figure S11). For ex-
ample, the characteristic two peaks, corresponding to the first
and second four-note motifs, are unified in a single peak with
the maximum at 16 seconds in the double concentration of
AN. Hence, we conclude that the observed harmonization, the
dynamic alignment of nanofiber to the sound of music, charac-
terizes short-scaled AN nanofibers capable of moving quickly
as well as reducing entanglements of the fibers in the solution.
As expected from these experimental results, the solution of
AN nanofiber also showed the characteristic acoustic LD pro-
files for a variety of music. A representative example of the LD
profile obtained from “Symphony No. 40 in G minor, K. 550,
first movement”, written by Wolfgang Amadeus Mozart, is
shown in Figure 7b. In this music, the AN nanofiber also
aligned in response to the changes of the acoustic streaming
flows in the solution, generated by the sound and silence of
the music to give the characteristic profile.
Figure 6. Schematic illustration of potential acoustic streaming in a fluid
medium caused by exposure to a sound wave. Side panels show velocity
gradients that occur owing to the crossing of downward and upward
streaming flows, and friction of a laminar flow with the glass surface of the
cuvette in the boundary layer.
ing of sound and silence in seconds. For example, if the
sample solution containing AN nanofiber was exposed to
120 Hz sound for 3.0 seconds with a 3.0 second interval of si-
lence, and subsequent 3.0 seconds of sound, the LD profile
showed two clear peaks at 11.2 and 14.5 seconds with LD in-
tensities of ꢀ0.009 and ꢀ0.015, respectively; nevertheless,
both the responses also showed time lags after the sound irra-
diation (Figure 5b). The observed peak interval corresponds to
the applied period of silence, so the results indicate that dy-
namic alignments of AN nanofiber occurred in response to the
changes in acoustic streaming of fluid, generated by the dis-
continuous irradiation of the sound wave, at light pass of the
LD spectroscopy.
Dynamic alignment of a supramolecular nanofiber with the
sound of classical music
With the above LD responses of AN nanofibers to the sinusoi-
dal sound waves in mind, we conducted LD spectral measure-
ments of an n-hexane solution of the nanofiber while playing
classical music. We initially chose Symphony No. 5 in C minor,
first movement: allegro con brio, written by Ludwig van Beet-
hoven, which is one of the most well-known symphonies in
the world.[38] The first movement of this symphony has a typical
sonata form and can be divided into four parts: exposition
with a repeat, development, recapitulation, and coda. It begins
by stating a distinctive four-note short-short-short-long motif
twice (eight-note motif) to compose the introductory part of
the music, which is known to represent “fate knocking at the
door” (Figure 7a, musical score). When we conducted a time
course LD spectral measurement, monitoring at 403 nm, for
the n-hexane solution of AN nanofiber while playing the
music, a characteristic LD profile for the melody was obtained
with high reproducibility (Figure 7a, black curve). Representa-
tively, the first and second four-note motifs in the introductory
part gave strong LD peaks at 11 and 14 seconds, respectively.
The sample solution then provided two peaks at 25 and
31 seconds, and multiple peaks at 48–60 seconds when the
Conclusion
A supramolecular nanofiber composed of anthracene deriva-
tive (AN) molecules, dissolved in an n-hexane solution, is capa-
ble of sensing weak fluid flows generated by audible sound
waves through its hydrodynamic alignment. The sample solu-
tion provided characteristic linear dichroism profiles under
playing of classical music with high reproducibility, in which
the nanofiber aligned in harmony with the sound of the music.
The sound vibrations of the music, which generate acoustic
streaming flows in liquid media, most likely allowed shear-in-
duced alignments of the AN nanofiber. This study encourages
investigation of the newly explored dynamics of molecules
and macromolecules in sounds, and we hope this will develop
into new acoustic nanotechnologies.
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standardized aluminum oxide 90
(Merck) were used. Anthracene de-
rivative AN was prepared by pro-
cedures analogous to those re-
ported in our previous study,[23]
and was characterized unambigu-
1
ously by means of H and 13C NMR
spectroscopy, IR spectroscopy, and
fast atom bombardment (FAB)
mass spectrometry.
Structural characterization
1H and 13C NMR spectra were re-
corded on
a Varian INOVA 400
spectrometer (400 MHz for 1H) or
a Bruker AVANCE 500 spectrome-
ter (500 MHz for 1H and 125 MHz
for 13C), for which chemical shifts
(d in ppm) were determined with
respect to tetramethylsilane as the
internal standard. Infrared absorp-
tion spectra were recorded on
a JASCO FTIR-4200 Fourier trans-
form infrared spectrometer. FAB
mass spectrometry was performed
on
a JEOL JMS-BU30 LC Mate
spectrometer with 3-nitrobenzyl
alcohol as the matrix. Dynamic
light scattering (DLS) measure-
ments were performed using an
Otsuka model ELS-Z2 instrument.
Scanning electron microscopy
(SEM) was performed using a JEOL
JSM-7600F FE-SEM instrument op-
erating at 30 kV. DLS measure-
ments were performed using an
Otsuka model ELS-Z2 instrument.
Synthesis of AN_C12
3,4,5-Tris(dodecyloxy)benzoic acid
(196 mg, 0.29 mmol) was dissolved
in thionyl chloride (5 mL), and the
reaction mixture was heated at
reflux for 4 h and then evaporated
to dryness. The residue was mixed
with 9,10-bis(aminomethyl)anthra-
cene (0.02 g, 0.08 mmol) and N,N’-
dimethyl-4-aminopyridine (0.07 g,
0.57 mmol) in dry CH2Cl2 (10 mL),
and the solution was heated at
reflux under Ar for 24 h and then
evaporated to dryness. The resi-
due was dissolved in CHCl3 and
Figure 7. LD spectroscopic visualization of dynamic acoustic alignment of AN nanofiber in response to classical
music. a) LD spectral profiles of an n-hexane solution of AN nanofiber at 258C when playing “Symphony No. 5 in
C minor, first movement: allegro con brio” written by Beethoven. LD intensity profile with respect to the playing
time of the music obtained at [AN]=4.2ꢁ10ꢀ5 m (black curve) and a band-filtered short-time RMS value profile
with a band-pass filter from 100 to 1000 Hz with a mean running time of 1.0 s (red curve, top). Insets: (left) a mag-
nified LD profile for 0–25 s and (right) a musical score of the four-note motif twice in the first introductory part of
the music. The LD intensity profile obtained at [AN]=8.3ꢁ10ꢀ5 m (bottom). b) LD spectral profile of an n-hexane
solution of AN nanofiber at 258C when playing “Symphony No. 40 in G minor, K. 550, first movement” written by
Mozart. [AN]=4.2ꢁ10ꢀ5 m.
washed with aqueous solutions of 1n HCl, saturated NaHCO3, and
saturated NaCl. The organic layer was then extracted, dried over
anhydrous Na2SO4, and evaporated to dryness. The residue was
washed with CH2Cl2/CH3OH to leave AN as an orange oil in 98%
Experimental Section
Materials
1
Unless otherwise noted, reagents and solvents were used as re-
ceived from Kishida Chemical Co., Ltd. (CHCl3 >99% and hexane
>96%). For column chromatography, Wakogel C-300HG (particle
size 40–60 mm, silica), C-400HG (particle size 20–40 mm, silica), and
yield. H NMR (500 MHz, CDCl3, 208C): d=8.45 (dd, J=3.1, 7.0 Hz,
4H; anthracene), 7.63 (dd, J=3.1, 7.0 Hz, 4H; anthracene), 6.90 (s,
4H; phenyl), 6.19 (t, J=4.5 Hz, 2H; amide), 5.64 (d, J=4.5 Hz, 4H;
methylene), 3.95 (t, J=6.5 Hz, 4H; ꢀOCH2ꢀ), 3,91 (t, J=6.3 Hz, 8H;
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ꢀOCH2ꢀ), 1.76–1.66 (m, 12H; alkyl), 1.46–1.36 (m, 12H; alkyl), 1.33–
1.21 (br, 96H; alkyl), 0.89–0.86 ppm (m, 18H; methyl); 13C NMR
(125 MHz, CDCl3, 208C): d=167.27 (C=O), 153.30 (aromatic), 141.81
(aromatic), 130.58 (aromatic), 130.26 (aromatic), 129.03 (aromatic),
126.85 (aromatic), 124.95 (aromatic), 106.23 (aromatic), 73.66 (ꢀ
OCH2ꢀ), 69.70 (ꢀOCH2ꢀ), 37.14, 32.09, 30.46, 29.9–29.7 (m), 29.54,
26.22, 14.25 ppm; FAB-MS: m/z calcd for C102H168N2O8: 1549 [M+];
found: 1550 (M+H+); elemental analysis calcd (%) for C102H168N2O8:
C 79.02, H 10.92, N 1.81; found: C 79.35, H 11.10, N 1.73.
time of 1.0 s, for which neither the relaxation factor nor possible
nonlinear response was employed.
Acknowledgements
We acknowledge Dr. Y. Nakajima and Dr. N. Kikuchi of JEOL Ltd.
for FE-SEM measurements. This study was sponsored by a Grant-
in-Aid for Scientific Research (B) (No. 25286017) and Challenging
Exploratory Research (No. 24655125) from the Ministry of Educa-
tion, Science, Sports, and Culture, Japan, and a Toray Science
and Technology Grant.
Acoustic LD spectral measurements
Prior to spectral measurements, sample n-hexane solutions ([AN]=
4.2ꢁ10ꢀ5 or 8.3ꢁ10ꢀ5 m) were prepared by dilution of a CHCl3 so-
lution of AN ([AN]=5.0ꢁ10ꢀ2 m), allowed to stand in the dark at
258C for 2 h, and then stirred at 1350 rpm in both clockwise and
counterclockwise directions for 1 h. LD spectra were recorded
using a JASCO type J-820 spectropolarimeter equipped with
Keywords: acoustic alignment · linear dichroism · nanofibers ·
sound · supramolecular chemistry
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Received: November 27, 2013
Published online on January 7, 2014
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ChemPlusChem 2014, 79, 516 – 523 523