Poly(diacetylene)-nanofibers can be fabricated through photo-irradiation using natural polysaccharide schizophyllan as a one-dimensional mold

Article abstract of DOI:10.1039/b510646j

Schizophyllan interacts with various 1,4-diphenylbutadiyne derivatives to induce their chirally-twisted packing. A series of referential experiments using other polysaccharides (amylose, pullulan, dextran, etc.) and a carbohydrate-appended detergent (dode

Full text of DOI:10.1039/b510646j

View Article Online / Journal Homepage / Table of Contents for this issue
A R T I C L E
Poly(diacetylene)-nanofibers can be fabricated through
photo-irradiation using natural polysaccharide schizophyllan
as a one-dimensional mold
Teruaki Hasegawa,a Shuichi Haraguchi,a Munenori Numata,a Chun Li,a Ah-Hyun Bae,a
Tomohisa Fujisawa,a Kenji Kaneko,b Kazuo Sakuraic and Seiji Shinkai*a
a Graduate School of Engineering, Kyushu University, Hakozaki, 6-10-1, Fukuoka, 812-8581,
Japan. E-mail: seijitcm@mbox.nc.kyushu-u.ac.jp; Fax: +81 (0)92 642 3611;
Tel: +81 (0)92 642 3585
b The Research Laboratory for High Voltage Electron Microscopy, Kyushu University, Fukuoka,
812-8581, Japan
c Department of Chemical Processes and Environments, Faculty of Environmental Engineering,
The University of Kitakyushu, Hibikino, 1-1, Wakamatsu-ku, Kitakyushu, Fukuoka, 808-0135,
Japan
Received 27th July 2005, Accepted 19th October 2005
First published as an Advance Article on the web 8th November 2005
Schizophyllan interacts with various 1,4-diphenylbutadiyne derivatives to induce their chirally-twisted
packing. A series of referential experiments using other polysaccharides (amylose, pullulan, dextran, etc.) and a
carbohydrate-appended detergent (dodecyl-b-D-glucopyranoside) indicates that these 1,4-diphenylbutadiyne
derivatives are accommodated within a tubular cavity constructed by a helical superstructure of schizophyllan. In
these 1,4-diphenylbutadiyne derivatives, 1,4-bis(p-propionamidophenyl)butadiyne can be easily polymerized
through UV-irradiation, in which schizophyllan acts as a one-dimensional mold to produce the corresponding
poly(diacetylene)s with fibrous morphologies. Detailed investigations on this unique approach to prepare the
nanofibers revealed that it includes two individual processes, that is, 1) UV-mediated polymerization of encapsulated
1,4-bis(p-propionamidophenyl)butadiyne to produce immature nanofibers and 2) their reorganization through
hydrophobic interfiber interactions into ordered nanofibers. The other 1,4-diphenylbutadiyne derivatives could not
be polymerized through UV-irradiation, indicating that the p-propionamido-functionalities play substantial roles for
a suitable packing of the monomer for the polymerization. The other 1,4-diphenylbutadiyne derivatives, however, can
be also polymerized through c-ray irradiation in the presence of schizophyllan to give the corresponding
poly(diacetylene)-nanofibers, emphasizing the wide applicability of the schizophyllan-based strategy for
polymerization of various 1,4-diphenylbutadiyne derivatives.
for their photo-mediated polymerization (topochemical poly-
merization). Poly(diacetylene)s can be, therefore, usually pre-
Introduction
Convenient approaches to design conductive nanofibers have
received an increasing research interest, since such nanofibers
can be used as conductive wires in nano-scaled electric
circuits in a coming age. There are two attractive candi-
dates for such nanofibers. One is a family of covalently-
bonded p-conjugated polymers including poly(acetylene)s,1
poly(phenylenethynylene)s,2 etc. and the other is a fam-
ily of noncovalently-assembled nanofibers of low molecular-
weight organic compounds having donor–acceptor complexes
(e.g., tetracyanobenzoquinone (TCNQ) and tetrathiafulvalene
(TTF))3. The p-conjugated polymers have one clear advantage
over the latter: that is, the stable conductivity is generated
even under harsh conditions, e.g., at high temperature where
the molecular assemblies are easily decomposed. However, they
also have a drawback as well: that is, simple polymerization
of the corresponding monomers usually results in amorphous
polymer-aggregates, in which the polymer strands are highly
entangled in a random fashion. It is strongly desired, therefore,
to establish convenient strategies to fabricate the nanofibers, in
which individual polymers are aligned in a parallel orientation.
Such nanofibers are expected to be useful molecular wires having
excellent conductivity through the long axis.
pared from molecular assemblies (crystals, micelles, Langmuir–
Blodgett films, etc.) of the corresponding monomers, in which
the monomers are aligned in a parallel but slightly slided
packing mode suitable for the topochemical polymerization.
Since the resultant morphologies of obtained poly(diacetylene)s
strikingly depend on the superstructure of the monomer-
assemblies before photo-irradiation, pre-organization of the
corresponding monomers into well-designed fibrous architec-
tures is, therefore, a prerequisite to obtain the nanofibers
composed of poly(diacetylene)s. Several research groups have
devoted their intense research efforts on the fabrication of such
fibrous monomer-assemblies, mainly utilizing the amphiphilic
diacetylene-monomers which are spontaneously assembled into
the fibrous superstructures.5
Schizophyllan (SPG, Fig. 1-a) produced by fungus Schizo-
phyllum commune is an extracellular b-1,3-glucan having a b-1,6-
glucoside-appendage at every three repeating units. This native
polysaccharide has been of great interest for many researchers
because of its anticancer activity as well as its gel-forming
ability.6 The most interesting structural feature of SPG is a
reversible and solvent-induced structural transition between a
triple-stranded helical structure (t-SPG) in water and individual
single-strands (s-SPG) in dimethyl sulfoxide (DMSO).7
Poly(diacetylene)s are a family of the most interesting research
targets among the p-conjugated polymers, since they are readily
produced through photo-irradiation (UV or c-ray) without
any initiators.4 It is known, however, that closely-packed pre-
organization of the corresponding monomers is indispensable
In a series of intense research on SPG, we found that SPG has
a one-dimensional (1D) cavity inside its helical superstructure
(Fig. 1-b) and accommodates various hydrophobic guests within
this 1D cavity through the structural transition from s-SPG to
T h i s j o u r n a l i s
T h e R o y a l S o c i e t y o f C h e m i s t r y 2 0 0 5
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 4 3 2 1 – 4 3 2 8
4 3 2 1
©

View Article Online
Fig. 2 Schematic illustration of our concept to use SPG as a 1D host
to accommodate DPBs within the helical superstructure of SPG and
construct poly(DPBs)-nanofibers through UV/c-ray irradiation.
Results and discussion
Synthesis of DPBs
DPBs were prepared through 1) amido-coupling of a com-
mercially available 4-ethynylaniline with the corresponding acid
chlorides or acid anhydrides, followed by 2) Cu(II)-catalyzed
homo-coupling of the resultant 1-amido-4-ethynylbenzene
derivatives (Scheme 1). We prepared 1,4-bis(p-propionamido-
phenyl)butadiyne (DPB-Pr), 1,4-bis(p-sec-butyramidophenyl)-
butadiyne (DPB-Bu) and 1,4-bis(p-(S)-2-methylbutyramido-
phenyl)butadiyne (DPB-(S)Pe) through this simple 2-step syn-
thesis. Structural proofs of the resultant DPBs were obtained
Fig. 1 (a) Chemical and (b) spatial structure of schizophyllan having a
triple-stranded helical structure (t-SPG).
1
from H NMR, MALDI-TOF-MS and IR spectral evidence.
t-SPG (renaturation process).8 It should be noted that this renat-
uration process is essential for the guest encapsulation: in fact,
no complexation can be observed by simple mixing of t-SPG
with the guests. We assumed that the 1D cavity inside the rigid-
helical structure of t-SPG is not ready for the complexation.
However, once SPG takes the random-coiled structure (s-SPG),
the 1D cavity is exposed to the solvent and the complexation can
occur during the water-induced renaturation process. One may
regard, therefore, that SPG can be induced to fit the guests of
various size and shape through this unique renaturation process
and in this respect, the complexation behaviour of SPG is quite
different from that of cyclodextrins, which have strict size- and
shape-selectivity.
Along with these DPBs, we also used commercially available
1,4-diphenylbutadiyne (DPB) having no p-substituent in our
experiments.
The first example of SPG–guest complexes was observed for
single-walled carbon nanotubes (SWNTs).9 In this example,
highly-stable and water-soluble SPG–SWNT complexes are
formed by mixing s-SPG in DMSO with a SWNT-dispersed
aqueous solution. Atomic force microscopic (AFM) observa-
tions of the resultant complexes revealed that the SWNTs
are accommodated within the 1D cavity of SPG. We also
reported that not only SWNTs but also polyaniline (PANI)
can form a stable macromolecular complex with SPG through
the renaturation process.10 Of great interest, the resultant SPG–
PANI complex has a fibrous superstructure, in which several
PANIs are packed in a parallel fashion within the helical
superstructure of SPG. This unique morphology is quite in
contrast to free PANI, which gives only amorphous aggregates.
This finding clearly indicates that SPG can act as a 1D host to
accommodate not only rod-like polymers (SWNTs) but also
flexible synthetic polymers (PANI) within the 1D cavity to
produce the fibrous polymeric assemblies. More recently, we also
found that small Au-nanoparticles can be entrapped by SPG to
produce the 1D Au nano-arrays.11 These findings consistently
support the view that SPG can act as a general 1D host to
accommodate a wide variety of guest metals and molecules to
produce their 1D architectures.
Scheme 1 Synthesis of 1,4-diphenylbutadiynes having propionamido
(DPB-Pr), sec-butyramido (DPB-Bu), and (S)-2-methylbutyramido-
substitutions (DPB-(S)Pe): i) propionyl chloride for DPB-Pr, isobu-
tyric anhydride for DPB-iBu, or (S)-(+)-methylbutyric anhydride for
DPB-(S)Pe, pyridine, rt, ii) Cu(acetate)2, pyridine, reflux.
Preparation of SPG–DPB complexes
SPG (Mw = 150 kDa) and DPBs were dissolved into DMSO and
the resultant DMSO solution containing s-SPG (random-coiled
single-strand) and DPBs was mixed with water to regenerate the
t-SPG helical structure (the final water content was 70 v/v%).
Formation of the desired SPG–DPBs complexes was confirmed
by their circular dichroism (CD) spectra. For example, SPG–
DPB-Pr complex gave a CD spectrum showing a negative Cotton
signal (Fig. 3-a, bold green line), clearly indicating that SPG
interacts with DPB-Pr monomers to arrange them in a chirally-
twisted packing. It should be noted that the resultant aqueous
DMSO solutions containing SPG–DPB complexes are slightly
turbid, but the linear dichroism is negligibly small.
Our research efforts are now focused on low molecular-weight
compounds as guests.12 Especially, it is of great significance
to establish SPG-templated polymerization of various low
molecular-weight monomers in the 1D cavity to construct the
corresponding polymers with fibrous morphologies.13 Herein,
we report one of such successful examples that SPG can ac-
commodate various 1,4-diphenylbutadiyne derivatives (DPBs)
within the 1D cavity and can produce poly(DPBs)s-assembled
nanofibers through UV or c-ray irradiations (Fig. 2).
We carried out a few reference experiments using different
solvent systems and polysaccharides in order to clarify the
detailed mechanism of the interaction. The CD spectra of the
4 3 2 2
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 4 3 2 1 – 4 3 2 8

View Article Online
Fig. 3 (a) CD spectra of DPB-Pr in the presence of s-SPG under various aqueous DMSO solutions with different water contents and (b) CD
spectra of DPB-Pr in the presence of s-SPG, amylose, dextran, pullulan, t-SPG and the detergent: d = 1.0 cm, 20 ◦C, [H2O] = 70 v/v%, [DPB-Pr] =
25 lg ml−1, [polysaccharide] or [detergent] = 25 lg ml−1, 24 h after sample preparation.
SPG–DPB-Pr complex was dramatically changed by a change
in the water content (Fig. 3-a). This solvent-dependent CD
spectral change is considerably complex, however, two apparent
characteristics can be seen. 1) The CD signal was observed only
under water-rich conditions ([H2O] = 60∼99 v/v%), suggesting
that the hydrophobic interactions, rather than the hydrogen-
bonding interactions, play major roles for the complexation.
This finding supports our assumption that hydrophobic DPBs
are entrapped within the 1D cavity of SPG, as already reported
for other guest molecules (SWNTs, PANI, Au-particles, etc.). 2)
All CD spectra observed herein show negative Cotton-effects,
indicating that DPB-Pr monomers are aligned in a left-handed
helical manner within the 1D cavity.
Reference experiments using other polysaccharides (amylose,
pullulan and dextran) also offered useful information on
the mechanism of the interaction between SPG and DPB-Pr
(Fig. 3-b). No other polysaccharide can induce any CD spectral
change of DPB-Pr, indicating that a few factors (hydrophobic
interactions, conformational changes, etc.), other than the
hydrogen-bonding interactions, play substantial roles in the
arrangement of DPB-Pr monomers in the 1D cavity of SPG.
Comparison between s-SPG and t-SPG also gave important
information on the mechanism of the interaction: that is, when
t-SPG (in water) was mixed with DPB-Pr (in DMSO), the
resultant mixed solution gave no CD signal, indicating that the
structural transition from s-SPG to t-SPG is essential for the
interaction. This finding is of great significance because it implies
that DPB-Pr molecules locate inside the helical structure of
renascent t-SPG, as already reported for other guest molecules.
We also carried out an additional experiment using a
carbohydrate-appended detergent (dodecyl-b-D-glucopyrano-
side) as a reference. DPB-Pr shows a small (compared with that
in the presence of SPG) but perceptible induced-CD signal at
around 280 nm in the presence of the detergent, indicating that
DPB-Pr molecules are chirally packed within a hydrophobic
inner space of the micelles having the chiral head groups. This
finding also supports our assumption that the hydrophobic
interactions play substantial roles for the complexations.
We also carried out CD spectral measurements on other
DPBs including DPB, DPB-Bu and DPB-(S)Pe to find that
these DPBs also showed SPG-induced CD signals, although
their intensities are quite different (Fig. 4). These data
indicate that their interactions with SPG are strikingly de-
pendent on the structure of DPBs. For example, as shown in
Fig. 4-a, the CD intensities of DPB-Bu and DPB are 3- and
10-fold weaker, respectively, than that of DPB-Pr. Comparison
between DPB-Pr and DPB suggests an important role of
p-amido-substituents for the interactions. We assume that the
p-amido-substitutions are indispensable for arranging DPB-Pr
molecules in the chirally-twisted packing, presumably through
the hydrogen-bonding interaction with the neighbouring DPBs
and/or SPG. Furthermore, comparison between DPB-Pr and
DPB-Bu shows that bulky-substituents strongly disrupt the close
and stable packing of DPBs in the 1D cavity.
UV-mediated polymerization of DPBs
UV-mediated polymerization of DPBs in the presence of SPG
was carried out under two different conditions: that is, using 1)
water-jacketted or 2) water-unjacketted cells. The temperature
of the reaction cell was controlled at 25 ◦C by using◦the water-
jacketted cell, however, it was elevated up to ca. 50 C on UV-
irradiation without using the water-jacketted cell. Before these
experiments, we thought that the controlled temperature would
play an important role to fabricate ordered nanofibers with
uniform diameters, however, we found that the UV-mediated
Fig. 4 (a) CD spectra of (dotted line) SPG–DPB complex, (plane line) SPG–DPB-Pr complex, and (thin line) SPG–DPB-Bu complex and (b) those
of (plane line) SPG–DPB-(S)Pe complex and (dotted line) free DPB-(S)Pe: d = 1.0 cm, 20 ◦C, [H2O] = 70 v/v%, [DPB], [DPB-Pr], [DPB-Bu], or
[DPB-(S)Pe] = 25 lg ml−1, [SPG] = 25 lg ml−1, 24 h after sample preparation.
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 4 3 2 1 – 4 3 2 8
4 3 2 3

View Article Online
polymerization without using the water-jacketted cell could
generate more ordered fibers than those produced under the
controlled temperature (25 ◦C).
stretching vibration).14 The difference between 4 and 16 h UV-
irradiation does not induce any significant shift of the Raman
peaks, again supporting that the elongated UV-irradiation time
does not result in the further growth of the poly(diacetylene)
strands. It should be emphasized that no such Raman peak
appeared without SPG, indicating that SPG accommodates
DPB-Pr within the 1D cavity to align them in a one-dimensional
packing mode suitable for the topochemical polymerization.
Other DPBs could not be polymerized through the UV-
irradiation, although these DPBs are accommodated within
the 1D cavity. These results closely correlate to the intensity of
their SPG-induced CD signals: that is, the DPBs showing weak
CD signals are not suitable monomers for the UV-mediated
polymerization, presumably owing to their loose packing mode
in the 1D cavity.
Transmission electron microscopic (TEM) observation
showed that the resultant SPG–poly(DPB-Pr)s complex has
a fibrous structure (Fig. 7-a) with diameters ranging from 2
to 20 nm. On the other hand, no such fibrous assembly was
obtained without SPG (data not shown). We also confirmed
that neither other polysaccharides (amylose, dextran, pullulan
and t-SPG) nor the carbohydrate-based detergent (dodecyl-b-
D-glucopyranoside) can produce such nanofibers (Fig. 7-c, d, e
and f). These data clearly demonstrate an advantage of SPG as
the 1D host to generate the nanofibers.
In the UV-mediated polymerization without using the water-
jacketted cell, SPG–DPB-Pr complex in aqueous DMSO was
placed at 5 cm distance from a high pressure Hg lamp and the
temperature of the reaction solution was, therefore, elevated up
◦
to ca. 50 C. A gradual colour change in the reaction solution
could be visibly detected during the UV-irradiation process, as
shown in Fig. 5-a. To our great interest, the solution colour
changed from colourless to pale red during the first 4 h UV-
irradiation and then gradually turned into pale blue during
the following 16 h UV-irradiation. The time-course of the UV-
vis spectra (Fig. 5-b) shows a biphasic spectral change during
the UV-irradiation. In the first phase, an absorption band at
540 nm which is characteristic of poly(diacetylene)s appears.
In the following phase, however, this new peak is gradually
diminished and another peak appears simultaneously at 720 nm.
Usually, such red-shifted absorption bands can be assigned to
poly(diacetylene)s having the extremely large molecular weight
and/or tight inter-stranded packing. We can exclude the former,
because an isosbestic point can be observed in this spectral
change. If the further UV-irradiation facilitates elongation of
the corresponding poly(diacetylene) strands, the peak should
continuously red-shift from 540 to 720 nm and the isosbestic
point should not exist. We assumed, therefore, that this spectral
change in the second phase arises from the inter-stranded
packing of the poly(diacetylene) strands. The mechanism of this
colour change will be further discussed below in detail.
Fig. 5 Solutions of SPG–DPB-Pr complex after (left) 0, (centre) 4,
and (right) 16 h UV-irradiation and (b) UV-vis spectra of SPG–DPB-Pr
complex after 0, 1.0, 2.5, 4.0, 5.5, 7.0, 9.0, 11.5, and 16 h UV-irradiation:
25 ◦C, d = 1.0 cm, aqueous DMSO ([H2O] = 70 v/v%).
The UV-mediated polymerization of DPB-Pr in the pres-
ence of SPG was also confirmed by the Raman spectra
(Fig. 6), in which the SPG–DPB-Pr complex shows a sharp
peak at 2000 cm−1 assignable to poly(diacetylene)s (–CH CH-
=
Fig. 7 TEM images of poly(DPB-Pr)s in the presence of (a) SPG (after
16 h UV-irradiation), (b) SPG (after 4 h UV-irradiation), (c) amylose,
(d) dextran, (e) pullulan, and (f) dodecyl-b-D-glucopyranoside.
Energy dispersive X-ray (EDX) spectroscopic analysis showed
the existence of oxygen and nitrogen in the nanofibers. Although
the spectrum was overlaid by an enormous amount of carbon
originating from the carbon grid, the analytical data gave an
excess amount of oxygen in comparison to that of nitrogen. Since
poly(DPB-Pr) itself contains an equal amount of oxygen and ni-
trogen, the presence of the excess amount of oxygen suggests that
SPG strands co-exist around poly(DPB-Pr)-nanofibers. The co-
existence of SPG strands is also supported by a morphological
Fig. 6 Raman spectra of DPB-Pr in the presence of SPG after 0, 4 and
16 h UV-irradiation: cast films.
4 3 2 4
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 4 3 2 1 – 4 3 2 8

View Article Online
change in the nanofibers through an acid-catalyzed degradation
of the co-existing SPG. This result is discussed in the following
section in detail.
We also confirmed the effects of SPG on the ordered
nanofibers by removing SPG from the SPG–poly(DPB-Pr)
complexes through an acid-catalyzed degradation of SPG. As
shown in Fig. 9-a, SPG–poly(DPB-Pr) complexes show a UV-
vis spectrum having an intensified peak at 720 nm after the acid-
catalyzed degradation. The removal of SPG from the complex,
which results in poly(DPB-Pr) exposed to the media, should
cause tight inter-stranded packings. TEM observation of the
resultant complexes after the acid-catalyzed degradation did
not show the ordered nanofibers but highly entangled net-like
morphologies, supporting our assumption that perturbation (or
removal) of the helical superstructure of SPG results in inter-
stranded packing of poly(DPB-Pr) and the resultant colour and
morphological changes.
Detailed investigations on the UV-mediated polymerization
Ordered nanofibers with uniform diameters can be observed
for SPG–poly(DPB-Pr) complexes after 16 h UV-irradiation,
however, shortened irradiation time (4 h) gives much differ-
ent morphologies, that is, short and disordered nanofibers
(Fig. 7-b). Together with the UV-vis spectral change during
the polymerization suggesting the interfiber interactions, it
is likely that the disordered nanofibers are organized into
ordered ones during the UV-irradiation. We assumed that this
structural transition should arise from temperature-induced re-
organization of the poly(DPB-Pr) strands. As mentioned above,
when the reaction cell was not water jacketted, the temperature
of the reaction solutions was elevated up to ca. 50 ◦C on the
UV-irradiation. This elevated temperature should disorder the
helical superstructure of SPG around the as-grown poly(DPB-
Pr) strands and then, the resultant poly(DPB-Pr) strands, which
are partially exposed to the solvent, should be packed through
interstrand hydrophobic interactions.
Comparison between the UV-mediated polymerization with
or without the water-jacketted cell clearly supports this assump-
tion: that is, when we used a water-jacketted reaction cell to
keep the solutions at 25 ◦C, UV-irradiation gave a red-coloured
solution and no further colour change from red to blue was
observed even after 16 h UV-irradiation. The UV-vis spectra
of the resultant solution confirm that no blue peak appears
(Fig. 8, bold line). Furthermore, incubation of the resultant red-
coloured solution in the dark at 50 ◦C resulted in an appearance
of a new absorption peak at around 720 nm (Fig. 8, thin lines).
These data also clearly support our assumption that the colour
change from red to blue is induced through the temperature-
induced re-organization of poly(DPB-Pr) strands.
c-Ray mediated polymerizations of DPBs
As we mentioned above, the UV-mediated polymerization is
only applicable for DPB-Pr, and no other DPBs, such as
DPB, DPB-Bu and DPB-(S)Pe can be polymerized to afford
the corresponding nanofibers. We, therefore, carried out c-ray
mediated polymerization of these DPBs, since c-ray irradiation is
known to produce poly(diacetylene)s very readily in comparison
to the UV-irradiation. The aqueous DMSO solutions containing
these SPG–DPBs complexes turned into pale blue after the
c-ray irradiation, indicating that the polymerization of all
these DPBs does take place. Their UV-vis spectra after the
c-ray irradiation showed small new peaks around 500 nm
(emphasized within closed circles, Fig. 10). Although these peaks
are quite weak, they clearly indicate that these monomers can
be polymerized through the c-ray irradiation. TEM observation
of the resultant SPG–poly(DPBs)s complexes showed fibrous
superstructures that are similar to that of SPG–poly(DPB-Pr)
complexes (Fig. 11-a). On the contrary, c-ray-irradiation on
DPBs in the absence of SPG gave amorphous aggregates with
disordered rectangular shapes (Fig. 11-b). These rectangular
poly(diacetylene)s should arise from amorphous aggregates of
the corresponding “water-insoluble” monomers in the aque-
ous solution. These data clearly indicate that our SPG-based
approach is a quite general one to obtain poly(diacetylene)-
nanofibers from various DPB monomers.
Chirality of the nanofibers
It is of great interest to prepare poly(diacetylene)s with the
helical superstructure, since they should be useful to develop
various catalytic and sensory devices for chiral materials. In this
respect, a conformation of poly(DPB-(S)Pe) is quite interesting.
Poly(DPB-(S)Pe) prepared through the SPG-templated c-ray
irradiation followed by a dialysis with DMSO (to remove the
unreacted monomer) showed a CD spectrum having a positive
CD signal at around 300 nm that is assignable to p–p* transition
of the phenyl-appendage (Fig. 12). On the other hand, no CD
signals can be observed at 540 or 720 nm that are assignable
Fig. 8 Temperature-induced UV-vis spectral change (0 to 256 min)
of SPG–poly(DPB-Pr) complexes in aqueous DMSO ([H2O]
=
70 v/v%): The original red-coloured solution was obtained through
16 h UV-irradiation on SPG–DPB-Pr complex using a water-jacketted
(25 ◦C) reaction cell: 25 ◦C, d = 1.0 cm.
Fig. 9 (a) UV-vis spectra of SPG–poly(DPB-Pr) complexes (dotted line) before and (plane line) after the acid-catalyzed degradation of SPG and
(b) TEM image of poly(DPB-Pr)s after the degradation followed by dialysis (MWCO 8000, water): for UV-vis, d = 1.0 cm, 25 ◦C.
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 4 3 2 1 – 4 3 2 8
4 3 2 5

View Article Online
Fig. 10 UV-vis spectra of (a) DPB-Pr, (b) DPB-Et, (c) DPB-Bu and (d) DPB-(S)Pe after c-ray irradiation in the (plane lines) presence and (dotted
line) absence of SPG: 25 ◦C, d = 1.0 cm, aqueous DMSO ([H2O] = 70 v/v%).
Fig. 11 TEM images of poly(DPB-(S)Pe)s in the (a) presence and (b) absence of SPG after c-ray irradiation followed by dialysis (MWCO 8000,
water).
packings between the polymer main chains would prohibit chiral
twisting of the main chains.
Conclusions
We established a unique, easy and general approach to prepare
nanofibers composed of various poly(DPBs)s. In our strategy,
SPG acts as a unique 1D host to accommodate various DPBs to
produce the corresponding poly(DPBs)s having highly ordered
fibrous superstructure through UV- or c-ray-irradiation. Recent
studies on the fabrication of polydiacetylene-nanofibers utilize
the corresponding monomers that are self-assembled into the
fibrous superstructure. These diacetylene monomers should be
carefully designed for their pre-organization into the nanofibers
before polymerization. On the other hand, the SPG-templated
Fig. 12 CD spectra of poly(DPB-(S)Pe): d = 1.0 cm, 20 ◦C, in DMSO,
the sample after the dialysis (DMSO) was directly used for this UV-vis
approach can be applicable to various DPBs having various
size and functionalities. Together with a series of our reports
on SPG to show its unique properties as 1D hosts, the results
we reported in this paper clearly show that SPG can be
also applicable to template polymerization of the encapsulated
monomers to produce the corresponding polymer-fibers. We
believe that, along with the tolerance of SPG to the guests,
measurement and therefore [poly(DPB-(S)Pe)] is unknown.
to p–p* transition of the polymer main chain. These data
indicate that packing and conformation of the polymer main
chain are not twisted in spite of the chiral substituents on
the phenyl-appendages. We assume that tight inter-stranded
4 3 2 6
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 4 3 2 1 – 4 3 2 8

View Article Online
the SPG-templated approach should be a potent one to prepare
nanofibers with other functional polymers.
for C24H24N2O2: C, 77.97; H, 7.05; N, 6.99. Found: C, 77.41; H,
7.16; N, 6.92%; [M + H]+ = 202.12 (calc. 202.11).
Syntheses of 1,4-bis(p-amidophenyl)butadiynes
Experimental
1,4-Bis(p-propionamidophenyl)butadiyne (DPB-Pr). To 1-
propionamido-4-ethynylbenzene (0.40 g, 2.31 mmol) in a mix-
ture of anhydrous pyridine (30 ml) and methanol (50 ml)
copper(II) acetate monohydrate (1.15 g, 5.47 mmol) was added
and then, the resultant mixture was refluxed for 2 days under
nitrogen atmosphere. The resultant reaction mixture was diluted
with ethyl acetate and then, the organic layer was washed
with NH4Cl-saturated aqueous solution. The resultant organic
layer was dried over anhydrous magnesium sulfate, filtrated,
evaporated. The residue was purified on silica-gel (hexane : ethyl
acetate = 5 : 1) to give 1,4-bis(p-propionamidophenyl)butadiyne
General
1H NMR spectra were acquired on a Brucker DRX600 (Brucker
Co., Ltd) in DMSO-d6 at 600 MHz. The chemical shifts
are reported in ppm (d) relative to Me4Si. IR spectra were
recorded on a Perkin Elmer Spectrumone Fourier transform
infrared spectrometer attached to a Universal ATR Sampling
Accessory. Circular dichroism (CD) spectra were measured
on JASCO 720WI Circular Dichroism Spectrometer. Matrix
assisted laser desorption ionization time-of-flight (MALDI-
TOF) mass spectra were recorded on PerSeptive Biosystems
Voyager-DERP Biospectrometry Workstation. Silica gel 60 N
(particle size 40–50 lm) for column chromatography was
purchased from KANTO CHEMICAL Co. INC. Thin layer
chromatography (TLC) was carried out with Merck TLC
aluminium sheets pre-coated with silica gel 60 F254. Native
schizophyllan (Mw = 1.5 × 105) was kindly supplied by Mitsui
SeitoCo. Ltd., (Japan). The other chemicals were purchased
from Aldrich.
1
(0.32 g, 80%) in a pale yellow powder. H NMR (DMSO-d6,
TMS): 10.11 (s, 2H), 7.64 (d, J = 8.70 Hz, 4H), 7.50 (d, J =
8.46 Hz, 4H), 2.36 (m, 4H), 1.07 (s, 6H); IR (KBr, cm−1) 3235,
3080, 2144, 1660, 1588, 1521; [M + H]+ = 344.12 (calc. 344.15).
1,4-Bis(p-sec-butyramidophenyl)butadiyne (DPB-Bu). To 1-
sec-butyramido-4-ethynylbenzene (0.50 g, 2.67 mmol) in anhy-
drous pyridine (50 ml) copper(II) acetate (0.97 g, 5.34 mmol) was
added and then, the resultant mixture was stirred at 50 ◦C for 3 h.
The resultant mixture was diluted with ethyl acetate and then,
the organic layer was washed with water, 1 M HCl (aq.), and
NaHCO3 saturated aqueous solution, repeatedly. The resultant
organic layer was dried over Na2SO4, filtrated, and evaporated
to give the product as pale yellow solid (0.69 g, 99%). 1H NMR
(DMSO-d6, TMS): 10.00 (s, 2H), 7.63 (d, J = 8.64 Hz, 4H), 7.52
(d, J = 8.52 Hz, 4H), 2.61 (m, 2H), 1.10 (d, J = 6.84 Hz, 12H);
IR (KBr, cm−1) 3305, 2150, 1667, 1526; [M + H]+ = 373.18 (calc.
373.18).
Syntheses of 1-amido-4-ethynylbenzenes
1 - Propionamido - 4 - ethynylbenzene. To 4 - ethynylaniline
(0.50 g, 4.27 mmol) and triethylamine (0.5 ml) in dichloro-
methane (30 ml) propionyl chloride (0.45 ml, 5.12 mmol) was
added and then, the resultant mixture was stirred for 5 min.
The resultant mixture was diluted with dichloromethane and
the resultant organic layer was washed with water, dried over
anhydrous magnesium sulfate, filtrated, and evaporated to give
1-propionamido-4-ethynylbenzene as a pale yellow powder
(0.70 g, 94%). 1H NMR (DMSO-d6, TMS): 10.00 (s, 1H), 7.61
(d, J = 8.40 Hz, 2H), 7.40 (d, J = 8.52 Hz, 2H), 4.06 (s,1H),
2.35 (m, 2H), 1.08 (t, J = 7.2 Hz, 3H); IR (KBr, cm−1) 3288,
2977, 2104, 1670, 1597, 1531; Anal. Calcd. for C22H20N2O2: C,
76.72; H, 5.85; N, 8.13. Found: C, 75.90; H, 5.90; N, 7.92%;
[M + Na]+ = 196.06 (calc. 196.07).
1,4-Bis(p-(S)-2ꢀ -methylbutyramidophenyl)butadiyne (DPB-
(S)Pe). To 1 - ( S)-2ꢀ -methylbutyramido-4-ethynylbenzene
(0.10 g, 0.48 mmol) in anhydrous pyridine (15 ml) copper(II)
acetate (0.18 g, 0.98 mmol) was added and then, the resultant
mixture was stirred at 50 ◦C for 3 h. The resultant mixture was
diluted with ethyl acetate and then, the organic layer was washed
with water and 1 M HCl (aq.) repeatedly. The resultant organic
layer was dried over Na2SO4, filtrated, and evaporated to give
1-sec-Butyramido-4-ethynylbenzene. To
4-ethynylaniline
(0.69 g, 5.89 mmol) in anhydrous pyridine (40 ml) isobutyric
anhydride (30 ml) was added and then, the resultant mixture
was stirred for 3 h. The resultant mixture was diluted with ethyl
acetate and then, the organic layer was washed with water, 1 M
HCl (aq.), and NaHCO3 saturated aqueous solution, repeatedly.
The resultant organic layer was evaporated and then, hexane
was added to the resultant syrup. The resultant precipitate was
washed with hexane several times to give the pure product in a
yellow solid (0.75 g, 80%). 1 H NMR (DMSO-d6, TMS): 9.99 (s,
1H), 7.74 (d, J = 8.46 Hz, 2H), 7.39 (d, J = 8.46 Hz, 2H), 4.27
(s, 1H), 2.59 (m, 1H), 1.09 (d, J = 6.60 Hz, 6H); IR (KBr, cm−1)
3316, 2106, 1666, 1530; Anal. Calcd. for C24H24N2O2: C, 77.39;
H, 6.49; N, 7.52. Found: C, 66.80; H, 6.47; N, 7.62%; [M +
H]+ = 188.10 (calc. 188.12).
1
the pure product as pale yellow solid (75 mg, 75%). H NMR
(DMSO-d6, TMS): 10.1 (s, 2H), 7.68 (d, J = 8.64 Hz, 4H), 7.52
(d, J = 8.70 Hz, 4H), 2.40 (m, 2H), 1.61 (m, 2H), 1.39 (m,
2H), 1.08 (d, J = 6.84 Hz, 6H), 0.86 (t, J = 7.44 Hz, 6H); IR
(KBr, cm−1) 3298, 2961, 2144, 1668, 1580, 1506; [M + H]+ =
401.22 (calc. 401.14).
Preparation of SPG–DPB complexes
s-SPG (Mw = 150 kDa) in DMSO (5 mg ml−1, 10 ll) was mixed
with DPBs in DMSO (5 mg ml−1, 10 ll) and then, the resultant
DMSO solution (20 ll) was diluted with an additional DMSO
(180 ll). The resultant DMSO solution (200 ll) was mixed with
water (200 ll) to give aqueous DMSO containing 50 v/v% of
water. This solution still has high DMSO content and, therefore,
DPDs should be loosely accommodated within the partially
renatured helical structure of SPG. The resultant solutions were
then subjected to a sonication (bath-type, ca. 5 min) followed by
mixing with additional water (266 ll) to give DPBs in aqueous
DMSO (water contents are 70 v/v%).
The referential solution using t-SPG was prepared as follows.
s-SPG in DMSO (5 mg ml−1, 10 ll) was diluted with DMSO
(180 ll) followed by mixing with water (200 ll). After a sonica-
tion, the resultant aqueous DMSO ([H2O] = 50 v/v%) was di-
luted with water (266 ll) and aqueous DMSO ([H2O] = 70 v/v%,
1334 ll) followed by incubation at room temperature for
overnight to ensure entire renaturing of SPG. Finally, DPBs in
DMSO (5 mg ml−1, 10 ll) was added into the resultant solution.
1-(S)-2ꢀ-Methylbutyramido-4-ethynylbenzene. To 4-ethynyl-
aniline (0.20 g, 1.7 mmol) and triethylamine (0.56 ml, 4.0 mmol)
in pyridine (20 ml) (S)-(+)-2-methylbutyric anhydride (0.40 ml,
2.0 mmol) was added and then, the resultant mixture was
stirred overnight. The resultant mixture was diluted with
dichloromethane and the resultant organic layer was washed
with water, 1.0 M HCl (aq.) and NaHCO3 saturated aqueous
solution and then, dried over anhydrous magnesium sulfate,
filtrated, and evaporated to give 1-(S)-2ꢀ-methylbutyramido-4-
ethynylbenzene as a pale yellow powder (0.12 g, 36%). 1H NMR
(DMSO-d6, TMS): 10.00 (s, 1H), 7.63 (d, J = 8.70 Hz, 2H), 7.40
(d, J = 8.64 Hz, 2H), 4.06 (s, 1H), 2.40 (m, 1H), 1.60 (m, 1H),
1.39 (m, 1H), 1.07 (d, J = 6.78 Hz, 3H), 0.85 (t, J = 7.34 Hz,
3H); IR (KBr, cm−1) 3292, 2963, 2105, 1771, 1506; Anal. Calcd.
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 4 3 2 1 – 4 3 2 8
4 3 2 7

View Article Online
Photo-mediated polymerization of SPG–DPB complexes
and C. E. Evans, Adv. Mater., 1999, 11, 131; K. C. Lim, C. R. Fincher,
Jr. and A. J. Heeger, Phys. Rev. Lett., 1983, 50(24), 1934–7.
5 M. Masuda, T. Hanada, K. Yase and T. Shimizu, Macromolecules,
1998, 31, 9403; T. Aida and K. Tajima, Angew. Chem., Int. Ed., 2001,
40, 3803.
Photo-mediated polymerization of SPG–DPB complexes was
carried out by using UVL-100P (Riko Kagaku Sangyo Co.
Japan) with a distance of 5 cm from the samples.
6 A. Bot, H. E. Smorenburg, R. Vreeker, M. Paques and A. H. Clark,
Carbohydr. Polym., 2001, 45, 363; H. Saito, Y. Yoshioka, N. Uehara,
J. Aketagawa, S. Tanaka and Y. Shibata, Carbohydr. Res., 1991, 217,
181.
7 T. Yanaki, T. Norisuye and H. Fujita, Macromolecules, 1980, 13,
1462; T. Norisuye, T. Yanaki and H. Fujita, J. Polym. Sci., Polym.
Phys. Ed., 1980, 18, 547; C. T. Chuah, A. Sarko, Y. deslandes and
R. H. Marchessault, Macromolecules, 1983, 16, 1375.
Acknowledgements
This work was supported by the Japan Science and Technology
Agency, SORST Program. We also thank Mitsui Seito Co.,
Japan, for providing native SPG.
8 K. Sakurai, K. Uezu, M. Numata, T. Hasegawa, C. Li, K. Kaneko
and S. Shinkai, Chem. Commun., 2005, 35, 4383.
References
1 J. G. Park, G. T. Kim, V. Krstic, S. H. Lee, B. Kim, S. Roth, M.
Burghard and Y. W. Park, Synth. Met., 2001, 119, 469; T. Miyagawa,
A. Furuko, K. Maeda, H. Katagiri, Y. Furusho and E. Yashima,
J. Am. Chem. Soc., 2005, 127, 5018.
2 J. Kim, I. A. Levitsky, D. T. McQuade and T. M. Swager, J. Am.
Chem. Soc., 2002, 124, 7710; A. Kokil, P. Yao and C. Weder,
Macromolecules, 2005, 38, 3800; U. H. F. Bunz, Acc. Chem. Res.,
2001, 34, 998; J. J. Lavigne, D. L. Broughton, J. N. Wilson, B. Erdogan
and U. H. F. Bunz, Macromolecules, 2003, 36, 7409; M. D. Disney, J.
Zheng, T. M. Swager and P. H. Seeberger, J. Am. Chem. Soc., 2004,
126, 13343.
3 M. Joergensen, K. Bechgaard, P. Bjoernholm, P. Sommer-Larsen,
L. G. Hansen and K. Schaumburg, J. Org. Chem., 1994, 59, 5877.
4 K. Morigaki, T. Baumgart, U. Jonas, A. Offenhausser and W. Knoll,
Langmuir, 2002, 18, 4082; M. Niwa, S. Shibahara, N. Higashi and
J. Mater, Chem., 2000, 10, 2647; H. Menzel, M. D. Mowery, M. Cai
9 M. Numata, M. Asai, K. Kaneko, T. Hasegawa, N. Fujita, Y. Kitada,
K. Sakurai and Seiji Shinkai, Chem. Lett., 2004, 232; T. Hasegawa,
T. Fujisawa, M. Numata, M. Umeda, T. Matsumoto, T. Kimura,
S. Okumura, K. Sakurai and S. Shinkai, Chem. Commun., 2004,
2150; M. Numata, M. Asai, K. Kaneko, A.-H. Bae, T. Hasegawa, K.
Sakurai and S. Shinkai, J. Am. Chem. Soc., 2005, 127, 5875.
10 M. Numata, T. Hasegawa, T. Fujisawa, K. Sakurai and S. Shinkai,
Org. Lett., 2004, 6, 4447.
11 A.-H. Bae, M. Numata, T. Hasegawa, C. Li, K. Kaneko, K. Sakurai
and S. Shinkai, Angew. Chem., Int. Ed., 2005, 44, 2030.
12 T. Hasegawa, T. Fujisawa, M. Numata, C. Li, A.-H. Bae, S.
Haraguchi, K. Sakurai and S. Shinkai, Chem. Lett., 2005, 34, 1118.
13 Preliminary communication:T. Hasegawa, S. Haraguchi, M. Nu-
mata, T. Fujisawa, C. Li, K. Kaneko, K. Sakurai and S. Shinkai,
Chem. Lett., 2005, 34, 40.
14 E. Shirai, Y. Urai and K. Itoh, J. Phys. Chem. B, 1998, 102, 3765.
4 3 2 8
O r g . B i o m o l . C h e m . , 2 0 0 5 , 3 , 4 3 2 1 – 4 3 2 8