Self-assembling structures of long-chain phenyl glucoside influenced by the introduction of double bonds

Article abstract of DOI:10.1021/ja020752o

Four long-chain phenyl glucoside amphiphiles possessing a saturated or unsaturated long alkyl chain group as the self-assembling unit of a highly organized molecular architecture were synthesized. Their self-assembling properties were investigated by EF-T

Full text of DOI:10.1021/ja020752o

Published on Web 08/16/2002
Self-Assembling Structures of Long-Chain Phenyl Glucoside Influenced by
the Introduction of Double Bonds
†
†
‡
,†,‡
Jong Hwa Jung, George John, Kaname Yoshida, and Toshimi Shimizu*
CREST, Japan Science and Technology Corporation (JST), Nanoarchitectonics Research Center (NARC),
National Institute of AdVanced Industrial Science and Technology (AIST), Tsukuba Central 4,
-1-1 Higashi, Tsukuba, Ibaraki 305-8562, Japan, and Nanoarchitectonics Research Center (NARC),
1
National Institute of AdVanced Industrial Science and Technology (AIST), Tsukuba Central 5, 1-1-1 Higashi,
Tsukuba, Ibaraki 305-8565, Japan
Received May 28, 2002
Self-assembled nanostructures of amphiphiles held together by
noncovalent interactions are currently the focus of interest due to
their potential application in controlled release, electroactive
composites, and multifunctional materials.1 Literature study
-7
1,7
reveals that tube-forming amphiphiles which mediated helical ribbon
require unsaturation in the lipophilic moiety to impart a bent
structure, leading to the induction of the supramolecular chirality,
although the evidence is limited.
Fuhrhop and co-workers have mainly studied morphologies of
amphiphiles affected by the introduction of different hydrophilic
parts such as glucose-, galactose-type sugar, noncyclic-sugar
moieties, and amino acids.7 However, there have never been any
systematic studies on the influence of unsaturation, that is, the
number and the position of the double bond units, or on the self-
assembly of synthetic amphiphiles into high-aspect-ratio nanostruc-
tures (HARNs) based on solid chiral bilayers, even though the
tubular structure of amphiphiles was already reported by several
groups.1 We herein report the self-assembly of a series of long-
chain phenyl glucosides 1-4 varying in number of cis double bonds
a-b
,5,7
(0-3) in the lipophilic part. We studied their influence on the final
morphologies by energy-filtering transmission electron microscopy
(EF-TEM), SEM, CD, FT-IR, and XRD.
Compounds 1-4 were synthesized according to a similar method
reported previously (Supporting Information).2d The gel-to-liquid
crystalline phase transition temperature of the hydrated matrix lipids
2-4 is found to be 90.0, 65.2, and 50.1 °C, respectively, showing
40-70 °C higher values as compared with those of related
glucopyranosides 6-8 lacking the amide group (Supporting
Information).6b This situation enables us to compare self-assembled
morphologies from 1-4 in a solid state. To date, no systematic
self-assembly study using multiple components 5-8 with unsatur-
ated bonds was achieved because the diene and triene derivatives
Figure 1. EF-TEM and SEM pictures of the self-assembled (a) 2, (b and
c) 3, and (d, and e) 4.
micrometers of length (Figure 1a), whereas 3 shows the left-handed
coiled tube with 150-200 nm inner diameters and ca. 20 nm of
wall (Figure 1b, less than 5%), and the helical ribbon (Figure 1c,
Supporting Information) structures as the major morphology,
showing the influence of double bonds on the final morphology of
the self-assembled structures.
7
and 8 are existing as liquid crystals at room temperature.
The self-assembly of the matrix lipids 1-4 occurred rapidly
under mild conditions. For example, 30 min of vortexing at 100
°C and 5 h of room-temperature incubation were sufficient to ensure
On the other hand, compound 4 possessing three cis double bonds
in the lipophilic region displays the helical ribbon morphology with
the formation of stable supramolecular assemblies in aqueous
solutions for 2-4. However, 1 was insoluble in water and only
formed a typical nanofiber structure with 100-350 nm diameters
and several micrometers of length in a mixture of water and
methanol (1:1 v/v). Figure 1 displays SEM and TEM images of
the self-assembled 2-4 in aqueous solutions. Compound 2 shows
the twisted fiber structure with 50-200 nm widths and several
80-100 nm of outer diameters and the nanotubular structure as
the major morphology with ca. 70 nm of inner diameters and a
wall thickness of 20-30 nm (Figure 1d and 1e, Supporting
Information). As far as can be determined, all chiral structures
possess a left-handed helical motif. These observations support the
view again that the unsaturated units are important to produce
nanotubes by self-assembly.
*
To whom correspondence should be addressed. Fax: +81-298-61-2659.
E-mail: tshmz-shimizu@aist.go.jp.
As alternative evidence for the nanotube formation of 3 and 4
in the microscopic structural view, we carefully observed CD
†
CREST.
NARC.
‡
10674
9
J. AM. CHEM. SOC. 2002, 124, 10674-10675
10.1021/ja020752o CCC: $22.00 © 2002 American Chemical Society

C O MMU N I C A T I O N S
Figure 2. CD spectra of the self-assembled (a) 2, (b) 3, (c) 4 at 25.0 °C,
(d) 3, and (e) 4 at 70.0 °C, respectively.
between lipophilic groups, which lead to the formation of the
nanotubular structure.
spectra of the self-assembled 2-4, as shown in Figure 2. CD spectra
of the self-assembled 3 and 4 in aqueous solutions show a strong
negative band at 225 and 237 nm, respectively, forming nanotubular
structures by chiral assembling, while they show only a weak CD
signal at temperatures above a phase transition temperature (Figure
In addition, 2 shows a highly ordered structure in the aliphatic
region, possibly due to hydrocarbon crystallization, further sup-
ported by Fourier transform infrared (FT-IR) spectroscopy studies
-1
-1
of the C-H stretching values at 2855 cm of 3-4, and 2851 cm
for 2. It is reasonable to argue that the lipophilic group of 3 and 4
possessing three cis double bonds formed a much more disordered
structure than that of 2. Also, CdO (amide I) stretching patterns
of the three compounds 2, 3, and 4 are different: 3 and 4 appeared
2
and Supporting Information) and shifted to longer wavelength,
which is probably composed of monomers or small lipid aggregates,
such as micelles or vesicles. The CD signal, however, became strong
again when the lipid self-assembled to form a nanotubular structure
after several hours. On the other hand, the CD spectrum of the
self-assembled 2 in aqueous solution shows a much weaker negative
band in comparison to 3 and 4, suggesting that the self-assembled
-
1
-1
at 1649 cm , whereas 2 appeared at 1656 cm , suggesting that 3
and 4 maintain a well-ordered structure of glucopyranoside head-
groups by the intermolecular hydrogen-bonding interaction between
amide groups.
2
forms a disordered chiral packing structure. The CD results
In conclusion, the present study has demonstrated that long-chain
phenyl glucoside formed twisted nanofiber, helical ribbon, and
nanotubular structures depending on the unsaturation of the double
bonds. These results are the first example for the systematic study
on the influence of cis double bond units in the hydrophobic portion
on self-assembled morphologies.
provide direct evidence for chiral molecular architecture in nanotube
and that the molecular packing of 3 and 4 is loosely chiral at
temperatures above the phase transition temperature. Furthermore,
phase transition temperatures of 3 and 4 are much higher than those
of glucoside amphiphiles 6-8 lacking the amide group,6b indicating
that the stabilization of self-assembled tubes 3 and 4 was enhanced
by mainly an intermolecular hydrogen-bonding interaction between
the amide groups. In addition, the contribution of linear dichroism
Supporting Information Available: Synthetic scheme for com-
pounds 1-4, phase transition temperature and IR results, SEM and
TEM pictures of the self-assembled 2-4, possible self-assembled
molecular packing structures (PDF). This material is available free of
charge via the Internet at http://pubs.acs.org.
(LD) for the self-assembled samples is negligible using the
conventional LD mode.
What would be the difference in the molecular packing structure
between the nanotubes from 3 and 4 and the twisted fiber from 2?
First, the molecular length of three amphiphiles was calculated by
CPK modeling on the basis of single crystalline data of oleic acid,
References
(
1) (a) Hartgerink, J. D.; Beniash, E.; Stupp, S. I. Science 2001, 294, 1684.
b) Stupp, S. I.; LeBonheur, V.; Walker, K.; Li, L. S.; Huggins, K. E.;
(
8
linoleic acid, and linolenic acid. They showed almost similar values
Keser, M.; Amstutz, A. Science 1997, 276, 384. (c) Song, J.; Kopta, S.;
Stevens, R. C. J. Am. Chem. Soc. 2001, 123, 3205. (d) Schnur, J. M.;
Ratna, B. R.; Selinger, J. V.; Singh, A.; Jyothi, G.; Easwaran, K. R. K.
Science 1994, 264, 945. (e) Schnur, J. Science 1993, 262, 1669.
despite the bending effect. Second, X-ray diffraction patterns were
measured. The small-angle diffraction patterns of the nanotubes 3
and 4 showed at least four ordered reflection peaks with a long
period of 4.62 nm, which is smaller than twice the extended
molecular length of 3 (3.15 nm by the CPK molecular modeling)
and 4 (3.02 nm), but larger than the length of one molecule. These
results strongly suggest that the self-assembled 3 and 4 form a
bilayer structure with a relative small region interdigitated by a
hydrophobic interaction (Support Information). On the other hand,
the diffraction diagram of the microcrystalline solid 2 (one
molecular length: 3.03 nm) formed a bilayer structure with 3.59
nm, supporting that 2 maintains a much stronger interdigitated
bilayer structure between lipophilic regions than those of 3 and 4.
According to CD and powder X-ray diffraction results, the relatively
strong intermolecular hydrogen-bonding interaction of an glucopy-
ranoside moiety of 3 and 4 provided a highly ordered chiral packing
structure even though they form a weak hydrophobic interaction
(
2) (a) Gronwald, O.; Shinkai, S. Chem.-Eur. J. 2001, 7, 4329. (b) Sakurai,
S.; Shinkai, S. J. Am. Chem. Soc. 2000, 122, 4520. (c) Yoza, K.;
Amanokura, N.; Ono, Y.; Akao, T.; Shinmori, H.; Takeuchi, M.; Shinkai,
S.; Reinhoudt, D. N. Chem.-Eur. J. 1999, 5, 2722. (d) Amanokura, N.;
Kanekiyo, Y.; Shinkai, S.; Reinhoudt, D. N. J. Chem. Soc., Perkin Trans.
2
1999, 1995.
(
3) (a) Menger, F. M.; Littau, C. A. J. Am. Chem. Soc. 1991, 113, 1451. (b)
Menger, F. M.; Caran, K. L. J. Am. Chem. Soc. 2000, 122, 11679.
4) (a) Engelkamp, H.; Middelbeck, S.; Nolte, R. J. M. Science 1999, 284,
785. (b) Hafkamp, R. J. H.; Feiters, M. C.; Nolte, R. J. J. Org. Chem.
(
1999, 64, 412.
(
5) Nakashima, N.; Asakuma, S.; Kunitake, T. J. Am. Chem. Soc. 1985, 107,
509.
(
6) (a) Shimizu, T. Macromol. Rapid Commun. 2002, 23, 311. (b) John, G.;
Masuda, M.; Okada, Y.; Yase, K.; Shimizu, T. AdV. Mater. 2001, 13,
715.
(
7) (a) Boettcher, C.; Schade, B.; Fuhurhop, J.-H. Langmuir 2001, 17, 873.
(
b) Fuhrhop, J.-H.; Helfrich, W. Chem. ReV. 1993, 93, 1565. (c) Frankel,
,
D. A.; O Brien, D. F. J. Am. Chem. Soc. 1991, 113, 7436.
(
8) Ernst, J.; Sheldrick, W. S.; Fuhrhop, J.-H. Z. Naturforsch. 1979, 34b, 706.
JA020752O
J. AM. CHEM. SOC.
9
VOL. 124, NO. 36, 2002 10675