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2010 American Chemical Society
Fabrication of Nanotubules and Microspheres from the Self-Assembly
of Amphiphilic Monochain Stearic Acid Derivatives
†
†
†
‡
,†
Lidong Zhang, Haiqing Li, Chang Sik Ha, Hongsuk Suh, and Il Kim*
†
The WCU Centre for Synthetic Polymer Bioconjugate Hybrid Materials,
Department of Polymer Science and Engineering and Department of Chemistry and
Chemistry Institute for Functional Materials, Pusan National University, Pusan 609-735, Korea
‡
Received July 2, 2010. Revised Manuscript Received October 4, 2010
A series of amphiphilic monochain derivatives of stearic acid, CH (CH ) CONH(CH ) NH (n = 2, 3, 4, 6),
3
2 16
2 n
2
CH
3
(CH
2
)
16CONH(CH
2
)
2
S
2
(CH
2
)
2
NH
2
, and [CH
3
(CH
2
)
16CONH]
2
2 2
(CH ) , are synthesized, and their self-assembly
behaviors have been investigated in 1,2-dichloroethane (DCE). In addition to the concentration of the compound in
DCE, the number of methylene units in hydrophilic segments play a crucial role in determining the final morphology of
self-assembling structures from nanotubules with 20 nm inner diameter to microspheres with an average diameter of 20 μm.
The external texture of the microsphere is also influenced by the number of methylene units in the hydrophilic segment.
The microspheres formed by highly ordered aggregattion of nanobelts show high thermal stability. The particular
processes and causations have been expatiated.
1
4,15
Introduction
similar works have been reported by previous researchers;
however, it is still attractive to continue this study more deeply
with simple monochain molecules because of some ambiguous
issues for the formation of nanotubular structure, such as the
control of dimension of tubular structure, concentration effect, and
achievement on the monodispersity of nanotubules for diversified
molecular structures.
Supramolecular nano- or microinerratic structures coming
from the self-assembly of low-molecular-mass monochain deri-
vatives has attracted much interest because of their potential
applications in materials science and supramolecular chemistry,
1-4
involving nanomaterials and delivery or modification agents for
5-8
drugs. In general, those monochain derivatives can self-assemble
1
9,10
The design and synthesis of novel morphology structure has
been an important starting point because nanoscale size, shape,
and morphology determine the properties of self-assembled supra-
molecular structure from the monochain derivatives. The hier-
archical self-assembly of nanoscale building blocks can lead to the
into aggregates of various morphologies, such as belts, tubes,
1
1,12
13
ribbons,
and fibers through hydrogen bonding, π-π stack-
ing, van der Waals interaction, coordination interaction, and other
weak interactions. Some attempts have been made to correlate the
properties of the structures of supramolecular nano- or micro-
inerratic structure. Nevertheless, to date, in contrast with large
numbers of reports on morphologies such as ribbon and fibers
forming from the self-assembly of low-molecular-mass mono-
chain derivatives, spherical structures with mesoporous surface for
the more effective applications of delivery or modification agents
for drugs have been investigated very little. To the fabrication of
tubular structure with greatly simple monochain molecules, some
1
6-18
formation of complex supramolecular assemblies.
Inspired by the reported results, we have synthesized a series
of low-molecular-weight monochain derivatives of stearic acid.
Although lots of compounds derived from stearic acid have been
19-22
synthesized, especially for various commercial applications,
to the best of our knowledge, the low-molecular-mass monochain
derivatives of stearic acid forming hollow microspheres and nano-
tubules are not reported. It is well feasible that the chiral mono-
chain derivatives with a diacetylenic segment and a secondary
*To whom correspondence should be addressed. E-mail: ilkim@pusan.ac.kr.
amine salt headgroups could self-assemble to form uniform nano-
Tel: þ82-51-510-2466. Fax: þ82-51-513-7720.
23,24
tubules in dichloromethane and hexane.
However, fabrication
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1
(
1
7890 DOI: 10.1021/la103480p
Published on Web 11/04/2010
Langmuir 2010, 26(23), 17890–17895