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engineering for well-defined nanostructures. This kind of directional
noncovalent interactions provide a great potential for the proper
design of supra-amphiphiles with desired topologies, thus leading
to the further development of supramolecular engineering.
Some of the architectures can never be realized in conventional
amphiphiles, such as rotaxane-type supra-amphiphile. To be more
detailed, an amphiphile-bearing azobenzene group and cyclodextran
are chosen as building blocks for the supra-amphiphiles (see Fig. 6.5)
[8]. In water, upon UV irradiation, the cyclodextran can slip reversibly
between the alkyl chains and azobenzene groups, functioning as a
molecular shuttle. The amphiphilicity of the supra-amphiphile can
be switched from more hydrophilic to more hydrophobic, leading to
self-assembly and disassembly in a controlled manner. The magic
of supra-amphiphile is: using limited building blocks, it seems that
we can create infinite supra-amphiphiles with various topologies,
greatly enriching the traditional colloid sciences.
Figure 6.5
Rotaxane-form
supra-amphiphile
based
on
host-guest
interaction.
Reproduced
with
permission
of
Ref.
[8].
Copyright 2007, Wiley-VCH Verlag GmbH & Co. KGaA.
6.4
Responsive Supra-Amphiphiles
As mentioned previously, functional moieties, such as stimuli-
responsive groups, can be attached to the supra-amphiphiles by
noncovalent interactions. Moreover, the noncovalent interactions
or DCB are sensitive to environmental stimulus themselves.
Therefore, supra-amphiphiles are the perfect building blocks for the
construction of responsive soft materials.
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