Supra-Amphiphiles for Controlled Self-Assembly and Disassembly - Molecular Self-Assembly: Advances and Applications - page 211

decomposes into nonamphiphilic components, resulting in the
disassembly of the aggregates and release of guest molecules. When
the pH changes back to 7.4, the benzoic-imine bond is re-formed and
aggregation is recovered. Since the disassembly occurs at pH 6.5, near
the extracellular pH of tumor cells, the supra-amphiphile is expected to
find potential application in drug delivery and cancer therapy [25].
Two important features of noncovalent interactions and
DCB should be noted. One is that the strength of the noncovalent
interactions and DCB can be well controlled by the rational design
of the donors and the acceptors. Therefore, the stability of the supra-
amphiphiles can be tuned for different purposes. The other is that
the noncovalent interactions and DCB are dynamic. Most of the
noncovalent interactions and DCB are very sensitive to environmental
stimuli, endowing the supra-amphiphiles with stimuli-responsive
properties.

6.3 The Architectural Engineering of Supra-

Amphiphiles

The architectures of supra-amphiphiles are various. They can be
low-molecule-weight or polymeric. Some of the architectures exist in
conventional amphiphiles, and some of them can never be realized for
conventional amphiphiles. For example, bolaform amphiphiles refer
to bola-amphiphilic molecules containing a hydrophobic skeleton
and two water-soluble groups on both ends. To fabricate a bolaform
supra-amphiphile, we have designed and synthesized an amphiphile
that contains an electron donor at one end (PYR) of the molecule,
which will pair with an acceptor in another molecule (DNB) [15].
PYR and DNB can preassemble in THF to form a bolaform supra-
amphiphile, driven by the charge transfer interactions between the
electron donors and acceptors (see Fig. 6.4). In detail, the PYR-DNB
complex was prepared by mixing PYR and DNB with a molar ratio of
2:1 in THF, which was a good solvent for both PYR and DNB. Then, the
solvent was removed under reduced pressure. This procedure was
repeated for three times to ensure complete complexation and the
resultant complex was finally dried at room temperature in vacuum.
Interestingly, the preassembled complex could readily disperse
in water, yielding a yellow transparent solution which was stable
for months. As DNB alone cannot disperse in water, the observed