Chemistry Reference
In-Depth Information
There are several key aspects of the transfer kinetics between ISAsomes:
1. New ISAsomes have been created with new structures, without the aid
of additional energy, such as ultrasonication, shearing, or vortexing,
which is generally required for the (initial) production of ISAsomes. In
contrast, the energy involved here arises simply from entropy-driven
events, albeit without destroying the ISAsome signatures.
2. No coalescence or uncontrolled aggregation was observed during the
mixing of two different LC nanostructured ISAsomes, despite the fact
that they are all involved in transferring their internal material to each
other and in equilibrating to the new type of LC-nanostructured ISA-
somes. Strong evidence for this is that the sizes of the initial and fi nal
ISAsomes were practically the same (
2 nm).
3. The transfer — and thus the equilibration — of the systems was relatively
fast (
±
2 h). This is astonishing given that the equilibration of lyotropic
phases, especially viscous cubic phases (e.g., Pn3m), takes much longer,
from hours to days.
4. The transfer behavior is universal with regard to the type of internal
nanostructure of ISAsomes.
5. Rather than random mixing of components, the transfer events occur
quite monotonically, as indicated by the fi rst-order kinetics of the trans-
fer (Fig. 6.7), and the dependence of the kinetics on the type of compo-
nent (Fig. 6.8). Thus, it was possible to control the transfer rates by
changing: (a) the carbon-chain length of oils (
n
- alkanes), (b) the concen-
tration of additional stabilizer (F-127,) and (c) the type of primary
ISAsome nanostructure (including EME). Currently, we are studying the
effects of arrested dynamics of ISAsomes in hydrogels and the effects of
stabilizer type on the rate of material transfer in ISAsomes.
6. Transfer of the hydrophobic material, that is, oil or lipid molecules (or
both), occurs through the aqueous medium. We speculate that these
hydrophobic molecules are transported preferentially via free F-127
micelles, which act as shuttles between the two different nanostructured
ISAsomes until they equilibrate into the average nanostructure, as estab-
lished by the temperature-composition phase diagram of the lipid and
the oil. We are currently investigating the transfer kinetics of surfactant-
free systems (i.e., Pickering emulsions) to provide evidence for this
hypothesis.
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The overall transfer kinetics among the ISAsome systems could function
as a potential microlaboratory in which it is possible to perform controlled
reactions that are otherwise too complex to follow. For instance, components
A and B could be loaded into two different ISAsomes, which would allow
slow, controlled, molecular-level transfer, and subsequent contact between
them for further reaction. This may prove advantageous for exothermic
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