Chemistry Reference
In-Depth Information
Figure 6.15
Rehydration of hydrogel fi lms to restore ISAsomes. (a) Thick solid curve
shows a broad peak from the L
2
nanostructure formed due to water loss from the H
2
-
nanostructured ISAsomes. Rehydration of the KC fi lm leads to restoration of H
2
nanostructure, indicated by the sharp peak. The H
2
nanostructure remains essentially
the same size upon hydration (as shown by the dotted line; lattice parameter 6.49 nm)
as it is in the loaded gel (thin curve with lower intensity). (b) The intensity of the fi rst
peak of the H
2
nanostructure [from (a)] plotted against fi lm hydration time. The absorp-
tion of water to restore H
2
nanostructure is very fast (300 s; fi rst point) and is complete
in about 900 s, after which there is very little change in the peak intensity. (c) The
upward and downward temperature scans on partially hydrated KC fi lm show ther-
moreversibility with respect to the nanostructural dimensions of the ISAsomes (6.49 nm
at 25°C, 5.93 nm at 45°C, and 5.53 nm at 65°C). (d) Resolubilization and dilution studies
by DLS indicate that the ISAsomes stay practically intact (with respect to their size)
during their entrapment and immobilization in gel and fi lm.
particulate (colloidal) form. However, it is also possible to form reverse (W/O)
emulsions, where the dispersed phase is water and the continuous phase can
be various LC phases (Caldero et al., 2009; Solans and Esquena, 2008; Solans
et al., 2001, 2003). These are usually concentrated emulsions,
5
the stability of
which is also usually governed by an external stabilizing agent. However, we
5
Concentrated emulsions are either stable due to emulsion stabilizer or due to a very high con-
centration of internal phase or both. When the dispersed phase is above 74%, they are called
HIPRE (high internal phase ratio emulsions) or HIPE (high internal phase emulsions), or alter-
natively gel emulsions or bi-liquid foams.
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