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Fig. 23
Selective vapor transport with a cross-linked Q
I
-phase LLC-BR membrane (
gray
areas
= hydrophobic organic domains;
white areas
= aqueous domains). Reproduced with
permission from [170]. © 2006 by Wiley-VCH
A follow-up study demonstrated that Q
I
phases further enhance the per-
formance of LLC-BR composite membranes in both water transport and
harmful chemical vapor rejection [170]. A cross-linkable, gemini phospho-
nium amphiphile (Fig. 23) was blended with BR and cross-linked to form
films exhibiting a Q
I
-phase nanostructure. Materials with a Q
I
-phase showed
300 times greater water vapor permeability and 500 times greater permea-
bility selectivity for water/CEES than pure cross-linked BR. Furthermore,
these Q
I
-phase composite films were far superior to their H
II
and L ana-
logues in both water vapor permeability and water/CEES transport selectivity.
Further studies were planned to process thinner films as well as test their
rejection properties against other types of chemical agents.
The use of LLC-based membrane systems is still in its infancy. Promising
early results indicate that research in this field will be expanded. The appli-
cations outlined here are just a few where functional LLC materials might
be implemented. More challenging separation materials, such as water de-
salination membranes, selective proton-conducting membranes for fuel cells,
catalytic membranes, chromatography, and chiral separation media are per-
haps future candidates for new LLC membrane materials.
7
Summary and Future Directions
Functional LLC systems offer great promise to revolutionize materials sci-
ence. The applications outlined herein have thus far received the most atten-
tion from researchers. The future of LLCs and LLC-based materials will not be
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