Chemistry Reference
In-Depth Information
L phase materials formed by combining a conventional RTIL with an am-
phiphilic LC mesogen has been found to have ca. three orders of magnitude
higher ionic conductivity parallel vs. perpendicular to the lamellae [88]. Simi-
lar anisotropic ion conductivity results have also been obtained with L phases
of imidazolium-based amphiphiles and also hydroxyl-terminated fluorinated
surfactants formed by mixing with imidazolium-based RTILs (Fig. 12) [89, 90].
3.2
Electrically Conducting LLC Materials
LLC systems incorporating materials that conduct electrons instead of salt ions
or protons have been investigated for electrically conducting materials. As de-
scribed previously in Sect. 2 of this review, LLC phases in non-polymerized
and polymerized form have been used as nanostructured organic templates
to define the growth of electrically conducting materials such as metals,
semiconductors, and conducting organic polymers in the hydrophilic do-
mains [40-51, 64-69]. This approach affords both structural replicas and LLC
nanocomposites containing electrically conductive nanowires and nanopar-
ticles as functional fillers. However, although functional properties such as
optical and catalytic properties have been measured for these materials, the
bulk electrical conductivity of only a few of these materials has been measured.
In addition to templated electrical conductor formation, LLCs have been
used in another way to make nanostructured electrically conductive mater-
ials. Several acidic surfactant molecules have been used to dope, encapsu-
late, and order the conducting polymer, polyaniline, to form nanostructured
LLC-conducting polymer nanocomposites. Recently, a bicontinuous cubic
phase was utilized as a templated scaffolding for the in situ polymeriza-
tion of an acidified, monomeric solution of aniline [91]. The cubic phase
was comprised of 55%surfactantof(EO)
10
nonyl phenol ether, 22%oc-
tane, and 23% of aqueous solution with monomer and initiator. The material
was successfully polymerized and formed the emeraldine salt, although no
conductivity testing was completed. Furthermore, materials such as dodecyl-
benzenesulfonic acid (DBSA) [92, 93], 1,2-benzenedicarboxylic acid, 4-sulfo,
1,2-di(2-ethylhexyl)ester [94],
n
-octyl- and
n
-hexyl phosphonic acid [95],
3-pentadecylphenylphophonic acid [96], and 3,4,5-tris(dodecyloxy)phenyl-
methylphosphonic acid [97] have all been used to protonate polyaniline into
its electrically conducting form and simultaneously generate L phases via
the resulting LLC-polyaniline salt complexes (Fig. 13). In these systems, only
DBSA and 3,4,5-tris(dodecyloxy)phenylmethylphosphonic acid have intrin-
sic LLC properties on their own. The rest of the systems could only form
LLC phases after salt formation with polyaniline. The measured bulk elec-
trical conductivities of these LLC-polyaniline complexes were found to range
from 10
1
Scm
-1
for the DBSA complexes to ca. 10
-5
Scm
-1
for the 3,4,5-
tris(dodecyloxy)phenylmethylphosphonic acid complex.
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