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having hydrophilic and hydrophobic domains, can segregate guest molecules
into the domain these guests most prefer. Once the guests are localized into
the domain of preference, they can be chemically manipulated (e.g., polymer-
ized, solidified) within the confines of the nano-environment that the LLC
phase provides. Thus, materials with no intrinsic self-assembling properties
can be organized into nanostructures that are often an exact replica of the
LLC phase template. These guests can be inorganic or organic molecules, and
are usually materials whose bulk properties benefit from being nanostruc-
tured (e.g., semiconductors, conductors, catalysts) but are unable to organize
themselves. Also, it has been proposed that these templated nanostructured
and nanocomposite materials may have unique and enhanced properties over
either of the individual components.
2.1
Direct Templating of Nanostructure in Inorganic Materials
Surfactant-templated formation of mesostructures in silica and other inor-
ganic materials is a rapidly growing field, and has been recently reviewed [26-
31]. Low surfactant concentrations (e.g., 0.1 M) lead to phases where micelles
and microemulsions dominate, from which the inorganic materials are tem-
plated via a co-assembly process. The surfactants by themselves, at those
low concentrations, do not form LLC mesophases. Typically, there are non-
covalent interactions between the surfactant and inorganic precursor that
result in the ordered co-assembly. On the other hand, high surfactant con-
centrations (e.g., 50 wt %) lead to LLC phases without the co-assembly, which
is the focus of this review and this section. This method is often called
“the direct templating method” or “nanocasting” because the replica is of-
ten a close-to-perfect copy of the template (Fig. 5) [32]. It has the advantage
of yielding mesostructures with predicable geometry and pore size. This is
typically accomplished by starting from a LLC phase, and then the liquid
continuous phase is simply solidified by some chemical or electrochemical
reaction. One can tailor the pore size by changing the tail length of the am-
phiphile, or tailor the architecture by changing the LLC phase (e.g., L, H, I,
and Q phases). Thus, this method offers enormous potential for control over
the geometries of these nanostructures. In the majority of the literature in
this area, the function of the LLC phase is to direct or template the organi-
zation of another material. Often this second material introduces additional
useful properties into the system, rather than the LLC system having addi-
tional functional properties. After solidification of this secondary material,
the LLC component is typically removed to allow access to the interior of
these mesoporous structures.
The first example of this method was reported in 1995, where silica
mesostructures were produced as a near-exact negative copy of the LLC
(H
I
phase) template [33]. As an indication of the versatility of this method,
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