True liquid crystal templating

The three major routes are (i) true liquid crystal templating at high surfactant concentrations, which is used for the formation of monoliths, thick layers or, via electrodeposition techniques, formation of thin films (ii) cooperative self assembly at surfactant concentrations where micelles are present in solution, which can be used to make powders (with either well-defined particle shapes or random structures), fibres and thin films grown at interfaces from solution and (iii) EISA at very low surfactant concentrations, where no micelles are initially present in solution, and solutions are in general prepared in nonaqueous solvents. This route is used to prepare thin films by dip or spin coating and powders via aerosol routes. The following sections will look at the current understanding of the mechanisms involved in each route to mesoporous materials. 

True liquid crystal templating refers to the replication of a high concentration water-surfactant phase in silica. It is also sometimes 

The advantage of this high surfactant concentration method is that the nanostructure obtained in the final materials matches that of the initial 

A variation on true liquid crystal templating is the vapour phase synthesis route reported by Tanaka et where the silica pre- 

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In-depth investigations into the formation process of these composite materials— which can be rightly called complex—have found that two different mechanisms can be involved On one hand, in true liquid-crystal templating (TLCT), the concentration of the surfactant is so high that under the prevailing conditions (temperature, pH) a... 

Figure 3.4 Formation of mesoporous materials by structure-directing agents (a) true liquid-crystal template mechanism, (b) cooperative liquid-crystal template mechanism.

Two kinds of template, viz. hard template and soft template, are usually available for nanocasting processes. The true liquid crystal templating synthesis can be considered a soft-template process. In general, the hard template means an inorganic solid. For example, mesoporous silica as a template to replicate other materials, such as carbon or metal oxides, by which the pore structure of the parent can be transferred to the generated porous materials. A 3-D pore network in the template is necessary to create a stable replica. Mesoporous silica and carbon are commonly used templates for nanocasting synthesis. 

Pre-formed surfactant assembfy ROUTE II True Liquid Crystal Templating... 

Five specific routes to mesoporous templated materials exist, although only three of these are used to prepare mesoporous silicates. These are true liquid crystal templating, cooperative self-assembly in solution and... 

True Liquid Crystal Templating and Eyaporation-induced Mesostructure Formation Non-silica Mesoporous Solids... 

Multimodal porous systems in the form of monolithic-shaped forms (bodies) were obtained from a process where a (true) liquid-crystal templating is combined with a sol-gel process [205]. One characteristic of such a process is the incompatibility of lyotropic surfactants with an alcohol, mostly an inherently produced alcohol, which is responsible for the phase separation during the sol-gel processing, stabilizing the resulting monolithic architecture of the monolith [206]. Different approaches use various components, namely, the alcohol source, the silicate sources (both are sometimes combined in one molecule), and molecular or supramolecular templating agents [207]. 

Scheme 4.2 The templated synthesis of mesoporous silica (a) true liquid crystal templating and (b) cooperative sol-gel and self-assembly.

Figure 18.1 Synthesis of periodic mesoporous materiais assisted by SDAs (A). Route 1 true liquid crystal templating mechanism. Route 2 cooperative self-assembly mechanism. (Adapted from Refs [44,45].)...

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