LLC Phases as Structural Media

The macroscopic characteristics of LLC phases are usually best described by a soft, sHmy or margarine-Hke consistency. Their domains undergo continuous structural rearrangement via molecular exchange of water and surfactant molecules. This is why these systems can be ruled out as structural components, e.g. for reinforcement purposes or for the creation of materials with defined diffusion pathways. Some recent appHcations of amphiphilic compounds in structure generation are summarized in [13]. The easiest approach to making full use of the structural potential of surfactant phases is a simple solidification process. 

The prerequisites to be fulfilled for a structural preservation of a preformed LLC assembly are as follows (i) the sohdification has to be irreversible, (ii) the resulting sohd product should not compete with the surfactant head groups for water, as this would result in substantial changes of the composition with the consequence of phase changes, (iii) no macroscopic demixing must occur, which indicates that the sohd substance has to be compatible either with the hydrophobic, or (more commonly) with the hydrophilic domains of the phase, (iv) the presence of reactants or the release of by-products should not affect the surfactant phase structure, and (v) the synthesis has to occur at moderate temperature or at least far below the boiling point of the least volatile component (usually water). 

To fulfil these aspects, three synthetic pathways appear particularly promising, namely precipitation, sol-gel processing and electrochemical conversion. In fact, all three approaches have been successfully applied. The synthetic procedures, outcome and properties of the respective products are described in this chapter. The ceramic oxide most frequently synthesized in LLC phases is silica therefore the following section is going to be focused mainly on its preparation. 

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