Structural and Physical Properties of the Lyotropic SmC Analog Phase

3 Structural and Physical Properties of the Lyotropic SmC Analog Phase 

The following section is devoted to the investigation of the structural properties of the lyotropic SmC analog phase. In this context three major issues will be addressed. The first issue is to provide further proof of the existence of the lyotropic analog of the thermotropic SmC phase. The second one is to find out if the structure of the lyotropic phase differs from its thermotropic counterpart and the last point is to examine the influence of the solvent concentration on the structural and physical properties of the lyotropic SmC analog phase. 

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Summing up, the only two solvents which possibly induce a lyotropic analog of the SmC phase in contact with the surfactant C50 are water and formamide. Both solvents possess quite small molecular volume and a highly polar stmcmre. However, this is true for most of the solvents used. Thus, the question is which properties of the solvents enable the formation of a lyotropic SmC analog phase. In Table 5.2 some physical data of the selected solvents, which might be useful to answer this question, are listed. AU of the solvents possess a quite polar chemical structure and thus have a relatively high dipole moment. But while formamide is almost on the upper end of the scale, water has the smallest dipole moment of the solvents used. Hence, the dipole moment of the solvent should not play an important part in the formation of the phase. 

Thennotropic and lyotropic liquid crystals share a common state of matter with many analogies in their structural and physical properties. However, these two fields of liquid crystal research are usually treated completely separately. This is partially due to historical reasons, but also to striking differences in some aspects of these two classes of liquid crystals. One of these differences is the occurrence of thermotropic phases which do not have a lyotropic counterpart A compelling example of this is the thermotropic ferroelectric SmC phase. Due to its unique chirality effects, i.e. ferroelectricity and a helical configuration of the tilt-direction, this phase attracted considerable scientific interest over the last decades. However, there are no reports found in literature about a SmC analog phase in lyotropic liquid crystals. 

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