Chirality Effects in the Lyotropic SmC Analog Phase

The investigated surfactant/solvent mixtures of the diol C50 and water or for-mamide, respectively, are the first lyotropic systems to form a lamellar, fluid and tilted liquid crystalline phase which contains chiral surfactant molecules. The main issue of the present chapter is thus to demonstrate whether or not the lyotropic SmC analog phase exhibits similar chirality effects as known from its thermotropic counterpart. The most outstanding manifestations of chirality in the thermotropic SmC phase are helicity, due to a chirality-induced precession of the director, and ferroelectricity, due to its polar C2-point group symmetry. Thus, the focus of this chapter is on the detection and analysis of those two macroscopic chirality effects. 

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On the basis of these observations it is possible to devise a structural model of the lyotropic SmC analog. However, chirality effects are not included in this model and it is thus also applicable to the achiral lyo-SmC 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. 

Study of potential chirality effects like the helical twist of the tilt-direction and ferroelectricity in the lyotropic analog of the SmC phase. 

The subject of this thesis is the discovery and characterization of the lyotropic analog of the well-known thermotropic ferroelectric SmC liquid crystal phase. In addition to providing evidence for the existence of this previously unknown phase, the main focus of the work presented is on the investigation of its stmctural properties and chirality effects. In particular, the following results were obtained ... 

In this thesis Johanna Bruckner reports the discovery of the lyotropic counterpart of the thermotropic SmC phase. By means of polarizing optical microscopy. X-ray diflfraction and electro-optic experiments she firmly establishes aspects of its stmcture and elucidates its fascinating properties, among them a pronounced polar electro-optic effect, analogous to the ferroelectric switching of its thermotropic counterpart. The helical ground state of this new lyotropic phase raises the fundamental question of how chiral interactions are communicated across layers of disordered and achiral solvent molecules which are located between adjacent... 

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