The use of non-ionic LC phases as anisotropic matrices for E/Z-isomerization of azo-guest molecules is often restricted due to limited solubilities and demixing effects. In this study we therefore employed an ionic liquid crystal (ILC) matrix to follow the photo-induced E/Z-isomerization of ionic mesogenic azobenzene guanidinium guests. The latter were prepared from 4-hydroxy-4'-(octyloxy)azobenzene, which was first treated with N-(bromoalkyl)phthalimides to introduce the spacer with varying chain length. Removal of phthalimide and final reaction with a formamidinium salt linked the ionic head group to the photoisomerizable azobenzene unit. Investigation of the mesomorphic behaviour revealed for all azobenzene ILCs smectic A mesophases with high translational order parameters and partial bilayers, as could be stated by layer spacing d. Similar packing behaviour was found for the solid state by X-ray crystal structure analysis. E/Z-isomerization of azobenzene ILCs which were completely miscible with the ionic LC phase of C12MIM-Br as anisotropic host was induced by irradiation with UV light and the reisomerization observed by time-resolved UV-Vis spectroscopy. For comparison, water was used as isotropic host. Z/E-reisomerization activation energies exhibited similar values of 97-100 kJ mol(-1) irrespective of spacer lengths and the type of host. The results demonstrate that a proper match of steric requirements of host and guest as well as layer spacings are needed for a decreased activation energy.

Two new examples of the lyotropic analog to the thermotropic ferroelectric SmC* phase were found recently.

In thermotropic chiral Sm-A^{*} phases, an electric field along the smectic layers breaks the D_{∞} symmetry of the Sm-A^{*} phase and induces a tilt of the liquid crystal director. This so-called electroclinic effect (ECE) was first reported by Garoff and Meyer in 1977 and attracted substantial scientific and technological interest due to its linear and submicrosecond electro-optic response [S. Garoff and R. B. Meyer, Phys. Rev. A 19, 338 (1979)0556-279110.1103/PhysRevA.19.338]. We now report the observation of an ECE in the pretransitional regime from a lyotropic chiral lamellar L_{α}^{*} phase into a lyo-Sm-C^{*} phase, the lyotropic analog to the thermotropic Sm-C^{*} phase which was recently discovered by Bruckner et al. [Angew. Chem. Int. Ed. 52, 8934 (2013)1433-785110.1002/anie.201303344]. We further show that the observed ECE has all signatures of its thermotropic counterpart, namely (i) the effect is chiral in nature and vanishes in the racemic L_{α} phase, (ii) the effect is essentially linear in the sign and magnitude of the electric field, and (iii) the magnitude of the effect diverges hyperbolically as the temperature approaches the critical temperature of the second order tilting transition. Specific deviations between the ECEs in chiral lamellar and chiral smectic phases are related to the internal field screening effect of electric double layers formed by inevitable ionic impurities in lyotropic phases.