An overview of the results obtained from the most recent experiments performed for revealing the structure of the twistbend nematic Ntb phase will be presented at the conference. This new phase provides typical X-ray diffraction pattern for the nematic phase and is found at temperatures below the conventional nematic phase in odd-chain hydrocarbon linked mesogenic dimers. The materials in the Ntb phase form self-deformed striped pattern parallel to the rubbing direction in planarly aligned rubbed cells with a well-defined period. The period is found to depend on the cell spacing. The selfdeformation stripes appear without any external electromagnetic field or thickness gradient across the cell. Although the materials are composed of non-chiral molecules, the low temperature nematic phase exhibits fast linear optical response of the order of a few microseconds. This response is reminiscent of the phase exhibiting chirality. Moreover, at higher fields some of the materials form striped domains with opposite direction of the optical response. These stripes appear normal to the rubbing direction and their periodicity depends on voltage and frequency. The Freedericksz transition in this phase also shows unusual properties and this is proven to be of the first order. The techniques to characterize this phase include polarized microscopy observation and optical contrast spectroscopy. Possible causes of the phenomena will be discussed.
The electromagnetic response of metamaterial can be managed by combining resonances and interferences of different materials and on different lengths scales. In our contribution we study composite metamaterials containing resonant plasmonic metallic nanoparticles that show organization. The material bases its non-conventional properties on short distance self-organization by mesogens that form a liquid crystal material. We analyze the properties of such materials with a structural model containing organized nanoparticles. Theoretically insight of the electromagnetic properties is provided and we give details on their optical properties.
In this work, the physical and optical properties of gold nanoparticles functionalized with laterally grafted nematic
ligands were studied. In particular, the influence of the nanoparticle size on the mesomorphic behavior and optical
properties of the composite was investigated. To obtain an in-plane alignment of the mesogens, thin oriented films were
prepared by shearing and characterized by polarized absorption spectroscopy. While the sub-2nm nanoparticle thin film
only showed birefringence due to a strong damping of the plasmon resonance, larger NPs exhibit a strong dichroism with
a shift of the NP plasmon resonance by about 50 nm. These results demonstrate the possibility to obtain a bulk NP
metamaterial with tunable plasmonic properties by chemical engineering of the NP ligands.
Switching molecular or supramolecular systems reversibly from one state to another, with both states having significantly different properties using light is widespread in biological systems and has been in the focus of materials research for many years. Such synthetic systems are promising as high density data storage systems, sensors, photonic switches or as molecular logic gates. There the concept of optically addressable molecules promises miniaturisation to the molecular level and potentially the direction towards optical computing on that level. Our approach is based on the concept that the functional groups and the properties in such molecules, if suitably selected can add up to attractive properties in the self-assembled molecular systems. Rational design allows of the photochromic core and the mesogenic groups for the modulation of the photochromic behaviour, the absorption properties, the quantum yields of the photo conversion processes and the conversion obtained at the photostationary state. The use of suitable mesogens allows for the use of the FRET effect for the switching behaviour.