Design Of Liquid Crystalline Materials Research Articles

Manipulation of Liquid Crystalline Properties by Dynamic Covalent Chemistry─En Route to Adaptive Materials.

Dynamic covalent bonds bear great potential for the development of adaptive and self-healing materials. Herein, we introduce a versatile concept not only for the design of low-molecular-weight liquid crystals but also for their in situ postsynthetic modification by using the dynamic covalent nature of imine bonds. The methodology allows systematic investigations of structure-property relationships as well as the manipulation of the materials' behavior (liquid crystallinity) and the introduction of additional properties (here, fluorescence) by a solvent-free method. For the first time, the transamination reaction is followed by variable-temperature 19F solid-state NMR in the mesophase, providing insights into the reaction dynamics in a liquid crystalline material. Finally, the application potential for the design of liquid crystalline materials with adaptive properties is demonstrated by a sequential combination of these reactions.

Liquid Crystalline Materials for Biological Applications.

Liquid crystals have a long history of use as materials that respond to external stimuli (e.g., electrical and optical fields). More recently, a series of investigations have reported the design of liquid crystalline materials that undergo ordering transitions in response to a range of biological interactions, including interactions involving proteins, nucleic acids, viruses, bacteria and mammalian cells. A central challenge underlying the design of liquid crystalline materials for such applications is the tailoring of the interface of the materials so as to couple targeted biological interactions to ordering transitions. This review describes recent progress toward design of interfaces of liquid crystalline materials that are suitable for biological applications. Approaches addressed in this review include the use of lipid assemblies, polymeric membranes containing oligopeptides, cationic surfactant-DNA complexes, peptide-amphiphiles, interfacial protein assemblies and multi-layer polymeric films.

Lanthanide-containing luminescent molecular edifices

The first part of this short review focuses on the insertion of luminescent lanthanide ions into molecular compounds. The main requirements for the development of highly luminescent chelates with potential applications in biomedical analysis and time-resolved luminescent microscopy are presented. We then describe the design of adequate macrocyclic receptors with potential applications in nuclear waste management and in the design of liquid crystalline materials. In the latter case, the luminescent properties of the lanthanide ions can be taken advantage of for the determination of the transition temperature. Finally, we turn to self-assembly processes, which allow a fine-tuning of the coordination sphere and, consequently, of the electronic, and associated, properties of the lanthanide ions. Heteropairs of lanthanide ions may be specifically recognized, which leads to the design of bifunctional (bicolour) probes. Moreover, the properties of one metal ion can be controlled by the presence of the other metal ion (either 4f or 3d) when both are inserted into polymetallic edifices.

Micro-segregation, molecular shape and molecular topology – partners for the design of liquid crystalline materials with complex mesophase morphologies

This article gives an overview of recent progress in the design of novel materials, capable of forming liquid crystalline phases with non-conventional mesophase morphologies. The materials include dendritic molecules, ternary block-copolymers, rod–coil molecules and linear as well as non-linear polyphilic low molecular weight block molecules incorporating rigid segments with a specific shape. Changing the shape of the rigid segments from rod-like to disc-like or to a bent shape leads to additional possibilities for the directed design of mesophase forming materials. Many of these molecules are able to form quite unusual mesophase morphologies, distinct from the conventional lamellar (smectic) and columnar mesophases of classical rod-like and disc-like liquid crystals; they include mesophases which combine lamellar and columnar organisation, columnar mesophases incorporating three discrete sets of columns, biaxial smectic phases, such as the SmAb-phase (McMillan Phase), polar smectic phases and non-conventional layer structures in which rigid units are aligned parallel to the layers. These novel mesophase morphologies were realised by increasing the number of incompatible units combined in these molecules, by changing the volume fractions of the incompatible segments, by tailoring the shape of rigid segments and by controlling the molecular topology.