Liquid Crystal Networks Research Articles

Thermotropic liquid crystals embedded in a high water gel system

An emulsion was formed when the thermotropic liquid crystal (LC) mixture E5 was added to an aqueous polyvinylalcohol (pva) solution and shaken. This emulsion was gelled by addition of an aqueous borax solution. The pva polymer functioned not only as the gelling agent but also appeared to act as a polymeric surfactant which stabilised the LC droplets. This high water gel-liquid crystal (HWG-LC) system contained nearly 80 wt % water and more LC wt % than polymer. The system was thermally reversible, undergoing a gel to sol transition upon heating to 70°C and reforming a gel upon cooling. The HWG-LC showed electrooptical behaviour dependent upon a switched electric field when constrained between transparent electrodes. The pressure required to form a thin film between these electrodes induced a structural emulsion in the dispersion causing LC droplet disruption and the formation of an LC network in the gel.

The cell‐plasma membranes as composite system of two‐dimensional liquid crystal and macromolecular network and how to mimick its physical properties

AbstractThe evolution of the cell has become possible after nature had invented the composite membrane by combining two states of matter: the two‐dimensional liquid crystalline lipid/protein bilayer and the macromolecular network.In the first part we introduce the essential structural features of the cell plasma membrane (case of erythrocyte) and describe their extraordinary mechanical properties. These are unmatched by the technical materials and allow migrating cells to squeeze through narrow gaps of the tissue or of the extracellular protein networks without loss of material or lysis. As an example, how nature manages to alter the structure and function of biomenbranes drastically by minor biochemical signals we consider chemically induced shape changes of cells.In the second part we describe some efforts to mimick mechanical properties of cell membranes with composite membranes of monomeric and polymeric amphiphiles. These model systems exhibit promising new material properties for future applications in chemistry and biotechnology.

On the Biomembranes as Composite Lamellae of Smectic A Liquid Crystal and Macromolecular Network: Elastic Properties, Local and Collective Dynamics

Some exceptional elastic and dynamic properties of biomembranes (in particular cell plasma membranes) which are based on their composite structure consisting of a smectic A liquid/protein bilayer to which a quasi-twodimensional macromolecular network is loosely coupled are discussed. Compared to technical materials, their elastic properties are remarkably soft with respect to bending and shearing whereas the lateral area compressibility modulus is comparable to that of organic materials (e.g., polymers). The latter is essential for the membrane function as electrically insulating barrier and may play an important role for the molecular organization of the lipid/protein bilayer as well as the activity of enzymes. In the second part local motional processes as observed by incoherent quasielastic neutron scattering experiments are reported and basic principles of lateral mobility and undulatory excitations are discussed.

Medical Student Teaching at Trudeau Sanatorium

The cis profile of azobenzene is a key factor in predicting the photodeformation of the nematic azobenzene liquid crystal network (LCN). An ab initio based method for predicting the photoisomerization profile of azobenzene is developed by coupling the stimulated Raman adiabatic passage (STIRAP) method with non-linear Beers law, and compared with experimental data. Using this combined method, we calculate the photoisomerization profile of azobenzene with various light input conditions. We identify the cis profile of the nematic LCN structure evolves into a step-like decaying shape when the direction of polarized light is parallel to the nematic direction.