Search results for "Liquid Crystal"

Growth of large liquid crystalline domains of phospholipids at air-water interfaces

1990

Abstract The fusion of condensed phase domains in a fluid environment in monolayers is studied. A system of electrodes permits the non-invasive and predetermined movement of single domains while the film is observed by fluorescence microscopy. Two domains fuse when they are brought into contact with special positions of their borderlines. The experiment yields information about the molecular structure of the domains and allows us to fabricate very large domains. The equilibrium size is estimated and verified.

1986

Hydrogen bonded ferroelectric liquid crystal gels in freely suspended film geometry

2003

We study freely suspended films of smectic C* liquid crystalline gels by means of polarizing microscopy. The gel point of the system is determined from the suppression of flow in the films. The network of hydrogen bonds is mechanically fragile but stabilizes orientation patterns of the sample, in particular it stores the texture present during gelation. Electro-optical experiments are performed to study the dynamics of the sample reorientation under the influence of in-plane electric fields. Mesogen orientation and optical properties can be switched in electric fields of a few kV m−1. After removal of electric fields, the network restores the ‘frozen-in’ texture. This texture can be erased …

Orientation of charged clay nanotubes in evaporating droplet meniscus.

2015

© 2014 Elsevier Inc. During drying, an aqueous suspension of strongly charged halloysite clay nanotubes concentrates at the edge of the droplet ("coffee-ring" effect) which provides alignment of the tubes along the liquid-substrate contact line. First, the surface charge of the nanotubes was enhanced by polyanion adsorption inside of the lumen to compensate for the internal positive charges. This increased the magnitude of the ξ-potential of the tubes from -36 to -81mV and stabilized the colloids. Then, colloidal halloysite was dropped onto the substrate, dried at 65°C and after a concentration of ~0.05mgmL-1 was reached, the alignment of nanotubes occurred starting from the droplet edges. …

Halogen Bonding beyond Crystals in Materials Science

2019

Halogen bonding has recently gained well deserved attention in present-day research for its importance in many fields of supramolecular science and crystal engineering. Although generally overlooked in comprehensive studies in the past, halogen bonding has become an important tool also in the field of materials science. An increased number of scientific reports are published every year where halogen bonding is exploited in soft materials rather than in crystal engineering. Here, we focus on a description of the most exciting contemporary developments in the field of halogen-bonded functional soft materials, assembled using the guiding principles of crystal engineering. We give a particular …

Unsteadiness and transition to turbulence in woven spacer filled channels for Membrane Distillation

2017

To characterize the performance of Membrane Distillation (MD) modules, channels filled with woven spacers were investigated by Computational Fluid Dynamics (including Direct Numerical Simulations and the use of the SST k-ω turbulence model) and by parallel experiments with Thermochromic Liquid Crystals. The cases considered here regard mutually orthogonal filaments with a spacer pitch to channel height ratio P/H=2, two spacer orientations θ with respect to the main flow (0° and 45°), and bulk Reynolds numbers Re from ∼200 to ∼2000, an interval of great interest in practical MD applications. For both values of θ, CFD predicted steady-state flow for Re up to ∼300, and chaotic flow …

Experimental investigation of two-side heat transfer in spacer-filled channels

2020

Abstract In Membrane Distillation (MD), spacers support the membranes and promote mixing, thus reducing temperature polarization. Their efficient design requires a knowledge of the distribution of the local heat transfer coefficient h and of its dependence on Reynolds number, spacer geometry and flow-spacer relative orientation. In previous work, we applied Thermochromic Liquid Crystals (TLC) and digital image processing to the measurement of h distributions for different spacer configurations; data were used to validate CFD simulations and select turbulence models. For constructive reasons, the test section allowed only one-side heat transfer, while in most MD configurations (e.g. spiral-w…

Selectivity in the direction of photoisomerization reactions in liquid-crystalline guest-host systems

1995

E ⇄ Z photoisomerization reactions of stilbenes la-c were studied in liquid-crystalline (LC) phases and in the corresponding isotropic melts. Whereas viscosity has a moderate influence on the photostationary states, a strong effect caused by the regular incorporation of the stilbene molecules in the LC phases was observed. The direction of the isomerization can be reversed, up to the case of a one-way isomerization Z E for the tailored guest-host system 1b/BS. Such an LC-matrix effect is of typical highly ordered (smectic) phases with free volumina which are strictly limited by hydrophobic interactions; it could not be detected in a much more mobile nematic phase. Textures based on the bire…

Gold Nanoparticle Growth Monitored in situ Using a Novel Fast Optical Single-Particle Spectroscopy Method

2007

Size- and shape-dependent optical properties of gold nanorods allow monitoring their growth using a novel fast single-particle spectroscopy (fastSPS) method. FastSPS uses a spatially addressable electronic shutter based on a liquid crystal device to investigate particles randomly deposited on a substrate, orders of magnitude faster than other techniques. We use fastSPS to observe nanoparticle growth in situ on a single-particle level and extract quantitative data on nanoparticle growth.

Spin crossover in iron(II) complexes: Recent advances

2009

In this review article, several representative multifunctional SCO materials exhibiting interplay/synergy between the spin transition and magnetic coupling or liquid crystalline properties together with the present pioneering works on nano-structuration of SCO materials are illustrated. As the Mossbauer spectroscopy has been decisive in the study of the physical properties of these multifunctional materials, special attention is given to their corresponding Mossbauer investigations.