Search results for " liquid crystal"

The Use of Thermochromic Liquid Crystals and Image Processing for Technical and Biomedical Thermography

1999

Combined Experimental and Numerical Study of Local Heat Transfer Coefficient by Liquid Crystal Thermography

1998

Study on the thermotropic properties of highly fluorinated 1,2,4-oxadiazolylpyridinium salts and their perspective applications as ionic liquid cryst…

2007

A new series of fluorinated salts, iodides and trifluoromethanesulfonates, was synthesized from perfluoroalkylated 1,2,4-oxadiazolylpyridines. Their thermotropic properties were investigated by combined temperature resolved small angle and wide angle X-ray scattering, differential scanning calorimetry and polarised optical microscopy. The UV–visible and photoluminescence properties were studied for all compounds. The results showed for two compounds the existence of an enantiotropic mesomorphic smectic liquid crystal phase. All iodides showed thermochromism phenomena suggesting prospective applications in optoelectronics.

Synthesis and mesomorphism of related series of triphilic ionic liquid crystals based on 1,2,4-triazolium cations

2021

Abstract The synthesis, liquid crystal and conductivity properties of a series of 27 salts based on the 5-(4-(alkyloxy)phenyl)-1,2,4-triazol-4-ium cation bearing a perfluoroalkyl chain with triflate, tetrafluoroborate and bistriflimide anion are reported. The cations are regarded as triphilic on account of their three distinct regions – hydrocarbon, fluorocarbon and ionic. The mesophases were characterised by a combination of polarised optical microscopy, calorimetry and small-angle scattering experiments using both X-rays and neutrons, while thermal stability was probed using thermogravimetric analysis. The liquid crystal properties are found to be dependent on the anion and the length of …

Tuneable multicoloured patterns from photonic cross-communication between cholesteric liquid crystal droplets

2014

Monodisperse droplets of planar-aligned cholesteric (N*) liquid crystal exhibit an intriguing capacity for photonic cross-communication, giving rise to colourful patterns that depend sensitively on the N* pitch, droplet positions and illuminated area. The phenomenon results from a combination of omnidirectional selective reflection of N* droplets—which thus act as spherically symmetric self-assembled photonic crystals—and total internal reflection at the continuous phase surface. We outline how the unique optical properties can be employed in numerous applications.

Ionic liquid crystals based on 1,2,4-triazolium rings

2017

Ionic liquids crystals (ILCs) are a class of organic materials of great current interest. They show unique properties that can be exploited in many different fields, for example their use as solvents for extraction processes as well as electrolytes for batteries, fuel cells, dye-sensitised solar cells etc. [1-4] Moreover, in perfluorinated ILCs, the segregation of the perfluorocarbon chains promotes further self-organisation of the LC phases, adding to the materials further properties such as affinity for gases suitable for example in gas-storage. [5-7] A series of salts based on 5-(4-alkyloxyphenyl)-1,4-dimethyl-3-(perfluoroalkyl)-1,2,4-triazol-4-ium structures, differing in the length of …

Tris(5-aryl-1,3,4-oxadiazolyl)benzotrithiophenes : discotic liquid crystals with enormous mesophase ranges

2021

High resolution electron microscopy of liquid crystalline polymers

1990

Les images de microscopie electronique a haute resolution des polymeres cristaux liquides calamitiques [CO−CH(R)−CO 2 −(CH 2 ) 6 −OPh−N:N−PhO−(CH 2 ) 6 −O] n (R=CH 2 −CH=CH 2 , (CH 2 ) 6 −O−Ph N=N−Ph−CN) et discotique poly (hexadecanedioate de triphenylene) sont simulees sur ordinateur et comparees avec les structures obtenues a partir des resultats experimentaux de diffraction electronique. Une theorie est developpee pour expliquer le bon accord observe

Viologen-based ionic liquid crystals: induction of a smectic A phase by dimerisation.

2014

The stability of thermotropic ionic liquid crystals is essentially due to micro-phase segregation between the ionic heads and the long alkyl chains. Here we show, using newly synthesized viologen dimers, that the structure of the central core is another key parameter to play with in order to tune the mesomorphic behaviour. © 2014 the Owner Societies.

Morphology and local organization of water-containing (1R,2S)-Dodecyl(2-hydroxy-1-methyl-2-phenylethyl)dimethylammonium bromide reverse micelles disp…

2014

The structure of (1R,2S)-dodecyl(2-hydroxy-1-methyl-2-phenylethyl)dimethylammonium bromide (DMEB) reverse micelles, at various water-to-surfactant molar ratio (R-w, R-w = [water]/[DMEB]) and DMEB concentrations, has been investigated by small angle X-ray scattering (SAXS) and extended X-ray absorption fine structure spectroscopy (EXAFS). SAXS data of dry reverse micelles are consistent with a model of spherical hydrophilic core surrounded by DMEB alkyl chains whose polydispersity decreases significantly with surfactant concentration. By adding water, a sphere to cylinder transition occurs leading to a one-dimensional growth of reverse micellar cores with R-w and surfactant concentration. Th…