10 research outputs found
Formation of net-like patterns of gold nanoparticles in liquid crystal matrix at the air–water interface
Lehmann rotatory power: a new concept in cholesteric liquid crystals
International audienc
Critical Exponents for Thermal Expansion and Isothermal Compressibility near the Nematic to Smectic-A Phase Transition
A nematic gap in mixtures of smectics A1 and Ad
The effect is tested of the smectic layer spacing ratio, r, on the phase diagram for the binary systems consisting of 80CB (smectic Ad) and one of the twelve compounds of the 5-n-alkyl-2-(4'-isothiocyanatophenyl) dioxane-1,3 homologous series (DBT compounds-smectics A1) has been studied The stability of the smectic phase in the mixture decreases with increasing r, and for r >> 1.4 a nematic gap separating the smectics A1 and Ad is observed The density, viscosity and scattering of X-rays as a function of temperature are measured and the enthalpy of the phase transitions is determined for the binary system 80CB-4DBT. The nematic phase reveals in the nematic gap a viscosity and structure characteristic for typical nematics. The binary system increases its molar volume as a result of mixing and assumes a maximum in the concentration range x8OCB > 1,4 on observe un intervalle nématique séparant les régions des smectiques A1 et Ad. Pour le système binaire particulier 80CB-4DBT on a examiné les densités, les viscosités et les données de la diffusion des rayons X en fonction de la composition et température. Enfin les enthalpies des transitions de phase ont été mesurées. Le nematique séparant les smectiques présente une viscosité et structure interne caractéristiques des nématiques typiques. Le volume molaire du système binaire dépasse ceux des composants; l'excès est maximal pour des concentrations en 80CB inférieures à 0,2