Dielectric spectroscopy studies of 4-cyano-3-fluorophenyl 4-butylbenzoate liquid crystal at high pressure

For 4-cyano-3- uorophenyl 4-butylbenzoate, nematic glassformer at ambient pressure, dielectric relaxation studies were performed under elevated pressure. In the isobaric experiment, on cooling the nematic phase two superarrhenius -relaxations, ascribed to the reorientations of molecules around short axes and precession of long molecular axes were found and the Arrhenius -relaxation related to intramolecular motions. Complexity of dynamics at elevated and ambient pressure is similar. Shift towards lower frequencies was found for both-relaxations

Studies of new antiferroelectric liquid crystal based on quantum-chemical model

Physical properties of new thermotropic antiferroelectric liquid crystal have been studied. Experiments were done by use of complementary methods such as differential scanning calorimetry, polarizing optical microscopy and X-ray powder diffractometry. Acquired data from X-ray powder diffractometry was examined under application of quantum chemical approach. It has been found that compound studied exhibits stable enantiotropic antiferroelectric SmC_{A}^{*} phase in the wide temperature range while ferroelectric phase SmC^{*} is very narrow

Scaling in 2-d Distribution of Topological Defects in a Liquid Crystal

Distribution of the topological point defects observed microscopically by Nagaya, Hotta, Orihira and Ishibashi in Schlieren texture of N-(4-n-methoxy benzylidene) 4'-n'-butylaniline has been analyzed. The same fractal dimensionality D$\text{}_{f}$=1.4 has been estimated for several sets of defects obtained in subsequent stages of evolution of the nematic sample after the transition from the isotropic liquid phase

Dynamics of the Molecules in Solid Phases of Few Chosen Schiff Bases Compounds

The dielectric relaxation processes observed in solid phases of MBBA, OH-MBBA, and EBBA belonging to the homologous series of the Schiff bases are discussed. The data are compared with the results completed by the present authors for EBPA compound. The uniform interpretation of the temperature changes of relaxation for all mentioned compounds is proposed

Molecular Dynamics of n-p-(Ethoxybenzylidene) P'-Propylaniline in Nematic and Solid Phases as Studied by Dielectric Relaxation Spectroscopy

The complex dielectric permittivity ε*(ν,T) = ε'(ν,T) - iε''(ν,T) of n-p-(ethoxybenzylidene) p'-propylaniline has been measured in the frequency range from 1 Hz to 13 MHz and temperature range from 360 K to 180 K on heating and on cooling the sample. Dielectric relaxations have been found in nematic and solid phases. A detailed analysis of the observed processes has been performed and the parameters describing molecular dynamics have been evaluated. The comparison of results with those obtained for the other Schiff bases is discussed

The Solid State Polymorphism and Dynamics of 2,3-Dimethylbutan-2-ol (2,3-DM-2-B)

In the paper we present adiabatic calorimetry and dielectric spectroscopy results for 2,3-dimethylbutan-2-ol (2,3-DM-2-B), one of the isomers of neohexanol. For 2,3-DM-2-B we have detected the following phase transitions: C2 (249.8 K) → C1 (262 K) → Is. No glass phase was found. In both crystalline phases C2 and C1 three relaxation processes were detected. These processes are discussed in relation to the calorimetric studies

Solid State Polymorphism and Dynamics οf 2,2-Dimethylbutan-1-ol as Studied by Adiabatic Calorimetry and Dielectric Spectroscopy

2,2-dimethylbutan-1-ol, known as neohexanol, was studied by adiabatic calorimetry and dielectric spectroscopy. Details of complex solid state polymorphism and relaxational dynamics were identified and described. System of phases of neohexanol was found to be monotropic with three orientationally disordered crystalline phases besides isotropic liquid and ordered crystal. Moreover, two subsequent glass transition anomalies of heat capacity $C_{p}(T)$ were detected on heating in one of the supercooled orientationally disordered crystalline phases. Thermodynamical properties of neohexanol are described in relation to the dielectric relaxation processes found