Belkis Bilgin-Eran

Investigation of thermodynamic and surface characterisation of 4-[4-(2-ethylhexyloxy)benzoyloxy]benzoic acid thermotropic liquid crystal by inverse gas chromatography

The inverse gas chromatography method was used to obtain thermodynamic and surface properties of the thermotropic liquid crystalline material, 4-[4-(2-ethylhexyloxy)benzoyloxy]benzoic acid (EBBA). The retention diagrams of undecane, dodecane, tridecane, ethyl acetate, n-butyl acetate, iso-butyl acetate, toluene, ethylbenzene, iso-propylbenzene, n-propylbenzene and chlorobenzene on EBBA were plotted at temperatures between 443.2 and 468.2 K. The specific retention volume, , Flory–Huggins interaction parameter, , equation-of-state interaction parameter, , and effective exchange energy parameter, , were determined. The dispersive component of the surface free energy, , of the studied adsorbent surface was estimated using retention times of different nonpolar organic solvents in the infinite dilution region. The specific free energy of adsorption, the enthalpy of adsorption, , and the entropy of adsorption, , of solvents on liquid crystal were determined. The values of were correlated with the donor and the acceptor numbers of the probes to quantify the acidic and the basic parameters of the liquid crystal surface. The values obtained for and parameters indicated an acidic character for the surface of EBBA.

A new liquid crystal of considerable value for the separation of closely related solvents by gas chromatography

The synthesis, characterisation and mesomorphic properties of a new chiral liquid crystal, (S)-5-(10-undecenyloxy)-2-[[[4-(2-methylbutoxy)phenyl]imino]methyl]phenol (UMBPIMP) are described. The phase transition temperatures of this mesogenic compound have been investigated by optical polarising microscopy, differential scanning calorimetry and inverse gas chromatography. The thermodynamics of UMBPIMP were investigated in order to understand its selectivity as a stationary phase in gas chromatography. Its liquid crystal selectivity was tested using the isomers n-butyl acetate, tert-butyl acetate and iso-butyl acetate, and the isomers n-butyl alcohol, tert-butyl alcohol and iso-butyl alcohol, as model chromatographic probes. The retention diagrams of the isomers were plotted between 30°C and 110°C using inverse gas chromatography. Using the specific retention volume, , parameters such as the Flory–Huggins polymer–solvent interaction, , and hard-core polymer–solvent interaction, , and exchange parameters such as effective energy, X eff, enthalpy, X 12 and entropy, Q 12, were determined for the solvents chosen.

Synthesis and Surface Characterizations of New Banana-Shaped Liquid Crystal 4-Bromo-1,3-phenylene-bis[4-[4′-(10- undecenyloxy)-benzoyloxy]]benzoate

A new banana-shaped liquid crystal compound, i.e., the bent-core mesogen, 4-Bromo-1,3-phenylene-bis[4-[4′-(10-undecenyloxy)-benzoyloxy]]benzoate (BPUBB), has been synthesized and characterized. Phase transition temperatures of BPUBB were determined by polarizing microscopy and differential scanning calorimetry. The inverse gas chromatography method was utilized to obtain the surface characterization of BPUBB. This compound was used as a stationary phase in the chromatographic column and nine solutes with a different chemical nature were used as eluents. The dispersive component of the surface free energy, γ D S , of studied adsorbent surface was estimated using retention times of different nonpolar organics in the infinite dilution region. The specific free energy of adsorption, ΔGS A , the enthalpy of adsorption, ΔHS A , and the entropy of adsorption, ΔSS A , of solvents on liquid crystal were determined. The values of the ΔHS A were correlated with both the donor and the acceptor numbers of the probes to quantify the acid KA and the basic KD parameters of the liquid crystal surface. The values obtained for the KA and KD parameters indicated a basic character for the surface of the BPUBB.

Thermodynamic and surface characterisation of 4-[4-((S)-citronellyloxy)benzoyloxy]benzoic acid thermotropic liquid crystal

ABSTRACT The inverse gas chromatography (IGC) method was used to obtain thermodynamic and surface properties of the thermotropic liquid crystalline material, 4-[4-((S)-citronellyloxy)benzoyloxy]benzoic acid (CBB). Liquid crystal (LC) selectivity was investigated using the alcohol and acetate isomers by the IGC method at temperatures between 338.2 K and 463.2 K. The retention diagrams of n-decane, undecane, dodecane, tridecane, n-butyl acetate, iso-butyl acetate, ethylbenzene and chlorobenzene on CBB were plotted in the temperature range between 468.2 K and 493.2 K. The specific retention volume, , Flory–Huggins interaction parameter, , equation-of-state interaction parameter, , the partial molar heat of sorption, , the partial molar heat of mixing, , the molar heat of vaporization, and the weight fraction activity coefficient, , were determined. The dispersive component of the surface free energy, , of the studied adsorbent surface was estimated in the infinite dilution region. The specific free energy of adsorption, , the enthalpy of adsorption, and the entropy of adsorption, , of solvents on LC were determined. The values of were correlated with the donor and the acceptor numbers of the probes to quantify the acidic and the basic parameters of the LC surface. The values obtained for and parameters indicated an acidic character for the surface of CBB. Graphical Abstract

New p-Substituted Salicylaldehyde Phenylhydrazone Derivatives: Synthesis, Characterization, and Antioxidant Activities.

Abstract A series of new p-nitrophenylhydrazone derivatives 3a–f were synthesized, characterized, and investigated for their antioxidant activities. These compounds have been synthesized by refluxing (p-nitrophenyl)hydrazine with 4-sub-stituted salicylaldehydes. The structures of the compounds were established by IR, 1H- and 13C-NMR, and MS data. The antioxidant activities (free radical-scavenging activity, reducing power, metal chelating activity, and total anti-oxidant activity) of the hydrazone compounds were evaluated. All of the compounds exhibited significant activities, while compound 3a, with the shortest chain, showed the highest antioxidant activity in all of the tests.

Miscibility in mixtures of liquid crystal 4-[4-(tetradecyloxy)benzoyloxy] benzoic acid and poly(ether imide)

ABSTRACT The miscibility behavior of binary mixtures of polymeric and low molecular weight molecule was studied using viscometric analysis, differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). The miscibility criteria of liquid crystal 4-[4-(tetradecyloxy) benzoyloxy]benzoic acid (TBBA) and poly(ether imide) (Ultem) was investigated at 30°C in dilute chloroform solutions by viscometric analysis. The intrinsic viscosity and viscometric parameters of this mixture system were determined for several TBBA/Ultem mixtures in compositions such as 80/20, 60/40, 40/60 and 20/80 in chloroform solutions. The miscibility criteria on the basis of the sign of Δbm, Δb′m, Δb″m and Δ[η]m which are the difference between their experimental and ideal values were calculated by applying equations proposed by Krigbaum–Wall, Catsiff–Hewett and Garcia et al. The methods were extended to the bulk state by obtaining the criteria from extrapolated experimental data to the zero of reciprocal of concentration. The miscibility of the mixtures was also studied by DSC and FTIR.