Fatih Cakar

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.

Use of inverse gas chromatography for the physicochemical characterisation of a new synthesised liquid crystal: (S)‐5‐(2‐methylbutoxy)‐2‐{[(4‐dodecyloxyphenyl)imino]methyl}phenol

A new liquid crystalline compound, i.e. (S)‐5‐(2‐methylbutoxy)‐2‐{[(4‐dodecyloxyphenyl)imino]methyl}phenol (MBDOPIMP), was prepared and characterised. Phase transition temperatures of MBDOPIMP were determined by polarising optical microscopy and differential scanning calorimetry. Trace amounts of ethyl acetate, butyl acetate, isobutyl acetate, hexane, heptane, octane, nonane and decane were passed through a chromatographic column loaded with MBDOPIMP coated on Chromosorb W. The retention diagrams of the solvents on MBDOPIMP were plotted using specific retention volumes at temperatures between 105 and 125°C. Thermodynamic parameters, such as Flory–Huggins liquid–solvent interaction, , equation‐of‐state liquid–solvent interaction, , effective exchange energy, X eff, the exchange enthalpy, X 12 and exchange entropy, Q 12, were determined for the liquid crystal–solvent systems. Subsequently, the partial molar heats of sorption, ΔH¯1,sorp and mixing, , were determined from the slopes of the plots of the logarithm of the specific retention volume, ln , versus 1/T and logarithm of the weight fraction activity coefficients, ln , versus 1/T, respectively.

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

Dispersive Surface Energy and Acid-Base Parameters of Tosylate Functionalized Poly(ethylene glycol) via Inverse Gas Chromatography

An inverse gas chromatographic (IGC) study of the sorption properties of poly(ethylene glycol) modified with tosylate (PEG-TOS) was presented. PEG-TOS was synthesized via the tosylation of the corresponding poly(ethylene glycol) (PEG) with p-toluenesulfonyl chloride in the basic medium. The synthesized PEG-Tos was characterized by FTIR-ATR and 1HNMR techniques. The retention diagrams of n-hexane, n-heptane, n-octane, n-nonane, n-decane, dichloromethane, chloroform, acetone, tetrahydrofuran, ethyl acetate, and ethanol on the PEG and PEG-Tos were plotted at temperatures in K between 303 and 373 by inverse gas chromatography technique. The dispersive component of the surface-free energy, , of studied adsorbent surface was estimated using retention times of different nonpolar organics in the infinite dilution region. Thermodynamic parameters of adsorption (free energy, , enthalpy, , and entropy, ), dispersive components of the surface energies, , and the acid, , and base, , constants for the PEG and PEG-Tos were calculated and the results were discussed.

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.

Synthesis, Preparation, and Characterization of Liquid Crystal/Organo-Montmorillonite Nanocomposites

A new chiral calamitic liquid crystal 4′-((S)-3,7-dimethyloctyloxy)phenyl 4-(10-undecen-1-yloxy)benzoate (DOPUB) has been synthesized and characterized by spectroscopic methods (1H-NMR and 13C-NMR). The focus is on the preparation of the nanocomposites of new chiral calamitic liquid crystal DOPUB/Organo-montmorillonite clay (OMMT) by solution intercalation method addition with OMMT contents 2.5, 5, and 7.5 wt% and determination of the morphology, thermal behavior, and crystalline properties of liquid crystal DOPUB/OMMT. Montmorillonite (MMT) modified by cationic surfactant cetyltrimethylammonium bromide (CTAB) for increasing the interaction of clay with DOPUB liquid crystal. The characterization of clay minerals and nanocomposites was investigated by X-ray diffraction. The mesomorphic behavior of liquid crystal (DOPUB) and the nanocomposites was investigated by differential scanning calorimetry (DSC) and optical polarizing microscopy (PM).