Dolunay Sakar

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.

Investigation of acid–base and surface characteristics of a thermotropic semifluorinated salicylaldimine liquid crystal by inverse gas chromatography

The surface energy of a semifluorinated salicylaldimine liquid crystal has been characterised by inverse gas chromatography over the temperature range 303 to 323 K using n-alkanes, tetrahydrofurane, dichloromethane, chloroform, acetone and ethyl acetate molecular probes. The dispersive component of the surface free energy of the adsorbent surface studied was calculated according to the approaches of Fowkes and Dorris–Gray in the infinite dilution region. The specific free energy, enthalpy and entropy of adsorption of polar probes on the liquid crystal were determined. The values of the specific enthalpy of adsorption were correlated with both the donor and the acceptor numbers of the probes to quantify the acidic and the basic parameters of the liquid crystal surface. The surface of the semifluorinated salicylaldimine liquid crystal was found to show a basic nature, which determined the nature of its interaction with the polar probes.

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.

Thermodynamic and surface characterisation of (S)-5-dodecycloxy-2-[[[4-(2-methylbutoxy) phenyl]imino]metheyl]phenol thermotropic liquid crystal by inverse gas chromatography

The inverse gas chromatography method was used to obtain thermodynamic and surface properties of the calamitic thermotropic liquid crystalline material, (S)-5-dodecyloxy-2-[[[4-(2-methylbutoxy)phenyl]imino]methyl]phenol, which is a Schiff base. The retention diagrams of the infinitely diluted solutions of acetate and alcohol isomers of (S)-5-dodecyloxy-2-[[[4-(2-methylbutoxy)phenyl]imino]methyl]phenol were plotted between 313 and 383 K using the inverse gas chromatography method. The isomer seperation of (S)-5-dodecyloxy-2-[[[4-(2-methylbutoxy)phenyl]imino]methyl]phenol isomers as chromatographic probes was represented by retention diagrams. The thermodynamic interaction parameters such as the Flory–Huggins liquid crystal–solvent parameter and the hard-core liquid crystal–solvent parameter, the weight fraction activity coefficient and the exchange parameters such as the effective energy, enthalpy and entropy were determined for the studied solvents at infinite dilution. Then the partial molar heat of sorption, the partial molar heat of mixing at infinite dilution and as well as the molar heat of vaporisation of the studied solvents were determined in the isotropic phase of (S)-5-dodecyloxy-2-[[[4-(2-methylbutoxy)phenyl]imino]methyl]phenol. To characterise the surface properties of (S)-5-dodecyloxy-2-[[[4-(2-methylbutoxy)phenyl]imino]methyl]phenol, retention diagrams of several non-polar and polar solvents with (S)-5-dodecyloxy-2-[[[4-(2-methylbutoxy)phenyl]imino]methyl]phenol were measured in the temperature range from 313 to 333 K by inverse gas chromatography. The surface energy, the thermodynamic adsorption parameters and the acid–base constants of (S)-5-dodecyloxy-2-[[[4-(2-methylbutoxy)phenyl]imino]methyl]phenol in the crystalline phase were determined.

Synthesis of tri-arm star di-block co-polymer containing poly(tetrahydrofuran-b-methyl methacrylate) arms via combination of cationic ring-opening polymerization and photosensitized free radical polymerization routes

Trimesic acid trichloride was used as a core to prepare a tri-arm star di-block co-polymer, namely poly(tetrahydrofuran-b-methyl methacrylate) (PTHF3-b-PMMA3), via combination of cationic ring-opening polymerization (CROP) and photo-induced radical polymerization routes. First, a trimesic acid trichloride–AgSbF6 or –AgCF3SO3 initiation system was utilized for the CROP of THF. The tri-arm star PTHF thus obtained was in situ terminated by 2-methyl pyridine N-oxide. Second, a sensitized irradiation of PTHF with a 2-methyl pyridinium N-oxide photoactive end-group in the presence of anthracene initiated the radical polymerization of MMA in order to give resulting star di-block co-polymer. The obtained polymers were characterized with gel-permeation chromatography (GPC) and 1H-NMR.

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.

Structural and Surface Characterization of Newly Synthesized D-π-D Type Schiff Base Ligand: (1E,2E)-3-[4-(Dimethylamino)phenyl]prop-2-en-1-ylidene)phenylamine

A new Schiff base with D-π-D type, (1E,2E)-3-[4-(dimethylamino)phenyl]prop-2-en-1-ylidene)phenylamine, has been successfully synthesized using the reaction of (2E)-3-[4-(dimethylamino)phenyl]acrylaldehyde with aniline. The Schiff base ligand has been characterized by FTIR, UV-visible, and 1H NMR as well as TG/DTA, SEM, BET, and elemental analyses and mass spectra. Surface properties and acid-base constants of Schiff base ligand were determined by IGC measurements.