Search

The aim of this study is to examine the interactions of composite materials obtained by adding single-walled carbon nanotubes (SWCNT) to polyetherimide (ULTEM) in different weight ratios with various organic solvents, and to evaluate the solubility of composites in these organic solvents. The characterization of prepared composites was performed with SEM analysis. Thermodynamic properties of ULTEM/SWCNT composites were determined by the inverse gas chromatography (IGC) method at 260–285°C in infinite dilution. According to the IGC method, the retention behaviors were examined by passing different organic solvent vapors over the composites used as stationary phase, and retention diagrams were drawn using the obtained retention data. Thermodynamic parameters including Flory–Huggins interaction parameters (⁠|${\chi}_{12}^{\infty }$|⁠), equation of state interaction parameters (⁠|${\chi}_{12}^{\ast }$|⁠), weight fraction activity coefficients in infinite dilution (⁠|${\Omega}_1^{\infty }$|⁠), effective exchange energy parameters (⁠|${\chi}_{\mathrm{eff}}$|⁠), partial molar sorption enthalpies (⁠|$\Delta{\overline{H}}_1^S$|⁠), partial molar dissolution enthalpies in infinite dilution (⁠|$\Delta{\overline{H}}_1^{\infty }$|⁠) and molar evaporation enthalpies (⁠|$\Delta{\overline{H}}_v$|⁠) were calculated using the linear retention diagrams. According to |${\chi}_{12}^{\infty }$|⁠ , |${\chi}_{12}^{\ast }$|⁠ , |${\Omega}_1^{\infty }$| and |${\chi}_{\mathrm{eff}}$| values, organic solvents were found to be poor solvents for composites at all temperatures. Besides, the solubility parameters of composites were determined by IGC method at infinite dilution. [ABSTRACT FROM AUTHOR]

In this study, Phenylbenzoate-based calamitic liquid crystals (LCs) were synthesized and characterized, and then the thermodynamic properties and phase transition temperatures were investigated by inverse gas chromatography (IGC) at infinite dilution. The phase transition temperatures of the LCs were determined in the range of 40–170°C by the IGC method. Finally, in the thermodynamic equilibrium region (the range of 160–200°C), Flory-Huggins theory and the equation of state theory with the LC-solvent interaction parameters, the effective exchange energy parameters, the weight fraction activity coefficient, and also the partial molar heat of mixing at infinite dilution of solvent, the molar heat of vaporization of solvent, and the partial molar heat of sorption of solvent were calculated. [ABSTRACT FROM AUTHOR]

The boron-based ceramics namely hexagonal boron nitride (h-BN) and boron phosphate (BPO4) were synthesized and characterized by Fourier transform infrared spectroscopy and X-ray diffraction analysis. The surface properties of h-BN and BPO4 were examined by inverse gas chromatography method. The dispersive surface energy and the acidic-basic character of h-BN, and BPO4 surfaces were estimated by the retention time with probes such as n -hexane, n -heptane, n -octane, n -nonane, n -decane, acetone, ethyl acetate, dichloromethane, chloroform and tetrahydrofuran at infinite dilution region. The dispersive surface free energies calculated using both Schultz and Dorris–Gray methods, decreased linearly with increasing temperature. The specific adsorption free energy and the specific adsorption enthalpy corresponding to acid–base surface interactions were determined. By correlating with the donor and acceptor numbers of the probes, the acidic and the basic parameters of the h-BN and BPO4 were calculated. The values obtained for and parameters indicated that h-BN has a basic character, whereas BPO4 has an acidic character. [ABSTRACT FROM AUTHOR]

The ability to separate isomer series and the surface properties of cholesteryl chloroformate (CC) liquid crystal were investigated by inverse gas chromatography (IGC). The retention diagrams of the selected solvents were plotted between 308.2 and 333.2 K using the IGC technique. The selectivity coefficients, α, of the structural isomers were determined for the CC liquid crystal in the infinite dilution. Besides, the dispersive energy, γ S D , the Gibbs specific energy, Δ G A S , the adsorption enthalpy, Δ H A S , the adsorption entropy, Δ S A S , of the selected solvents were also determined. The Δ H A S values were associated with the number of acidic and basic group to calculate the acidity constant ( K A ) and the basicity constant ( K D ). When the Δ H A S values calculated in experimental studies were examined, it was seen that the adsorption takes place exothermically. According to K A and K D constants, CC surface was found to be basic character ( K D / K A ≅ 3.11). [ABSTRACT FROM AUTHOR]

Introduction: Urtica dioica (nettle) is a plant species of the Urticaceae family that grows in various parts of the world and exerts antioxidant, antibacterial, antiulcer, antiviral, and anti‐inflammatory effects. Their leaves, roots, and seeds are used in various fields such as food, medicine, and cosmetics. Objectives: Inverse gas chromatography (IGC) was used to evaluate the surface characteristics and separation ability of U. dioica leaves, roots, and seeds. Characterization of these biomasses was performed by Fourier transform infrared spectroscopy (FTIR) analyses. Methodology: The surface properties of the biomasses including dispersive surface energy, adsorption enthalpy, Gibbs free energy, and acidity‐basicity constants were determined at infinite dilution using various organic solvents. These properties were compared with each other. Dispersive surface energies were calculated using the Dorris–Gray, Donnet–Park, and Schultz methods. The accuracy of these methods and their applicability were evaluated. In the last stage of this study, the separation of xylene isomers was investigated by using U. dioica biomasses as stationary phases. Results: The surface functional groups were determined by FTIR analysis. As a result of the IGC studies, it was found that the adsorption of polar solvents on biomasses occurred exothermically and spontaneously. Besides, it was found that the surfaces of biomasses were basic. From the retention diagrams and selectivity coefficients, it was determined that xylene isomers were effectively separated. Conclusion: IGC is a promising, low‐cost, easy‐to‐apply, and high‐accuracy technique for the investigation of the surface properties of biomasses and their ability to separate isomers. The surface properties and separation ability of xylene isomers of Urtica dioica leaves, roots and seeds were investigated using the inverse gas chromatography (IGC) technique. Characterization of biomass was carried out by FTIR analysis. The surfaces of biomasses were determined to be a basic by IGC. It was also observed that it effectively separate Xylene isomers. [ABSTRACT FROM AUTHOR]

The thermodynamic properties of 4-(octyloxy) benzoic acid (OBA) liquid crystal (LC) were investigated at infinite dilution by inverse gas chromatography (IGC). The phase transition temperatures of OBA LC were determined by differential scanning calorimetry (DSC) and IGC. The thermodynamic region was determined to be between 160 and 170 °C. Specific retention volumes were calculated using IGC measurements to prepare retention diagrams. The results from the diagrams were used to characterize the thermodynamic properties of the OBA LCs. Based upon these properties, the solvents used in this study were determined to be unsuitable for OBA LCs. The separation of structural isomer series (butyl acetate, butyl alcohol, and amyl alcohol series) was studied by an OBA LC coated Chromosorb W stationary phase in the thermodynamic region. This system was able to distinguish the isomers according to the determined selectivity coefficients. [ABSTRACT FROM AUTHOR]