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    Synthesis, characterization and electrochemical properties of poly (phenoxy-imine)s containing carbazole unit
    (Springer Heidelberg, 2017) Kaya, İsmet; Çöpür, Sebra; Karaer, Hatice
    Several new Schiff base polymers were synthesized via oxidative polymerization method in an aqueous alkaline medium in the presence of NaOCl as an oxidant and were confirmed by FT-IR, H-1-NMR, C-13-NMR and UV-Vis spectroscopic techniques. Furthermore, cyclic voltammetry measurements were carried out and the HOMO-LUMO energy levels and electrochemical band gaps (E-g') were calculated. Additionally, the optical band gaps (E-g) were determined using their UV-Vis spectra of the materials. The morphologic properties of the polymers were investigated by scanning electron microscopy. In addition, the number average molecular weight (M-n), weight average molecular weight (M-w) and polydispersity index values of the polymers were determined by gel permeation chromatography technique. Electrical conductivity measurements of the doped (with iodine) and undoped polymer related to doping time were carried out by four-point probe technique using a Keithley 2400 electrometer. Their thermal behaviors were determined by TG-DTA and DSC measurements. The synthesized compounds were soluble in common solvents such as DMF, THF and DMSO. Photoluminescence properties of the polymers were determined in different concentrations of DMF solvent.
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    Synthesis, characterization and electrochemical properties of poly(phenoxy-imine)s containing peril and tert-butyl units
    (Elsevier Science Bv, 2019) Kaya, İsmet; Sandal, Bekir Süleyman; Karaer, Hatice
    Schiff bases were obtained by condensation reactions of 2-aminophenol and 4-aminophenol with 4-iso propenylcyclohex-1-ene-1-carbaldehyde (peril aldehyde) and 3,5-di-tert-butyl-2-hydroxy benzaldehyde. Then, polymers of these compounds were prepared via oxidative polymerization method in THF in the presence of NaOCI as an oxidant. The structures of compounds were confirmed by some techniques such as FT-IR, H-1 NMR, C-13 NMR and UV-vis. Moreover, cyclic voltammetry (CV) was used to calculate the HOMO-LUMO energy levels and electrochemical band gaps (E-g') of compounds. Electrochemical band gaps (E-g') values of P1, P2, P3 and P4 polymers were found as 2.61, 2.65, 2.89 and 2.28 eV, respectively. Furthermore, TGA and DSC were employed to determine thermal properties of the Schiff bases and polymers. The photoluminescence (PL) properties of polymers were also determined in DMSO. Then, we found that their number-average molecular weight (M-n), weight average molecular weight (M-w) as well as polydispersity index (PDI) values by the size exclusion chromatography (SEC). Finally, we carried out their solubility tests in acetone, THF, chloroform, acetonitrile, methanol, ethyl acetate, n-hexane and DMSO. (C) 2017 The Authors. Production and hosting by Elsevier B.V. on behalf of King Saud University.
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    Synthesis, characterization and using at the copper adsorption of chitosan/polyvinyl alcohol magnetic composite
    (Elsevier, 2017) Karaer, Hatice; Kaya, İsmet
    A chitosan/polyvinyl alcohol (CTN/PVA-Fe3O4) magnetic composite was prepared in one step and examined by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy-energy dispersive X-ray analysis (SEM-EDX), transmission electron microscopy (TEM), dynamic light scattering (DLS), Brunauer-Emmett-Teller (BET), thermal gravimetric analysis/differential thermal analysis (TGA-DTA) and differential scanning calorimetry (DSC). Effects of several parameters, such as temperature, pH, and initial concentration on removal of Cu(II) from aqueous solution by the CTN/PVA magnetic composite were studied as a function of contact time. Equilibrium data obtained from sorption of Cu(II) solutions having initial concentrations of 25 to 400 mg L-1 by sorption of the CTN/PVA magnetic composite at different temperatures (25, 35 and 45 degrees C) were applied to Langmuir and Freundlich adsorption isotherms. Maximum adsorption capacity (Q(max))was found to be 143 mg g(-1) by using Langmuir isotherm model, by which thermodynamic parameters (Delta H degrees, Delta G degrees and Delta S degrees) were also calculated. Activation energy was calculated by using rate constants for this model and its value was found 26.52 kJ mol(-1). (C) 2017 Elsevier B.V. All rights reserved.
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    Synthesis, characterization of magnetic chitosan/active charcoal composite and using at the adsorption of methylene blue and reactive blue4
    (Elsevier Science Bv, 2016) Karaer, Hatice; Kaya, İsmet
    In this study, a chitosan/activated charcoal (or carbon) (CTN/AC-Fe3O4) composite was obtained in one step, characterized several techniques such as by Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, dynamic light scattering, Brunauer-EmmetTeller, thermogravimetric analysis/differential thermal analysis and differential scanning calorimetry techniques. The sorption the composite were investigated as kinetically and thermodynamically for removal of methylene blue (MB) and reactive blue4 (RB4) from aqueous solution. Effects of several parameters, such as initial temperature and initial concentration on removal of MB and RB4 from aqueous solution by the composite were investigated as a function of contact time. Maximum adsorption capacity (Qmax) was found to be 500 mg g(-1) at and 250 mg g(-1) at 318 K for MB, 298 K for RB4 respectively. Also, thermodynamic parameters such as Delta H-0, Delta G(0)and Delta S-0 were calculated by Langmuir adsorption isotherm model. Negative Gibbs free energy (Delta G(0)) implies that the adsorption is spontaneous and positive adsorption enthalpy (Delta H-0) demonstrates the process is endothermic for MB while negative adsorption enthalpy (Delta H-0) demonstrates the process is exothermic for RB4, respectively. (C) 2016 Elsevier Inc. All rights reserved.
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    Synthesis, characterization, and thermal decompositions of Schiff base polymers containing chitosan unit
    (Springer, 2015) Karaer, Hatice; Kaya, İsmet
    The most plentiful natural biopolymer chitin and chitosan have become center of attraction of all party because of an unusual combination of biological activities, mechanical and physical properties. The several chemical modifications such as oligomerization, alkylation, quternization, enzymatic modifications, and graft copolymerization along with many assorted modifications have been carried out. However, its applications have only been shown in acidic medium because of its poor solubility in neutral and basic pH. In view of rapidly growing interest in chitosan its chemical aspects and chemical modification studies are reviewed. Four different aldehyde types, namely 4-hydroxybenzaldehyde (4HBA), 2-hydroxybenzaldehyde (2HBA), vanillin (VAN), 3-thiophenecarboxaldehyde (3TPCA), and their poly(4-hydroxybenzaldehyde) (P4HBA), poly(2-hydroxybenzaldehyde) (P2HBA), and poly (vanillin) (PVAN) were treated with chitosan to obtain Schiff base polymers. Although some of the chitosan-based Schiff bases were present in the literature, contrary to the literature the aldehydes (4HBA, VAN, 2HBA) were polymerized via oxidative polycondensation, followed by their reaction with chitosan to provide the Schiff base polymers, which were characterized by several techniques such as FTIR, TGA-DTA, DSC, SEM-EDX, and UV-Vis. Also, the solid-state electrical conductivities values of the compounds were measured by four-point probe technique.
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    Synthesis, characterization, thermal and electrochemical properties of imine polymers containing pyridine and pyrimidine units
    (Industrial Chemistry Research Inst, 2017) Karaer, Hatice; Kaya, İsmet; Aydın, Haluk
    Schiff bases polymers were synthesized from 2-hydroxybenzaldehyde (2-HBA) vin oxidative polymerization method in an aqueous alkaline medium in the presence of NaOCI as an oxidant. Then, these polymeric Schiff bases were prepared from the polyaldehyde by grafting each of them with different amines containing pyridine and pyrimidine groups. The structures of polymers were confirmed by FT-IR, H-1 NMR, C-13 NMR, and UV-Vis measurements. The polymers were characterized by GPC and SEM analyses. Furthermore, their optical properties were determined by UV-Vis and fluorescence spectroscopy, their electrochemical properties by cyclic voltammetry (CV) analysis and solid state conductivity measurements by the four-point probe technique, their thermal behavior by TG, DTA, and DSC measurements. The electrical conductivity of the polymers was also measured and found that they are semiconductive. The number average molecular weight ((M) over bar (u)), the weight average molecular weight ((M) over bar (w)), and dispersity (D) values of the polymers were found from GPC analysis and were equal 5900, 5450 and 1.08, respectively, for poly(2-hydroxybenzaldehyde) (P-2HBA) polymer. Electrochemical energy gap (E-s) was found by CV, whereas optical band gap (E-s,) was determined by UV-Vis measurements.