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Öğe Chemoenzymatic polycondensation of para-benzylamino phenol(Springer International Publishing Ag, 2016) Yildirim, Pinar; Gokturk, Ersen; Turac, Ersen; Demir, Haci O.; Sahmetlioglu, Ertugrulpara-Benzylamine substituted oligophenol was synthesized via enzymatic oxidative polycondensation of 4-(benzylamino) phenol (BAP). Polymerization involved only the phenolic moiety without oxidizing the sec-amine (benzylamine) group. Chemoselective polycondensation of BAP monomer using HRP enzyme yielded oligophenol with sec-amine functionality on the side-chain. Effects of various factors including solvent system, reaction pH and temperature on the polycondensation were studied. Optimum polymerization process with the highest yield (63 %) and molecular weight (M-n = 5000, degree of polymerization approximate to 25) was achieved using the EtOH/buffer (pH 5.0; 1 : 1 vol. ratio) at 25 degrees C in 24 h under air. Characterization of the oligomer was accomplished by H-1 NMR and C-13 NMR, Fourier transform infrared spectroscopy (FT-IR), gel permeation chromatography (GPC), ultraviolet-visible spectroscopy (UV-Vis), cyclic voltammetry (CV) and thermogravimetric analysis (TGA). The polymerization process involved the elimination of hydrogen from BAP, and phenolic -OH end groups of the oligo(BAP), confirmed using H-1 NMR and FT-IR analyses. The oligomer backbone possessed phenylene and oxyphenylene repeat units, and the resulting oligomer was highly soluble in common organic solvents such as acetone, CHCl3, 1,4-dioxane, N, N-dimethylformamide (DMF), tetrahydrofurane (THF) and dimethylsulfoxide (DMSO). Oligo(BAP) was thermally stable and exhibited 5 % and 50 % mass loss determined by thermogravimetric analysis at 247 degrees C and 852 degrees C, respectively. (c) 2015 Institute of Chemistry, Slovak Academy of SciencesÖğe Chemoenzymatic Polymerization of Hydrazone Functionalized Phenol(Maik Nauka/Interperiodica/Springer, 2016) Isci, Irfan; Gokturk, Ersen; Turac, Ersen; Sahmetlioglu, ErtugrulHydrazone substituted oligophenol was synthesized via enzymatic oxidative polymerization of (E)-2-((2-phenylhydrazono) methyl) phenol. Enzymatic polymerization catalyzed by Horseradish peroxidase (HRP) enzyme and H2O2 oxidizer yielded oligophenol with hydrazone functionality on the side-chain. Effects of various factors including solvent system, reaction pH and temperature on the polymerization were studied. Optimum polymerization conditions with the highest yield (84%) and molecular weight (M-n = 8 x 103, DP approximate to 37, PDI - 1.11) was achieved using MeOH/pH 6.0 buffer (1 : 1 vol %) at 25 degrees C in 24 h under air. Synthesized oligomer was characterized by H-1 and C-13 NMR, FTIR, UV-Vis spectroscopy, GPC, cyclic voltammetry and thermo-gravimetric analyses. The polymerization involved hydrogen elimination from the monomer, and terminal units of the oligomer structure consisted of phenolic hydroxyl (-OH) end groups. The oligomer backbone possessed phenylene and oxyphenylene repeat units. The resulting oligomer was completely soluble in common organic solvents. The oligomer was thermally robust and exhibited 5% mass loss at 375 degrees C and 50% mass loss at 440 degrees C.Öğe Enzymatic oxidative polymerization of para-imine functionalized phenol catalyzed by horseradish peroxidase(Wiley-Blackwell, 2015) Kumbul, Altug; Gokturk, Ersen; Turac, Ersen; Sahmetlioglu, ErtugrulEnzymatic oxidative polymerization of a new para-imine functionalized phenol derivative, 4-(4-hydroxybenzylideneamino)benzoic acid (HBBA), using horseradish peroxidase enzyme and hydrogen peroxide oxidizer has been investigated in an equivolume mixture of an organic solvent (acetone, methanol, ethanol, dimethylformamide, 1,4-dioxane, and tetrahydrofuran) and phosphate buffer (pH=5.0, 6.0, 6.8, 7.0, 7.2, 8.0, and 9.0) at different temperatures under air for 24h. The resulting oligomer, oligo(4-(4-hydroxybenzylideneamino)benzoic acid) [oligo(HBBA)], was characterized using ultraviolet-visible, Fourier transform infrared (FT-IR), H-1 nuclear magnetic resonance (NMR), cyclic voltammetry, size exclusion chromatography, differential scanning calorimetry, and thermogravimetric analyses. Polymerization involved carbon dioxide and hydrogen elimination from the monomer, and terminal units of the oligomer structure consisted of phenolic hydroxyl (-OH) groups at the ends. The polymer is mainly composed of a mixture of phenylene and oxyphenylene units according to H-1 NMR and FT-IR analyses. Effects of solvent system, temperature and buffer pH on the polymerization have been investigated in respect to the yield and molecular weight (M-n) of the product. The best condition in terms of the highest molecular weight (M-n=3000g/mol, DP similar to 15) was achieved in an equivolume mixture of 1,4-dioxane/pH 5.0 phosphate buffer condition at 35 degrees C. Electrochemical characterization of oligo(HBBA) was investigated at different scan rates. The resulting oligomer has also shown relatively high thermal stability according to thermogravimetric analysis. Copyright (c) 2015 John Wiley & Sons, Ltd.Öğe Horseradish peroxidase-based hybrid nanoflowers with enhanced catalytical activities for polymerization reactions of phenol derivatives(Wiley, 2020) Gokturk, Ersen; Ocsoy, Ismail; Turac, Ersen; Sahmetlioglu, ErtugrulCatalytic activity and stability of HRP-Cu2+ hybrid nanoflowers (hCu-NFs) in the polymerization reactions of phenol derivatives was investigated. It was observed that the catalytic activity and stability of hybrid nanoflowers on the polymerization of the phenol derivatives was considerably higher compared to free Horseradish peroxidase (HRP) enzyme. The hCu-NFs effectively polymerized phenolic compounds as a novel nanobiocatalyst and led to polymers having quite high yields, molecular weights, and thermal stabilities compared to free HRP enzyme. The hCu-NFs provide substantial repeated use and showed some degree of catalytic activity even after fourth cycle experiment in the polymerization reactions.Öğe Synthesis of Conducting Polymer/Zinc Sulfide Nanocomposite Films and Investigation of Their Electrochemical and Morphological Properties(Wiley-Hindawi, 2015) Turac, Ersen; Sahmetlioglu, Ertugrul; Gokturk, ErsenPolypyrrole-zinc sulfide (PPy-ZnS) and poly(3,4-ethylenedioxythiophene)-zinc sulfide (PEDOT-ZnS) composite films were synthesized and characterized. Their electrochemical behaviors were investigated. The synthesis of PPy-ZnS and PEDOT-ZnS composite films was carried out by electropolymerization of pyrrole and 3,4-ethylenedioxythiophene in the presence of ZnS nanoparticles dispersed in the electrolytic solution. The structures of the PPy-ZnS and PEDOT-ZnS composite films were characterized by the use of scanning electron microscopy, atomic force microscopy, and UV-vis spectroscopy. Cyclic voltammetry was used to determine the electrochemical behavior of the resulting materials. The Energy Dispersive X-Ray mapping (EDX mapping) method was used to detect the existence of Zn and S ions on PPy-ZnS and the Zn ion on PEDOT-ZnS composite films. A four-probe technique was used to measure the conductivity of PPy-ZnS and PEDOT-ZnS composite films along with PPy and PEDOT.
