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    Enzymatic oxidative polymerization of para-imine functionalized phenol catalyzed by horseradish peroxidase
    (WILEY-BLACKWELL, 2015) Kumbul, Altug; Gokturk, Ersen; Turac, Ersen; Sahmetlioglu, Ertugrul
    Enzymatic 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.
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    Synthesis and characterization of conducting copolymer of (N (1),N (3)-bis(thiophene-3-ylmethylene)benzene-1,3-diamine-co-3,4-ethylenedioxythiophene)
    (VERSITA, 2010) Kumbul, Altug; Turac, Ersen; Dursun, Tugba; Sahmetlioglu, Ertugrul
    Electrochemical copolymerization of N (1),N (3)-bis(thiophene-3-ylmethylene)benzene-1,3-diamine (TMBA) with 3,4-ethylenedioxythiophene (EDOT) was carried out in a CH3CN/LiClO4 (0.1 M) solvent-electrolyte via potentiodynamic electrolysis. Chemical structure of the monomer was determined by nuclear magnetic resonance (H-1 NMR) and Fourier transform infrared (FTIR) spectroscopy. The resulting copolymer was characterized by cyclic voltammetry (CV), FTIR, scanning electron microscopy (SEM), and thermogravimetry analyses (TGA). Conductivity measurements of the copolymer and PEDOT (poly(3,4-ethylenedioxythiophene)) were carried out by the four-probe technique.
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    Synthesis and characterization of imine-functionalized polyphenol via enzymatic oxidative polycondensation of a bisphenol derivative
    (SPRINGER, 2016) Kocak, Aysegul; Kumbul, Altug; Gokturk, Ersen; Sahmetlioglu, Ertugrul
    Enzymatic oxidative polycondensation of a new bisphenol derivative 3,3'-((1E,1'E)-(1,3-phenylenebis(azanylylidene))bis(methanylylidene))diphenol, (3,3'-PBAMD), using horseradish peroxidase (HRP) enzyme and hydrogen peroxide (H2O2) oxidizer for initiation of the reaction, has been investigated in an equivolume mixture of an organic solvent (acetone, methanol, ethanol, dichloromethane, 1,4-dioxane and tetrahydrofuran) and phosphate buffer (pH = 5.0, 6.0, 7.0, 8.0 and 9.0) at different temperatures under air for 24 h. The resulting polymer, poly(3,3'-PBAMD), was characterized using ultraviolet-visible (UV-Vis), Fourier transform infrared (FT-IR), H-1 nuclear magnetic resonance (NMR), gel permeation chromatography (GPC) and thermogravimetric (TGA) analyses. Effects of solvent system, reaction temperature and pH on the polymerization have been investigated with respect to the yield and molecular weight (M-n) of the product. The optimum reaction condition in terms of the highest yield (81 %) and molecular weight (M-n = 10,500 g/mol, DP similar to 33) was achieved in an equivolume mixture of tetrahydrofuran/pH 7.0 phosphate buffer medium at 25 degrees C. Polymerization involved hydrogen elimination from the monomer, and terminal units of the polymer 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. The resulted product has shown relatively high thermal stability against thermal decomposition, and 35 % of the initial weight of the sample (carbonaceous residue) remained after heating to 1000 degrees C.
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    Synthesis, characterization, thermal stability and electrochemical properties of ortho-imine-functionalized oligophenol via enzymatic oxidative polycondensation
    (SPRINGER, 2016) Kumbul, Altug; Gokturk, Ersen; Sahmetlioglu, Ertugrul
    Ortho-imine functionalized oligophenol was synthesized via enzymatic polymerization of 2-((4-nitrophenylimino) methyl) phenol (NPIMP). Enzymatic polymerization was catalyzed by Horseradish peroxidase (HRP) enzyme and hydrogen peroxide (H2O2) oxidizer yielded oligophenol with imine functionality on the side-chain. Effects of various factors including reaction pH, temperature and solvent system on the polymerization were studied. Optimum polymerization with the highest yield (96 %) and number-average molecular weight (M-n = 7300 g/mol, degree of polymerization approximate to 30) was accomplished using equivolume mixture of acetone/pH 7.0 phosphate buffer medium at 35 degrees C in 24 h under air. Characterization of the resulting oligomer was accomplished by ultraviolet-visible spectroscopy (UV-Vis), fourier transform infrared spectroscopy (FT-IR), H-1 and C-13 nuclear magnetic resonance (H-1 and C-13 NMR), thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), cyclic voltammetry (CV) and gel permeation chromatography (GPC). The polymerization involved elimination of hydrogen from NPIMP, and the oligomer possessed phenolic -OH end groups. The oligomer backbone was composed of oxyphenylene and phenylene repeat units. The optical band gaps (Eg) of NPIMP and oligo(NPIMP) were measured as 3.21 and 3.39 Eg, respectively. Thermal stability of the oligo(NPIMP) was also found to be relatively high, and lost 5 % of its mass at 175 degrees C and lost 50 % of its mass at 600 degrees C.