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    Alternative Approach for Synthesizing Polyglycolic Acid Copolymers from Cl Feedstocks and Fatty Ester Epoxides
    (Amer Chemical Soc, 2019) Reyhanoglu, Yusuf; Sahmetlioglu, Ertugrul; Gokturk, Ersen
    Over the past couple of years, replacement of petroleum-based products with biodegradable and biorenewable is an emerging topic in polymer science. Biodegradable polyglycolic acid (PGA), the simplest aliphatic linear polyester, can traditionally be synthesized through the ring-opening polymerization of glycolide. Our previous studies revealed that PGA can alternatively be produced via one-step cationic polymerization of formaldehyde from trioxane and carbon monoxide (CO), which are potentially sustainable C1 feedstocks, under Bronsted acidic conditions. In this study, trioxane, CO, and a minor amount of fatty ester epoxides are copolymerized to improve on the physical properties of PGA, such as solubility and appearance, under the same reaction conditions for PGA homopolymer synthesis (in DCM, at 800 psi CO, with triflic acid catalyst, reaction duration of 72 h). The results have shown that the addition of minor quantities of epoxide comonomers vastly improved the solubility and decreased the melting temperature of the PGA. The melting temperatures of the obtained copolymers decreased by increasing incorporation percentages of the epoxide comonomers and decreasing polymerization temperatures. The solubility of the copolymers increased with incorporation of the epoxides in the PGA backbone.
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    Chemoenzymatic polycondensation of para-benzylamino phenol
    (Springer International Publishing Ag, 2016) Yildirim, Pinar; Gokturk, Ersen; Turac, Ersen; Demir, Haci O.; Sahmetlioglu, Ertugrul
    para-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 Sciences
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    Chemoenzymatic Polymerization of Hydrazone Functionalized Phenol
    (Maik Nauka/Interperiodica/Springer, 2016) Isci, Irfan; Gokturk, Ersen; Turac, Ersen; Sahmetlioglu, Ertugrul
    Hydrazone 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.
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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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    Horseradish peroxidase-based hybrid nanoflowers with enhanced catalytical activities for polymerization reactions of phenol derivatives
    (Wiley, 2020) Gokturk, Ersen; Ocsoy, Ismail; Turac, Ersen; Sahmetlioglu, Ertugrul
    Catalytic 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.
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    Horseradish peroxidase-catalyzed polymerization of ortho-imino-phenol: Synthesis, characterization, thermal stability and electrochemical properties
    (Elsevier Science Bv, 2017) Topal, Yasemin; Tapan, Senem; Gokturk, Ersen; Sahmetlioglu, Ertugrul
    Enzymatic polymerization of phenols has been investigated extensively over the last decades. However, involving imine functional group in the side chain of an oligophenol and its effect on polymerization is poorly understood. Therefore, the influence of the imine functionality in the side chain of oligophenol for enzymatic polymerization is explored in this work. Ortho-imine substituted phenol, (E)-2-((p-tolylimino) methyl) phenol (PTIMP), was enzymatically polymerized using horseradish peroxidase (HRP) enzyme in aqueous organic solvents and hydrogen peroxide (H2O2) as an oxidant. Different parameters (solvent system, pH and reaction temperature) on polymerization were investigated. EtOH/pH 6.0 buffer (50: 50 vol.%) at 25 degrees C in 24 h under air was found to be the optimum polymerization condition with 65% of yield and Mn = 6100 g/mol (DP approximate to 29, PDI = 1.09). Polymerization of PTIMP in the presence of HRP enzyme catalyst leads to the formation of an oligophenol containing phenylene and oxyphenylene repeat units. The resulting oligophenol is soluble in most of the organic solvents. Characterization of oligo(PTIMP) was achieved by NMR, UV-Vis, CV, FT-IR spectroscopy and thermogravimetric analysis. (C) 2017 King Saud University. Production and hosting by Elsevier B. V. This is an open access article under the CC BY-NC-ND license.
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    Nature-derived renewable polymers to replace commodity plastics
    (Amer Chemical Soc, 2018) Nsengiyumva, Olivier; Sahmetlioglu, Ertugrul; Ha Thi Hoang Nguyen; Gokturk, Ersen; Miller, Stephen
    [Abstract Not Available]
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    Silicon Acetal Metathesis Polymerization
    (Amer Chemical Soc, 2016) Sahmetlioglu, Ertugrul; Ha Thi Hoang Nguyen; Nsengiyumva, Olivier; Gokturk, Ersen; Miller, Stephen A.
    A kinetic study revealed that the acid-catalyzed (p-TSA) equilibration of Me2Si(OMe)(2) and Me2Si(OEt)(2), forming Me2Si(OEt)OMe, is established in 300 min in benzene at room temperature. This silicon acetal metathesis reaction is exploited for the step-growth polymerization of bissilicon acetals (MeOSiMe2OROSiMe2OMe) with metathetical loss of Me2Si(OMe)(2). Thus, a convenient and generalized silicon acetal metathesis polymerization (SAMP) method is introduced as the acid-catalyzed copolymerization of a diol (HOROH) and Me2Si(OMe)(2), driven by elimination of methanol and/or Me2Si(OMe)(2). SAMP constitutes an effective and powerful strategy for manipulating the most common bond in the Earth's crust, the silicon oxygen bond.
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    Sustainable polysiloxanes via siloxane metathesis
    (Amer Chemical Soc, 2015) Sahmetlioglu, Ertugrul; Gokturk, Ersen; Nsengiyumva, Olivier; Miller, Stephen
    [Abstract Not Available]
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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 of Conducting Polymer/Zinc Sulfide Nanocomposite Films and Investigation of Their Electrochemical and Morphological Properties
    (Wiley-Hindawi, 2015) Turac, Ersen; Sahmetlioglu, Ertugrul; Gokturk, Ersen
    Polypyrrole-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.
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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.