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Öğe Alternative Approach for Synthesizing Polyglycolic Acid Copolymers from Cl Feedstocks and Fatty Ester Epoxides(Amer Chemical Soc, 2019) Reyhanoglu, Yusuf; Sahmetlioglu, Ertugrul; Gokturk, ErsenOver 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.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 Comparisons of pulsed ultrasound-assisted and hot-acid extraction methods for pectin extraction under dual acid mixtures from onion (Allium cepa L.) waste(Wiley, 2023) Sen, Emine; Gokturk, Ersen; Hajiyev, Vugar; Uguzdogan, ErdalThe aim of this study is to compare the physicochemical properties and yields of pectins extracted from onion waste under hot acid (HAE) and pulsed ultrasound-assisted extraction (PUAE) methods using different organic-inorganic acids, their mixtures, and pure water. The extraction temperature for experiments carried out under HAE was kept at 90? for 90 min, whereas PUAE experiments were accomplished at RT in 15 min. In general, HAE gave better pectin yields compared with PUAE due to the significance of the increasing extraction temperature for the release of pectin from the plant matrix. While the maximum pectin yield from onion waste was 16.22% for HAE, the highest yield for PUAE was 9.83%. PUAE provides less time- and energy-consuming extraction of pectin within 15 min and thus seems to be more economic compared with the HAE. According to the physicochemical properties (equivalent weight (EW), degree of esterification (DE), methoxyl (MeO), and galacturonic acid (Gal-A) contents) of obtained pectins, extracted pectins were mostly high methoxy pectin. While the DE and MeO values of pectins extracted in organic acid conditions under HAE were higher, these values were found to be higher for pectins extracted in inorganic acids under PUAE. For acid mixtures, the DE and MeO values of pectins under HAE were mostly found to be lower than those under PUAE. Sequential PUAE and HAE methods for the extraction of pectin from onion waste were also found to be useful in terms of obtaining higher yields and better physicochemical properties. The highest pectin yield was 20.32% for the sequential PUAE and HAE methods. FT-IR analyses of the extracted pectins by both HAE and PUAE methods showed similar vibration bands compared with those of commercial citrus pectin.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 Flowerlike hybrid horseradish peroxidase nanobiocatalyst for the polymerization of guaiacol(Tubitak Scientific & Technological Research Council Turkey, 2020) Gokturk, ErsenIn this study, the catalytic activity and stability of flowerlike hybrid horseradish peroxidase (HRP) nanobiocatalyst (HRP-Cu2+) obtained from Cu2+ ions and HRP enzyme in the polymerization reaction of guaiacol were analyzed. We demonstrated that HRP-Cu2+ and hydrogen peroxide (H2O2) initiator showed significantly increased catalytic activity and stability on the polymerization of guaiacol compared to that of free HRP enzyme. Poly(guaiacol) was observed with quite high yields (88%) and molecular weights (38,000 g/mol) under p11 7.4 phosphate-buffered saline (PBS) conditions at 60 degrees C. with 5 weight% of HRP-Cu2+ loading. HRP-Cu2+ also shows very high thermal stability and works even at 70 degrees C reaction temperature; free HRP enzyme denatures at that temperature. Furthermore, HRP-Cu2+ provided considerable repeated use and showed some degree of catalytic activity, even after the fourth recycle, in the polymerization of guaiacol.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 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, ErtugrulEnzymatic 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.Öğe Investigation of Peroxidase-Like Activity of Flower-Shaped Nanobiocatalyst from Viburnum Opulus L. Extract on the Polymerization Reactions(Turkish Chemical Society, 2024) Kalayci, Berkant; Kaplan, Naime; Mirioglu, Muge; Dadi, Seyma; Ocsoy, Ismail; Gokturk, ErsenHere, we report the effects of peroxidase-mimicking activity of flower shaped hybrid nanobiocatalyst obtained from Viburnum-Opulus L. (Gilaburu) extract and Cu2+ ions on the polymerization of phenol and its derivatives (guaiacol and salicylic acid). The obtained nanoflowers exhibited quite high catalytic activity upon the polymerization of phenol and guaiacol. The yields and the number average molecular weights of the obtained polymers were significantly high. Due to solubility issue of salicylic acid in aqueous media, polymerization of salicylic acid resulted in very low yields. Free-horseradish peroxidase (HRP) enzyme is known to be losing its catalytic activity at 60 °C and above temperatures. However, the synthesized nanoflowers exhibited quite high catalytic activity even at 60 °C and above reaction temperatures. This provides notable benefits for reactions needed at high temperatures, and it is very important to use these kinds of nanobiocatalysts for both scientific studies and industrial applications. © 2024, Turkish Chemical Society. All rights reserved.Öğe Microwave-assisted extraction of pectin from onion and garlic waste under organic, inorganic and dual acid mixtures(Springer, 2024) Sen, Emine; Gokturk, Ersen; Uguzdogan, ErdalThis study aims to investigate pectin extraction from garlic (GW) and onion waste (OW) by microwave-assisted (MAE) and sequential microwave assisted-hot acid extraction (MAHE) methods. All extractions were performed under three different media including organic acids [citric (CA) and acetic (AA)], inorganic acids [sulfuric (H2SO4) and hydrochloric (HCl)] and their mixtures. GW provided more pectin yields compared with OW. While the highest pectin yields from GW and OW by MAE in H2SO4 were respectively 24.62 +/- 0.65 and 24.93 +/- 0.59%, these yields under MAHE were 27.99 +/- 0.36 and 28.43 +/- 0.42%, respectively. Higher pectin yields and galacturonic acid (Gal-A) contents were mostly achieved in inorganic acids. However, degree of esterification (DE), methoxyl content (MeO) and equivalent weight (EW) values were higher for the pectins extracted under organic acids. Extraction of pectin from GW and OW was also accomplished in dual acidic media by MAE. Addition of inorganic acids to the organic acid solutions resulted in increasing pectin yields. The highest pectin yields from GW and OW under dual acid solutions were respectively 23.36 +/- 0.66 and 21.88 +/- 0.52%, and achieved in 1/3 HCl-H2SO4 and 1/3 CA-H2SO4 mixtures by MAE. While increasing inorganic acid contents in dual acid solutions resulted in enhanced Gal-A contents, increasing organic acid volume also generated higher DE and MeO values of the pectins. Obtained successful outcomes indicate that MAHE method could be used as an efficient extraction technique for the higher pectin yields, and utilization of organic-inorganic dual acid mixtures during MAE provides enhanced yields and controlled physicochemical properties of pectin.Öğe 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]Öğe One-Step Solvent-Free Synthesis of Polyglycolic Acid from Sustainable C1 Feedstocks(Wiley-V C H Verlag Gmbh, 2021) Reyhanoglu, Yusuf; Kalayci, Berkant; Gokturk, ErsenPolyglycolic acid (PGA) is an aliphatic biodegradable polyester commonly synthesized through the ring opening polymerization of glycolide using mostly tin (II) octoate catalyst. Previously, a very convenient method for the synthesis of PGA from the cationic alternating copolymerization of formaldehyde (from trioxane) and carbon monoxide (CO) with triflic acid (TfOH) catalyst in dichloromethane (DCM) at 170 degrees C is described with 92% of yield. The need of using harmful DCM solvent for this polymerization directs to discover solvent-free polymerization of formaldehyde and CO. Here, one-step solvent-free synthesis of PGA from the cationic alternating copolymerization of formaldehyde and CO is presented. Unlike the polymerization carried out in DCM solvent, optimum polymerization in solvent-free conditions with TfOH catalyst is achieved in 80% of yield at 130 degrees C. It is considered that utilization of solvent-free conditions and lower reaction temperatures compared to the previous report provides a more green and economic way of the synthesis of PGA. The method is also extended to copolymerization strategy by adding a minor amount of an epoxide compound to the reaction mixture, and PGA-based copolymer with improved physical properties (such as solubility and appearance) is obtained in solvent-free conditions.Öğe Pectin extraction from garlic waste under dual acid condition(Wiley-Hindawi, 2022) Sen, Emine; Gokturk, Ersen; Uguzdogan, ErdalA novel approach for the extraction of pectin from garlic waste (peel, stem, and straw) was accomplished under dual acid solution conditions including two organic (citric acid [CA] and acetic acid [AA]), two inorganic (hydrochloric acid [HCl] and sulfuric acid [H2SO4]) and six different mixtures of these acids (CA-HCl, CA-H2SO4, CA-AA, AA-H2SO4, AA-HCl, and HCl-H2SO4) with 1/30 (v/w) solid-liquid ratio at 90 degrees C in 90 min extraction duration. The effects of acid mixture on the yields and physicochemical properties of the extracted pectins from garlic waste were investigated. Applying different acid mixtures during the extraction process allowed to obtain pectin samples with controlled physicochemical properties and higher yields. The maximum pectin yield of 22.4% was observed in the extraction condition carried out HCl-H2SO4 (1/3 v/v) mixture. Extractions carried out under dual acid mixtures showed higher Gal-A contents compared with the conditions where organic or inorganic acids were used alone. The extracted pectin samples were generally composed of high methoxyl pectin and their methoxyl contents are observed to be close to that of commercial citrus pectin. FT-IR spectra results of the extracted samples from garlic waste confirmed the pectin structure compared with the FT-IR spectrum of commercial citrus pectin. Results indicate that organic-inorganic dual acid mixtures could be used as an efficient extraction media for the controlled physicochemical properties and higher yields of pectin extraction. Considering that about 3.7 million tons of garlic waste is annually produced worldwide, it could be very beneficial to obtain pectin from these wastes as a useful product for the industry. Practical applications Garlic waste was converted into a valuable product for the industry and used as an alternative pectin source. Applying organic-inorganic dual acid mixtures during the pectin extraction process from garlic waste allowed to obtain pectin samples with controlled physicochemical properties and higher yields. Extracted pectin samples showed higher Gal-A contents compared with the conditions where organic or inorganic acids used alone. Obtained pectins were generally composed of high methoxyl pectins and their methoxyl contents are observed to be close to that of the commercial citrus pectin.Öğe Polyglycolic acid copolymers from one-step cationic polymerization of formaldehyde, carbon monoxide, and epoxides derived from PEG(Wiley, 2019) Reyhanoglu, Yusuf; Gokturk, ErsenBiodegradable polyglycolic acid (PGA) is conventionally produced via the ring-opening polymerization of glycolide, the cyclic dimer form of glycolic acid, in the presence of mostly tin-based catalyst initiators which are rather known to be cytotoxic materials. Our previous studies revealed an alternative method for the synthesis of PGA from the perfectly alternating copolymerization of formaldehyde (from trioxane) and carbon monoxide (CO) under Bronsted acidic conditions. The poor physical properties of PGA (insolubility in many organic solvents, brown color, etc.) limit its use in other marketing applications in the industry. To improve on the physical properties of PGA, such as solubility and appearance, copolymerization of trioxane, CO, and a minor amount of epoxides derived from polyethylene glycol (PEG) were performed under the same reaction conditions for PGA synthesis (in DCM, at 800 psi CO pressure, with triflic acid catalyst, reaction duration of 72 hours). The results have shown that the addition of minor quantities of epoxide comonomers vastly improves the appearance of the obtained PGA copolymers and allows for the control of the polymeric properties, such as solubility and melting temperature.Öğe Polyglycolic acid from the direct polymerization of renewable C1 feedstocks(Royal Soc Chemistry, 2015) Gokturk, Ersen; Pemba, Alexander G.; Miller, Stephen A.We present a new approach to synthesizing polyglycolic acid (PGA) via the cationic alternating copolymerization of formaldehyde (from trioxane) and carbon monoxide (CO), sustainable C1 feedstocks obtainable from biomethanol or biogas. This method constitutes an inexpensive and efficient pathway for the synthesis of PGA, circumventing the usual route requiring glycolide. PGA was successfully synthesized with yields up to 92% from trioxane, 800 psi of CO, and 1 mol% triflic acid (TfOH) initiator at 170 degrees C over three days. H-1 NMR, C-13 NMR, and FT-IR spectra of the polymer from CO and trioxane are identical to those of commercial PGA prepared via the ring-opening polymerization of glycolide-confirming the alternating microstructure. Although high copolymerization conversions were obtained, molecular weight analysis usually suggested the formation of oligomeric glycolic acid (OGA). High molecular weight PGA can be obtained via post-polymerization polycondensation of OGA catalyzed by Zn(OAc)(2)center dot 2H(2)O. Alternatively, increased molecular weight PGA can be achieved by inclusion of glycerol as a branching agent during the C1 copolymerization.Öğe Production of flower-shaped nanobiocatalysts from green tea and investigation of their peroxidase mimicking activity on the polymerization of phenol derivatives(Wiley, 2024) Kalayci, Berkant; Kaplan, Naime; Dadi, Seyma; Ocsoy, Ismail; Gokturk, ErsenEnzyme catalyzed reactions are known to be environmental friendly and easy method for many applications. However, utilization of enzymes in a variety of reactions is strictly limited due to their high cost, instability in aqueous solutions, denaturation in organic solvents and high temperatures. For this reason, it is important to discover new generation catalyst systems indicating enzyme-like catalytic activity. Here, we report hybrid organic-inorganic flower-shaped green tea-Cu2+ nanobiocatalyst synthesized from green tea extract as an organic component and copper (II) ions (Cu2+) as inorganic component. The effect of the peroxidase-mimicking activity of green tea-Cu2+ nanobiocatalyst was investigated on the polymerization of phenol and derivatives (guaiacol and salicylic acid) through Fenton-like reaction mechanism. Obtained successful outcomes showed that the synthesized nanobiocatalyst showed very high catalytic activity upon polymerization of phenol and guaiacol. The slight solubility of salicylic acid in water limited to achieve its polymerization under-performed reaction conditions. The yields and molecular weights of the obtained polymers were found to be quite high. While free peroxidase enzymes like horseradish peroxidase (HRP) enzyme loses its catalytic activity at 60 degrees C and above temperatures, green tea-Cu2+ nanobiocatalyst exhibited very high catalytic activity upon polymerization reactions even at 60 degrees C reaction temperature. This outcome provides significant advantages in some reactions requiring high temperatures. In order to understand the origin of the catalytic activity of the green tea-Cu2+ nanoflowers, similar biocatalysts were also synthesized from caffeine and catechin alkaloids which are the active components of green tea. Caffeine-Cu2+ and catechine-Cu2+ nanobiocatalysts also exhibited quite high catalytic activity toward polymerization of phenol and derivatives. We suggest that green tea-Cu2+ and similar types of nanobiocatalysts may expand their utilization in polymer chemistry as promising catalytic agents for radicalic polymerizations.Öğe 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.Öğe Sustainable polysiloxanes via siloxane metathesis(Amer Chemical Soc, 2015) Sahmetlioglu, Ertugrul; Gokturk, Ersen; Nsengiyumva, Olivier; Miller, Stephen[Abstract Not Available]Öğe Synthesis and characterization of imine-functionalized polyphenol via enzymatic oxidative polycondensation of a bisphenol derivative(Springer, 2016) Kocak, Aysegul; Kumbul, Altug; Gokturk, Ersen; Sahmetlioglu, ErtugrulEnzymatic 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.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.
