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    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, Ersen
    Here, 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.
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    One-Step Solvent-Free Synthesis of Polyglycolic Acid from Sustainable C1 Feedstocks
    (Wiley-V C H Verlag Gmbh, 2021) Reyhanoglu, Yusuf; Kalayci, Berkant; Gokturk, Ersen
    Polyglycolic 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.
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    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, Ersen
    Enzyme 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.