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    Comparative Study of Enzymatic and Oxidative Polymerization of a Benzothiazole-Based Schiff Base and Its Antibacterial Properties
    (Springer Heidelberg, 2025) Kaya, Ismet; Solmaz, Adnan; Abuawad, Mohammed Majed Shible
    In this study, the Schiff base 1-(((6-nitrobenzo[d]thiazol-2-yl) imino)methyl)naphthalen-2-ol (NBTIMN) was synthesized and subsequently polymerized by two different methods. Oxidative polymerization in the presence of organic (o-(NBTIMN)-O) and aqueous alkaline media (o-(NBTIMN)-A) was one of the techniques. The other was enzyme-catalyzed oxidative polymerization (o-(NBTIMN)-E), which was conducted at room temperature with hydrogen peroxide and the enzyme horse radish peroxidase (HRP). The structures of the obtained oligomers were characterized using FT-IR, 1H-13C-NMR, UV-Vis, CV, and GPC analyses, and their electrochemical and optical band gaps were determined as 2.68, 2.66, and 2.49 eV, and 3.08, 2.90, and 3.07 eV for o-(NBTIMN)-O, o-(NBTIMN)-A, and o-(NBTIMN)-E, respectively. Thermal analyses demonstrated that the o-(NBTIMN)-O and o-(NBTIMN)-A derivatives exhibited enhanced thermal stability, characterized by higher decomposition temperatures and LOI values. SEM analyses revealed distinct differences in surface morphologies depending on the polymerization conditions. Antibacterial assays showed that o-(NBTIMN)-O exhibited the strongest broad-spectrum inhibition, whereas NBTIMN displayed pronounced activity against S. aureus. In contrast, o-(NBTIMN)-A and o-(NBTIMN)-E were found to be inactive. These results highlight the critical influence of polymerization conditions on both the physicochemical characteristics and the biological activities of the synthesized structures. Importantly, the comparative design of enzymatic and chemical polymerization demonstrates the potential for environmentally friendly synthesis strategies. The distinct electrochemical and thermal properties suggest applicability in electronics and sensor-related fields, while the pronounced antibacterial activity of o-(NBTIMN)-O holds promise for biomedical and antimicrobial applications.
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    Öğe
    Design and thermal profiling of ethyl carbazole-based poly(phenoxy-imine)s: synthesis and characterization
    (Springer, 2025) Kaya, Ismet; Yilmaz, Mehmet Hakan; Kolcu, Feyza
    A series of Schiff base monomers were synthesized via the condensation of 3-amino-9-ethylcarbazole with various aldehydes, including 3-hydroxybenzaldehyde (3-HBA), 4-hydroxybenzaldehyde (4-HBA), 2-hydroxy-1-naphthaldehyde (2-HNA), and ortho-vanillin. These monomers were subsequently polymerized through oxidative polycondensation using NaOCl as the oxidant to yield corresponding poly(phenoxy-imine)s, namely Poly(3ECIMP), Poly(4ECIMP), Poly(ECIMN), and Poly(ECIMMP). The chemical structures of the synthesized compounds were confirmed using FTIR, UV-Vis, and both 1H and 13C NMR spectroscopy. Thermal characterization using TG-DTA and DSC demonstrated that the synthesized polymers possess excellent thermal stability, as evidenced by their glass transition temperatures between 145 and 161 degrees C and char yields reaching up to 38.22% at 1000 degrees C. Furthermore, limiting oxygen index values exceeding 28% indicate that these materials exhibit self-extinguishing behavior. Photoluminescence studies conducted in DMF demonstrated intense fluorescence, particularly for Poly(ECIMN), which exhibited yellow-orange emission upon excitation at 502 nm due to the presence of naphthalene moieties that enhance pi-electron delocalization. Optical and electrochemical band gap analyses indicated significantly reduced Eg values for the polymers compared to their monomers, with Poly(ECIMN) showing the lowest band gap of 2.39 eV. Cyclic voltammetry results aligned with optical measurements, confirming improved charge-transfer characteristics in the conjugated polymer backbone. Surface morphology assessed by FE-SEM revealed porous structures, suggesting applicability in gas adsorption or catalytic systems. Size exclusion chromatography confirmed the formation of high molecular weight polymers with narrow polydispersity indices. Collectively, the unique combination of thermal durability, photophysical responsiveness, and structural robustness highlights the potential of these ethyl carbazole-based poly(phenoxy-imine)s in applications spanning optoelectronics, thermal protection, and fluorescence-based sensing.
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    Öğe
    High thermal stability and dielectric performance of phenylhydrazine-based Schiff base oligomers obtained via oxidative polycondensation
    (Springer, 2025) Solmaz, Adnan; Kaya, Ismet; Bayir, Erdal
    In this study, the 2-PHMBD Schiff base, synthesized through the condensation of 2,4-dihydroxybenzaldehyde (2,4-DHBA) with phenylhydrazine (PH), was subjected to oxidative polymerization in a basic medium using hydrogen peroxide (H2O2), sodium hypochlorite (NaOCl), and molecular oxygen (O2) as oxidizing agents. Three oligomers, designated as o-(2-PHMBD)-P, o-(2-PHMBD)-H, and o-(2-PHMBD)-O, were successfully obtained and comprehensively characterized by FT-IR, 1H-13C-NMR, UV-Vis, CV, GPC, SEM, TGA, and DSC analyses. Spectroscopic results confirmed the successful polymerization, while morphological and thermal analyses revealed the distinct physical characteristics of the oligomers. According to GPC data, o-(2-PHMBD)-H exhibited the highest average molecular weight of 4700 Da, and TGA analysis demonstrated that o-(2-PHMBD)-O had the highest thermal stability with a residue of 46% at 1000 degrees C. The DSC results showed the highest glass transition temperature of 132 degrees C for o-(2-PHMBD)-H. UV-Vis and CV measurements indicated reduced optical and electrochemical band gaps compared with the monomer, with the lowest optical band gap determined as 2.74 eV. Dielectric measurements revealed that o-(2-PHMBD)-H displayed the highest dielectric constant of 2.57 and conductivity of 2.49 x 10(-)7 S cm(-)1. These results demonstrate that phenylhydrazine-based Schiff base oligomers possess high thermal stability and favorable dielectric properties, making them promising materials for optoelectronic and dielectric device applications.
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    Synthesis and characterization of oligomers contain phenylhydrazyne unit via oxidative polycondensation: Adsorption studies, kinetic modeling and validation methods
    (Elsevier, 2025) Bayir, Erdal; Solmaz, Adnan; Kaya, Ismet; Yagmur, Hatice Karaer
    In this study, 4-((2-phenylhydrazono)methyl)benzene-1,2-diol (4-PHBD) Schiff base was obtained from the condensation reaction between 3,4-dihydroxybenzaldehyde (3,4-DHBA) and phenylhydrazine (PH). The obtained Schiff base (4-PHBD) was polymerized using H2O2, NaOCl, and O2 oxidants in an aqueous basic medium (10 % KOH) and 4-PHBD was converted to o-(4-PHBD)-P (by H2O2 oxidant), o-(4-PHBD)-H (by NaOCl oxidant) and o-(4-PHBD)-O (by O2 oxidant). The structures of Schiff base and oligomers were characterized with FT-IR, NMR, SEM, TGA, UV-Vis, CV and GPC measurements. The Cyclic Voltammetry and UV-Vis measurements were used to ascertain the compounds' optical (Eg) and electrochemical (Eg') band gaps, respectively. The Eg values of o-(4-PHBD)-P, o-(4-PHBD)-O and o-(4-PHBD)-H were found be 2.99, 2.63 and 3.26 eV, respectively. o-(4-PHBD)-O was used as an adsorbent in the removal of methylene green (MG) from an aqueous solution. The obtained data were applied to pseudo-first order and pseudo-second order kinetic models. It was determined that the adsorption process obeyed the pseudo first order kinetic model. The kinetic model was validated with R2, RMSE, SSE, SD, Delta qe (%), MSE and ARE validation methods. The activation energy (Ea) was calculated as 7.31 kJ mol-1 using the Arrhenius equation. It was determined that the adsorption of MG on o-(4-PHBD)-O was physical adsorption.