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    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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    Öğe
    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.