Browsing by Author "Avci A."
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Item Synthesis, characterization, and thermal stability of novel poly(azomethine-urethane)s and polyphenol derivatives derived from 2,4-dihydroxy benzaldehyde and toluene-2,4-diisocyanate(2012) Kaya I.; Avci A.Up to date, only a few kinds of poly(azomethine-urethane)s (PAMUs) were synthesized and studied with thermal degradation steps. However, polyphenol based PAMUs including azomethine linkages have not been investigated yet. The polyurethanes were prepared by condensation reaction of 2,4- dihydroxybenzaldehyde (2,4-DHBA) with toluene-2,4-diisocyanate (TDI) under argon atmosphere. Synthesized polyurethane was converted to its poly(azomethine urethane) species (TP-2AP, TP-3AP, and TP-4AP) by graft copolymerization reactions with amino phenols (2-amino phenol, 3-amino phenol, and 4-amino phenol). Obtained poly(azomethine urethane)s were converted to their polyphenol species (P-TP-2AP, P-TP-3AP, and P-TP-4AP) by oxidative polymerization reaction (OP) using NaOCl as the oxidant. The structures of the obtained compounds were confirmed by FT-IR, UV-vis, 1H NMR, and 13C NMR techniques. The molecular weight distribution parameters of the synthesized compounds were determined by the size exclusion chromatography (SEC). The synthesized compounds were also characterized by solubility tests, TG-DTA, and DSC. Fluorescence measurements were carried out in various concentrated DMF solutions to determine the optimum concentrations to obtain the maximal PL intensities. © 2012 Elsevier B.V.Item Synthesis, characterization, and thermal degradation of new aromatic poly(azomethine-urethane)s and their polyphenol derivatives(Kluwer Academic Publishers, 2012) Kaya I.; Avci A.A new polyurethane was synthesized by condensation reaction of 2,4-dihydroxy benzaldehyde (DHB) with methylene-di-p-phenyl-diisocyanate (MDI) under argon atmosphere. The synthesized polyurethane was converted to its poly (azomethine urethane) species (MP-2AP, MP-3AP, and MP- 4AP) by graft copolymerization reactions with amino phenols (2-amino phenol, 3-amino phenol, and 4-amino phenol). Obtained poly(azomethine urethane)s (PAMUs) were converted to their polyphenol species (P-MP-2AP, P-MP-3AP, and P-MP-4AP) by oxidative polymerization reaction (OP) using NaOCl as the oxidant. The structures of the obtained compounds were confirmed by FT-IR, UV-vis, 1H-NMR, and 13C-NMR techniques. The molecular weight distribution parameters of the synthesized compounds were determined by the size exclusion chromatography (SEC). The synthesized compounds were also characterized by solubility tests, TGDTA, and DSC analyses. Thermal decomposition steps at various temperatures were clarified by FT-IR analyses of degraded products. Fluorescence measurements were carried out in various concentrated DMF solutions to determine the optimum concentrations to obtain the maximal PL intensities. © 2012 Springer Science+Business Media B.V.Item Syntheses and characterization of poly(iminophenol)s derived from 4-bromobenzaldehyde: Thermal, optical, electrochemical and fluorescent properties(Springer Verlag, 2012) Kaya I.; Avci A.; Gültekin O.Schiff base monomers [2-(4-bromobenzylideneamino)phenol and 2-(4-bromobenzylideneamino)-5-methylphenol] were synthesized by the condensation reaction of 4-bromobenzaldehyde with aromatic aminophenols. Then, the monomers were converted to their polyphenol derivatives by oxidative polycondensation reactions (OP) in an aqueous alkaline medium. The structures of the synthesized compounds were characterized by solubility tests, FT-IR, NMR, TG-DTA, DSC and SEC techniques. The HOMO-LUMO energy levels and electrochemical ( E'g ) and optical (Eg) band gaps were calculated from cyclic voltammetry (CV) and UV-Vis measurements, respectively. Cyclic voltammetry (CV) was used to determine the electrochemical oxidation-reduction characteristics. Optical properties were investigated by UV-Vis and fluorescence analyses. Solid state electrical conductivities were measured on polymer films by four point probe technique using a Keithley 2400 electrometer. The effects of electron-donating (?CH3) group at p-position of ?NH2 group in aminophenol on electrochemical and thermal properties were also discussed. Photoluminescence (PL) properties of the synthesized materials were determined in solution forms using different solvents. Fluorescence measurements were carried out in various concentrated solutions to determine the optimum concentrations to obtain the maximal PL intensities. © 2012 Chinese Chemical Society Institute of Chemistry, CAS Springer-Verlag Berlin Heidelberg.Item Improving the mechanical, physical, thermal, and morphological properties of isotactic polypropylene with dialkylperoxide(PRINTS PUBLICATIONS PVT LTD, 2013) Şirin K.; Yavuz M.; Çanli M.; Avci A.; Doǧan F.In this study, the influence of the visbreaking agent (DAP) on mechanical, physical, thermal and morphological properties of PP has been studied. For this reason, isotactic polypropylene (PP) matrices containing 0.01, 0.02, 0.04, 0.06, 0.08, and 0.1 wt% of dialkylperoxide [2, 5dimethyl-2,5-di (tert-butyl peroxy)-hexane, (DAP)] were prepared by using a single-screw extruder. As a result of DAP addition, the crystallinity ratio of the PP matrices has changed between 2.67-7.80%. Mechanical properties of the matrices have been improved. Particularly, the mechanical tests of PP have given Interesting results when compounded with 0.02 wt.% dialkyl peroxide. The microstructure of isotactic polypropylene matrix was investigated by scanning electron microscopy (SEM). From SEM analysis, it was observed that the surface disorder increased by the increasing amount of DAP. Thermal analyses of the matrices were investigated using thermogravimetry in dynamic nitrogen atmosphere at different heating rates. The Flynn-WallOzawa (FWO), Kissinger and master plots method were employed to determine the kinetic model and kinetic parameters of the decomposition processes under non-isothermal conditions. It was found that the thermal stability, activation energy and thermal decomposition processes were all changed by increasing amount of DAP in the matrix structure. © MD Publications Pvt. Ltd.Item Fluorescence, thermal, electrochemical, and morphological properties of new poly(Urethane-İmide)s: Synthesis and characterization(Taylor and Francis Inc., 2014) Avci A.; Şirin K.New thermally stable poly(urethane-imide)s (PUIs) were synthesized to investigate aliphatic and aromatic group effects on various properties such as thermal stability and electrochemical properties. Thermal characterizations were carried out by TG-DTA and DSC techniques. TGA results showed that the PUIs derived from aromatic diisocyanates had relatively higher thermal stabilities as compared to the aliphatic diisocyanate. They have between 223-245°C onset temperature and above 37% char at 1000°C. Also, thermal degradation values show that PUIs have higher stability than conventional PU. DSC results showed that the new PUIs have Tg values between 134 and 138°C. Fluorescence measurements were performed using dimethyl sulfoxide solutions and also, the optimization of the concentrations maximal emission intensity was investigated in dimethyl sulfoxide. As a result, the remarkable properties related to the fluorescence and thermal measurements of the polymers were obtained. Therefore, these polymers could be used in various application fields because of the fluorescent and thermal properties. © Taylor & Francis Group, LLC.Item Synthesis, characterization, optical, and electrochemical properties of thermal stable novel poly(azomethine-ether)s(2014) Kaya I.; Avci A.; Kolcu F.; Çulhaoǧlu S.In this study, the novel Schiff base monomers were synthesized by condensation reactions. Then, these monomers were converted to poly(azomethine-ether)s by oxidative polycondensation (OP) reactions in an aqueous alkaline medium. The structural characterizations of compounds were carried out by FT-IR, NMR, and size exclusion chromatography (SEC). According to the SEC analysis, the calculated number-average molecular weight (M n), weight average molecular weight (Mw), and polydispersity index values of P-2 and P-4 were found to be 17,500 g mol -1, 24,400 g mol-1, and 1.39; and 18,700 g mol -1, 25,600 g mol-1, and 1.36, respectively. The HOMO-LUMO energy levels, electrochemical (), and optical (Eg) band gaps of polymers were calculated from cyclic voltammetry (CV) and UV-vis measurements, respectively. CV was used to determine the electrochemical oxidation-reduction characteristics of polymers. Thermal characterizations of compounds were made by using TG-DTA and DSC techniques. According to TG analysis, polymers with higher initial degradation temperatures (Ton) than those of their monomers indicate that the synthesized polyphenols have higher thermal stabilities than their monomer species. © 2013 Taylor & Francis.Item Synthesis, Characterization and Conductivity Properties of Novel Oligomer Schiff Bases Derived from 4-Amino-3-hydrazino-5-mercapto-1, 2, 4-triazole and Their Reactions with VO(IV), Cu(II) Ions(Springer New York LLC, 2014) Kaya I.; Erçaǧ A.; Avci A.; Çulhaoǧlu S.A new Schiff base, 4-(4-hydroxysalicylidenamino)-3-hydrazino-5-mercapto-1,2,4-triazole (4HSAHMT), and novel Schiff base oligomers of 4-salicylidenamino-3-hydrazino-5-mercapto-1,2,4-triazole (SAHMT), 4-(2-hydroxynaphthylidenamino)-3-hydrazino-5-mercapto-1,2,4-triazole (2HNAHMT), 4-(4-hydroxysalicylidenamino)-3-hydrazino-5-mercapto-1,2,4-triazole (4HSAHMT) and 4-(5-bromosalicylidenamino)-3-hydrazino-5-mercapto-1,2,4-triazole (BrSAHMT) were synthesized via oxidative polymerization using NaOCl as the oxidant. The structures of the oligomers were supported by FT-IR, UV-Vis, 1H-NMR, and 13C-NMR techniques. The compounds were further characterized by solubility tests, TG-DTA, and elemental analysis. The molecular weight distribution parameters of the compounds were determined by the size exclusion chromatography (SEC). According to SEC, the number average molecular weight (M n) values of O-SAHMT, O-BrSAHMT, O-4HSAHMT and O-2HNAHMT were 2,700, 2,100, 2,700 and 1,000 g mol-1, respectively. The weight losses of O-SAHMT, O-BrSAHMT, O-4HSAHMT and O-2HNAHMT were 73, 76, 80 and 54 %, respectively, at 1,000 °C. TG analyses showed that the synthesized oligomers were stable toward thermal decomposition. The synthesized oligomers were converted to metal complexes with salts of VO(IV) and Cu(II). The doped and undoped electrical properties of oligomers and oligomer-metal complexes were determined by the four-point probe technique at room temperature and atmospheric pressure. © 2014 Springer Science+Business Media New York.Item A new selective fluorescent sensor for Zn(II) ions based on poly(azomethine-urethane)(Elsevier Ltd, 2015) Avci A.; Kaya I.A new and selective fluorescent sensor based on poly(azomethine-urethane) (PAMU) is synthesized and characterized by FT-IR, 1H NMR, and size exclusion chromatography (SEC) techniques. The new sensor shows a high selectivity for Zn(II) over other metal cations in DMF/deionized H2O (1:2, v/v). The fluorescence sensor gives a linearly and highly stable response to Zn(II) as an increasing emission peak at 595 nm. The sensitivity limit of the new sensor is found to be 11.4 × 10-3 mol L-1. The results show that the proposed sensor can be efficiently used as a simple method for the detection of Zn(II) ions. © 2015 Elsevier Ltd. All rights reserved.Item Synthesis of Novel crosslinked Poly(azomethine-urethane)s: Photophysical and thermal properties(Elsevier Ltd, 2015) Avci A.; Kamaci M.; Kaya I.; Yildirim M.This paper describes synthesis, photophysical, electrochemical and thermal properties of some new flexible crosslinked poly(azomethine-urethane)s. Synthesis procedure includes two main steps: The first one is the synthesis of a polyurethane prepolymer (TP) using toluene-2,4-diisocyanate and 2,4-dihydroxy benzaldehyde, and the second step is the synthesis of resulting flexible crosslinked poly(azomethine-urethane) derivatives by conventional polycondensation reaction of TP with different aliphatic diamines. Diamines with various chain lengths (6-12 methylene numbers) were used to obtain various resulting polymers with different physical properties. Photophysical properties of the flexible crosslinked poly(azomethine-urethane)s were investigated using photoluminescence (PL). PL results showed that the flexible crosslinked poly(azomethine-urethane)s exhibited multicolor emission behavior. A linear relationship was observed between the excitation energies and the obtained emission maxima. This characteristic enabled adjusting the PL color at the desired scale. Thermal and morphological properties of the polymers were also investigated using TG-DTA, DSC and AFM techniques. © 2015 Elsevier B.V. All rights reserved.Item Improved mechanical performance of three-dimensional woven glass/epoxy spacer composites with carbon nanotubes(SAGE Publications Ltd, 2021) Yildirim F.; Aydin M.; Avci A.Three-dimensional polymer composites offer various features and design options due to their hollow structure and lightweight. However, to exploit their advantages, it is a must to improve their structural features and mechanical performances including out-plane direction. Although introducing thermoplastic fillers between the plies or multilayered design addresses on this critical issue, the benefits offered by the nanoparticles with superior mechanical properties come a step forward as an another engineering solution. Based on this motivation, the goal of this study is to investigate the impact of multiwalled carbon nanotubes on the mechanical and thermomechanical performances of three-dimensional woven glass/epoxy spacer composites. Therefore, multiwalled carbon nanotubes at various content were introduced into epoxy matrix, and the multiwalled carbon nanotubes–epoxy mixture was infused to three-dimensional woven fabric with the vacuum-assisted resin transfer method. The obtained results indicated that the three-point bending strength and modulus were enhanced up to 25 and 80% for warp direction and enhanced up to 44 and 85% for weft direction with carbon nanotube addition, respectively. Tensile strength developed in the warp direction by 7%, while the strength value in the weft direction did not change. The tensile strain values for warp and weft directions enhanced up to 19 and 12% with carbon nanotube addition, respectively. In addition, thermomechanical analysis has revealed that the glass transition temperature and storage modulus were also improved. Particle dispersion detection with color measurement and scanning electron microscopy analyses revealed the effectiveness of the ultrasonic mixing on the dispersion of carbon nanotubes in the epoxy matrix. The consequences of carbon nanotube addition on microscale morphology were discussed based on the fracture morphologies to nanoscale and microscale toughening mechanisms in the existence of carbon nanotube reinforcement. © The Author(s) 2021.Item Reply to Letter to the Editor: "Management of Ventricular Pseudoaneurysms"(Turkish Society of Cardiology, 2024) Şaşmaz M.İ.; Demir B.; Uçar M.; Avci A.[No abstract available]Item Two Rare Complications of Post Myocardial Infarction: A Case Report(Republic of China Society of Cardiology, 2024) Ucar M.; Sasmaz M.I.; Avci A.[No abstract available]Item Interpretation of acid–base metabolism on arterial blood gas samples via machine learning algorithms(Springer Science and Business Media Deutschland GmbH, 2025) Ozdemir H.; Sasmaz M.I.; Guven R.; Avci A.Background: Arterial blood gas evaluation is crucial for critically ill patients, as it provides essential information about acid–base metabolism and respiratory balance, but evaluation can be complex and time-consuming. Artificial intelligence can perform tasks that require human intelligence, and it is revolutionizing healthcare through technological advancements. Aim: This study aims to assess arterial blood gas evaluation using artificial intelligence algorithms. Methods: The study included 21.541 retrospective arterial blood gas samples, categorized into 15 different classes by experts for evaluating acid–base metabolism status. Six machine learning algorithms were utilized; accuracy, balanced accuracy, sensitivity, specificity, precision, and F1 values of the models were determined; and ROC curves were drawn to assess areas under the curve for each class. Evaluation of which sample was estimated in which class was conducted using the confusion matrices of the models. Results: The bagging classifier (BC) model achieved the highest balanced accuracy with 99.24%, whereas the XGBoost model reached the highest accuracy with 99.66%. The BC model shows 100% sensitivity for nine classes and 100% specificity for 10 classes, and the model correctly predicted 6438 of 6463 test samples and achieved an accuracy of 99.61%, with an area under the curve > 0.9 in all classes on a class basis. Conclusion: The machine learning models developed exhibited remarkable accuracy, sensitivity, and specificity in predicting the status of acid–base metabolism. However, implementing these models can aid clinicians, freeing up their time for more intricate tasks. © The Author(s) 2024.