Yazar "Okudan, Ahmet" seçeneğine göre listele
Listeleniyor 1 - 10 / 10
Sayfa Başına Sonuç
Sıralama seçenekleri
Öğe Characterization and dual functionalization of polystyrene with propionic anhydride and cyanate derivatives(WILEY, 2013) Gunes, Hasan Huseyin; Okudan, AhmetFirst, Friedel-Crafts reactions were used for the acylation process. For this, polystyrene (PS) was reacted with propionic anhydride in the presence of Lewis acid catalyst. The amount of acyl group linked PS as a result of acylation has been identified as volumetric. Second, the bromination and lithiation reactions of acylated PS containing carbonyl groups were realized. Also, the lithiated PS containing acyl groups has been modified a second time with various isocyanates and isothiocyanate derivatives in the presence of n-BuLi catalyst. Some important reaction parameters were assigned in order to optimize the process. The structure all of the products were characterized by Fourier transform infrared, H-1 NMR (Proton Nuclear Magnetic Resonance), and thermogravimetric methods. In addition, reaction yields were determined according to the result of elemental analysis. Dual functionalization yields were realized between 62.2% and 69.9%. For kinetic analysis, the TG/DTG (Thermal Gravimetric Analysis/Differantial Thermal Analysis) data obtained at three different heating rates were processed by Kissinger-Akahira-Sunose method. The results demonstrated that the acylation reaction, bromination and lithiation reactions, and dual functionalization reactions with cyanate derivatives can be carried out to obtain a significantly functionalized polymer. (C) 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 1351-1362, 2013Öğe The Effect of H-Bonding on Radical Copolymerization of Maleic Anhydride with N-tert-Butylacrylamide and Its Characterization(HINDAWI PUBLISHING CORPORATION, 2013) Okudan, Ahmet; Karasakal, AyseThe copolymerization reaction between N-tert-butylacrylamide (NTBA) and maleic anhydride (MA) in p-dioxane solution at 65 degrees C using 2,2'-azoisobutyronitrile (AIBN) as an initiator in nitrogen atmosphere was carried out. The chemical structure of the obtained copolymers from a wide range of monomer feeds was determined by elemental analysis (content of N for NTBA units), Fourier transform infrared (FTIR), and H-1-NMR spectroscopy. Also, the amounts of MA units in the copolymers were found using the chemical titration method. An observed tendency toward alternating copolymerization at <= 50 mol% NTBA concentration in monomer feed and relatively high activity of NTBA growing radical was explained by H-bond formation between C=O (anhydride) and NH (amide) fragments during chain growth reactions. Intrinsic viscosity and the molecular weights of the synthesized copolymers depend on the type of comonomer and the amount of NTBA units in the copolymers. The synthesized poly(NTBA-MA)s containing a functional amphiphilic group show both temperature and pH sensitivity and can be used for biological proposes as a physiologically active macromolecular system.Öğe Esterification Reaction of Polystyrene Modified with Maleic Anhydride in the Presence of Resin Catalyst(WILEY-BLACKWELL, 2013) Okudan, Ahmet; Baktir, Serdar; Sagdic, AhmetIn this study, primary modification of polystyrene (PS) was carried out with maleic anhydride using the FriedelCrafts reaction. Its secondary modification was realized through esterification of modified polystyrene (MPS) containing a carboxyl group with various alcohols in the presence of Amberlyst-36 as a heterogeneous catalyst. The heterogeneous catalyst gave moderate yields, whereas the reaction catalyzed by a homogeneous catalyst did not occur. The amount of carboxyl groups in the structure of MPS and unreacted carboxyl groups in the structure of the esterified MPS (EMPS) was found by using a chemical titration method for the determination of esterification yield. Some important reaction parameters were assigned to optimize the esterification process. FT-IR, 1H NMR, and thermogravimetric studies indicate that the esterification reaction was successfully realized for each alcohol in the presence of the heterogeneous catalyst. The results demonstrated that both the acylation reaction and esterification reaction can be carried out to obtain a significantly functionalized polymer. (c) 2012 Wiley Periodicals, Inc. Adv Polym Techn 32: E451E461, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.21292Öğe Investigation of the effects of different hydrophilic and hydrophobic comonomers on the volume phase transition temperatures and thermal properties of N-isopropylacrylamide-based hydrogels(HINDAWI LTD, 2019) Okudan, Ahmet; Altay, AbdullahIn this work, a series of thermally responsive terpolymers of N-isopropylacrylamide (NIPA) with three different comonomer contents was synthesized, and their swelling behaviour was studied as a function of composition and temperature. Temperature-sensitive, random cross-linked terpolymers of NIPA were prepared from methyl methacrylate (MMA), N-tert-butylacrylamide (NTBA), and acrylic acid (AA) using a free radical polymerization method. In the synthesis of terpolymer hydrogels, N,N-methylene bisacrylamide (BIS) was used as cross-linkers and ammonium persulfate (APS) as initiator. The NIPA content of the monomer feed varied from 80 to 50mol %, and other comonomer feed varied from 40 to 5mol %. The swelling equilibrium of these hydrogels was studied as a function of temperature and hydrophobic and hydrophilic comonomer contents. The swelling properties of the polymers were investigated in pure water at temperatures from 10 to 80 degrees C. All of the synthesized gels were found to be sensitive to temperature. Glass transition temperature analyses and thermal analyses of the synthesized hydrogels were studied. The volume phase transition temperature and the swelling equilibrium (r) values of NIPA-based hydrogels synthesized in different feed ratios and in varying monomer contents were found in the range of 17-52 degrees C and 14-51g H2O/g polymer, respectively. The glass temperature (Tg) of the NIPA/AA/(MMA or NTBA) hydrogels synthesized with feed ratios of 50/40/10 was found to be 133 or 142 degrees C, respectively. The initial and the end degradation that were determined for hydrogels at high temperatures indicated the quite good thermal stability of hydrogels. When the mass loss of the synthesized hydrogels was 50%, the temperatures were measured between 247 and 258 degrees C.Öğe 'Naked-eye' detection of fluoride and acetate anions by using simple and efficient urea and thiourea based colorimetric sensors(ELSEVIER, 2013) Okudan, Ahmet; Erdemir, Serkan; Kocyigit, OzcanSimple and efficient sensors 1 and 2 possessing azo and nitrophenyl as signaling units and urea and thiourea moieties as binding sites were designed and synthesized. These sensors were characterized by combination of H-1, C-13, APT, COSY NMR, FTIR, elemental analysis, and UV-vis spectral data. The interaction and colorimetric sensing properties of receptor 1 and 2 with different anions were investigated by the naked eye, as well as UV-visible and H-1 NMR experiments. It was found that the receptor 1 and 2 are highly selective toward fluoride and acetate anions in CHCl3. (c) 2013 Elsevier B.V. All rights reserved.Öğe Polistirenin İzobutirik Anhidrit ve Siklohekzil İzosiyanat ile Çift Fonksiyonlaştırılması(Selçuk Üniversitesi Fen Fakültesi, 2019) Okudan, Ahmet; Güneş, Hasan HüseyinBu çalışmada ilk olarak polistirenin izobutirik anhidrit ile BF3.O(C2H5)2 Lewis asidi katalizörü ortamındaki kimyasal modifikasyonu gerçekleştirilmiş ve modifikasyon için Friedel-Crafts reaksiyonlarından faydalanılmıştır. Bu reaksiyon için önceden belirlenen optimum şart kullanılmıştır. Sentezlenen açil grup içeren modifiye polistiren, siklohekzil izosiyanat ile n-BuLi katalizörü varlığında ikinci kez modifiye edilmiştir. Elde edilen açil ve amit grup içeren polistirenlerin yapısı spektroskopik yöntemler kullanılarak aydınlatılmış, modifikasyon sonucu polistirene bağlanan karboksil grubu miktarı volumetrik olarak belirlenmiştir. Ayrıca elementel analiz sonuçlarına göre de ikinci modifikasyon verimleri tespit edilmiştir. Farklı fonksiyonel gruplar içeren yeni tür polistiren zincirindeki her 6 stiren biriminden 3 tanesinde amit fonksiyonel grubu, 1 tanesinde açil fonksiyonel grubu bulunan ve 1 tanesinde de hiçbir fonksiyonel grup bulunmamaktadır. Polistirene bağlanan farklı her iki fonksiyonel grubun polistirenin uygulama alanlarının daha da genişletilmesine katkısı olacaktır.Öğe Side-chain Functionalization of Polystyrene with Maleic Anhydride in the Presence of Lewis Acids(JOHN WILEY & SONS INC, 1996) Kurbanova, R. A.; Mirzaoğlu, R.; Akovalı, G.; Rzaev, Zakir M. O.; Karataş, I.; Okudan, AhmetPolystyrenes with different molecular weights were chemically modified with maleic anhydride by use of certain cationic catalysts of Lewis acid type (BF3 . OEt(2), AlCl3, TiCl4, ZnCl2, FeCl3, and SnCl4) in chloroform. The effects of molecular weight of polystyrene, as well as type of Lewis acid used, on properties and structure of products were investigated. The interrelation between the molecular weight of polystyrene and content of carboxyl groups in the products was made. A direct relationship between the activity of catalyst used and the number of carboxyl groups was found. For characterization of side-chain functionalized polystyrene, fractional precipitation was applied which yielded carboxyl groups in all fractions. The carboxyl group concentrations were found to be the highest in the case of BF3 . OEt(2). Modified polystyrene samples containing - CO - CH = CH - COOH fragments in side chains are easily crosslinked at 140-150 degrees C and by UV irradiation as proved by IR, DTA, and TGA analyses. Functionalized polymers obtained are characterized by their high thermostability, adhesion, and photosensitivity.Öğe Synthesis and characterization of nickel(II) and copper(II) complexes of the Schiff bases derived from 4-/6-methyl-Delta(3)-tetrahydrobenzaldehyde and glycine(ASIAN JOURNAL OF CHEMISTRY, 2008) Gueler, Ersin; Ertul, Seref; Okudan, Ahmet; Kocyigit, OezcanNickel(II) and copper(II) complexes with the Schiff bases derived from 4-methyl-Delta(3)-tetrahydrobenzaldehyde or 6-methyl-Delta(3)-tetrahydrobenzaldehyde and glycine were synthesized. These compounds have been characterized by elemental analysis, conductivity measurements and infrared spectroscopy. The Schiff base ligands and their complexes have been further characterized by H-1 NMR. The results suggest that the Schiff base acts as a bidentate ligand which bonds to the metal ions through the imino nitrogen and carboxylate oxygen. The potassium salts of the Schiff bases are 1: 1 electrolytes, but all the complexes are non-electrolytes.Öğe Vinil Pivalat-ko-Maleik Anhidrit Kopolimerinin Sentezi ve Reaktivite Oranlarının Belirlenmesi(Selçuk Üniversitesi Fen Fakültesi, 2019) Şengöz, Onur; Okudan, AhmetBu çalışmada, Maleik Anhidrit (MA) ve vinil Pivalat (VP)’ın birbirleri ile reaksiyona girebilme yeteneğinin ve kopolimer yapısındaki dizilimlerinin belirlenebilmesi için VP-ko-MA kopolimeri farklı besleme oranlarında çalışılarak sentezlenmiştir. Sentezlenen VP-ko-MA kopolimer yapısının aydınlatılabilmesi için kızılötesi (FT-IR) ve nükleer manyetik rezonans spektroskopilerinden (1 H-NMR) ve jel geçirgenlik kromotografisinden yararlanılmıştır. Ayrıca sentezlemiş olan VP-ko-MA kopolimerinin volumetrik olarak asit sayıları, titrimetrik yöntemle Kohezif Enerji Yoğunluğu (KEY) değerleri bulunmuştur. Kopolimer bileşimindeki monomerlerin mol fraksiyonlarının FT-IR ve 1 H-NMR spektroskopisi yardımıyla tayini yapılmış olup FinemanRoss ve Kelen-Tüdos metotları yardımıyla da VP-ko-MA kopolimerinin reaktivite oranları belirlenmiştir.Öğe YAPAY SİNİR AĞLARI İLE ÜÇ BOYUTLU OBJE SINIFLANDIRMADA KONVOLÜSYON FİLTRELERİNİN ETKİSİNİN İNCELENMESİ(Selçuk Üniversitesi, 2019) Okudan, Ahmet; Şahin, Ömer SinanSonlu elemanlar analizi (FEA), yapıların fiziksel davranışlarını tespit etmek için bilgisayar ortamında tasarlanan ve belirli formülasyonlar ile çözülen simülasyon yöntemidir. Problemin büyüklüğüne veya karmaşıklığına göre hazırlık ve çözüm süresi artmaktadır. Sonlu elemanlar analizi için olması gerekenler, geometri ve sınır koşullarıdır. FEA’nın zor ve yorucu olmasının sebebi hazırlık aşamasının çok fazla girdi istemesidir. Ayrıca FEA yapabilmek için ileri düzeyde mühendislik bilgisi de gereklidir. Üç boyutlu yazıcı kullanımının artması da FEA’ya olan ihtiyacı arttırmıştır. Cep telefonu ve tabletlerin işlem gücünün gelişmesi ile sonlu elemanlar analizinin, girdiye ihtiyaç duymadan telefon kamerası ile yapılabilirliğinin mümkün kılınması adına altyapı oluşturulmuştur. Basit analizlerin otomatik olarak yapılabilmesi için derin öğrenme algoritmaları tasarlanmıştır ve eğitilmiştir. Hayatımızın her alanına giren yapay zekânın, sonlu elemanlar analizi alanında ne gibi çözümler sunacağı incelenmiştir. Ağ örgüsü (mesh) olmadan çözüm yapma hacimsel piksellenme metoduna dayandığı için bu çalışmada vokselizasyon tabanlı öğrenme üzerine inceleme yapılmıştır. Bu çalışmada, sonlu elemanlar analizi girdisi için gerekli olan üç boyutlu geometrik verilerin, bir kamera vasıtası ile taranan objelerin sınıflandırılmasına yarayacak yapay sinir ağı (YSA) oluşturulmuştur ve doruluğu test edilmiştir. Üç boyutlu geometrilerin sınıflandırılabilmesi için özelleştirilmiş bir evrişimli (konvolüsyonel) sinir ağı tasarlanmıştır. Çalışmada, üç boyutlu bilgisayar geometrilerinin konvolüsyon filtresine sahip yapay sinir ağları ile konvolüsyon fitresi bulundurmayan yapay sinir ağları arasındaki parametre sayısı, öğrenme süresi, öğrenme doğruluğu ve maliyet değerleri karşılaştırılmıştır. Konvolüsyon filtreli YSA’nın validasyon değeri %97,92’dir. Konvolüsyon filtresiz YSA %97,08 validasyon değeri ile öğrenme işlemini tamamlamıştır. Konvolüsyon filtresiz YSA eğitimi 440 saniyede tamamlarken, Konvolüsyon filtreli YSA’nın eğitimi 6260 saniye sürmüştür.
