Kimya Bölümü Koleksiyonu
Bu koleksiyon için kalıcı URI
Güncel Gönderiler
Öğe Nanotitania supported ruthenium(0) nanoparticles as active catalyst for releasing hydrogen from dimethylamine borane(Pergamon-Elsevier Science Ltd, 2024) Al-Areedhee, Ahmed Hammoodi Yousif; Karaboğa, Seda; Morkan, İzzet ; Özkar, SaimWe reports the ex situ preparation of nanotitania supported ruthenium(0) nanoparticles (NPs) and their catalytic testing in dehydrogenation of dimethylamine borane (DMAB) in toluene solvent. Ru0/TiO2 NPs are prepared following a 2-step process: Ru3+ ions are first impregnated from the aqueous solution on titania nanopowder and then, reduced by aqueous solution of sodium borohydride. The prepared Ru0/TiO2 NPs are dried, bottled under inert N2 gas atmosphere, and used for characterization by XRD (X-ray powder diffraction), TEM (transmission electron microscopy), ICP-OES (inductively coupled plasma optical emission spectroscopy) and XPS (X-ray photoelectron spectroscopy). Ru0/TiO2 NPs with various Ru loadings are tested as catalysts in hydrogen generation from DMAB and the Ru0/TiO2 (0.48% wt. Ru) with an average diameter of 6.7 +/- 1.3 nm is found to have the highest initial turnover frequency value of 1700 h-1 for the release of 1.0 mol H2 per mole of DMAB at 60 degrees C. Results of the recyclability test indicate quite high durability of Ru0/TiO2 NPs in dehydrogenation of DMAB.(c) 2023 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.Öğe Adsorption of uranium (VI) from aqueous solutions using boron nitride/polyindole composite adsorbent(Wiley, 2024) Emre, Deniz; Zorer, Özlem Selçuk; Bilici, Ali; Budak, Erhan; Yılmaz, Selehattin; Kılıç, Necla Calışkan; Söğüt, Eda GökırmakTurbostratic boron nitride (tBN) surface is modified with polyindole (PIn) by a facile polymerization technique and the uranyl adsorption efficiency of this mesoporous hybrid is investigated. The successful surface modification is confirmed by FT-IR, Raman, XRD, TEM, SEM, EDX, EDS mapping XPS, BET, and zeta potential techniques. The batch experiments are performed in various temperatures (T), contact times (t), pH, and initial solution concentrations (C-0) to evaluate its adsorption performance. The optimum adsorption performance is achieved at pH = 5.0-5.5, T = 307 K, t = 10 min, C-0 = 18 mg L-1. These experimental results are evaluated using Freundlich, Redlich-Peterson, and Langmuir isotherm models, which presents equivalent regression coefficients. Maximum adsorption capacity (q(m)) of the nanoadsorbent (tBN/PIn), determined by the Langmuir isotherm, is 315.29 mg g(-1). The adsorption kinetics of uranyl ions on tBN/PIn are in harmony with the pseudo-second order model. tBN/PIn nanoadsorbent provides high adsorption efficiency even at exceptionally low UO22+ concentration range (4-40 mg L-1) and low adsorbent mass (0.005 g). XPS analysis results show that 0.05% of uranium is adsorbed on tBN/PIn via mainly U-O coordination. The results of present study demonstrate that tBN/PIn can a potential adsorbent for removing uranium from aqueous solutions.Öğe Synthesis and biological activities of pyridine N-oxide bearing 5-aminoisoxazoles as potential acetylcholinesterase and monoamine oxidase inhibitors for Alzheimerʼs disease(Elsevier B.V., 2024) Saleh, Lange Yakubu; Özdemir, Soner; Sağlık, Begüm Nurpelin; Döndaş, Hacı Ali; Altuğ, CevherA series of ten novel pyridine N-oxide-bearing 5-aminoisoxazoles was efficiently synthesized in moderate yields by reacting 2-(cyanomethyl)pyridine 1-oxide with ?-chlorooximes, employing sodium ethoxide as a base. The synthesized compounds were verified with a variety of spectra. Subsequently, the inhibitory potency of compounds 4c, 4e, 4f, 4h, and 4i against AChE and BChE, primary targets in Alzheimer's disease, was assessed. In silico docking analyses were conducted to evaluate the interaction of compounds 4c, 4e, 4f, 4h, and 4i with AChE and MAO-B. Among the tested compounds, 4e and 4h demonstrated remarkable AChE inhibition, exhibiting IC50 values of (0.050 µM and 0.039 µM, respectively), comparable to the inhibition achieved by donepezil (IC50 = 0.020 µM). Additionally, compounds 4c, 4e, 4f, 4h, and 4i displayed potent MAO-A inhibition, with IC50 values of (0.203, 0.067, 0.083, 0.044, and 0.159 µM, respectively), surpassing the efficacy of moclobemide (IC50 = 6.061 µM). Compounds 4e, 4f, and 4h also inhibited MAO-B, with IC50 values of (0.076, 0.058, and 0.049 µM, respectively), close to the inhibitory effects of Selegiline (IC50 = 0.037 µM). Compound 4h emerged as a multi-target inhibitor, effectively inhibiting AChE, MAO-A, and MAO-B. These findings underscore the therapeutic potential of these novel compounds in the treatment of Alzheimer's disease, warranting further investigation into their clinical application. © 2024Öğe Chain-extended bismaleimides. II. A study of chain-extended bismaleimides as matrix elements in carbon fiber composites(John Wiley and Sons Inc., 1996) Yerlikaya, Zekeriya; Erinç, N. Kutay; Öktem, Zeki; Bayramlı, ErdalA series of chain-extended bismaleimide resins as matrix elements in carbon fibers were cured and characterized in terms of their thermal and thermomechanical properties. The cured resins were stable up to 430°C and EDABMI/MDA has the highest Tg value and the lowest low modulus value. To understand the compatibility and the degree of adhesion between the resin and the fiber, their surface properties were determined in terms of the surface energy component and single-fiber pull-out tests. The surfaces of the resins were found to have a basic character. The resins containing ether groups have a higher degree of basicity than does the resin containing methylene groups. Similarly, an increasing trend in the interlaminar shear strength (ILSS) and the work of adhesion values were observed with the increasing number of the ether groups in the resin structure. © 1996 John Wiley & Sons, Inc.Öğe Chain-extended bismaleimides. I. preparation and characterization of maleimide-terminated resins(John Wiley and Sons Inc., 1996) Yerlikaya, Zekeriya; Öktem, Zeki; Bayramlı, ErdalStarting from aromatic diamines, a series of bismaleimides (BMIs) and maleimide-terminated structural resins were prepared in solution and characterized. Maleimide-terminated resins were prepared through Michael addition reaction with 3/2 molar ratio of bismaleimide and aromatic diamine as reactants. The structural analysis was performed by FTIR and 1H-NMR spectroscopy. Thermal properties are investigated by TGA, DTA, and DSC. Number-average molecular-weights of the resins were determined by cryoscopy. The presence of methylene ( - CH2 - ) and ether ( - O - ) groups in the starting materials affect the reactivity and the degree of chain extension of the resins. From the viscosity measurements it was also found that thermal polymerization of BMIs could be taking place together with the Michael addition. © 1996 John Wiley & Sons, Inc.Öğe SPICE modeling of RADFETs with different gate oxide thicknesses(Institute of Electrical and Electronics Engineers Inc., 2023) Marjanovic, M.; Gürer, Umutcan; Mitrovic, N.; Yılmaz, Ozan; Dankovic, D.; Budak, Erhan; Yılmaz, ErcanThis paper will present guidelines for creating a SPICE model of RADFETs with different gate oxide thicknesses. Model parameters, such as threshold voltage and carrier mobility, were extracted from the transfer characteristics in the saturation region. The model was satisfactorily used to simulate RADFETs with oxide thicknesses ranging from 40 nm to 300 nm. © 2023 IEEE.Öğe Detailed investigation on the insulation and permeability characteristics of rigid polyurethane foam loaded with micron-sized Turkey feather powder depending on the free volume change(SAGE Publiscations Ltd, 2023) Soykan, Uğur; Çetin, Sedat; Yahşi, UğurThis study brokes new ground to understand the insulation and permeability performances of rigid polyurethane foams (RPUFs) containing the different contents of micron-sized turkey feather powders (TFPs) depending on the free volume change for the first time. The effects of TFPs loading on the RPUFs were investigated by the examination of their structural and chemical features (particle size and ATR-FTIR analyses), free volume property (PALS analysis), insulation features (thermal conductivity and sound absorption tests), permeability performance (air and water vapor permeability tests) and cellular topology (SEM). PALS analysis results revealed that the addition of TFPs into the foams led to the sharp decrease in all free volume parameters since TFPs caused the formation of the disordered cells by occupying the holes in the matrix. Furthermore, both thermal conductivity and acoustic performance of the resulting foams get worse when compared to unfilled RPUF. This results were attributed to the formation of thinner and weaker cells during polymerization, reduction in the amount of CO2 inside the cells, enhancement in the solid-phase level in the matrix due to the increasing of volumetric density. Additionally, the foam samples with high content of TFPs showed considerably lower air and water vapor permeabilities when compared to neat RPUFs due to the dominant hydrophobic character of the keratin and reduction in the degree of vacancies in the matrix. SEM analysis also revealed that TFPs showed good compatibility with RPUF, but the distorted and irregular shaped cellular morphology was obtained at high contents.Öğe Properties of the uniaxial and biaxial nematic phases of the dodecyltrimethylammonium bromide/1-dodecanol/water lyotropic mixture including azo dye and drug molecules(Taylor & Francis Ltd, 2024) Akpınar, Erol; Tabak, Merve; Reis, Dennys; Neto, Antonio Martins FigueiredoLyotropic nematic phase properties of novel mixtures of dodecyltrimethylammonium bromide (DTMABr)/1-dodecanol (DDeOH)/water, doping with anionic azo dyes (amaranth and tartrazine) and a drug molecule disodium cromoglycate (cromolyn, DSCG), were investigated. The textures of the uniaxial and biaxial nematic phases were observed by polarizing optical microscopy (POM). Uniaxial-to-biaxial nematic phase transitions were determined from the temperature dependence of the birefringences via laser conoscopy. Partial phase diagrams of the mixtures were constructed as a function of concentrations of dyes and drug molecules by combining the POM and laser conoscopy results. Small-angle X-ray scattering (SAXS) was performed to evaluate micellar structure parameters. The results indicate that those dyes and drug molecules have a greater effect on (a) the nematic-nematic phase transition temperatures, (b) the biaxial-nematic phase-domain range in the partial phase diagrams, and (c) micelle-shape anisotropy, comparing to the addition of other conventional inorganic electrolyte ions. Furthermore, dye and drug molecules may be sequenced in the Hofmeister series of ions, considering the number of ionic groups in their molecular structures and also the chaotropic and/or kosmotropic degrees of the ionic groups. Since these molecules may have a resonance structure (e.g. DSCG), as a result of the existence of the aromatic parts in their structures, this resonance structure should be considered to investigate their effects on the stabilization of the lyotropic nematic phases.Öğe Comparative de novo transcriptome analysis and random UV mutagenesis: Application in high biomass and astaxanthin production enhancement for Haematococcus pluvialis(Springer, 2023) Telli, Murat; Ünlü, Ercan SelçukBackgroundAstaxanthin is a natural carotenoid with strong antioxidant capacity. The high demand on astaxanthin by cosmetic, food, pharmaceutical and aquaculture industries promote its value in the biotechnological research. Haematococcus pluvialis Flotow 1844 has been characterized as one of the most promising species for natural astaxanthin biosynthesis. Even though H. pluvialis as an advantage in producing astaxanthin, its slow grow-yield limits usage of the species for large-scale production.Methods and ResultsIn this study we generated mutated H. pluvialis strain by using one-step random UV mutagenesis approach for higher biomass production in the green flagellated period and in turn higher astaxanthin accumulation in red stage per unit algae harvest. Isolated mutant strains were tested for the astaxanthin accumulation and yield of biomass. Among tested strains only mutant strain designated as only MT-3-7-2 showed a consistent and higher growth pattern, the rest had shown a fluctuated and then decreased growth rate than wild type. To demonstrate the phenotypical changes in MT-3-7-2 is associated with transcriptome, we carried out comparative analysis of transcriptome profiles between MT-3-7-2 and the wild type strains. De novo assembly was carried out to obtain the transcripts. Differential expression levels for the transcripts were evaluated by functional annotation analysis.ConclusionsData showed that increased biomass for the MT-3-7-2 strain was different from wild type with expression of transcripts upregulated in carbohydrate metabolism and downregulated in lipid metabolisms. Our data suggests a switching mechanism is enrolled between carbohydrate and lipid metabolism to regulate cell proliferation and stress responses.Öğe Chemical composition and source apportionment of PM2.5 at a suburban site in the northwestern part of Turkey(Vinca Inst Nuclear Sci, 2023) Karadeniz, Hatice; Sağırlı, Eda; Karakaş, Serpil YenisoyIn this study, daily fine particulate matters (PM2.5) were sampled between Febru-ary 22, 2011 and February 22, 2012 in Bolu Abant Izzet Baysal University Cam-pus. 277 PM2.5 samples were collected by using a stacked filter unit. The 51 ele-ments (Li, Be, Na, K, Mg, Al, P, S, Ca, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ge, As, Se, Rb, Sr, Y, Mo, Cd, Sn, Sb, Cs, La, Ce, Pr, Nd, Eu, Sm, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Hf, W, Pt, Au, Pb, Bi, Tl, Th, U) were determined using ICP-MS technique. The most frequently observed elements were Ti, V, Cr, Mn, Fe, Ce, and Cd in PM2.5. Aluminum, Ca, Na, Fe, K, and Mg were the elements having the largest arithmetic means. The concentrations of elements in the summer seasons were higher than the concentrations of elements in the winter season except for As and Bi. Source apportionment of elements was performed by using positive matrix factorization. Five sources were determined for the samples namely sea salt (Na, K, Mg, Ca), coal combustion (As, Pb, Bi, Tl, Cd, Sb, Se, Mo), wood and coal combustion (K, Rb, Se, Cs, Sb, Pb, Bi, Tl, Fe, Mn, Cd), soil (Ca, Mg, Ti, Fe, Y, La, Ce, Pr, Nd, Sm, Gd, Th), and industrial activity - iron-steel works (Cr, Mo, Fe, Ni, Cu, Mn, Cd, Sb, Ca). The factor of wood and coal combustion showed the same trend in the region for the whole year.Öğe Meta-analysis of sugar beet (Beta vulgaris L.) transcriptome profiles under different biotic and abiotic stress conditions(Springer, 2023) Bulut, Burak; Gürel, Songül; Ünüvar, Ömer Can; Gürel, Ekrem; Ünlü, Ercan SelçukSugar beet (Beta vulgaris L.) meets the 21% of world sugar production. Soil pollution, biotic and abiotic factors in production areas greatly reduce product quantity and quality. Sugar beet responds to biotic and abiotic stresses such as drought, salt, heat, light, and infections of nematode, bacteria and fungi at the molecular level. Understanding molecular mechanisms require comprehensive genomics studies in order to control these mechanisms to increase the yield and quality. Transcriptome studies performed under stress conditions can shed light on the responses of plants at the molecular level. In addition, meta-analysis can help to find common responses under different stress conditions. In this study four different stress-related transcriptome data were used: two of them are related with biotic stress (nematode and fungi infection) and two of them are related with abiotic stress (ABA treatment and salt stress). In this study, we performed meta-analysis of studies conducted under biotic and abiotic stress conditions. Our results revealed 460 commonly regulated genes from biotic stress related data and 1031 commonly regulated genes from abiotic stress related data. Our data also showed that expression of ten genes is controlled regardless of the type of stress condition. The data can be useful for understanding the molecular aspect of adaptive stress response in sugar beet.Öğe Microwave-mediated approach to highly substituted nitropyrimidines via double Mannich reactions and their biological propertie(Pergamon-Elsevier Science Ltd, 2022) Yıldırım, Muhammet; Yıldırım, Arzu; Gülbenek, CansuIn the current study, new polysubstituted nitropyridimines were efficiently synthesized via double Mannich cyclizations of diaryl substituted b-nitroenamines with formaldehyde and aniline derivatives under microwave irradiation for 30-40 min. Furthermore, an antioxidant study showed that some of the nitropyridimines have moderate to low scavenging activity against DPPH radical. Also, in a preliminary antibacterial activity test of selected products, only one product exhibited moderate antibacterial effect against S.Epidermidis bacteria. (c) 2022 Elsevier Ltd. All rights reserved.Öğe H2(g) production from dimethylamine borane by Cu0/WO3 NPs catalyst(Scientific and Technological Research Council Turkey, 2023) Al-Hameedaw, Doaa; Karaboğa, Seda; Morkan, İzzetCu0 NPs supported on tungsten (VI) oxide (WO3) were in situ generated from the reduction of Cu2+ ions during dehydrogenation of dimethylamine borane (DMAB). The Cu0/WO3 NPs displayed tangible catalytic activity in H2 (g) releasing reaction and they were identified by using advanced techniques. Cu0/WO3 NPs were found as active catalyst providing one equiv. H2(g) per mole of DMAB. The results from TEM images display the formation of Cu0 NPs with an average particle size of 4.6 ± 1.0 nm on the surface of WO3. Moreover, Cu0/WO3 NPs with various metal loadings were prepared and tested as catalyst in dehydrogenation reaction to find the optimum metal loading on WO3 support. The highest H2 generation rate was achieved for 4.0% wt. Cu0/WO3 catalyst with TOF value of 39 h?1 in the reaction conditions. Additionally, effect of various catalyst concentration and temperature is discussed on the reaction kinetics for reaction catalyzed by Cu0/WO3 NPs.Öğe Design, synthesis and human carbonic anhydrase I, II, IX and XII inhibitory properties of 1,3-thiazole sulfonamides(Pergamon-Elsevier Science Ltd, 2022) Erigür, Esra Caner; Altuğ, Cevher; Angeli, Andrea; Supuran, Claudiu T.Carbonic anhydrases (CAs, EC 4.2.1.1) are categorized as metalloenzymes and are widespread in both eukaryotes and prokaryotes. In mammals, 16 different isoforms of carbonic anhydrase were isolated and categorized as catalytic human isoform; cytosolic CAs (CA-I, II, III, VII and XIII), membrane-associated CAs (CA-IV, IX, XII, XIV and XV), mitochondrial CAs (CA-VA and VB), secreted CAs (CA-VI) and non- catalytic human isoform; inactive CA-related proteins (CA-VIII, X, and XI).1,2 Carbonic anhydrases, which are included in the enzyme family, help to the reversible conversion of carbon dioxide and water to bicarbonate anion and proton presence of Zn2+ ion at the catalytic site. They also provide transportation of carbon dioxide (CO2), keeps acid-base balance, regulation of pH, etc.3,4 By means of their critical participation in many regulatory physiologic processes, they play an active role in the treatment of many diseases such as glaucoma, epilepsy, obesity edema, cancer, neuropathic pain, etc.5Öğe Quercetin- and caffeic acid-functionalized chitosan-capped colloidal silver nanoparticles: One-pot synthesis, characterization, and anticancer and antibacterial activities(Beilstein-Institut, 2023) Kurt, Akif Hakan; Olutaş, Elif Berna; Avcıoğlu, Fatma; Karakuş, Hamza; Sungur, Mehmet Ali; Öztabağ, Cansu Kara; Yıldırım, MuhammetThe presented study comprises the one-pot synthesis and the characterization of quercetin-and caffeic acid-functionalized chitosan-capped colloidal silver nanoparticles (Ch/Q-and Ch/CA-Ag NPs), and their antibacterial and anticancer activities. The formation of Ch/Q-and Ch/CA-Ag NPs has been confirmed by ultraviolet-visible (UV-vis) spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM). The characteristic surface plasmon resonance (SPR) absorption band has been found at 417 and 424 nm for Ch/Q-and Ch/CA-Ag NPs, respectively. The formation of a chitosan shell comprising quercetin and caffeic acid, which surround the colloidal core Ag NPs, was confirmed by UV-vis, and FTIR analyses, and moni-tored by TEM microscopy. The size of nanoparticles has been determined as 11.2 and 10.3 nm for Ch/Q-and Ch/CA-Ag, respec-tively. The anticancer activity of Ch/Q-and Ch/CA-Ag NPs has been evaluated against U-118 MG (human glioblastoma) and ARPE-19 (human retinal pigment epithelium) cells. Both NPs showed anticancer activity, but Ch/Q-Ag NPs seemed to be more effective on cancer cell lines (U-118 MG) in comparison to healthy ones (ARPE-19). Furthermore, the antibacterial activity of Ch/Q-and Ch/CA-Ag NPs against Gram-negative (P. aeruginosa and E. coli) and Gram-positive (S. aureus and S. epidermidis) bacteria was determined, and dose-dependent antibacterial effects were found.Öğe Current-voltage characteristics of nano whisker ZnO/Si heterojunction under UV exposition(Elsevier Science Sa, 2022) Koç, Nevin Soylu; Altıntaş, Sevgi Polat; Gökçen, Muharrem; Doğruer, Musa; Altuğ, Cevher; Varilci, AhmetIn/ZnO/p-Si heterojunction diode was produced to investigate the photo-responsivity and electrical features under ultraviolet (UV) light. A hydrothermal synthesis technique was used to coat the ZnO layer on the p-Si single crystal as nanowhisker/rods. The formation of surface and nanowhisker properties of the ZnO layer were investigated by scanning electron microscope (SEM). The I-V (current-voltage) analysis of the In/ZnO/p-Si diode was realized in dark and under UV (290-400 nm) illumination. Further, the main electrical parameters of the diode; such as reverse bias saturation current (I-V), ideality factor (n), zero bias barrier height (Phi(Bo)), resistance (R) and interface state density (N-ss) were obtained from the experimental I-V measurements by thermionic emission (TE) and Card and Rhoderick's function. Also, the power law of the photocurrents (I-PC), photoresponsivity (PR) and response time were extracted. Photo-responsivity and response time values of In/ZnO/p-Si heterojunction diode were obtained as 2.0 A/W and (rise/decay) 160/200 ms, respectively.Öğe The effects of Ni/Cu co-doped ZnO nanorods: Structural and optoelectronic study(Springer, 2022) Şenol, Sevim Demirözü; Arda, LütfiThe hydrothermal method was used to synthesize Zn0.99-xNixCu0.01O (x = 0.00 to 0.05 with a 0.01 increment) nanorods. The X-ray diffraction method was used to provide the structural analysis. It was observed that all Ni/Cu co-doped ZnO nanorods are single phases. The Scanning Electron Microscope and Electron Dispersive Spectroscopy were employed to monitor the surface morphology, shapes, size, and elemental compositions of the Ni/Cu co-doped ZnO nanorods. The Fourier Transform Infrared studies were performed and detailed. The UV-Spectrophotometer was used to obtain the optical properties of the nanorods. The energy band gaps of Ni/Cu-doped ZnO nanorods were calculated and their effects on optical properties were discussed. Five different models were used to calculate the refractive index. Multi-doped (Ni and Cu) ZnO nanorods were successfully produced using the hydrothermal method and their structural, band gap and refractive indexes were discussed for optoelectronic and sensor applications.Öğe Evaluation of crystallinity, thermal, mechanical and morphological features of high density polyethylene composites reinforced with crosslinked semifluorinated acrylate polymer microspheres(SAGE Publications Ltd, 2023) Soykan, Uğur; Çetin, SedatThis study mainly aims both to prepare well-shaped crosslinked 3,3,4,4,5,5,6,6,7,7,8,8,8 tridecafluorooctyl-4-(acrloyloxy) benzoate (ABCF13) polymer microspheres and to investigate the influences of the prepared microspheres addition on the crystallinity, thermal, mechanical and morphological features of high density polyethylene (HDPE). The suspension polymerization method was used for the production of well-defined microspheres and, the content of the microspheres varied from 1.0% to 10.0% in the composites. The characterization of crosslinked poly(ABCF13) microsphere-loaded HDPE composites were performed via powder X-ray diffraction, differential scanning calorimeter, universal mechanical (tensile and impact) testers and scanning electron microscope (SEM) techniques. According to the experimental findings, a and b unit cell parameters increased initially and reached maxima with the sample including 5.0% microsphere, which were followed by dramatic decreases, while c parameter remained relatively unchanged. Thermal analysis also showed that the melting temperature of HDPE reduced with the initial loading of the microspheres, then stayed at a plateau value of about 129 degrees C due to the formation of lattice distortions, generation of microstructural disorders and the defects in the crystal structures. The mechanical test results revealed that there existed considerable improvements in tensile strength, modulus and impact strength. The maximum tensile strength 25.66 MPa, elastic modulus 499.30 MPa and maximum absorbed energy in the impact test 26.84 kJ/m(2) (29%, 42% and 41% improvement, respectively) were achieved with the blend involving 5.0% microsphere. After the maxima, the mechanical characters depicted weakening trend as the microsphere content increased in the matrix. The SEM analyses revealed that although there existed fibrillar formations in all samples, the extensions decreased with the increase of the microsphere content. While ductile behavior was observed with the formation of long-bulky extensions at low contents, brittleness started to prevail at high contents with some short and thin fibrils.Öğe Synthesis and organogelation properties of bis-carbamate compounds bearing spacers with a stereogenic center(Springer, 2023) Ordu, Öznur DemirA series of bis-carbamates with a stereogenic center were prepared as low-molecular-weight organic gelators. The gelating propensity of racemates and pure enantiomers was examined in a range of organic solvents to explore the effects of chirality and the para-alkyl chain length on self-assembly. It was found that the gelation abilities in vegetable oils and esters were mainly affected by the para-alkyl chain length and the number of carbons in the spacer between the carbamate groups. In addition, molecular chirality was found to have a significant effect on the gelation properties of bis-carbamate derivatives with three-carbon spacer. Furthermore, morphology of the bis-carbamate gels was investigated by optical microscopy and scanning electron microscopy. Birefringent helix-like structures between birefringent spherulites were observed by polarized optical microscopy in the gel structures of chiral bis-carbamate derivatives with three-carbon spacer. The bulk properties of the gels were evaluated through rheological studies. The results can be used for developing novel chiral gels and relevant applications such as enantiomeric separation. [GRAPHICS] .Öğe Novel benzodioxatriaza and dibenzodioxadiazacrown compounds carrying 1,2,4-oxadiazole moiety(De Gruyter Poland Sp. z o.o., 2022) Özer, Besra; Dürüst, YaşarA series of benzo (dibenzo)dioxadiaza and triazamacrocyclic ether compounds carrying 1,2,4-oxadiazole group has been successfully synthesized through N-substitution with 3-p-phenylsubstituted-5-chloromethyl-1,2,4-oxadiazoles. The structures of all the novel macrocycles were confirmed by spectral/physical data including HRMS measurements.
