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    Ferrocene Containing Polyimides as a Route to Low-? Dielectric Materials
    (Wiley-V C H Verlag Gmbh, 2010) Seckin, Turgay; Koytepe, Suleyman; Kivilcim, Nilufer
    Polyimides incorporating the ferrocene unit were prepared by in situ curing of poly (amic acid) macromolecules with ferrocene, for the molecular-level design of low dielectric constant (low-kappa) materials. The effects of ferrocene on dielectric properties of polyimide are investigated in detail in this study. Ferrocene containing polyimides exhibit a number of desirable properties including low-water absorption and admirable thermal stability. Systematic studies demonstrate that proper insertion of ferrocene into a polyimide backbone can give rise to a reduction in the material's dielectric constant. All composites were subjected to DSC measurements for the purpose of examining Tg from all composition. Scanning electron microscopy (SEM), X-ray diffraction (XRD) and the other conventional techniques were used for structural characterization.
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    Hydrothermal Synthesis of Polyoxometalate Containing Cobalt Ion, and Its Polyurethane Composites for Dielectric Material Applications
    (Taylor & Francis Inc, 2020) Kucuk, Ilhan; Vural, Sema; Kivilcim, Nilufer; Adiguzel, Ibrahim; Koytepe, Suleyman; Seckin, Turgay
    Polyurethane (PU) composites were prepared with different diisocyanate and diol compounds by adding cobalt ion-based polyoxometalate (Co-POM) as reinforcement. For the determination of using potential in microelectronic applications, the dielectric behavior and dielectric constant of these PU composites were investigated and compared to pure polyurethane structures. For this aim, firstly, Co-POM with Keggin structure was obtained from ammonium heptamolybdate, 1,10-phenanthroline ligand and a cobalt (II) salt by hydrothermal synthesis technique. Then, polyurethane/Co-POM composites (PU/Co-POM) were prepared with ethylene glycol, nonaromatic diisocyanate and different amounts of Co-POM reinforcement (1%, 3%, 5% and 10%, w/w) by in situ polymerization and mix-blend technique. Obtained PU/Co-POM composites were characterized in detail by infrared spectroscopy, Elemental Mapping, Energy-dispersive X-ray spectroscopy (EDX) and X-ray powder diffraction (XRD) spectroscopy. The surface structure, morphology and roughness of PU/Co-POM composites were investigated by SEM and AFM analysis. The elemental maps of the PU/Co-POM surface were examined by EDX elemental mapping analysis methods. Thermal stability, Tg values and thermal decomposition temperatures of PU/Co-POM structures were determined by different thermal analysis techniques. Thermal analysis results showed that the PU/Co-POM composites are thermally stable up to approximately 200 degrees C and Tg values of synthesized PU composites are seen between 54.72 degrees C and 75.15 degrees C. The dielectric properties and dielectric constants of the PU/Co-POM composites were determined in the frequency range 1 Hz to 1000 kHz at room temperature using impedance analyzer. Dielectric constants of these composites were ranged from 5.50 to 9.26 according to their polarizability and H-bonding ability of PU matrix structure. According to the dielectric measurements, the dielectric constants of the PU/Co-POM structures were significantly decreased compared to the pure PU structures.
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    Porous pyridine based polyimide-silica nanocomposites with low dielectric constant
    (Springer, 2013) Kivilcim, Nilufer; Seckin, Turgay; Koytepe, Suleyman
    Highly porous polymer-silica hybrid materials were prepared based on the organo-soluble polyimides of four various dianhydride and 2,5-diaminopyridine. 3-Aminopropyltriethoxysilane (APS) was used to increase the intrachain chemical bonding and interchain hydrogen bonding between the polyimide and silica moieties, respectively. The chemical interaction would significantly affect the morphologies and properties of the prepared films. The produced polyimide-silica composites were investigated by X-ray diffraction analysis, scanning electron microscope and thermal analysis tecniques. The effect of silica modified with functional group of 3-aminopropyltriethoxy silane on the porous structure and dielectric properties as well as the thermal stability of films were investigated. Capacitances were determined with a HP4294A at a frequency between 1 kHz and 1 MHz. The dielectric constant was significantly reduced with increasing silica modified with APS. The result indicates that the composite materials are potentially useful in low dielectric materials.
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    Preparation of the copper-based polyoxometalate/polyurethane composites and their dielectric properties
    (Sage Publications Ltd, 2020) Kucuk, Ilhan; Vural, Sema; Kivilcim, Nilufer; Adiguzel, Ibrahim; Koytepe, Suleyman; Seckin, Turgay
    The aim of this study is synthesis of polyurethane (PU) composites from 4,4 '-methylenebis(cyclohexyl isocyanate), 1,2-ethanediol and different amounts of copper-based polyoxometalate (Cu-POM) and investigation of their dielectric properties. Firstly, Cu-POM structure as reinforcement was synthesized with ammonium heptamolybdate and Cu metal ion salt by a hydrothermal synthesis method. Then, Cu-POM-PU composites were prepared by in situ polymerization process. The prepared Cu-POM-PU composites were characterized by means of various techniques for their structure, morphology and thermal behaviour. The chemical structure, surface and morphological properties of the obtained composites were studied by Fourier transform infrared spectroscopy, X-ray diffraction spectroscopy, scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX) techniques. Thermal properties of these Cu-POM-PU composites were determined by thermogravimetric analysis, differential thermal analysis and differential scanning calorimetry analysis techniques. Dielectric properties of the Cu-POM-PU composites were also determined. The dielectric measured results showed that the dielectric constants decreased with the increase of the Cu-POMs content. The Cu-POM-PU composites showed relatively low dielectric constant compared to pure PUs.
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    Preparation, characterization, and biocompatibility of chondroitin sulfate-based sol-gel coatings and investigation of their effects on osseointegration improvement
    (Taylor & Francis As, 2023) Pasahan, Aziz; Sevimli, Resit; Kivilcim, Nilufer; Acari, Idil Karaca; Erenler, A. Sebnem; Sezer, Selda; Durmat, H. Turgut
    In this work, implants with enhanced antibacterial and surface properties besides mechanical, biological, and chemical properties were prepared with the replacement of traditional titanium and titanium alloys in the field of biomedical materials. Titanium substrates were coated with chondroitin sulfate (CS) containing (3-glycidoxypropyl)trimethoxysilane (GLYMO) and tetraethoxysilane (TEOS) based thin film using sol-gel technology. Chondroitin sulfate is a preferred material due to its characteristics antioxidative and osseointegresion properties besides its collagen-forming properties. Coated implants were morphologically elucidated with atomic force microscopy (AFM), and scanning electron microscopy (SEM). The structure of the chondroitin sulfate-containing films was investigated with Fourier Transform Infrared Spectroscopy (FTIR) and Energy Dispersive X-Ray Analysis (EDX) techniques. The obtained CS-based sol-gel surface coatings are thermally stable up to similar to 200 degrees C according to TGA and DTA analysis results. The biological and antibacterial properties of the coatings were also determined. The biocompatibility and osseointegration properties of the coatings developed within the scope of the study were, determined by in vivo studies on rats. According to biocompatibility results of CS/Sol-Gel coated surfaces, Cell viability (%) rates of CS-based coatings showed between 89 and 66%. According to the experimental data, it has been claimed that implants improved with antibacterial, stable, homogeneous, and biocompatible coatings can be used as a new alternative product for dental and orthopedic applications.
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    Synthesis of Triazine-Based Polyimide Nanocomposites with Flower-Like ZnO by Microwave-Assisted Solvothermal Technique
    (Taylor & Francis Inc, 2013) Seckin, Turgay; Kivilcim, Nilufer; Koytepe, Suleyman
    Flower-like ZnO nanoparticles were synthesized by microwave-assisted solvothermal techniques in a simple system at 120 degrees C for 5h with the microwave synthesis method. Polyimide-ZnO nanocomposites were prepared by blending flower-like ZnO and the poly(amic acid). The prepared polyimide-ZnO nanocomposite films were characterized for their structure, morphology, and thermal behavior employing Fourier transform infrared spectroscopy (FTIR), scanning electron micrograph (SEM), X-ray diffraction (XRD), and thermal analysis (DTA/TGA/DSC) techniques. These studies showed the homogenous dispersion of ZnO in the polyimide matrix with an increase in the thermal steadiness of the composite films on ZnO loadings.