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Öğe 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, TurgayPolyurethane (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.Öğe 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, TurgayThe 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.