Yazar "Adiguzel, H. Ibrahim" seçeneğine göre listele

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    Preparation, Characterization, and Properties of Novel Polyimide-SiO2 Hybrid Composites Based on Bipyridine for Low Dielectric Applications
    (Taylor & Francis Inc, 2015) Koytepe, Sueleyman; Kucuk, Ilhan; Seckin, Turgay; Adiguzel, H. Ibrahim
    Novel low dielectric polyimide-SiO2 hybrid materials containing bipyridine were prepared with three-step sol-gel process from poly(amic acid)s. (3-Aminopropyl)triethoxysilane as coupling agent was used to increase the intrachain chemical bonding between the polyimide and SiO2 groups. The thermal, dielectric, and physical properties of the hybrid materials were investigated and correlated with the porous structure. The glass transition temperatures of all the hybrids were found to be higher than polyimides. The effect of SiO2 groups on the porous structure and dielectric properties was investigated. The dielectric constant of the hybrid materials was observed a decrease from 3.30 to 2.15 with increased SiO2 amount.
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    Synthesis and dielectric properties of polyimide-titania hybrid composites
    (Springer, 2008) Koytepe, Suleyman; Seckin, Turgay; Kivrilcim, Nilufer; Adiguzel, H. Ibrahim
    A new class of polyimide-titania (TiO2) composites with chemical bonds between the polyimide and titania system has been synthesized by the sol-gel reaction and characterized. The hybrid composite films were obtained by the reaction of lysine-organotitane monomer, which is formulated as [(EtO)(3)Ti (lysinate)](2,) followed by polycondensation with dianhyride in N-methyl-2-pyrrolidone (NMP) solution, followed by heating at 100, 200, and 300 degrees C. The presence of chemical bonds between polyimide (PI) and titania has great effect on the properties of polyimide films, especially on their thermal and dielectric properties. The dielectric constants of the resultant nanocomposites are lower than the usual polyimide films due to the increased free volume and less polar Ti-O-Ti groups, and can be tuned by varying the molar ratio of tetraethoxysilane (TEOT) in the feed. The polyimide units offer additional advantages of imparting thermal and mechanical strength.
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    Synthesis of nickelocene containing polyimides with low-dielectric constants
    (Elsevier Science Sa, 2009) Koytepe, Suleyman; Adiguzel, H. Ibrahim; Seckin, Turgay
    Polyimides embedding the nickelocene unit were prepared by in situ curing of poly(amic acid) macromolecules with nickelocene, for the molecular-level design of low-dielectric constant (IOW-kappa) materials. The effects of nickelocene on dielectric properties of polyimide are investigated in detail in this study. Nickelocene containing polyimides exhibit a number of desirable properties including low-water absorption and admirable thermal stability. Systematic studies demonstrate that proper insertion of nickelocene 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 microscopic miscibility. DSC thermograms of all composites showed only one T-g from all composition. (C) 2008 Elsevier B.V. All rights reserved.