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Permanent URI for this collectionhttps://hdl.handle.net/20.500.14288/3

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    Synthesis and characterization of block-graft copolymers [poly(epichlorohydrin-b-styrene)-g-poly(methyl methacrylate)] by combination of activated monomer polymerization, nmp and atrp
    (Springer, 2007) Taşdelen, M. Atilla; Biedron, Tadeusz; Kubisa, Przemyslaw; Department of Chemistry; Department of Chemistry; Demirel, Adem Levent; Researcher; Faculty Member; Department of Chemistry; College of Sciences; College of Sciences; N/A; 6568
    Synthesis of block-graft copolymers, namely poly(epichlorohydrin-b-styrene)-g-poly(methyl methacrylate) (PECH-b-St)-g-PMMA) by combination of Activated Monomer (AM), Nitroxide Mediated Polymerization (NMP) and Atom Transfer Radical Polymerization (ATRP) methods was described. For this purpose, first epichlorohydrin (ECH) was polymerized by using BF3THF complex in the presence of 4-hydroxy-2,2,6,6-tetramethyl-1-piperidinyl-1-oxy (HTEMPO) via AM mechanism. The resulting stable radical terminated polymer was subsequently used as a counter radical in the NMP of styrene (St) initiated by benzoyl peroxide to yield block copolymers of ECH and St. Finally, the ATRP of methyl methacrylate (MMA) by using chloromethyl groups of the PECH segment as initiating sites resulted in the formation of (PECH-b-St)-g-PMMA). The structures of the intermediate polymers at various stages were characterized by H-1-NMR spectral investigations. The thermal behavior and surface morphology of the copolymers were also investigated by DSC and AFM measurements.
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    Polyisobutylene-based segmented polyureas. I. synthesis of hydrolytically and oxidatively stable polyureas
    (Wiley, 2009) Jewrajka, Suresh K.; Kennedy, Joseph P.; Department of Chemistry; Department of Chemistry; Yılgör, Emel; Yılgör, İskender; Researcher; Faculty Member; Department of Chemistry; College of Sciences; College of Sciences; 40527; 24181
    Novel segmented polyurea elastomers containing soft polyisobutylene (PIB) segments were synthesized and characterized. The key ingredient, primary amine-telechelic PIB oligomers (NH2-PIB-NH2) with number average molecular weights of 2500 and 6200 g/mol were synthesized. PIB-based polyureas were prepared by using various aliphatic diisocyanates and diamine chain extenders with hard segment contents between 9.5 and 46.5% by weight. All copolymers displayed microphase morphologies as determined by dynamic mechanical analysis. Tensile strengths of nonchain-extended and chain-extended polyureas showed a linear dependence on the urea hard segment content. PIB-based polyureas prepared with NH2-PIB-NH2 of M-n = 2500 g/mol, 4,4'-methylendbis(cyclohexylisocyantate), and 1,6-diaminohexane containing 45% hard segment exhibited 19.5 MPa tensile strength which rose to 23 MPa upon annealing at 150 degrees C for 12 h. With increasing hard segment content, elongation at break decreased from similar to 450% to a plateau of 110%. The hydrolytic and oxidative stability of PIB-based polyureas were unprecedented. Although commercial "oxidatively resistant" thermoplastic polyurethanes degraded severely upon exposure to boiling water or concentrated nitric acid, the experimental polyureas survived without much degradation in properties.
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    Effect of surface modification of colloidal silica nanoparticles on the rigid amorphous fraction and mechanical properties of amorphous polyurethane-urea-silica nanocomposites
    (Wiley, 2019) Oguz, Oğuzhan; Candau, Nicolas; Bernhard, Stephane H. F.; Heinz, Ozge; Stochlet, Gregory; Plummer, Christopher J. G.; Menceloğlu, Yusuf Z.; N/A; Department of Chemistry; Department of Chemistry; Söz, Çağla Koşak; Yılgör, Emel; Yılgör, İskender; PhD Student; Researcher; Faculty Member; Department of Chemistry; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; College of Sciences; College of Sciences; N/A; N/A; 24181
    Colloidal silica nanoparticles (NPs) modified with eight different silane coupling agents were incorporated into an amorphous poly(tetramethylene oxide)-based polyurethane-urea copolymer matrix at a concentration of 10 wt % (4.4 vol %) in order to investigate the effect of their surface chemistry on the structure-property behavior of the resulting nanocomposites. The rigid amorphous fraction (RAF) of the nanocomposite matrix as determined by differential scanning calorimetry and dynamic mechanical analysis was confirmed to vary significantly with the surface chemistry of the NPs and to be strongly correlated with the bulk mechanical properties in simple tension. Hence, nanocomposites with an RAF of about 30 wt % showed a 120% increase in Young's modulus, a 25% increase in tensile strength, a 15% decrease in elongation at break with respect to the neat matrix, which had no detectable RAF, whereas nanocomposites with an RAF of less than 5% showed a 60% increase in Young's modulus, a 10% increase in tensile strength and a 5% decrease in the elongation at break.