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    Maltose-Containing Polyurethane Films: Synthesis, Characterization, and Their Use for Determination of Dopamine in the Presence of the Electroactive and Nonelectroactive Interferents
    (Taylor & Francis As, 2013) Pasahan, Aziz; Koeytepe, Sueleyman; Cengiz, M. Alper; Seckin, Turgay
    A series of polyurethanes were prepared from the maltose-ethylene glycol-diphenylmethane diisocyanate and used to construct a novel polyurethane electrode for the detection of dopamine. The polyurethanes were characterized by FT-IR, differential scanning calorimetry, and thermogravimetric analysis. The intrinsic viscosity and adhesive properties were also evaluated. Selectivity behaviour of films prepared from polyurethane solutions containing 1%, 3%, 5%, and 10% maltose to electroactive and nonelectroactive substances was examined by DPV. The results demonstrated that polymer electrode by 2 mu L polyurethane solutions containing 3% maltose was allowed penetration of dopamine while blocking the permeation of ascorbic acid and uric acid through film.
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    Molecular design of POSS core star polyimides as a route to low-? dielectric materials
    (Elsevier Science Sa, 2008) Seckin, Turgay; Koeytepe, Sueleyman; Adiguezel, H. Ibrahim
    Star polyimides incorporating the polyhedralsilsesquioxane (POSS-NH2) unit were prepared by in situ curing of polyamic acid macromolecules with amino POSS, octa (aminopropylsilsesquioxane), for the molecular-level design of low dielectric constant (low-kappa) materials that can be used to manufacture integrated circuits. Octameric POSS-NH2 having restricted rotation by multiple point attachment to the polyimide backbone is shown to introduce free volume into the films, thereby lowering their dielectric constants. A process for synthesizing POSS-polyimide star nanocomposites is reported, comprising a step forming porous-type POSS and subsequent step with polyimide precursor. The POSS-NH2 containing polyimides exhibit a number of desirable properties including low-water absorption and high thermal stability. Systematic studies demonstrate that proper insertion of POSS into a polyimide backbone can give rise to a reduction in the material's dielectric constant while also improving its mechanical and thermal properties. (C) 2008 Elsevier B.V. All rights reserved.
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    Synthesis of polyimide from 5,5-bis(bromomethyl)-2,2?:6?,2-terpyridine and investigation of the polymer sorption behavior towards some metal ions
    (Elsevier, 2009) Koeytepe, Sueleyman; Erdogan, Selim; Seckin, Turgay
    The synthesis of a terpyridine-based polyimide sorbent for solid-phase extraction (SPE) of some metal ions is described. For this purpose, 5,5 ''-bis(bromomethyl)-2,2':6',2 ''-terpyridine was polymerized with the corresponding diimide derivatives of dianhyrides to give polyimides utilizing terpyridine unit in the main chain. This polymer was used for its extraction capabilities for Pb(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II), at different pH. Under competitive conditions and at pH < 0.6, the selectivity order was Pb approximate to Cd approximate to Zn. Enhanced selectivity was observed at pH 3.5, the order was Cu > Ni > Zn approximate to Cd approximate to Pb. Quantitative recoveries > 97% were observed for all metals in case loading was stopped before reaching the point of breakthrough. As the synthesized polyimides are insoluble in water, solid-liquid extractions have been carried out and the resins sorption for mixture of basic and/or precious metals have been studied under various experimental conditions (reaction time and hydrochloric acid concentration). (C) 2008 Elsevier B.V. All rights reserved.
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    Synthesis, characterization of phosphine oxide-containing polyimides and their use as selective membrane for dopamine
    (Springer, 2008) Koeytepe, Sueleyman; Pasahan, Aziz; Ekinci, Ergun; Alici, Buelent; Seckin, Turgay
    Tris-(p-aminophenoxy)phosphineoxide, t-APPO, was prepared from 4-nitrophenol and POCl3, followed by hydrogenation. A series of polyimides prepared from t-APPO and the corresponding dianhydrides by two-stage polycondensation method was characterized by Fourier Transform Infrared Spectrometer (FTIR), GPC, thermal analysis and physical methods. Moreover, in order to check the permeation properties of the resulting polyimide film, the selectivity of the polyimide-coated electrode toward electroactive species (ascorbic acid and dopamine) was examined by means of cyclic voltammetry (CV), differential pulse voltammetry (DPV) and time-base amperometric measurement (TB) techniques. As a result, it has been found that polyimide electrode showed selective permeation for dopamine while blocking the permeation of ascorbic acid through film. Therefore, it has been claimed that phosphine oxide-containing polyimide electrode can be used as a dopamine-selective membrane in the presence of ascorbic acid.