Researcher:
Bilgin, Sevilay

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PhD Student

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Sevilay

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Bilgin

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Bilgin, Sevilay

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2008 - 200912010 - 20134

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Researcher Of Publications: search.filters.isAuthorOfPublication.9b724d7e-7595-4531-8065-dfc172d6e8d1

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    Facile preparation of superhydrophobic polymer surfaces
    (Elsevier Sci Ltd, 2012) Department of Chemistry; N/A; N/A; Department of Chemistry; Yılgör, İskender; Bilgin, Sevilay; Işık, Mehmet; Yılgör, Emel; Faculty Member; PhD Student; Researcher; Researcher; Department of Chemistry; College of Sciences; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; 24181; N/A; N/A; N/A
    A simple and general method has been developed for the preparation of polymeric materials with superhydrophobic surfaces. The process is applicable to a large number of polymers, thermoplastic or thermoset. In this manuscript preparation and characteristics of superhydrophobic surfaces prepared from a segmented polydimethylsiloxane-urea copolymer (TPSU), a polyether based polyurethaneurea (TPU), poly(methyl methacrylate) (PMMA), polystyrene (PS), polycarbonate (PC) and a crosslinked epoxy resin (EPOXY) are discussed. All samples were prepared onto glass surfaces by using a simple, multi-step spin-coating procedure. In the first step a thin film of the desired polymer was coated onto the glass slide. This was followed by spin-coating of two layers of hydrophobic fumed silica using a dispersion in tetrahydrofuran. Finally to obtain a durable surface, a very thin film of the parent polymer was spincoated from a very dilute solution containing 2.5% by weight hydrophobic silica and 0.25% by weight matrix polymer in tetrahydrofuran. Surfaces were characterized by scanning electron microscopy (SEM), which clearly showed the formation of rough surfaces with homogeneously distributed silica particles in 1-10 mu m range. Static water contact angle and contact angle hysteresis measurements proved the formation of superhydrophobic surfaces. Samples displayed static water contact angles larger than 170 degrees and very low contact angle hysteresis of less than 3 degrees.
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    Hydrophilization of silicone-urea copolymer surfaces by UV/ozone: influence of PDMS molecular weight on surface oxidation and hydrophobic recovery
    (Elsevier Sci Ltd, 2013) N/A; N/A; Department of Chemistry; Department of Chemistry; Bilgin, Sevilay; Işık, Mehmet; Yılgör, Emel; Yılgör, İskender; PhD Student; Researcher; Researcher; Faculty Member; Department of Chemistry; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; College of Sciences; N/A; N/A; N/A; 24181
    Hydrophilization of polydimethylsiloxane urea copolymer (PSU) surfaces and the extent of hydrophobic recovery were investigated as a function of; (i) UV/ozone (UV/O) exposure time, (ii) the aging period after UV/O exposure, (iii) sample preparation method, and (iv) polydimethylsiloxane (PDMS) soft segment molecular weight of the copolymer (1500, 3000 and 11,000 g/mol). All copolymers had a constant urea hard segment content of 15% by weight. Samples were prepared by three different methods, which were; solution casting, spin-coating and electrospinning. XPS spectra clearly showed transformation of PDMS into SiO2 and sub-oxides, which increased gradually with increasing UV/O exposure time. XPS and ATR-FTIR measurements also revealed that the copolymer based on PDMS-11000 displayed the highest amount of SiO2 formation and overall surface modification. Static water contact angle values of the spincoated silicone urea copolymer films decreased significantly from 1100 to 430 after 3 h of UV/O exposure. Interestingly, the hydrophobicity of the electrospun fibers was retained under similar UV/O exposure conditions, most probably due to the preserved surface roughness. Hydrophobic recovery was evaluated after 2 months of storage at ambient conditions. The slowest recovery was observed for spincoated copolymer film based on PDMS-11000, due to higher amount of surface oxidation and formation of a thicker SiO2 barrier layer. (C) 2013 Elsevier Ltd. All rights reserved.
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    Effect of UV/ozone irradiation on the surface properties of electrospun webs and films prepared from polydimethylsiloxane-urea copolymers
    (Elsevier Science Bv, 2012) Department of Chemistry; N/A; N/A; N/A; Department of Chemistry; Yılgör, Emel; Kaymakçı, Orkun; Işık, Mehmet; Bilgin, Sevilay; Yılgör, İskender; Researcher; Researcher; Researcher; PhD Student; Faculty Member; Department of Chemistry; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); College of Sciences; N/A; N/A; College of Social Sciences and Humanities; College of Sciences; N/A; N/A; N/A; N/A; 24181
    Highly hydrophobic surfaces of silicone-urea copolymers were transformed into hydrophilic ones upon UV/ozone treatment. The extent of surface modification was strongly dependent on the sample preparation method and the exposure time. The physical and chemical changes at the copolymer surfaces were analyzed by spectroscopic (XPS, ATR-FTIR), microscopic (SEM) techniques and static water contact angle measurements. ATR-FTIR spectra clearly showed the dramatic change in the strongly hydrogen bonded urea hard segments and the degradation of dimethylsiloxane units in silicone-urea copolymers. XPS results revealed the formation of SiOx on the surface, which gradually increased with exposure time. After 3 h of UV/ozone exposure, Si( 2p) binding energy shifted from 101.9 to 102.85 eV, which is a clear indication of an increase in the oxidation state of silicon. The deterioration of microroughness of the electrospun webs upon UV/ozone exposure, which was revealed by SEM, resulted in a dramatic decrease in the static water contact angle values from 129 to 62 degrees. These results clearly show that UV/ozone process is a very simple and facile method to transform hydrophobic silicone-urea copolymer surfaces into fairly hydrophilic ones.
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    Poly 622-effect of reaction procedure on the degree of branching and polymer properties in highly branched polyureas obtained by A2+B3 polymerization
    (Amer Chemical Soc, 2008) N/A; N/A; Department of Chemistry; Department of Chemistry; Bilgin, Sevilay; Eynur, Tuğba; Yılgör, Emel; Yılgör, İskender; PhD Student; Master Student; Researcher; Faculty Member; Department of Chemistry; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; College of Sciences; N/A; N/A; N/A; 24181
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    Tunable wetting of polymer surfaces
    (Amer Chemical Soc, 2012) Department of Chemistry; N/A; N/A; Department of Chemistry; Yılgör, İskender; Bilgin, Sevilay; Işık, Mehmet; Yılgör, Emel; Faculty Member; PhD Student; Researcher; Researcher; Department of Chemistry; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); College of Sciences; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; 24181; N/A; N/A, 40527
    A simple method was developed for the preparation of polymeric materials with controlled surface wettability or tunable surface wetting. The method is applicable to a large number of polymers, thermoplastic or thermoset. With this method, it is possible to prepare polymer surfaces with static water contact angles ranging from 0 degrees (superhydrophilic) to greater than 170 degrees (superhydrophobic). The method developed is based on spin-coating of a hydrophilic/hydrophobic silica mixture dispersed in an organic solvent or solvent mixture onto the polymer surface. Depending on the hydrophilic/hydrophobic silica ratio in the coating mixture, it is possible to obtain polymer surfaces displaying gradually changing wettability from superhydrophilic to superhydrophobic. In this article, preparation and surface characteristics of polystyrene (PS) and cross-linked epoxy resin (ER) films are provided as general examples. Polymer surfaces obtained were characterized by scanning electron microscopy, white light interferometry, atomic force microscopy, X-ray photoelectron spectroscopy, and static water contact angle measurements. Effects of the type of polymeric substrate and composition of the silica mixture on the surface behavior of the composite systems were investigated.