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Öğe The grafting of Rhodamine B onto sol-gel derived mesoporous silicas(Elsevier Sci Ltd, 2003) Seçkin, T; Gültek, A; Kartaca, SAmorphous meseporous silica, silica foams and silica nanotubes have been prepared by the controlled hydrolysis of tetraethoxysilane in various environments. A self-similar structure was obtained in all cases. Rhodamine B was post grafted onto the meseporous silica foam which has been modified with gamma-glycidyloxypropyl trimethoxysilane. The grafting and post grafting efficiency of gamma-glycidyloxypropyl trimethoxysilane as well as the post grafting efficiency of Rhodamine B on meseporous silica foam were studied, respectively. Basic physicochemical properties of the modified particles are given. When the hybrid pigments were exposed to UV radiation pulses, the emission of the hybrid pigments was increased. (C) 2002 Elsevier Science Ltd. All rights reserved.Öğe Hydrolysis, polycondensation, and catalytic properties of Ru(II) complex of 3-4,5-dihydroimidazol-1-ylpropyltriethoxysilane(John Wiley & Sons Inc, 2001) Seçkin, T; Özdemir, I; Çetinkaya, BThe preparation and measurements of some properties of organic-inorganic hybrid materials derived from Ru(II)-3-4,5-dihyroimidazol-1-yl-propyltriethoxysilane inside a polysiloxane network have been achieved. The hydrolysis and polycondensation of Ru(II)-3-4,5-dihyroimidazol-1-yl-propyltriethoxysilane were performed in different experimental conditions, producing a new organic-inorganic silica. The alkoxysilyl groups available were used for the construction of inorganic backbone by the sal-gel process, and the imidazole group was found suitable for incorporating Ru(II) by coordination. The coordination of metal complex is retained because there is no leaching from the metal complex containing gels. To ensure sufficient catalytic properties, a series of hybrid materials from tetraethoxysilane was prepared. These materials were identified and catalytic activities were tested for cyclization of (Z)-3-methylpent-2-en-4-yn-1-ol to 2,3-dimethylfuran. Heterogeneous Ru(II) catalyst can also be recycled and reused without significant loss of selectivity or activity. (C) 2001 John Wiley & Sons, Inc.Öğe Novel type of metal-containing polyimides for the heck and Suzuki-Miyaura cross-coupling reactions as highly active catalysts(Springer, 2003) Seçkin, T; Köytepe, S; Demir, S; Özdemir, I; Centinkaya, BNovel palladium (II)-containing polyimides with exceptional catalytic properties for the Heck and Suzuki-Miyaura cross-coupling reactions were prepared from Pd(II)-alpha-bis(imine) complex and the corresponding dianhyrides. The glass transition temperatures (T-g) of the polymers ranged from 169 to 241degreesC. The temperatures at which 10% weight loss occurred in air ranged from 415 to 579degreesC. Polyimides based on the palladium (II) complex were tested for catalytic activity in the Heck coupling reaction between styrene and several aryl halides and the Suzuki coupling reaction between phenylboronic acid and several aryl halides. The negative effects (e. g., expense, low reaction rates, air-sensitivity) experienced by using phosphines, particularly electron-rich phosphines, as catalysts in large scale applications is overcome by using polymer supported catalysis.Öğe Poly(methacrylic) acid and ?-methacryloxypropyltrimethoxy silane/clay nanocomposites prepared by in-situ polymerization(Tubitak Scientific & Technological Research Council Turkey, 2002) Gültek, A; Seçkin, T; Önal, Y; Içduygu, MGPoly(methacrylic acid) and poly(acrylic acid) nanocomposites were prepared by in-situ polymerization of gamma-methacryloxypropyltrimethoxysilane (A174)/clay nanocomposites in which the macromonomer was generated by grafting A-174 onto activated clay samples via hydroxyl groups or via intercalation. In- situ polymerization was carried out in the presence of an initiator. It was found that the structural affinity between the methacrylic or acrylic acid monomers and the amount of clay played an important role in the hybrid structure. The nanocomposites were quantified by both X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), thermo-gravimetric analysis (TGA), and differential thermal analysis (DTA).Öğe Polymerization and characterization of acrylonitrile with ?-methacryloxypropyltrimethoxy-silane grafted bentonite clay(Wiley, 2002) Seçkin, T; Gültek, A; Içduygu, MG; Önal, YNovel natural clay-polymer hybrid materials are prepared from natural bentonite that was modified with silane-coupling agent, gamma-methacryloxypropyltrimethoxysilane (A-174), and acrylonitrile. By changing the molar ratio of acrylonitrile in the initial monomer feed, several clay-hybrid materials were prepared. The structure and thermal stability of hybrid materials were investigated by various methods. The A-174-modified bentonite was dispersed in a solution of acrylonitrile in toluene. In this system, radical polymerization in the presence of AIBN was carried out. Product formed at the particle surface was either physically bound by entanglement or chemically bound by covalent bonding to the silane. In this way, core-shell morphology was obtained with an inorganic core and a polymer shell. The results showed that bonding at the surface of bentonite took place by hydrolytic cleavage of methoxy groups of A-174 with hydroxy groups of bentonite. (C) 2002 John Wiley Sons, Inc.Öğe Postgrafting of Congo red dye onto hyperbranched mesoporous silica with terminal amino groups(John Wiley & Sons Inc, 2003) Seçkin, T; Gültek, ACongo red dye has been postgrafted onto mesoporous silica that was prepared by the controlled hydrolysis of tetraethyl orthosilicate in the presence of organic agents. Surface grafting of mesoporous silica having amino groups as initiator sites was prepared from gamma-aminopropyl-trimethoxysilane by sol-gel process. The postgraffing reaction of Congo red onto silica with terminal amino groups was achieved by a repeated step of the addition of methyl acrylate to amine groups followed by the amidation of the resulting ester moieties with ethylene diamine. Postgrafting efficiency of all materials has been outlined. Because postgrafting efficiency values have been found to be smaller than theoretical values, it is concluded that the resulting product was more likely to be a hyperbranched polymer rather than a true dendrimer at higher generations. The postgrafted structures with amino-terminal groups provide an attractive site for binding Congo red dye that not only persists in its characteristic properties, but also has exceptional hybrid properties possessed by mesoporous silica. (C) 2003 Wiley Periodicals, Inc.Öğe Preparation and characterization of polybenzimidazole-clay hybrid materials(Elsevier Science Sa, 2004) Gültek, A; Icduygu, MG; Seçkin, TThermally stable bentonite-polybenzimidazole (PBI) nanocomposites were synthesized from reactive organoclay and polybenzimidazole. The reactive organoclay was formed by using hexadecylpyridinium chloride (CPC) as a swelling agent for silicate layers of bentonite. The swelling process was carried out through ion exchange reaction between the end group of hexadecylpyridinium chloride salt and the sodium ion in bentonite. This irreversible swelling monitored by measuring the cation exchange capacity (CEC) of the bentonite solutions. Dispersion of the modified clay in the polybenzimidazole matrix resulted in nanostructured material containing intercalated polymer between the silicate layers. X-ray and thermal analysis confirmed structure of the now hybrid materials. The glass transition temperature and the thermal decomposition temperatures of this type bentonite-PBI were found to be higher than that of pure PBI. (C) 2003 Elsevier B.V. All rights reserved.Öğe Preparation, characterization and H2O2 selectivity of hyperbranched polyimides, containing triazine(Springer, 2005) Ekinci, E; Emre, FB; Köytepe, S; Seçkin, TNovel polyimides based on aromatic dianhyride and various hexahydrotriazine monomers were synthesized via two-stage solution polycondensation method. The resulting polyimides were characterized by solubility, viscosity, density, spectroscopic and thermal analysis methods. The results showed that polyimides soluble in polar solvents and had inherent viscosities ranging from 1.92 to 2.32 dL/g. The glass transition temperatures were 315 and 344 degrees C, and the 10% weight loss Then, polyimide-modified electrodes were prepared for the selective determina-temperatures were above 604 and 628 degrees C. Then, polyimide-mofified electrodes were prepared for the selective determination of hydrogen peroxide. The electrochemical behavior of the resulting polyimide film electrodes to the electroactive and non-electroactive species such as ascorbic acid, oxalic acid, hydrogen peroxide, lactose, sucrose and urea was examined by CV, DPV and TB techniques. From the obtained findings, it was shown that polyimide-coated electrode (PI-2) was only permitted to hydrogen peroxide among the species examined. As a result, it is claimed that polyimide electrode could be used as a selective membrane for hydrogen peroxide.Öğe Silica-supported 3-4,5-dihydroimidazol-1-yl-propyltriethoxysilanedichloropalladium(II) complex(Wiley, 2003) Gurbuz, N; Özdemir, I; Çetinkaya, B; Seçkin, TA novel mesoporous silica-nanotube-supported 3-4,5-dihydroimidazol-1-yl-propyltriethoxysilanedichloropalladium(II) complex was prepared and characterized. 3-4,5-Dihydroimidazol-1-yl-propyltriethoxysilanedichloropalladium(II) and mesoporous silica-supported 3-4,5-dihydroimidazol-1-yl-propyltriethoxysilanedichloropalladium(II) were tested for catalytic activity for Heck coupling reactions between styrene and several aryl halides and Suzuki coupling reactions between phenylboronic acid and several aryl halides. Copyright (C) 2003 John Wiley Sons, Ltd.Öğe Sol-gel synthesis of Ru(II) complex of 3-4,5-dihydroimidazol-1-yl-propyltriethoxysilane aerogels and xerogels(Springer Verlag, 2000) Seçkin, T; Çetinkaya, B; Özdemir, IThe preparation and the measurement of some properties of Ruthenium (II) coordinated 3-4,5-dihyroimidazol-1-yl-propyltriethoxysilane have been achieved. The organosilicon precursor chosen for this study was N-aminoethyl-3-aminopropyltriethoxysilane converted to 3-4,5-dihydroimidazol-1-yl-propyltriethoxysilane that was then coordinated with ruthenium (II). FT-IR spectroscopy, DTA and TGA analysis were used to characterize the bond formation during gelation, aging and drying of gels. The prepared aerogels are low-density 0.19-0.30 g/cm(3) amorphous materials with surface areas of 405 to 530 m(2)/g. The resulting aerogel catalysts exhibited unique structural and chemical properties.Öğe Surface modification of inorganic oxide particles with a carbene complex of palladium(Springer, 2004) Gürbüz, N; Özdemir, I; Seçkin, T; Çetinkaya, BThe reaction of 1-(2,4,6-trimethylbenzyl)-3-(propyltriethoxysilane) imidazolidinium chloride, with the Pd(OAc)(2) complex proceeded smoothly in DMSO to give the bis[1-(2,4,6-trimethylbenzyl)-3-(propyltriethoxysilane)imidazolidin-2-ylidene] dichloropalladium(II) complex that was grafted onto the surface of amorphous silica. The effects of various factors, such as reaction temperature and time, on the grafting efficiency was evaluated. Inorganic oxide particles that were modified with a carbene complex of palladium(II) were tested for catalytic activity in the Suzuki coupling reaction between phenylboronic acid and several aryl halides.Öğe Syntheses and catalytic properties of alternating copolymers of poly[4-maleimidopyridyl(p-cymene)dichloro Ru(II)] with ?-methacryloxypropyl trimethoxysilane(Elsevier Science Bv, 2002) Özdemir, I; Çetinkaya, B; Seçkin, T; Köytepe, SA new monomer, 4-maleimidopyridyl(p-cymene)dichloro Ru(II), was synthesized by the reaction of maleic anhyride with p-dimethylaminopyridine(p-cymene)dichloro ruthenium(II). The homopolymer ofmaleimidopyridyl(p-cymene)dichloro Ru(II) and its copolymers with gamma-methacryloxypropyl trimethoxysilane were prepared by radical polymerization with benzoyl peroxide as an initiator at 75 degreesC. The structures of the synthesized monomer and polymers were identified by Fourier transform infrared, H-1 NMR, and C-13 NMR spectroscopies. Thermal behavior of the polymers were determined by differential thermal analysis, and thermogravimetric analysis, glass transition temperature was determined by differential scanning calorimeter. Excellent selectivities were observed by using Ru (II) complex as the catalyst in hydrosilylation reactions. The heterogeneous Ru(II) catalyst can also be recyled and reused without significant loss of selectivity or activity. (C) 2002 Elsevier Science B.V. All rights reserved.Öğe Synthesis and characterization of asbestos-silane hybrid materials(Elsevier, 2005) Onal, Y; Yakinci, ME; Seçkin, T; Içduygu, MGIn this study, interaction of the silane coupling agent 3-(trimethoxysilyl)propylmethacrylate (A-174) and asbestos was investigated. A-174 grafted onto the surface of the asbestos was polymerized by radical initiator. FT-IR, thermogravimetric analysis (TGA), X-ray diffractometer (XRD), differential thermal analyzer (DTA) and scanning electron microscopy (SEM) were used to characterize modified particles. The effects of temperature on modified particles and were evaluated by differential thermal analysis. After modification with A-174, the effects of grafting on asbestos were discussed in terms of structural change and thermal stability. These results lead us to conclude that the silane coupling agent in asbestos serve as polymeric precursor to form polymer onto asbestos matrix resulting the hybrid materials in which the harmful effect of asbestos was prevented by covering the asbestos particles with polymer. (c) 2004 Elsevier B.V. All rights reserved.Öğe Synthesis and characterization of novel polyimides starting from 1,2-bis(p-dimethylaminobenzylideneimino)alkane homologues and various dianhydrides(Wiley, 2004) Koytepe, S; Gök, Y; Alici, B; Seçkin, T; Çetinkaya, EThe objective of this research was the preparation of polyimides from 1,2-bis(p-dimethylaminophenylimino)alkane homologues and various dianhydrides in N-methylpyrrolidone by one-stage polycondensation. The monomers were prepared via condensation of p-dimethylaminobenzaldehyde and the corresponding diamines, 1,4-diaminobutane, 1,3-diaminopropane and 1,2-diaminoethane. The influence of the incorporation of this moiety into the polymer backbone on the properties of the polyimides has been evaluated. The thermogram of the polyimides indicated that PI-10 to PI-32 had T-g values ranging from 181 to 290degreesC. The inherent viscosities of the polymers ranged from 0.99 to 2.05 dl g(-1), and the highest solubility was obtained without significant loss of the thermal properties. (C) 2004 Society of Chemical Industry.Öğe Synthesis and characterization of polyimides containing a chiral dimine link that mimics the salen ligand(Vsp Bv, 2004) Seçkin, T; Köytepe, S; Yigit, M; Çetinkaya, EWe report the synthesis of a covalently linked complex that mimics the salen ligand within the main chain of the polyimide network. The thermally-stable solid polyimides offer suitable sites for metal coordination, which is a crucially important step in establishing steroselectivity. The ligand synthesized by the sequential treatment of a chiral trans-1,2-diaminocyclohexane and p-dimethylaminobenzaldehyde was used to prepare polyimides by a one-step polymerization in the dipolar media. A series of stable polyimides was synthesized from (IS,2S)- and (1R,2R)-bis(p-dimethylaminobenzylideneamino)-1,2-cyclohexyl and various aromatic dianhydrides had inherent viscosities ranging from 1.45 to 2.21 dl/g and were soluble in polar solvents. The glass transition temperatures were 264-319degreesC, and the 10% weight loss temperatures were above 406-487degreesC.Öğe Synthesis and immobilization of N-heterocyclic carbene complexes of Ru(II)(Elsevier, 2002) Çetinkaya, B; Gürbüz, N; Seçkin, T; Özdemir, ISynthesis, characterization and immobilization of ruthenium(II) complexes of the type [RuCl2L(eta(6)-arene)] (L=CN(CH2PH)CH2CH2N(CH2)(3)Si(OEt)(3), arene = p-cymene, 3 and arene = C6Me6, 4) and [RuCl2L] (L = eta(1)-carbene-eta(6)-arene bidentate ligand, CN[(CH2)(3)Si(OEt)(3)]CH2CH2NCH2C6H2Me3-eta(6)), 5, morphologically different silicas by sol-gel method are described and their reactivity and recyclability in the furan formation were also reported. (C) 2002 Elsevier Science B.V. All rights reserved.Öğe Synthesis and properties of novel selenium containing polyimides with various dianhydrides(Springer, 2005) Köytepe, S; Seçkin, T; Çetinkaya, E; Gök, YNovel selenium-containing polyimides were prepared from bis(1,3-di-p-dimethylaminobenzylpyrimidine-2- selenon) and bis(1,3-di-p-dimethylaminobenzyldiazepane-2-selenon) and with various aromatic dianhydrides in a one-stage polycondensation at high temperature in N-methyl-2-pyrrolidone. The polyimides have inherent viscosities that range from 1.55 to 2.05 dL/g in NMP at 30 degrees C. These polymers showed glass transition temperatures between 188 and 268 degrees C, and an initial decomposition temperature from 421 to 502 degrees C with a 10% mass loss occurring from 480 to 547 degrees C in air.Öğe Synthesis and radical polymerization of 2-(vinylbenzylmercapto) heterocyclic salts(Vsp Bv, 1999) Çetinkaya, E; Seçkin, T; Alici, BHeterocyclic group-containing vinyl monomers, 2-(vinylbenzylmercapto) heterocyclic salts, were synthesized and their polymerization and copolymerization with styrene were investigated. Cyclic thioureas incorporating imidazoline, hexahydropyrimidine and benzimidazole nuclei were alkylated by chloromethyl styrene to give quaternary salts that were used as monomers. Homopolymerization of the monomers afforded mainly soluble polymers on high dilution. In the copolymerization with styrene, an alternating nature was suggested from the copolymerization parameters obtained by either the Finemann-Ross method or the Mao-Huglin method. A decrease in alternating copolymerizability was demonstrated.Öğe Synthesis of Ru(II) complex with 3-(4,5-dihydroimidazol-1-yl)propyltriethoxysilane containing viologen group(Maik Nauka/Interperiodica, 2005) Gürbüz, N; Seçkin, T; Özdemir, I; Çetinkaya, BThe nanostructured metallopolymers consisting of the partially quaternized 3-(4,5-dihydroimidazol-1-yl)propyl having the viologen group linked covalently through the alkyl spacer and its Ru(II) complex have been prepared by sol-gel method. Structural elucidation was done with Fourier transform infrared spectroscopy, ultraviolet spectroscopy and differential thermal analysis.Öğe Synthesis of silica-supported rhodium carbene complex as efficient catalyst for the addition of phenylboronic acid to aldehydes(Wiley, 2005) Özdemir, I; Gürbüz, N; Seçkin, T; Çetinkaya, BSilica-supported catalytically active functional materials, such as the rhodium(l) carbene complex with 1-(triethoxysilylpropyl)-3-(2,4,6-trimethylbenzyl)imidazolidine-2-ylidine (L), were prepared using the sol-gel method. The complex (1; COD = 1,5-cyclooctadiene) RhCl(COD)[1-(triethoxysilylpropyl)3-(2,4,6-trimethylbenzyl)imidazolidin-2-ylidine] was characterized by conventional spectroscopic methods and elemental analyses and the silica-supported functional material RhCl(COD)(L) were tested for the catalytic addition of phenylboronic acid to aldehydes. Copyright (c) 2005 John Wiley & Sons, Ltd.
