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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 Preparation and characterization of novel polyimides from 2,6-bis[1-(p-dimethylaminophenylimino)ethyl] pyridine for the selective extraction of some metals(Springer, 2005) Seckin, T; Köytepe, SA group of new polyimides has been prepared by solution condensation of 2,6-bis[1-(p-dimethylaminophenylimino)ethyl] pyridine containing pendant NMe2 units and various dianhyrides in N-methylpyrrolidone (NMP). The tridentate (N-N'-N) pydim ligands were prepared by Schiff-base condensation of 2,6-diacetylpyridine and 4-dimethylaminoaniline in the presence of formic acid as catalyst. These polymers were investigated for their extraction capabilities for Zn(II), Mn(II), Cu(II), Cd (II) and Ni(II) and at different pH. Under different conditions enhanced selectivity was observed. Up to 98% quantitative recoveries were observed for all metals.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 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 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 properties of novel polyimides from dichloro (1,3-p-dimethylaminobenzylimidazolidine-2-ylidene) p-cymene ruthenium (II)(Taylor & Francis Ltd, 2003) Seckin, T; Köytepe, S; Çetinkaya, B; Özdemir, I; Yigit, BA novel diamine derivative, dichloro (1,3-p-dimethylaminobenzylimidazolidine-2-ylidene) p-cymene ruthenium (11), bearing a potential site for imide formation, was prepared starting from p-dimethylaminobenzaldehyde. It was used as a monomer to prepare polyimides with several dianhydrides via a one-stage procedure without going through tedious steps. The polyimides have inherent viscosities that range from 1.18 to 1.24 dl/g in N-methyl-2-pyrrolidinone at 30degreesC. These new polymers are soluble in polar aprotic solvents. The polymeric catalyst was added to (Z)-3-methylpent-2-en-4-yn-1-ol without a solvent and the pure furan was isolated by distillation under reduced pressure and GC determined the conversion of the starting enynol.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 properties of polyimides from 1,3-di(p-dimethylaminobenzyl)-imidazolidine-2-thion(Springer, 2003) Seckin, T; Çetinkaya, E; Köytepe, S; Yigit, BA synthetic strategy is presented that allows the preparation of dimethylamino functionalized. heterocyclic system 1,3-di (p-dimethylaminobenzyl)-imidazolidine-2-thion that was then used to prepare polyimides by the two-stage polycondensation method. The key to this success was the development of an efficient procedure leading highly pure dimethylamino monomer. Polyimides derived from 1,3-di(p-dimethylaminobenzyl)-inmidazolidine-2-thion and commercial dianhydrides exhibited excellent solubility in various polar solvents. These polymers showed glass transition temperatures between 290-360degreesC, and initial decomposition temperature 490-485 degreesC and 10% mass loss ranging from 505-575degreesC in air.Öğe Synthesis, characterization and dopamine selectivity of 1,4-bis(3-aminopropyl)piperazine -: Containing polyimide(Springer, 2004) Pasahan, A; Köytepe, S; Ekinci, E; Seçkin, TA novel polyimide prepared from 1,4-bis(3-aminopropyl) piperazine and pyromellitic dianhydride (PMDA) was characterized by thermal, FTIR, GPC and microanalysis techniques. Thermal properties of the polyimide were evaluated by differential scanning calorimetry (DSC), differential thermal analysis (DTA) and thermogravimetry (TGA). Moreover, platinum electrodes were covered with this polyimide and permeation properties of the resulting polyimide-coated electrodes to dopamine and ascorbic acid were examined by electrochemical method. On the basis of the permselectivity data obtained, it was found that the polyimide-coated electrode exhibited selective permeation for dopamine while blocking ascorbic acid.Öğe Synthesis, characterization and H2O2-sensing properties of pyrimidine-based hyperbranched polyimides(Pergamon-Elsevier Science Ltd, 2005) Köytepe, S; Pasahan, A; Ekinci, E; Seçkin, TA series of hyperbranched polyimides having pyrimidine core in the backbone was prepared by solution polycondensation of pyromellitic dianhydride (A(2) type) and 2,4,6-triaminopyrimidine (B-3 type). The resulting polyimides were characterized by IR, GPC, DTA, DSC, TGA, density and viscosity measurement. The results showed that polyimides were obtained in 82-86 % yield, had inherent viscosities of 1.58-1.87 dL/g and highly thermal stability. From the solubility tests, it was found that all the polyimides were soluble in NMP, DMAc and DMSO at room temperature. In addition, because of their interesting film properties, attempts were made to prepare H2O2-sensing polyimide material. For this reason, selectivity of film-coated electrodes obtained from the chemically prepared hyperbranched polyimides toward electroactive (ascorbic acid, oxalic acid and hydrogen peroxide) and non-electroactive (lactose, sucrose and urea) species was examined by means of CV, DPV and TB techniques. From the electrochemical data obtained, it has been demonstrated that polyimide (HPI-2) film responded to only hydrogen peroxide among the species examined. In other words, it has been claimed that the mentioned polyimide-coated electrode can be used as H2O-selective membrane in the presence of the electroactive and non-electroactive interferents. (C) 2004 Elsevier Ltd. All rights reserved.
