Yazar "Yagci, Yusuf" seçeneğine göre listele

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    Fluorene-Carbazole-Based Porous Polymers by Photoinduced Electron Transfer Reactions
    (Amer Chemical Soc, 2020) Koyuncu, Sermet; Hu, Peng; Li, Zhiquan; Liu, Ren; Bilgili, Hakan; Yagci, Yusuf
    A new photoinitiating system for the metal-free preparation of conjugated microporous polymers (CMPs) is reported. In this approach, irradiation of solutions containing an electroactive monomer, possessing both carbazole and fluorene units, 9,9'-(9,9-dihexyl-9H-fluorene-2,7-diyl)bis-9H-carbazole (CFD), and the iodonium salt (Ph2I+PF6-) as the oxidizing agent resulted in the formation of CMPs. Photoinduced step-growth polymerization proceeded through the successive electron transfer between the excited CFD and iodonium salt, proton release, and coupling reactions. The polymers formed were characterized by FT-IR and H-1 NMR analyses. The electrochemical and optical properties of CMPs before and after the dedoping process were evaluated by cyclic voltammetry, differential pulse voltammetry, and UV-vis absorption and photoluminescence techniques. The porous structure of the obtained polymers was confirmed by atomic force microscopy and scanning electron microscopy studies.
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    Photoinduced Step-Growth Polymerization of N-Ethylcarbazole
    (Amer Chemical Soc, 2018) Sari, Erdem; Yilmaz, Gorkem; Koyuncu, Sermet; Yagci, Yusuf
    A novel method for photochemical step growth synthesis of poly(N-ethylcarbazole) (PEC) via consecutive diphenyl iodonium hexafluorophospate (Ph2I+PF6-) mediated electron transfer and coupling reactions is reported. The photoinduced electron transfer reaction of the excited N-ethylcarbazole (EC) in the presence of Ph2I+PF6- as the oxidizing salt proceeded efficiently giving EC radical cations (EC+center dot). Subsequently, the protons released concomitantly with coupling of two EC radical cations. The successive reactions involving excitation, electron transfer, proton release, and coupling lead to the formation of PEC. The electrochemical properties and surface morphology of the thin films of the formed polymers before and after dedoping were investigated by cyclic voltammetry, differential pulse voltammetry, and atomic force microscopy techniques, respectively.
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    Photoinduced step-growth polymerizations of thiophene-carbazole based covalent organic polymer
    (Elsevier Sci Ltd, 2023) Celiker, Tugba; Altinisik, Sinem; Yagci, Yusuf; Koyuncu, Sermet
    A novel metal-free photochemical method for the synthesis of porous conjugated polymers was used to inves-tigate the effects of introducing thiophene co-monomer to the carbazole-based polymer, 4,4 '-bis(3,6-di(thiophen-2-yl)-9H-carbazol-9-yl)-1,1 '-biphenyl (CBP-Th), in terms of its structural, optical, electrochemical and morphological properties. Irradiation of a CBP-Th monomer solution led to the formation of a dark-colored polymer, PCBP-Th, and the role of thiophene on polymerization was investigated, involving electron transfer between CBP-Th and the iodonium ion in the exciplex produced by proton release and radical coupling reactions. The UV-Vis spectra broadened and redshifted due to the elongation of conjugation and solid-state pi-pi in-teractions by extra thiophene additive after the polymerization process. The addition of thiophene co-monomer also resulted in decreasing the onset potentials and thus slightly raised HOMO positions determined by the DPV technique. In theoretical calculations, it has been observed that the charge distribution of PCBP-Th at HOMO is over the entire conjugated structure and it has localization in thiophene-thiophene bridges at LUMO. Since the thiophene co-monomer changes the intermolecular distance, the thermal stability of PCBP-Th polymers de-creases and accordingly increases the amorphous characters. According to AFM, TEM and SEM images, intro-ducing the thiophene co-monomer led to the formation of larger clusters, resulting in a more pronounced surface texture on both the powders and thin films.
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    Photoinduced synthesis of poly(N-ethylcarbazole) from phenacylium salt without conventional catalyst and/or monomer
    (Royal Soc Chemistry, 2019) Kaya, Kerem; Koyuncu, Sermet; Yagci, Yusuf
    We report a new method for the photoinduced synthesis of poly(N-ethylcarbazole) (PEC). Inspired by the photochemical decomposition and electron transfer reactions of N-phenacylethyl carbazolium hexafluorophosphate (ECPhAc) salt, we used ECPhAc as the single molecule possessing both initiator and monomer structures to form PEC with relatively higher yield and higher molecular weight compared to that obtained from the bare monomer. This step-growth approach, eliminating the use of additional oxidizing agent, involves successive photoexcitation, cleavage, electron transfer, proton release, and coupling steps. The structural characteristics, electrochemical properties, and surface morphologies of the obtained PEC before and after the dedoping process were investigated by UV-vis, FT-IR, fluorescence, NMR, MALDI-TOF, SEC, AFM, cyclic voltammetry (CV), and differential pulse voltammetry (DPV). Doped PEC exhibited white light emission covering all visible regions offering a potential application in white light OLEDs.
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    Poly(cyclohexene oxide)/Clay Nanocomposites by Photoinitiated Cationic Polymerization via Activated Monomer Mechanism
    (Wiley, 2009) Oral, Ayhan; Tasdelen, Mehmet Atilla; Demirel, Adem Levent; Yagci, Yusuf
    Poly(cyclohexene oxide) (PCHO)/clay nanocomposites were prepared by in situ photoinitiated activated monomer cationic polymerization. The polymerization of cyclohexene oxide through the interlayer galleries of the clay can provide distribution of the clay layers in the polymer matrix homogenously and results in the formation of PCHO/clay nanocomposites. The exfoliated structures were characterized by X-ray diffraction spectroscopy, thermogravimetric analysis, transmission electron microscopy, and atomic force microscopy. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5328-5335, 2009
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    Poly(methyl methacrylate)/clay nanocomposites by photoinitiated free radical polymerization using intercalated monomer
    (Elsevier Sci Ltd, 2009) Oral, Ayhan; Tasdelen, Mehmet Atilla; Demirel, Adem Levent; Yagci, Yusuf
    A series of poly(methyl methacrylate)/montmorillonite (PMMA/MMT) nanocomposite were prepared by Successfully dispersing the inorganic nanolayers of MMT clay in an organic PMMA matrix via in situ photoinitiated free radical polymerization. Methyl methacrylate monomer was first intercalated into the interlayer regions of organophilic clay hosts by click chemistry followed by a typical photoinitiated free radical polymerization. The intercalated monomer was characterized by FT-IR spectroscopy, elemental analysis and thermogravimetric analysis methods. The intercalation ability of the modified monomer and exfoliated nanocomposite structure were confirmed by X-ray diffraction spectroscopy (XRD), transmission electron microscopy (TEM) and atomic force microscopy (AFM). Thermal stability of PMMA/MMT nanocomposites was also studied by both differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). (c) 2009 Elsevier Ltd. All rights reserved.
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    Poly(styrene-b-tetrahydrofuran)/Clay Nanocomposites by Mechanistic Transformation
    (Wiley, 2009) Yenice, Zuleyha; Tasdelen, M. Atilla; Oral, Ayhan; Guler, Cetin; Yagci, Yusuf
    Synthesis of poly(styrene-block-tetrahydrofuran) (PSt-b-PTHF) block copolymer on the surfaces of intercalated and exfoliated silicate (clay) layers by mechanistic transformation was described. First, the polystyrene/montmorillonite (Pst/MMT) nanocomposite was synthesized by in situ atom transfer radical polymerization (ATRP) from initiator moieties immobilized within the silicate galleries of the clay particles. Transmission electron microscopy (TEM) analysis showed the existence of both intercalated and exfoliated structures in the nanocomposite. Then, the PSt-b-PTHF/MMT nanocomposite was prepared by mechanistic transformation from ATRP to cationic ring opening polymerization (CROP). The TGA thermogram of the PSt-b-PTHF/MMT nanocomposite has two decomposition stages corresponding to PTHF and PSt segments. All nanocomposites exhibit enhanced thermal stabilities compared with the virgin polymer segments. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2190-2197, 2009
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    Polypyrenes by Photoinduced Step-Growth Polymerization
    (Amer Chemical Soc, 2020) Celiker, Tugba; Kaya, Kerem; Koyuncu, Sermet; Yagci, Yusuf
    Photoinduced processes have been widely utilized in macromolecular synthesis through radical, cationic, anionic, and controlled/living polymerizations and ligation processes. 'While widely utilized, their application in step-growth polymerization has been scarcely investigated. In the present work, we report a new facile photochemical approach for the synthesis of polypyrene (PPy) by step-growth polymerization. Inspired by our previous studies on photoinduced electron-transfer reactions occurring between electron-rich monomers such as thiophene and carbazole derivatives and iodonium salt, we show that pyrene (Py) readily polymerizes under 350 nm irradiation at room temperature in the presence of iodonium salt by consecutive excitation, electron transfer within the exciplex, proton release, and coupling reactions. A detailed investigation on the structural, morphological, electrochemical, and molecular weight characteristics of the polymers revealed that the ratio of iodonium salt/Py plays a crucial role in the chain length and properties. The approach developed here is broadly adaptable to functional pyrenes and other conjugated monomers.
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    Sequential and Simultaneous Photoinduced Radical and Step- Growth Polymerizations of Carbazole Functional Styrene
    (Amer Chemical Soc, 2022) Celiker, Tugba; Altinisik, Sinem; Vaitusionak, Aliaksei; Kostjuk, Sergei V.; Koyuncu, Sermet; Yagci, Yusuf
    Photoinduced radical and step-growth polymerizations of carbazole functional styrene (vinyl phenyl carbazole, VPC) by sequential and one-pot strategies have been investigated. The obtained polymers were characterized by FTIR, H-1-NMR, GPC, UV-Vis, PL, CV, and BET analyses. The theoretical charge distribution and HOMO-LUMO calculation by DFT were well-matched with those obtained from optical and electrochemical measurements. In the sequential approach, visible light-induced free-radical photopolymerization of VPC by using bisacyl phosphineoxide results in the formation of linear polymers with side-chain carbazole moieties. The resulting polymers exhibit a smooth surface as a consequence of decreasing crystallinity. As evidenced by TEM analysis, the subsequent photoiniated step-growth polymerization of the carbazole groups by using diphenyliodonium hexafluorophosphate (DPI) yields hyperbranched and cross-linked polymers with the microspheres on the surface. In the one-pot approach, concomitant photoinitiated free-radical and step-growth polymerizations by using DPI results in the formation of cross-linked polymers with dispersed distribution. The total nitrogen uptake of VPC-based polymers by using Brunauer-Emmett-Teller (BET) surface area was found to be between about 150 and 190 m(2)/g at 77 K.
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    Visible Light-Induced Synthesis of Conjugated Poly(phenylene butadiynylene) by a Combination of Halide Abstraction and Coupling Reactions
    (Amer Chemical Soc, 2023) Nakipoglu, Busra; Aydogan, Cansu; Ozdemir, Mucahit; Yagci, Yusuf; Koyuncu, Sermet; Kiskan, Baris
    This study describes a simple and efficient method forsynthesizingconjugated poly(phenylene butadiynylene) (PPB)polymers using photo-inducedradical homocoupling. The approach involves irradiating 1,4-bis(bromoethynyl)benzenewith visible light in the presence of dimanganese decacarbonyl (Mn-2(CO)(10)), which acts as a radical generator by abstractinghalides and promoting subsequent radical coupling reactions. The resultingconjugated PPB exhibited a remarkable red shift, andthe optical band gap decreased from -2.76 to -2.27 eV.A similar effect was observed in the electrochemically measured oxidationpotential; the highest occupied molecular orbital position regressedfrom -6.06 to -5.69 eV. Transmission electron microscopyand atomic force microscopy measurements revealed the self-organizationof the polymers to planar 2D nanorods, and the 2D structures of thepolymers were further supported by density functional theory calculations.Moreover, the surface area of the polymer was found to be 53.61 and30.69 m(2)/g according to Brunauer-Emmett-Tellerand Barrett-Joyner-Halenda methods, respectively.