Person: TEMEL, BİNNUR
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Publication Metadata only Thermally curable main-chain benzoxazine prepolymers via polycondensation route(2013-02-01T00:00:00Z) Demir, Kubra Dogan; Kışkan, Barış; Aydogan, BİNNUR; Yağcı, Yusuf; TEMEL, BİNNURPolybenzoxazines are addition-cure thermosetting polymers exhibiting versatility in a wide range of applications due to their good mechanical properties, dimensional stability, chemical resistivity, flame resistance property phenolic or epoxy resins have myriad applications in diverse fields starting from commodity materials to high technology aerospace industries. In this paper, we present synthetic strategies to incorporate thermally curable benzoxazine functionality into polymers as main-chain fashion in order to further improve various properties. The strategies successfully employed including monomer synthesis and polycondensation routes like Mannich reaction, click chemistry, hydrosilylations, and coupling reactions. The structure-property relationships of the cured materials have also been presented and discussed. (C) 2012 Elsevier Ltd. All rights reserved.Publication Metadata only Photoinduced Electron Transfer Reactions of Highly Conjugated Thiophenes for Initiation of Cationic Polymerization and Conjugated Polymer Formation(2012-10-09T00:00:00Z) Aydogan, BİNNUR; Yağcı, Yusuf; Toppare, Levent; Jockusch, Steffen; Turro, Nicholas J.; TEMEL, BİNNURPhotoinduced electron transfer reactions of highly conjugated thiophene derivatives, 4,7-di(2,3-dihydrothieno[3,4-b] [1,4]dioxin-5-yl)benzo[1,2,5]thiadiazole (DTDT) and 5,8-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-2,3-di(thiophen-2-yl)quinoxaline (DTDQ), with diphenyl-iodonium hexafluorophosphate (Ph2I+PF6-) and triphenylsulfonium hexafluorophosphate (Ph3S+PF6-) were investigated by laser flash photolysis, fluorescence and phosphorescence spectroscopy, and polymerization studies. High fluorescence quantum yields, long fluorescence lifetimes (similar to 10 ns in aprotic solvents), and absence of detectable phosphorescence at 77 K for both compounds indicate inefficient intersystem crossing into the triplet state and dominant role of singlet excited state. Photolysis of DTDT or DTDQ in the presence of iodonium salt with visible light results in the formation of radical cations of DTDT and DTDQ as detected by laser flash photolysis. Sulfonium salts do not undergo such electron transfer reactions due to the unfavorable redox potentials. The importance of the described photoinduced electron transfer process with respect to the initiation of cationic polymerization and formation of conjugated polymers was demonstrated.Publication Metadata only Long wavelength photoinitiated free radical polymerization using conjugated thiophene derivatives in the presence of onium salts(2011-01-01T00:00:00Z) Beyazit, Selim; Aydogan, BİNNUR; Osken, Ipek; Öztürk, Turan; Yağcı, Yusuf; TEMEL, BİNNURLong wavelength free radical photopolymerization of (meth) acrylic monomers using a conjugated thiophene derivative, namely 3,5-diphenyldithieno[3,2-b: 2-,3--d]-thiophene (DDT) and one of the following compounds, namely diphenyliodonium hexafluorophosphate (Ph(2)I(+)PF(6)(-)), triphenylsulfonium hexafluorophosphate (Ph(3)S(+)PF(6)(-)) and N-ethoxy-2-methylpyridinium hexafluorophosphate (EMP(+)PF(6)(-)), as photosensitizer and coinitiator, respectively, was described. Polymerization occurred only when DDT, in the presence of the onium salts, was irradiated at wavelengths where the salts have no absorption. A feasible initiation mechanism involves intermolecular electron transfer from photoexcited thiophene compound to the onium salt. The relative initiation efficiencies of the salts were investigated and evaluated in terms of their redox potentials.Publication Metadata only Thioxanthone-Fluorenes as Visible Light Photoinitiators for Free Radical Polymerization(2010-05-25T00:00:00Z) Yilmaz, Gorkem; Aydogan, Binnur; Temel, Gokhan; ARSU, Nergis; MOSZNER, Norbert; Yağcı, Yusuf; TEMEL, BİNNURTwo thioxanthone derivatives with fluorene additional chromophoric groups, namely thioxanthone-fluorenecarboxylie acid (TX-FLCOOH) and thioxanthone fluorene sodium carboxylate (TX-FLCOONa), as visible light absorbing oil- and water-soluble photoinitiators, respectively, were synthesized and characterized. Their ability to initiate photopolymerization of methyl methacrylate (M MA), 2-(2-phosphonoethoxymethyl)acrylic acid ethyl ester (EAEPA), and a multifunctional monomer, trimethylolpropane triacrylate (TMPTA), were examined. The initiation efficiency of TX-FLCOOH was compared with the parent thioxantone (TX) both in the presence and in the absence of a co-initiator, and TX-FLCOOH was found to be more effective in :ill cases. Photopolymerization and laser flash photolysis studies revealed that depending on the concentration initiation by TX-FLCOOH occurs by intra and intermolecular H-abstraction of the triplet (3)(TX-FLCOOH)*. No polymerization was observed when TX-FLCOONa was used as photoinitiator in the absence of a co-initiator. However, TX-FLCOONa acts as an efficient initiator in the visible range in the presence of H donors in water.Publication Metadata only Polysiloxane-Containing Benzoxazine Moieties in the Main Chain(2010-11-15T00:00:00Z) Aydogan, BİNNUR; Sureka, Dilek; Kışkan, Barış; Yağcı, Yusuf; TEMEL, BİNNURPolysiloxanes containing thermally curable benzoxazine units in the main chain have been synthesized. For this purpose, first the diallyl functional benzoxazine monomer is synthesized through the Mannich and respective ring closing reactions of 4,4--isopropylidenediphenol (bisphenol A), formaldehyde, and allyamine. Subsequent hydrosilylation reaction of the resulting allylic monomer (B-ala) with 1,1,3,3-tetramethyldi-siloxane (TMDS) in the presence of Pt catalyst yields the corresponding oligo(B-ala-tetramethyldisiloxane)s (OBTMDS). Using the anionic polymerization route, OBTMDS was then converted to poly(bisbenzoxazinedimethylsiloxane)s (PBDMSs) by reacting with readily available cyclic oligomer octamethylcyclotetrasiloxane (D4) or decamethylcyclopentasiloxane (D5) in the presence of tetrabutylammonium hydroxide as catalyst. The structures of the precursor diallyl monomer, the intermediate oligomer, and the resulting polymers are confirmed by Fourier transform infrared and H-1 NMR analysis. Curing behavior of the products at various stages has also been studied by differential scanning calorimetry. Flexible transparent films of the PBDMSs are obtained by solvent casting. Thermal properties of the cured polymers are also investigated by thermogravimetric analysis. (C) 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 5156-5162, 2010Publication Metadata only Synthesis of H-Shaped Complex Macromolecular Structures by Combination of Atom Transfer Radical Polymerization, Photoinduced Radical Coupling, Ring-Opening Polymerization, and Iniferter Processes(2013-11-01) Temel, BİNNUR; AMICI, Julia; SANGERMANO, Marco; Yağcı, Yusuf; TEMEL, BİNNURThree controlled/living polymerization processes, namely atom transfer radical polymerization (ATRP), ring-opening polymerization (ROP) and iniferter polymerization, and photoinduced radical coupling reaction were combined for the preparation of ABCBD-type H-shaped complex copolymer. First, -benzophenone functional polystyrene (BP-PS) and poly(methyl methacrylate) (BP-PMMA) were prepared independently by ATRP. The resulting polymers were irradiated to form ketyl radicals by hydrogen abstraction of the excited benzophenone moieties present at each chain end. Coupling of these radicals resulted in the formation of polystyrene-b-poly(methyl methacrylate) (PS-b-PMMA) with benzpinacole structure at the junction point possessing both hydroxyl and iniferter functionalities. ROP of epsilon-caprolactone (CL) by using PS-b-PMMA as bifunctional initiator, in the presence of stannous octoate yielded the corresponding tetrablock copolymer, PCL-PS-PMMA-PCL. Finally, the polymerization of tert-butyl acrylate (tBA) via iniferter process gave the targeted H-shaped block copolymer. (c) 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4601-4607Publication Metadata only Synthesis, characterization and thermally activated curing of polysulfones with benzoxazine end groups(2011-03-23T00:00:00Z) Ates, Sahin; Dizman, Cemil; Aydogan, BİNNUR; KISKAN, Bans; TORUN, Lokman; Yağcı, Yusuf; TEMEL, BİNNURPolysulfones with benzoxazine end groups (PSU-B-a) were obtained using monomer synthesis method from the phenol terminated polysulfone (PSU-OH), aniline and paraformaldehyde as starting materials. For this purpose, the precursor PSU-OHs with different molecular weights were prepared by condensation of bisphenol-A and bis(p-chlorophenyl) sulfone in presence of potassium carbonate. The structure of the polymers before and after functionalization was confirmed by proton nuclear magnetic resonance spectroscopy (H-1 NMR) and Fourier transform infrared spectroscopy (FT-IR). Thermally activated crosslinking behavior of these polymers was investigated by differential scanning calorimetry (DSC). Thermal and tensile properties of the crosslinked polymers obtained from PSU-B-a alone or with low molar mass benzoxazine (P-a) were studied by thermal gravimetric analysis (TGA) and dynamic mechanical analysis (DMA). (C) 2011 Elsevier Ltd. All rights reserved.Publication Metadata only Naphthodioxinone-1,3-benzodioxole as Photochemically Masked One-Component Type II Photoinitiator for Free Radical Polymerization(2012-07-01T00:00:00Z) Kumbaraci, Volkan; Aydogan, BİNNUR; Talinli, Naciye; Yağcı, Yusuf; TEMEL, BİNNURA 1,3-benzodioxole derivative of naphthodioxinone, namely 2-(benzo[d][1,3]dioxol-5-yl)-9-hydroxy-2-phenyl-4H-naphtho[2,3-d][1,3]dioxin-4-one was synthesized and characterized. Its capability to act as caged one-component Type II photoinitiator for free radical polymerization was examined. Upon irradiation, this photoinitiator releases 5-benzoyl-1,3-benzodioxole possessing both benzophenone and 1,3-dioxole groups in the structure as light absorbing and hydrogen donating sites, respectively. Subsequent photoexcitation of the benzophenone chromophore followed by hydrogen abstraction generates radicals capable of initiating free radical polymerization of appropriate monomers. (C) 2012 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 50: 2612-2618, 2012Publication Metadata only Synthesis of block copolymers by selective H-abstraction and radical coupling reactions using benzophenone/benzhydrol photoinitiating system(2015-01-01T00:00:00Z) Taskin, Omer Suat; Temel, Binnur Aydogan; Tasdelen, Mehmet Atilla; Yağcı, Yusuf; TEMEL, BİNNURBlock copolymers were synthesized by a simple photochemical strategy based on selective H-abstraction and radical coupling reactions of ketyl macroradicals. Benzophenone (BP) and benzhydrol (Bzh) end functional polymers were synthesized by atom transfer radical polymerization (ATRP) using functional initiators. Subsequently, the resulting end functional polymers were mixed in 1:1 M ratio and irradiated to form ketyl radicals by hydrogen abstraction of the excited BP moieties from Bzh moieties. The influence of various experimental parameters on the polymerization such as type of polymers and solvents were examined. H-1 NMR, UV and GPC measurements clearly pointed out an efficient photoinduced end coupling reaction between ketyl radicals. (C) 2014 Elsevier Ltd. All rights reserved.Publication Metadata only New Photoinitiating Systems for Cationic Polymerization Acting at Near UV and Visible Range(2011-01-01T00:00:00Z) Aydogan, BİNNUR; Durmaz, Yasemin Yuksel; Kahveci, Muhammet Übeydullah; Uygun, Mustafa; Tasdelen, M. Atilla; Yağcı, Yusuf; TEMEL, BİNNURNew photoiniting systems for cationic polymerization acting at near UV and visible range are described. The applicability of acylgermanes as a new class of free radical promoters for photoinitiated cationic polymerization is demonstrated. Moreover, the use of substituted vinyl halides as source for readily oxidizable free radicals is presented. The polymerization of vinyl ethers can be initiated by the irradiation of substituted vinyl halides in the presence of Lewis acids such as zinc halide. Furthermore, possibilities for conducting cationic polymerization at visible range by using highly conjugated thiophene derivatives are demonstrated. Mechanistic aspects of all initiating systems are discussed.