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 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, 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 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.Publication Metadata only Synthesis and characterization of triptycene type cross-linker and its use in photoinduced curing applications(2010-02-15T00:00:00Z) Ates, Sahin; Aydogan, BİNNUR; TORUN, Lokman; Yağcı, Yusuf; TEMEL, BİNNURA novel triptycene type diacrylate cross-linker, triptycene hydroquinone diacrylate (THDA) was synthesized from the reaction of triptycene hydroquinone with acryloyl chloride and characterized. The photocuring behaviour and the reaction kinetics of the synthesized cross-linker were investigated by means of photo-differential scanning calorimetry (photo-DSC) experiments. Formulations containing monofunctional (meth)acrylate monomers, namely glycidyl methacrylate (GMA), 2-hydroxyethyl acrylate (HEA), 2-hydroxyethyl methacrylate (HEMA), and 2-ethylhexyl methacrylate (EHMA), crosslinker, THDA and 2,2-dimethoxy-2-phenylacetophenone (DMPA) as a photoinitiator were irradiated. A conventional cross-linker without triptycene unit Such as hydroquinone diacrylate (HDA) was used under the same conditions for comparison. The effects of the Structure of the monofunctional monomer and triptycene moiety on the photopolymerization kinetics were evaluated and discussed. (C) 2010 Elsevier Ltd. All rights reserved.Publication Metadata only Intramolecular Cross-linking of Polymers Using Difunctional Acetylenes via Click Chemistry(2011-01-01T00:00:00Z) Cengiz, Halime; Aydogan, BİNNUR; Ates, Sahin; Acikalin, Engin; Yağcı, Yusuf; TEMEL, BİNNURAn efficient approach was described for the intramolecular cross-linking of azide-functionalized poly(styrene-co-chloromethyl styrene) co-polymers (PS-N-3) via click chemistry at room temperature. Reaction of PS-N-3 with the appropriate diacetylene functional compounds such as 1,4-diethynylbenzene (DEB) and 1,10-dipropargyloxy decane (DPD) in ultra-dilute solutions led to unimolecular particle-like structures. The resulting polymers were characterized in detail by H-1-NMR, FT-IR, GPC and DSC measurements. (C) Koninklijke Brill NV, Leiden, 2011Publication Metadata only Highly Conjugated Thiophene Derivatives as New Visible Light Sensitive Photoinitiators for Cationic Polymerization(2010-01-12T00:00:00Z) Aydogan, BİNNUR; Gunbas, Gorkem E.; Durmus, Asuman; Toppare, Levent; Yağcı, Yusuf; TEMEL, BİNNURA visible light sensitive photoinitiator system for the cationic polymerization of typical monomers, e.g. of oxiranes such as cyclohexene oxide, of vinyl ethers such as n-butyl vinyl ether, and of other vinyl monomers such its N-vinylcarbazole, using highly conjugated thiophene derivatives is described. The cationic polymerization of these monomers was initiated at room temperature upon irradiation in the visible region (lambda(inc) = 480 nm) in CH2Cl2 solutions with 4,7-di(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)benzo-[1,2,5]thiadiazole (DTDQ) or 5,8-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-2,3-di(thiophen-2-yl)quino-xaline (DTDQ) in the presence of diphenyliodonium hexafluorophosphate (Ph2I+PF6-). A feasible mechanism, as correlated with optical absorption and fluorescence spectroscopic measurements, free energy changes (Delta G), and proton Scavenging Studies, involves formation of exciplex by the absorption of light in the First Step, Subsequent electron transfer from excited DTDT or DTDQ to iodonium ion Yields radical cations of the thiophene derivatives. The resulting strong Bransted acid derived from this process catalyzes the cationic polymerization of variety of monomers.