Researcher: Demirel, Adem Levent
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Demirel, Adem Levent
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Publication Metadata only Motion of single terrylene molecules in confined channels of poly(butadiene)-poly(ethylene oxide) diblock copolymer(Amer Chemical Soc, 2009) N/A; Department of Physics; Department of Chemistry; Yorulmaz, Mustafa; Kiraz, Alper; Demirel, Adem Levent; Master Student; Faculty Member; Faculty Member; Department of Physics; Department of Chemistry; Graduate School of Sciences and Engineering; College of Sciences; College of Sciences; N/A; 22542; 6568The motion of terrylene probe molecules in confined PB channels of an asymmetric PB-PEO diblock copolymer has been investigated by single molecule tracking. The one-dimensional diffusion coefficients were found to be significantly smaller and had a narrower distribution compared to two-dimensional diffusion coefficients in PB. The trajectories of some single molecules showed unusual behavior of directed motion where mean square displacement had a parabolic dependence oil lag time. The likely origin of this behavior is discussed in terms of local variations in the PB channel width and the resulting change in the local density. The results show the effect of nonuniformities and heterogeneities in the channels on the motion of single molecules and demonstrate the sensitivity of single molecule tracking in characterizing self-assembled block copolymer morphologies.Publication Metadata only Synthesis, characterization and properties of naphthoxazine-functional poly(propyleneoxide)s(PERGAMON-ELSEVIER SCIENCE LTD, 2006) Yıldırım, Ayfer; Kıskan, Barış; Yağcı, Yusuf; Department of Chemistry; Demirel, Adem Levent; Faculty Member; Department of Chemistry; College of Sciences; 6568Thermally curable naphthoxazine-functionalized polymers were synthesized by the reaction of linear (diamines) and branched (triamines) poly(propyleneoxide)s (Jeffamine series) having various molecular weights, with p-formaldehyde, and 2-naphthol. The structures of the resulting polymers were characterized by using FT-IR and H-1-NMR. In addition, curing behavior of these polymers was studied using differential scanning calorimeter (DSC). Hydrophilicity of these polymers, both in cured and non-cured states, was investigated by water contact angle measurements. The surface topographies of the polymers were also examined by atomic force microscope (AFM).Publication Metadata only Crystallization of poly(ethylene oxide) in thin films(Taylor & Francis Inc, 2003) N/A; Department of Chemistry; Department of Chemistry; Ok, Salim; Demirel, Adem Levent; Undergraduate Student; Faculty Member; Department of Chemistry; College of Sciences; College of Sciences; N/A; 6568Crystallization of poly(ethylene oxide) (PEO) in thin films was studied using hot-stage polarized optical microscopy. Isothermal linear crystal growth rates were measured for various film thicknesses at various degrees of undercooling. At a given crystallization temperature, the linear crystal growth rate decreased exponentially with decreasing film thickness below a film thickness of 80 nm. Films showed similar spherulitic morphology down to a film thickness of 30 nm. Control experiments on hydrophilic and hydrophobic surfaces showed that surface chemistry affects stability of the polymer films and causes a competition between crystallization and dewetting.Publication Metadata only Heteroarm H-shaped terpolymers through click reaction(Wiley, 2007) Güngör, Eda; Cote, Gülay; Erdoğan, Tuba; Durmaz, Hakan; Hızal, Gürkan; Tunca, Ümit; Department of Chemistry; Demirel, Adem Levent; Faculty Member; Department of Chemistry; College of Sciences; 6568Heteroarm H-shaped terpolymers, (polystyrene)(poly(methyl methacrylate))poly(tert-butyl acrylate)-(polystyrene)(poly(methyl methaerylate)), (PS)(PMMA)-PtBA-(PMMA)(PS), and, (PS)(PMMA)-poly(ethylene glycol)(PEG)-(PMMA)(PS), through click reaction strategy between PS-PMMA copolymer (as side chains) with an alkyne functional group at the junction point and diazide end-functionalized PtBA or PEG (as a main chain). PS-PMMA with alkyne functional group was prepared by sequential living radical polymerizations such as the nitroxide mediated (NMP) and the metal mediated-living radical polymerization (ATRP) routes. The obtained H-shaped polymers were characterized by using H-1-NMR, GPC, DSC, and AFM measurements. (c) 2006 Wiley Periodicals, Inc.Publication Metadata only Formation of polyamide nanofibers by directional crystallization in aqueous solution(Wiley-V C H Verlag Gmbh, 2007) Department of Chemistry; Demirel, Adem Levent; Faculty Member; Department of Chemistry; College of Sciences; 6568N/APublication Metadata only A novel photoinduced ligation approach for cross-linking polymerization, polymer chain-end functionalization, and surface modification using benzoyl azides(Wiley-V C H Verlag Gmbh, 2021) Kocaarslan, Azra; YIlmaz, Görkem; Yağcı, Yusuf; Department of Chemistry; Department of Chemistry; Demirel, Adem Levent; Topçu, Gökhan; Faculty Member; Researcher; Department of Chemistry; College of Sciences; College of Sciences; 6568; N/AVarious ligation processes have recently become a powerful tool in synthetic polymer chemistry. Herein, the use of a new photochemical ligation process as a versatile approach for the cross-linking polymerization, functionalization of polymer chain ends, and surface modification of various materials such as silica and graphene oxide, is demonstrated. The process is based on the formation of urethane linkages by the reaction of photochemically in situ generated isocyanates from benzoyl azides with hydroxyl moieties in the presence of organobase, bicyclo[2.2.2]-1,4-diazaoctane (DABCO) under ambient conditions. The intermediates and obtained materials are characterized by NMR, FTIR, TGA, and TEM analyses. It is believed that this simple and efficient ligation process will expand future applications to fabricate complex macromolecular structures, biomaterials, and gels.Publication Metadata only The effect of nanoparticles on the surface hydrophobicity of polystyrene(Springer, 2008) N/A; Department of Chemistry; Yüce, Mehdi Yavuz; Demirel, Adem Levent; PhD Student; Faculty Member; Department of Chemistry; Graduate School of Sciences and Engineering; College of Sciences; N/A; 6568The surface hydrophobicity of polystyrene-nanoparticle nanocomposites has been investigated as a function of the nanoparticle content. The addition of hydrophobically coated nanoparticles in polystyrene increased the contact angle θ of a water drop with respect to that on polystyrene surface due to change of surface composition and/or surface roughness. When the nanoparticles dispersed well in the polymer, cos θ decreased linearly with increasing amount of nanoparticles indicating a composite surface consisting of smooth polystyrene regions and rough nanoparticle regions. In case of formation of nanoparticle aggregates in polystyrene, cos θ decreased sharply at a critical concentration of nanoparticles. The observed behaviour was modeled in terms of a transition from Wenzel regime to Cassie-Baxter regime at a critical roughness length scale below which the Laplace pressure prevented the penetration of the water drop into the surface undulations. We argue that multiple length scales are needed below the critical roughness length scale to increase the contact angle further by decreasing the fraction of surface area of solid material (increasing the fraction of surface area of air) underlying the water drop.Publication Metadata only Poly(p-phenylene methylene)-based block copolymers by mechanistic transformation(2011) Taşdelen, Mehmet Atilla; Beyazıt, Selim; Güneş, Deniz; Bıçak, Niyazi; Tatar, Pınar; Yağcı, Yusuf; Department of Chemistry; Department of Chemistry; Demirel, Adem Levent; Güner, Pınar Tatar; Faculty Member; Teaching Faculty; Department of Chemistry; College of Sciences; College of Sciences; 6568; 188227Publication Metadata only Effect of anions on the cloud point temperature of aqueous poly(2-ethyl-2-oxazoline) solutions(Amer Chemical Soc, 2012) Department of Chemistry; Department of Chemistry; Güner, Pınar Tatar; Demirel, Adem Levent; Teaching Faculty; Faculty Member; Department of Chemistry; College of Sciences; College of Sciences; 188227; 6568Poly(2-alkyl-2-oxazoline)s have recently gained attention in especially biological applications due to their lower critical solution temperature being close to the body temperature and their biocompatibility. The understanding of how cloud point temperature (T-c) depends on the salt concentration and the molecular mechanisms responsible for such behavior are important to tune T-c as desired by the applications. In this paper, we report the effect of a series of sodium salts on T-c of aqueous poly(2-ethyl-2-oxazoline) (PEOX) solutions by dynamic light scattering. PEOX samples having four different molecular weights were investigated, and the results were compared with those of poly(N-isopropylacrylamide) (PNIPAM), the mostly investigated and used thermoresponsive polymer. Kosmotropic anions decreased T-c linearly while chaotropic anions increased T-c nonlinearly with salt concentration. The contributions of different mechanisms to T-c change have been discussed. Our results indicate that the dominant mechanism is the dehydration of PEOX for divalent kosmotropic anions (CO32-, SO42-, S2O32-) and direct binding for chaotropic anions (NO3-, I-, ClO4-, SCN-). For the remaining monovalent kosmotropic anions (H2PO4-, F-, Cl-, Br-), a combination of dehydration and surface tension mechanisms was in effect. The additional contribution of the surface tension mechanism for the monovalent kosmotropic anions was inferred for different molecular weight PEOX samples and also for PNIPAM. With PEOX molecular weight decreasing from 500 000 to 5000 g/mol, T-c decreased less with salt concentration which was attributed to the contribution of the surface tension mechanism. For PEOX samples, the decrease of T-c with kosmotropic anion concentration was faster compared to PNIPANI due to differences in their chemical structure. Our results show that the molecular mechanisms of interactions between PEOX chains and specific anions can simply be inferred from determination of T-c by a common technique-dynamic light scattering.Publication Metadata only Poly(2-oxazoline)s as smart bioinspired polymers(Wiley-Blackwell, 2010) Schlaad, Helmut; Diehl, Christina; Gress, Anja; Meyer, Matthias; Nur, Yusuf; Bertin, Annabelle; Department of Chemistry; Demirel, Adem Levent; Faculty Member; Department of Chemistry; College of Sciences; 6568Poly(2-alkyl-2-cocazoline)s can be regarded as pseudo-peptides or bioinspired polymers, which are available through living/controlled cationic polymerization and polymer ("click") modification procedures. Materials and solution properties may be adjusted via the nature of the side chain (hydrophilic-hydrophobic, chiral, bio-functional, etc.), opening the way to stimulus-responsive materials and complex colloidal structures in aqueous environments. Herein, we give an overview over the macromolecular engineering of polyoxazolines, including the synthesis of biohybrids, and the "smart"/bioinspired aggregation behavior in solution Chemical Equation Presentation © 2010 WILEY-VCH Verlag GmbH and Co. KGaA.