Person: ABDURRAHMANOĞLU, SUZAN
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ABDURRAHMANOĞLU
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SUZAN
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Publication Metadata only Rheological characterization of starch gels: A biomass based sorbent for removal of polycyclic aromatic hydrocarbons (PAHs)(ELSEVIER, 2019) ABDURRAHMANOĞLU, SUZAN; Tuncaboylu, Deniz Ceylan; Abdurrahmanoglu, Suzan; Gazioglu, IsilEnvironmental awareness increased the demand for the biomass based materials with superior properties instead of petroleum products. This study aims to prepare starch networks as sorbents for the removal of polycyclic aromatic hydrocarbons (PAHs). Two types of crosslinker, epichlorohydrine (ECH) and glutaraldehyde (GA), were choosed for the preparation of Gel-E and Gel-G networks, respectively. Rheological, swelling and morphological properties of the resulted materials were investigated as a function of various reaction parameters as starch, crosslinker and base concentration and also reaction temperature. The rheological measurements showed that while network formation of Gel-E hydrogels was strongly affected by the NaOH and starch concentration, the strength of the Gel-G hydrogels mainly depends on the crosslinker amount. Starch networks showed high PAH sorption capacities up to 1.42 g per gram sorbent with three model PAH molecules. Although PAH sorption capacities of the Gel-E networks are higher than those of Gel-G gels due to the pore sizes differences of the gel samples, both of them are promising materials as biosorbent for the PAH sorption applications due to the relatively high sorption capacities, low cost and simple preparation methods.Publication Metadata only Antibacterial properties of cationic copolymers as a function of pendant alkyl chain length and degree of quaternization(WILEY, 2021) ABDURRAHMANOĞLU, SUZAN; Gokkaya, Damla; Topuzogullari, Murat; Arasoglu, Tulin; Trabzonlu, Kubra; Ozmen, Mehmet Murat; Abdurrahmanoglu, SuzanAntibacterial polymers are promising materials in the fight against bacterial infection which is a vital health problem. Among these materials, cationic (co)polymers with quaternary ammonium groups are of great interest and importance as they interact with the bacterial membrane causing cell death. The antibacterial efficacy can be improved by modifying the pendant alkyl groups and charge density of the polycation. In this study, alkylbromides with different chain lengths were used to obtain quaternized poly(4-vinylpyridine-co-N-vinylpyrrolidone) (P(4VP-co-NVP)) copolymers of various positive charge densities and pendent alkyl chain lengths. While the chemical structures of the produced copolymers were characterized by Fourier transform infrared and H-1 NMR spectroscopy, physicochemical properties such as size and zeta potential were measured by dynamic light scattering spectrometry. It was determined that the zeta potentials and hydrodynamic diameters of the samples vary between +10 and +32 mV and 10 and 16 nm, respectively. The antibacterial activity of the copolymers were tested against Escherichia coli and Staphylococcus aureus bacteria by broth microdilution and standard 'plate' count methods. The results revealed that the antibacterial activity of the copolymers against Escherichia coli can be successfully adjusted through varying the chain length of the alkylating agent (hydrophobic chains) and the degree of quaternization (positive charge density). (c) 2020 Society of Chemical IndustryPublication Metadata only Preparation of homogeneous hydrogels by controlling the crosslinker reactivity and availability(TAYLOR & FRANCIS INC, 2008) ABDURRAHMANOĞLU, SUZAN; Abdurrahmanoglu, Suzan; Okay, OguzNetwork microstructures of polyacrylamide (PAAm) hydrogels were investigated by static light scattering measurements. The gels were prepared by free-radical crosslinking polymerization of acrylamide (AAm). To suppress the degree of gel inhomogeneity, the crosslinker reactivity during gelation was controlled by decreasing its availability in the reaction system. Our first approach was the addition of the crosslinker N,N'-methylenebis(acrylamide) (BAAm) in one or three portions during the course of the gelation reactions. As a second approach, a slightly water soluble crosslinker, namely ethylene glycol dimethacrylate (EGDM) was used as a crosslinker in AAm polymerization. Due to the low water solubility of EGDM, EGDM phase in the gelation system act as a reservoir of crosslinker so that the crosslinker can be supplied continuously to the aqueous reaction zone during the course of gelation. It was found that the delayed crosslinker addition technique further increases the degree of inhomogeneity of PAAm hydrogels. The results were explained with increasing viscosity of the reaction solution at the time of the crosslinker addition so that the crosslinking reactions are limited to local regions in the reaction system. The second approach, namely use of the slightly water soluble crosslinker EGDM significantly increases the degree of structural homogeneity of PAAm hydrogels.Publication Metadata only Preparation and characterization of modified nanosilica/PNIPAm hybrid cryogels(SPRINGER, 2015) KAYAMAN APOHAN, NİLHAN; Dogru, Ozen; Abdurrahmanoglu, Suzan; Kayaman-Apohan, NilhanA series of macroporous hybrid cryogels based on poly(N-isopropylacrylamide) (PNIPAm) were synthesized by free radical polymerization in the presence of organically modified nanosilica. To improve the interaction of silica nanoparticles with polymer structure, the silica surface was first treated with 3-methacryloxypropyltrimethoxysilane (MPTMS). Then a series of hybrid cryogels each containing 1 wt.% nanosilica and various amounts of MPTMS (1-4 wt.% to monomer NIPAm) were prepared. The yield of methacrylate modification of the nanosilica surface determined by TGA analysis was 11.2 wt.%. The particle size distribution of modified nanosilica particles was investigated by dynamic light scattering technique (DLS) and the mean particle diameter with respect to number was found as 68 nm. The morphology of cryogels was evaluated by SEM. The improvement in the thermal and mechanical properties using the addition of modified silica nanoparticles was achieved.Publication Metadata only Synergetic effect of the crosslinker size and polysaccharide type on the acrylamide networks(2022-06-16) ABDURRAHMANOĞLU, SUZAN; ABDURRAHMANOĞLU S., Keten S., Gönülkırmaz F., Karacan P., CEYLAN TUNCABOYLU D.Publication Open Access An InSilico Study of Chirality of Benzimidazole Amine Hybrids on The Inhibition Effects on Human Carbonic Anhydrase Isoenzymes and Acetylcholine Esterases(2022-05-12) ABDURRAHMANOĞLU, SUZAN; TUNÇ T., ABDURRAHMANOĞLU S., GÜNEL A., DEMİREL N., ALIM Z.Benzimidazole-hybrid have a unique chemical structure which show tremendous pharmacological activity such as anti-inflammatory, antiviral, anti-histaminic, antimicrobial [1,2]. Due to their biological and therapeutic activity they have been studied extensively in recent years. For instance, Richards et.al. showed that the main benzimidazole structure has good efficacy in treating allergy and asthma [3]. Carbonic anhydrase (CA) regulates the acidity of the chemical environment in the body and prevents body functions from being damaged. Due to these vital physiological properties extensive studies have been performed on CA enzymes. Anti-acetylcholineesterases (anti-AChE) are used as anti-Alzheimer drugs to treat moderate Alzheimer disease because of their enhanced cognitive connectivity cholinergic neurotransmission in clinic applications. There are many CA and AChE inhibitiors identified and used in clinic treatments [4]. In this study, efficacy of novel chiral benzimidazole amine hybrids as CA and AChE inhibitors have been studied in silico and compared with the in vitro results. The binding energies (scoring based) were obtained as negative scores which proves that all compounds were successfully docked at the active sites of CA isoenzymes and AChE. The highest binding energies were observed in the case of AChE and these results are in consistent with the experimental data since all of the compounds have shown very good inhibition activity by means of IC50 values. The ADME (adsorption, distribution, metabolism and excretion) were also showed that these compounds could be recognised as drug like potential towards AChE and CA proteinsPublication Metadata only Synthesis and characterization of new dextran-acrylamide gels(WILEY, 2007) ABDURRAHMANOĞLU, SUZAN; Abdurrahmanoglu, Suzan; Firat, YurdunDextran-acrylamide gels were synthesized in a single step reaction by using 4,4'-azobis(4-cynovaleric acid) as bi-functional initiator at 60 degrees C. Corresponding acrylamide (AaM) gels in the absence of dextran were also prepared for comparison. Several parameters such as reaction period (6, 12, and 24 h), monomer and crosslinker concentrations were varied and their effects on the properties of gels were investigated. Gels were characterized by their mechanical and swelling behaviors and in terms of structural changes using SEM. It was observed that swelling degree decreased by increasing the monomer concentration due to formation of more crosslinking points that cause tighter network structure. Mechanical measurements showed that elastic modulus of AaM gels was higher than that of dextran-AaM gel which indicating the importance of dextran concentration on the flexibility of the network.Publication Metadata only Unusual swelling behavior of polymer-clay nanocomposite hydrogels(ELSEVIER SCI LTD, 2007) ABDURRAHMANOĞLU, SUZAN; Can, Volkan; Abdurrahmanoglu, Suzan; Okay, OguzThe swelling behavior and the elastic properties of nanocomposite hydrogels have been investigated. The hydrogels were prepared by freeradical polymerization of the monomers acrylamide (AAm), N,N-dimethylacrylamide (DMA), and N-isopropylacrylamide (NIPA) in aqueous clay suspensions at 21 degrees C. Laponite with a radius of gyration in distilled water of 20 nm was used as clay particles in the hydrogel preparation. The reactions with AAm monomer were carried out in the presence of the chemical crosslinker N,N-methylenebis(acrylamide) (BAAm). It was found that the volume of nanocomposite hydrogels immersed in water rapidly increases and attains a maximum value after about one day. Surprisingly, further increase in the swelling time results in the deswelling of the gels until they reach a limiting swelling ratio after about 5 days. This unusual swelling behavior is observable only when the clay concentration in the hydrogel is above the overlap threshold c*. Swelling measurements combined with the elasticity tests show that the effective crosslink density first decreases, but then increases with increasing time of swelling of the hydrogels. The results were explained in terms of the rearrangements of the highly entangled polymer chains and clay particles during the gel volume change. (c) 2007 Elsevier Ltd. All rights reserved.Publication Metadata only Design of high-toughness polyacrylamide hydrogels by hydrophobic modification(ELSEVIER SCI LTD, 2009) ABDURRAHMANOĞLU, SUZAN; Abdurrahmanoglu, Suzan; Can, Volkan; Okay, OguzPolyacrylamide (PAAm) hydrogels possessing a very large extensibility at break have been prepared via micellar crosslinking copolymerization of acrylamide monomer and N,N'-methylenebis(acrylamide) crosslinker in the presence of hydrophobic comonomers. N-butyl-, N-hexyl-, N-octyl-, and N,N-dihexylacrylamides were used as the hydrophobes in the hydrogel preparation. Incorporation of hydrophobes with an alkyl chain length x > 4 results in an increase in the loss factor tan 6 of hydrogels due to the formation of temporary junction zones inside the gel network. The number N-H of the hydrophobes per hydrophobic block together with the alkyl chain length x of the pendant hydrophobic group were used to tune the loss factor of the hydrogels over two orders of magnitude. Tensile mechanical measurements show that increasing N-H or x also increases the degree of toughness of PAAm hydrogels. Keeping constant the hydrophobe level (20 mol%) at an alkyl chain length x=6, increasing N-H from 9 to 30 increased the elongation ratio at break from 125 to 250%. Hydrogels exhibiting a high toughness, i.e., about 300% elongation ratio at break were obtained by modification of PAAm network chains with 10 mol% N-octylacrylamide. (C) 2009 Elsevier Ltd. All rights reserved.Publication Open Access POSS-vinyl-urethane acrylate-based nanohybrid coating materials(2023-01-01) ABDURRAHMANOĞLU, SUZAN; KARATAŞ, SEVİM; Eren Y., Şen F., ABDURRAHMANOĞLU S., KARATAŞ S.The effect of POSS-vinyl-heptaisobutyl-substituted (POSSV) compounds as an inorganic additive on the thermal and physical properties of nanohybrid coating materials based on urethane acrylate (UA) resin has been investigated. A diol compound obtained from the reaction of itaconic acid and 1,2-epoxy cyclohexane has been used to produce an UV curable epoxy-based urathane acrylate resin. Nanohybrid coating materials were obtained by curing the UA resin with UV radiation through the thiol–ene reaction, mixed with various amounts of POSSV compounds. The structure of the UA resin was characterized by Fourier-transform infrared spectroscopy and nuclear magnetic resonance spectroscopy techniques. The UV curing process was also studied by the double bond conversion method. Aggregation of the nanohybrid materials was determined by X-ray diffraction. The thermal, non-flammability, and thermomechanical properties of the samples were examined by thermogravimetric analysis, limiting oxygen index, and dynamic mechanical analysis techniques. Light transmittance of the samples was determined by UV–Vis spectrophotometry, and their morphological structure was determined by scanning electron microscopy. In addition, gel contents, swelling rates, hardness, adhesion, contact angles, and resistance to chemicals and solvents of the samples were examined. In conclusion, nanohybrid materials obtained from the synthesized UA resin and improved with POSSV additive can be used in the coating industry.