Chemistry / Kimya
Permanent URI for this collectionhttps://hdl.handle.net/11147/4072
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Article Citation - WoS: 14Citation - Scopus: 13Investigations of Polyamide Nano-Composites Containing Bentonite and Organo-Modified Clays: Mechanical, Thermal, Structural and Processing Performances(Walter de Gruyter GmbH, 2021) Akar, Alinda Öykü; Yıldız, Ümit Hakan; Tayfun, ÜmitPolyamide 6 (PA) matrix was reinforced with Na-activated bentonite, amino functional silane treated bentonite and organo-modified clays at different concentrations. The preparation of composites was carried out using melt-blending method and the test samples were prepared by injection-molding process. Mechanical, thermal, structural and processing investigations of PA based composites were reported performing via tensile, hardness, and impact tests, differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), scanning electron microscopy (SEM), X-ray diffraction analysis (XRD) and force measurements, respectively. According to mechanical test results, additions of fillers to PA matrix caused slight improvements for tensile strength and modulus parameters. Silane treated BNT exhibited improvement in mechanical results compared to Na-activated bentonite additions. Thermal studies revealed that decomposition and melting temperatures of PA shifted to higher values after inclusion of clay into polymer matrix. Results confirmed that organo-clay and bentonite additions with their lower filling ratios yielded enhancements for the mechanical and thermal performance of polyamide.Article Citation - WoS: 13Citation - Scopus: 15Synthesis of Poly-2 Methacrylate-Montmorillonite Nanocomposite Via in Situ Atom Transfer Radical Polymerization(Cambridge University Press, 2008) Oral, Ayhan; Shahwan, Talal; Güler, ÇetinThe poly-2-hyroxyethyl methacrylate (PHEMA)/clay nanocomposite was synthesized by in situ atom transfer radical polymerization (ATRP) from initiator moieties immobilized within the silicate galleries of the clay particles. To produce organically modified montmorillonite (MMT) that has ATRP initiator moiety, a new catalyst that consists of quaternary ammonium salt moiety and an initiator moiety was synthesized. This initiator was intercalated into the interlayer spacing of the MMT. The polymerization reaction was carried out in a mixed solvent system consisting of methyl ethyl ketone and 1-propanol at 50 °C, using the initiator that has been already synthesized with a copper bromide catalyst. The 2, 2′-bipyridyl (bpy) complex was used as ligand. The products were characterized via Fourier transform infrared, nuclear magnetic resonance (1H NMR, 12C NMR), transmission electron microscopy, x-ray diffraction, thermogravimetric analysis, and differential scanning calorimetry. © 2008 Materials Research Society.Article Citation - WoS: 16Citation - Scopus: 18Polyglycolide-Montmorillonite as a Novel Nanocomposite Platform for Biosensing Applications(Royal Society of Chemistry, 2017) Ünal, Betül; Yalçınkaya, Esra Evrim; Gümüştaş, Sıla; Sönmez, Burak; Özkan, Melek; Balcan, Mehmet; Odacı Demirkol, Dilek; Timur, SunaIn catalytic biosensors, the immobilization of biomolecules in a suitable matrix is one of the vital parameters for obtaining improved systems. Clays, which are intercalated with various organic compounds, have a great tendency to develop biosensors with high stability, sensitivity and reproducibility. Herein, a polymer/clay nanocomposite based on natural silicate montmorilonite (Mt) and a biodegradable polymer polyglycolide (PGA) was prepared and characterized by FT-IR, thermogravimetric analysis, differential thermogravimetric analysis and X-ray diffraction. Then, the resulting matrix was used as a fixation matrix for pyranose oxidase (POx), which was selected as a model enzyme. The bioactive layer was fabricated by immobilization of POx on glassy carbon electrodes by means of PGA-Mt and bovine serum albumin. The POx biosensor revealed a good linear range from 0.01 to 0.5 mM glucose with a LOD of 1.2 μM. After the optimization of the working and preparation conditions, characterization studies were performed for glucose detection. Finally, the PGA-Mt/POx biosensor was confirmed to have detected glucose in beverages without needing any sample pre-treatment.Article Citation - WoS: 33Citation - Scopus: 33Folic Acid Modified Clay/Polymer Nanocomposites for Selective Cell Adhesion(Royal Society of Chemistry, 2014) Barlas, Fırat Barış; Ağ Şeleci, Didem; Özkan, Melek; Demir, Bilal; Şeleci, Muharrem; Aydın, Muhammed; Taşdelen, M. A.; Zareie, Hadi M.; Timur, Suna; Özçelik, Serdar; Yağcı, YusufA folic acid (FA) modified poly(epsilon-caprolactone)/clay nanocomposite (PCL/MMT-(CH2CH2OH)2-FA) resulting in selective cell adhesion and proliferation was synthesized and characterized as a cell culture and biosensing platform. For this purpose, first the FA modified clay (MMT-(CH2CH2OH)2-FA) was prepared by treating the organo-modified clay, Cloisite 30B [MMT-(CH2CH 2OH)2] with FA in chloroform at 60°C. Subsequent ring opening polymerization of ε-caprolactone in the presence of tin octoate (Sn(Oct)2) using MMT-(CH2CH2OH)2-FA at 110°C resulted in the formation of MMT-(CH2CH 2OH)2-FA with an exfoliated clay structure. The structures of intermediates and the final nanocomposite were investigated in detail by FT-IR spectral analysis and DSC, TGA, XRD, SEM and AFM measurements. The combination of FA, PCL and clay provides a simple and versatile route to surfaces that allows controlled and selective cell adhesion and proliferation. FA receptor-positive HeLa and negative A549 cells were used to prove the selectivity of the modified surfaces. Both microscopy and electrochemical sensing techniques were applied to show the differences in cell adherence on the modified and pristine clay platforms. This approach is expected to be adapted into various bio-applications such as 'cell culture on chip', biosensors and design of tools for targeted diagnosis or therapy.Article Citation - WoS: 12Citation - Scopus: 14Anomalous Transmittance of Polystyrene-Ceria Nanocomposites at High Particle Loadings†(Royal Society of Chemistry, 2013) Parlak, Onur; Demir, Mustafa MuammerOptical nanocomposites based on transparent polymers and nanosized pigment particles have usually been produced at low particle concentrations due to the undesirable optical scattering of the pigment particles. However, the contribution of the particles to many physical properties is realized at high concentrations. In this study, nanocomposites were prepared with transparent polystyrene (PS) and organophilic CeO2 nanoparticles using various compositions in which the particle content was up to 95 wt%. The particles, capped by 3-methacryloxypropyltrimethoxysilane (MPS), were dispersed into PS and the transmittance of the spin-coated composite films was examined over the UV-visible region. When the particle concentration was <20 wt%, the transmittance of the films showed a first-order exponential decay as the Rayleigh scattering theory proposes. However, a positive deviation was observed from the decay function for higher particle contents. The improvement in transmittance may be a consequence of interference in the multiple scattering of light by the quasi-ordered internal microstructure that gradually develops as the particle concentration increases.Article Citation - WoS: 5Citation - Scopus: 6Tailored Ceo2 Nanoparticles Surface in Free Radical Bulk Polymerization of Methyl Methacrylate(American Chemical Society, 2013) Tunusoğlu, Özge; Demir, Mustafa MuammerPolymerization of monomer/nanoparticle dispersion, namely in situ polymerization, has been frequently used for the fabrication of polymer nanocomposites. However, the interference of nanoparticle surface with polymerization in the course of composite formation has been tacitly neglected. In this work, surface-functionalized ceria nanoparticles were prepared using various capping agents: 3-(mercaptopropyl) trimethoxy silane, thioglycolic acid, 3-mercaptopropionic acid, and hexadecyltrimethyl ammonium bromide. Both in situ and ex situ approaches were applied for surface functionalization. The particles were dispersed into methyl methacrylate and free radical polymerization was carried out. The process of nanocomposite formation was examined in terms of conversion, molecular weight, and molecular weight distribution. The polymerization responded merely to the in situ functionalized particles. Regardless of the capping agents used, the particles function as a retarder and inhibitor. Their interaction with polymerization medium showed many complexities such that molecular weight was found to be strongly dependent on the capping agent employed.Article Citation - WoS: 51Citation - Scopus: 53Challenges in the Preparation of Optical Polymer Composites With Nanosized Pigment Particles: a Review on Recent Efforts(John Wiley and Sons Inc., 2012) Demir, Mustafa Muammer; Wegner, GerhardBlends of nanosized pigment particles and polymers are widely believed to offer the potential for the design of novel or at least improved materials. This review critically evaluates the recent literature with regard to the following issues: (a) why and how does the size of the particles matter, (b) what are the requirements to create compatibility between amorphous polymers and nanoparticles, (c) carbon allotropes as nanosized pigments, (d) bulk polymerization of monomer/pigment mixtures, (e) interaction of growing chains with the particles in the polymerization, (f) depletion flocculation as a mechanism to counteract homogeneous distribution of the particles in the polymer matrix and ways to suppress the undesirable flocculation, and (g) optical properties of the blends as well as methods of optical characterization.Article Citation - WoS: 8Citation - Scopus: 8Highly Efficient Orange–red Electroluminescence From a Single Layer Meh-Ppv Hybrid Pled(Elsevier Ltd., 2012) Saygılı, Gamze; Ünal, Gülçin; Özçelik, Serdar; Varlıklı, CananIn this study, poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] end capped with polyhedral oligomeric silsesquioxanes (MEH-PPV-POSS): cadmium sulfide selenide quantum dots (CdS0.75Se0.25 QDs) nanocomposites based OLEDs were fabricated. By the addition of CdS0.75Se0.25QDs into the polymer active layer, a considerable enhancement was observed in terms of hole and electron injection in devices. Additionally, the presence of QDs reduced the interchain interaction of polymer that resulted in narrower electroluminescence (EL) spectrum. The device structure of ITO/PEDOT: PSS/MEH-PPV-POSS: 25 wt% CdS0.75Se0.25/Ca (40 nm)/Al demonstrated the best performance with a brightness of 8672 cd/m 2 at 10 V, current efficiency of 2.5 cd/A at 8 V, and an EQE of 0.55% at 150 mA/cm2 .