Chemical Engineering / Kimya Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/14
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Article Citation - WoS: 10Citation - Scopus: 12Enhanced Model Protein Adsorption of Nanoparticulate Hydroxyapatite Thin Films on Silk Sericin and Fibroin Surfaces(Springer, 2022) Özcan, Selçuk; Çiftçioğlu, MuhsinHydroxyapatite coated metallic implants favorably combine the required biocompatibility with the mechanical properties. As an alternative to the industrial coating method of plasma spraying with inherently potential deleterious effects, sol-gel methods have attracted much attention. In this study, the effects of intermediate silk fibroin and silk sericin layers on the protein adsorption capacity of hydroxyapatite films formed by a particulate sol-gel method were determined experimentally. The preparation of the layered silk protein/hydroxyapatite structures on glass substrates, and the effects of the underlying silk proteins on the topography of the hydroxyapatite coatings were described. The topography of the hydroxyapatite layer fabricated on the silk sericin was such that the hydroxyapatite particles were oriented forming an oriented crystalline surface. The model protein (bovine serum albumin) adsorption increased to 2.62 µg/cm2 on the latter surface as compared to 1.37 µg/cm2 of hydroxyapatite on glass without an intermediate silk sericin layer. [Figure not available: see fulltext.].Article Citation - WoS: 28Citation - Scopus: 29Development of a High-Flux Thin-Film Composite Nanofiltration Membrane With Sub-Nanometer Selectivity Using a Ph and Temperature-Responsive Pentablock Co-Polymer(American Chemical Society, 2019) Bar, Canbike; Çağlar, Nagahan; Uz, Metin; Mallapragada, Surya K.; Alsoy Altınkaya, SacideProducing block co-polymer-based nanofiltration (NF) membranes with sharp molecular weight cutoffs via an efficient method exhibiting persistent size-based separation quality is challenging. In this study, this challenge was addressed by reporting a facile approach to fabricate pentablock co-polymer (PBC)-based thin-film composite (TFC) NF membranes. The PBC, consisting of temperature-responsive Pluronic F127 (PEO-b-PPO-b-PEO) middle blocks and pH-responsive poly(N,N-(diethylamino)ethyl methacrylate) end blocks, were synthesized by atom-transfer radical polymerization. This polymer was then attached electrostatically to the surface of polysulfone/sulfonated polyether-sulfone support membranes fabricated using a non-solvent-induced phase separation technique. The conformational changes of the PBC chains in response to pH and temperature determined the, pure water flux and neutral solute (PEG 1000) rejection performance of TFC membranes. Permeability of the membranes increased from 13.0 +/- 0.63 to 15.9 +/- 0.06 L/m(2).h bar and from 6.7 +/- 0.00 to 13.9 +/- 0.07 L/m(2).h.bar by changing the solution pH from 4 to 8.5 and temperature from 4 to 25 degrees C, respectively. The pH- and temperature-responsive conformational changes did not affect the PEG 1000 rejection and membrane pore radius, which remained constant at similar to 89% and similar to 0.9 nm, respectively. This important finding was attributed to the high grafting density of co-polymer chains, resulting in spatial limitations among the grafted chains. The pore size of similar to 0.9 nm achieved with the proposed membrane design is the smallest size reported so far for membranes fabricated from block copolymers. TFC membranes demonstrated high stability and maintained their flux and rejection values under both static (storage in an acidic solution for up to 1 month) and dynamic (filtering PEG 1000 solution over 1 week) conditions. Pentablock copolymers enable a NF membrane with a sharp molecular weight cutoff suitable for size-selective separations. The membrane fabrication technique proposed in this study is a scalable and promising alternative that does not involve complex synthetic routes.Article Citation - WoS: 10Citation - Scopus: 12Transparent block copolymer thin films for protection of optical elements via chemical vapor deposition(Elsevier Ltd, 2018) Karabıyık, Merve; Ebil, ÖzgençIn this study, glycidyl methacrylate and 1H, 1H, 2H, 2H-perfluorodecyl acrylate copolymer p(GMA-co-PFDA) thin-films fabricated via Initiated Chemical Vapor Deposition (iCVD) were investigated as protective coatings on optical BK7 glass substrates and commercial optical filters. Durability tests based on military standards MIL-F-48616 and MIL-C-48497A were performed to evaluate performance of coatings for the protection of surfaces of optical elements. Cross-linked p(GMA-co-PFDA) copolymer coatings successfully passed all durability tests showing excellent mechanical properties and protection against humidity, salt water, swelling in water, and resistance to organic solvents while providing excellent adhesion to substrate. iCVD process enabled fine tuning of film morphology, mechanical properties and hydrophobicity by controlling the process parameters. Fabricated films were hydrophobic and highly transparent (>98%) in the wavelength range from 300 nm to 1000 nm. Optical transmittance measurements before and after coating process proved that while providing chemical and physical protection, p(GMA-co-PFDA) copolymer thin-films do not cause any detectable change in optical performance of commercial narrow band and wide band filters.Article Citation - WoS: 10Citation - Scopus: 10Morphology, Order, Light Transmittance, and Water Vapor Permeability of Aluminum-Coated Polypropylene Zeolite Composite Films(John Wiley and Sons Inc., 2011) Balköse, Devrim; Oğuz, Kaan; Özyüzer, Lütfi; Tarı, Süleyman; Arkış, Esen; Özmıhçı Ömürlü, FilizIn this study, the polypropylene-zeolite composite films having 2-6 wt % natural zeolite were coated with a thin film of aluminum (Al) by magnetron sputtering, and the contribution of the Al coating on film properties was investigated. The samples were characterized by EDX, X-ray diffraction, SEM, AFM, UV-visible spectroscopy, and water vapor permeation analyses. The surface of the films coated with a smooth Al film having 98-131 nm thickness. EDX revealed that Al percentage on the surface appeared to be as 8-10 wt % indicating contribution of polymer surface under Al film to analysis. XRD analysis showed that the grain size of Al at the surface was 22-29 nm. The surface roughness increased after Al-coating process. The transmission of coated films was very low for both UV and visible regions of the light spectrum. Permeation analysis indicated that water vapor permeation was lower for Al-coated material.Article Citation - WoS: 3Citation - Scopus: 3Particulate Sol Route Hydroxyapatite Thin Film-Silk Protein Interface Interactions(Gazi Üniversitesi, 2010) Özcan, Selçuk; Çiftçioğlu, MuhsinHydroxyapatite (HAp) thin film coatings were prepared on bioinert glass slides by a particulate sol method and the effects of intermediate silk fibroin and silk sericin coatings on the HAp film formation and surface topography were examined. The films prepared with smaller crushed particle sols had a higher agglomeration tendency during the drying consolidation step of the thin film formation, and contained agglomerates larger in number and size, which was demonstrated experimentally and in accordance with the DLVO theory. In the thin films prepared on intermediate sericin and fibroin films the number and size of agglomerates were decisively reduced, forming homogeneous films of predominantly primary particles, especially for the larger particle size sols. The regular surface electrostatic potential arrangements of the β-sheet structures of the sericin and fibroin, and of hydroxyapatite crystals, gave rise to the coulombic attraction driven surface energy minimization, enhancing the hydroxyapatite thin film formation process. The positive degree of cooperativity in the hydroxyapatite particle deposition on the silk protein coatings was disrupted by the particle agglomeration tendency.Article Citation - WoS: 51Citation - Scopus: 57Characterization of Waterborne Acrylic Based Paint Films and Measurement of Their Water Vapor Permeabilities(Elsevier, 2006) Topçuoğlu, Özge; Alsoy Altınkaya, Sacide; Balköse, DevrimRecently, production of waterborne coatings has increased significantly as a consequence of strict pollution regulations. Waterborne coatings are sensitive to humidity, thus, their barrier properties with respect to permeation of moisture needs to be determined. Among various coating constituents, binder represents the matrix structure and its amount relative to the amounts of pigments and fillers can significantly affect the structure, hence the barrier property of the coating. In this study, waterborne acrylic based paints applied as protective coating on interior and exterior wall of the buildings are studied. The paint samples formulated with four different binder contents by a commercial paint company are used in the experiments. We first determine unknown ingredients of the paint samples using different characterization tools and then investigate the effect of the binder content on the structure of the paint films. In addition, water vapor permeability of the paint films is measured using a permeation cell. Results show that the barrier property of the waterborne acrylic based paint films against humidity decreases with decreased binder content due to uneven distribution of the pigments, consequently, porous structure formation in the films.