Researcher: Söz, Çağla Koşak
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Söz, Çağla Koşak
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Publication Metadata only Wetting behavior of superhydrophobic poly(methyl methacrylate)(Elsevier Science Sa, 2018) Department of Chemistry; N/A; Department of Chemistry; Yılgör, Emel; Söz, Çağla Koşak; Yılgör, İskender; Researcher; PhD Student; Faculty Member; Department of Chemistry; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); College of Sciences; Graduate School of Sciences and Engineering; College of Sciences; 40527; N/A; 24181Superhydrophobic PMMA surfaces were prepared by spin-coating and doctor blade coating of PMAA/hydrophobic silica (1/10 by weight) dispersions in toluene onto glass substrates. Influence of the number of coating layers applied and gauge thickness of the doctor blade used on surface properties were investigated. Formation of dual scale, micro/nano surface topographies were demonstrated by scanning electron microscopy, atomic force microscopy and white light interferometry studies. Roughness factor (r) and average surface roughness (R-a) values of the surfaces were determined. Wetting behavior of superhydrophobic PMMA surfaces obtained by introducing micro-nano, hierarchical roughness to inherently hydrophilic smooth PMMA films cannot be explained by Wenzel model. Therefore, wetting behavior of these surfaces were analyzed using Cassie-Baxter model and area fraction of surface protrusions were estimated.Publication Metadata only 3D coffee stains(Royal Soc Chemistry, 2017) N/A; N/A; Department of Electrical and Electronics Engineering; N/A; N/A; N/A; Department of Molecular Biology and Genetics; Department of Chemistry; Department of Chemistry; Department of Electrical and Electronics Engineering; Doğru-Yüksel, Itır Bakış; Söz, Çağla Koşak; Press, Daniel Aaron; Melikov, Rustamzhon; Begar, Efe; Çonkar, Deniz; Karalar, Elif Nur Fırat; Yılgör, Emel; Yılgör, İskender; Nizamoğlu, Sedat; PhD Student; PhD Student; Researcher; PhD Student; PhD Student; PhD Student; PhD Student; Faculty Member; Researcher; Faculty Member; Faculty Member; Department of Molecular Biology and Genetics; Department of Chemistry; Department of Electrical and Electronics Engineering; N/A; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); N/A; N/A; N/A; N/A; N/A; N/A; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; College of Sciences; College of Sciences; College of Sciences; College of Engineering; N/A; N/A; N/A; N/A; N/A; N/A; 206349; N/A; 24181; 130295When a liquid droplet (e.g., coffee, wine, etc.) is splattered on a surface, the droplet dries in a ring-shaped stain. This widely observed pattern in everyday life occurs due to the phenomenon known as a coffee stain (or coffee ring) effect. While the droplet dries, the capillary flow moves and deposits the particles toward the pinned edges, which shows a 2D ring-like structure. Here we demonstrate the transition from a 2D to a 3D coffee stain that has a well-defined and hollow sphere-like structure, when the substrate surface is switched from hydrophilic to superhydrophobic. The 3D stain formation starts with the evaporation of the pinned aqueous colloidal droplet placed on a superhydrophobic surface that facilitates the particle flow towards the liquid-air interface. This leads to spherical skin formation and a cavity in the droplet. Afterwards the water loss in the cavity due to pervaporation leads to bubble nucleation and growth, until complete evaporation of the solvent. In addition to the superhydrophobicity of the surface, the concentration of the solution also has a significant effect on 3D coffee stain formation. Advantageously, 3D coffee stain formation in a pendant droplet configuration enables the construction of all-protein lasers by integrating silk fibroin with fluorescent proteins. No tools, components and/or human intervention are needed after the construction process is initiated; therefore, 3D coffee-stains hold promise for building self-assembled and functional 3D constructs and devices from colloidal solutions.Publication Metadata only Fast-Tracking of the segmental orientation in r poly(ethylene oxide)-based polyurethane urea by mechano-optical (infrared dichroism and birefringence) properties: degree of the soft-segment ordering effect(American Chemical Society, 2023) Nugay, Işık Işıl; Ünsal, Emre; Çakmak, Mükerrem; N/A; N/A; Department of Chemistry; Söz, Çağla Koşak; Yılgör, Emel; Yılgör, İskender; Researcher; Researcher, Faculty Member; Department of Chemistry; N/A; N/A; College of Sciences; N/A; 40527; 24181The orientation behavior of segment-specific chemical groups of NH and CH was investigated for poly(ethylene oxide) (PEO)-based polyurethane urea (PUU) during uniaxial stretching using a uniaxial stretching system integrated with spectral birefringence and ultrafast IR spectrometers that capture two polarization states simultaneously. PUUs with 30% by-weight urethane-urea hard segment content were prepared using PEO oligomers with number average molecular weights of 2000, 4600, and 8000 g/mol. High-molecular weight PEO-based PUUs exhibited microphase morphologies with sharp interfaces between the PEO matrix and urethane-urea hard segments, while low-molecular weight PEO-2000 (2000 g/mol)-based PUU exhibited a gradient interphase. This is primarily due to substantial hydrogen-bonding interactions between the urea hard segments and ether groups of highly amorphous PEO-2000 compared with highly crystalline soft segments in PEO-4600 and PEO-8000, which lack significant hydrogen-bonding interactions with urea groups and hence a sharper interface and improved microphase separation. The segment-specific chemical group orientation study revealed that the relaxation and reorganization behaviors are closely dependent on the initial morphology. In microphase-separated PUU with a gradient interphase, responses of the hard and soft segments to deformation are similar even at lower strain levels. For the microphase-separated PUUs with a sharp interface, the low-strain level orientation is localized in the soft-segment regions until the connection with the hard segments drive the orientation in the chain axis toward the stretching direction. This network transition is also reflected in the mechano-optical behavior as a change from a high-strain optical constant to a lower-strain optical constant.Publication Metadata only Influence of the coating method on the formation of superhydrophobic silicone-urea surfaces modified with fumed silica nanoparticles(Elsevier Science Sa, 2015) N/A; Department of Chemistry; Department of Chemistry; Söz, Çağla Koşak; Yılgör, Emel; Yılgör, İskender; PhD Student; Researcher; Faculty Member; Department of Chemistry; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; College of Sciences; College of Sciences; N/A; N/A; 24181Effect of the coating method on the formation of superhydrophobic polydimethylsiloxane-urea copolymer (TPSC) surfaces, modified by the incorporation of hydrophobic fumed silica nanoparticles was investigated. Four different coating methods employed were: (i) layer-by-layer spin-coating of hydrophobic fumed silica dispersed in an organic solvent onto TPSC films, (ii) spin-coating of silica-polymer mixture onto a glass substrate, (iii) spray coating of silica/polymer mixture by an air-brush onto a glass substrate, and (iv) direct coating of silica-polymer mixture by a doctor blade onto a glass substrate. Influence of the coating method, composition of the polymer/silica mixture and the number of silica layers applied on the topography and wetting behavior of the surfaces were determined. Surfaces obtained were characterized by scanning electron microscopy (SEM), white light interferometry (WLI) and advancing and receding water contact angle measurements. It was demonstrated that superhydrophobic surfaces could be obtained by all methods. Surfaces obtained displayed hierarchical micro-nano structures and superhydrophobic behavior with static and advancing water contact angles well above 150 degrees and fairly low contact angle hysteresis values.Publication Metadata only Synthesis, properties, and applications of polycaprolactone-polydimethylsiloxane-polycaprolactone triblock copolymers(Amer Chemical Soc, 2015) N/A; Department of Chemistry; Department of Chemistry; Söz, Çağla Koşak; Yılgör, Emel; Yılgör, İskender; PhD Student; Researcher; Faculty Member; Department of Chemistry; Graduate School of Sciences and Engineering; College of Sciences; College of Sciences; N/A; N/A; 24181Poly(ε-caprolactone)–polydimethylsiloxane–poly(ε-caprolactone) (PCL-PDMS-PCL) triblock copolymers with block lengths in 1,000 – 32,000 g/mol range were synthesized by the ring-opening polymerization of ε-caprolactone using aminopropyl terminated PDMS oligomers as initiators. Reactions were carried out in bulk or solution at 125±5 ºC using tin octoate catalyst. Products obtained in high yields were characterized by FTIR, GPC, DSC, AFM, SEM, XRD, OM and water contact angle measurements. Effect of the copolymer composition and the molecular weight of the PDMS and PCL blocks on; (i) microphase separation and copolymer morphology, (ii) crystallization of PCL segments, and (iii) surface properties of the copolymers were investigated. Regardless of the block lengths, all copolymers displayed microphase separated morphologies. The extent of microphase separation, resultant morphology and sizes of the microphases were strongly dependent on copolymer composition and block lengths of PCL and PDMS. Crystalline PCL microphase was observed in all copolymers, which increased as a function of PCL content and molecular weight. All copolymers displayed hydrophobic surfaces as determined by static water contact angle measurements. Hydrophobicity improved with an increase in the PDMS block length. Copolymer morphologies were also obtained by computational studies at the molecular and mesoscopic levels via density functional theory (DFT) and dissipative particle dynamics (DPD) methods respectively. Computational results obtained were in very good agreement with the microphase morphologies determined by AFM studies. PCL-PDMS-PCL copolymers can be used as reactive oligomers or surface or bulk modifying additives for polymeric systems. We evaluated them as a processing aid in the melt extrusion of polyolefins, where they improved the extruder output substantially. They were also used as surface modifying additives for electrospun polyacrylonitrile fibers and silica modified epoxy networks, which led to the formation of superhydrophobic surfaces.Publication Metadata only Simple processes for the preparation of superhydrophobic polymer surfaces(Elsevier Sci Ltd, 2016) N/A; Department of Chemistry; Department of Chemistry; Söz, Çağla Koşak; Yılgör, Emel; Yılgör, İskender; PhD Student; Researcher; Faculty Member; Department of Chemistry; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; College of Sciences; College of Sciences; N/A; N/A; 24181Two simple processes; (i) spin-coating, and (ii) doctor blade coating of silica/polymer dispersions are described for the preparation of superhydrophobic polymer surfaces. To demonstrate the versatility and broad applicability of the processes, polymeric surfaces modified included a thermoplastic resin, polystyrene (PS) and a thermoset, crosslinked epoxy resin (ER). Micro/nano hierarchical nature of the surface topographies obtained were demonstrated by scanning electron microscopy (SEM), atomic force microscopy (AFM) and white light interferometry (WLI) studies. Roughness factor (r) and average surface roughness (R-a) values, which are critical in obtaining superhydrophobic surfaces were determined for each polymeric system. It was clearly demonstrated that increased (r) and (R-a) values resulted in superhydrophobic behavior with very high static, advancing and receding water contact angles, well above 150 degrees and contact angle hysteresis values of less than 10 degrees. Incorporation of small amounts (1.0% by weight) of a silicone copolymer or a perfluoroether glycol oligomer reduced the contact angle hysteresis in the epoxy resin system well below 10 degrees and produced truly superhydrophobic surfaces.Publication Metadata only Influence of the average surface roughness on the formation of superhydrophobic polymer surfaces through spin-coating with hydrophobic fumed silica(Elsevier Sci Ltd, 2015) N/A; Department of Chemistry; Department of Chemistry; Söz, Çağla Koşak; Yılgör, Emel; Yılgör, İskender; PhD Student; Researcher; Faculty Member; Department of Chemistry; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; College of Sciences; College of Sciences; N/A; N/A; 24181Formation of superhydrophobic polymer surfaces were investigated through successive spin-coating of hydrophobic fumed silica dispersed in an organic solvent onto polymer films. Two different polymers, a hydrophobic segmented silicone-urea copolymer (TPSC) and hydrophilic poly(methyl methacrylate) (PMMA) were used as model substrates. Influence of the polymer type and structure, silica concentration and the number of silica layers applied on the topography, average roughness and the wetting behavior of the surfaces were determined. Polymer surfaces obtained were characterized by scanning electron microscopy, white light interferometry, atomic force microscopy and advancing and receding water contact angle measurements. It was possible to obtain superhydrophobic surfaces displaying hierarchical micro/nano features both for TPSC and PMMA. A close correlation was observed between the number of silica layers applied and average surface roughness obtained. It was demonstrated that an average surface roughness value of 125-150 nm was necessary for the formation of superhydrophobic surfaces, both for TPSC and PMMA. Chemical structure and nature of the polymeric substrate seem to play a significant role on the topography and average roughness of the silica coated surfaces formed. Superhydrophobic surfaces displayed static and advancing water contact angles well above 150 degrees and fairly small contact angle hysteresis.Publication Metadata only Mussel inspired coatings based on tannic acid and polyamines(American Chemical Society (ACS), 2017) Department of Chemistry; Department of Chemistry; N/A; Yılgör, İskender; Yılgör, Emel; Söz, Çağla Koşak; Faculty Member; Researcher; PhD Student; Department of Chemistry; College of Sciences; College of Sciences; Graduate School of Sciences and Engineering; 24181; 40527; N/AN/APublication Metadata only PTMO based TPU/silica nanocomposites: preparation and properties(Amer Chemical Soc, 2012) Malay, Özge; Oğuz, Oğuzhan; Menceloğlu, Yusuf Z.; N/A; Department of Chemistry; Department of Chemistry; Söz, Çağla Koşak; Yılgör, Emel; Yılgör, İskender; PhD Student; Researcher; Faculty Member; Department of Chemistry; Graduate School of Sciences and Engineering; College of Sciences; College of Sciences; N/A; N/A; 24181N/APublication Metadata only Effect of soft segment molecular weight on tensile properties of poly(propylene oxide) based polyurethaneureas(Elsevier, 2012) Wilkes, Garth L.; Zhang, Mingqiang; N/A; Department of Chemistry; N/A; Department of Chemistry; Ertem, S. Pırıl; Yılgör, Emel; Söz, Çağla Koşak; Yılgör, İskender; Master Student; Researcher; PhD Student; Faculty Member; Department of Chemistry; Graduate School of Sciences and Engineering; College of Sciences; Graduate School of Sciences and Engineering; College of Sciences; N/A; 40527; N/A; 24181Influence of soft segment molecular weight and hard segment content on the morphology, thermomechanical and tensile properties of homologous polyurethaneurea copolymers based on narrow molecular weight poly(propylene oxide)glycol (PPG) oligomers were investigated. A series of polyurethaneureas with hard segment contents of 12-45% by weight and PPG number average molecular weights of 2000 to 11,800 g/mol were synthesized and characterized structurally by SAXS and mechanically by DMA and stress strain analysis. Bis(4-isocyanatocyclohexyl)methane and 2-methyl-1,5-diaminopentane were used as the diisocyanate and the chain extender respectively. All copolymers displayed microphase separation by SAXS and DMA. The critical entanglement molecular weight (M-e) of PPG is reported to be around 7700 g/mol. Our mechanical results suggest that when copolymers possess similar hard segment contents and are compared to those based on soft segments with number average molecular weights (M-n) greater than M-e, they generally displayed higher tensile strengths and particularly lower hysteresis and creep than those having soft segment molecular weights below Me. These results imply that soft segment entanglements in thermoplastic polyurethaneureas may provide a critical contribution to the tensile properties of these copolymers particularly in the range where the soft segment content is dominant. (c) 2012 Elsevier Ltd. All rights reserved.