Researcher:
Şenses, Erkan

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Erkan

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Şenses

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Şenses, Erkan

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2018 - 201932020 - 202420

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    Suppression of segmental chain dynamics on a particle's surface in well-dispersed polymer nanocomposites
    (AMER CHEMICAL SOC, 2024) Kim, Jihyuk; Thompson, Benjamin R.; Tominaga, Taiki; Osawa, Takahito; Egami, Takeshi; Foerster, Stephan; Ohl, Michael; Faraone, Antonio; Wagner, Norman J.; Department of Chemical and Biological Engineering; Department of Chemical and Biological Engineering; Şenses, Erkan; College of Engineering
    The Rouse dynamics of polymer chains in model nanocomposite polyethylene oxide/silica nanoparticles (NPs) was investigated using quasielastic neutron scattering. The apparent Rouse rate of the polymer chains decreases as the particle loading increases. However, there is no evidence of an immobile segment population on the probed time scale of tens of ps. The slowing down of the dynamics is interpreted in terms of modified Rouse models for the chains in the NP interphase region. Thus, two chain populations, one bulk-like and the other characterized by a suppression of Rouse modes, are identified. The spatial extent of the interphase region is estimated to be about twice the adsorbed layer thickness, or approximate to 2 nm. These findings provide a detailed description of the suppression of the chain dynamics on the surface of NPs. These results are relevant insights on surface effects and confinement and provide a foundation for the understanding of the rheological properties of polymer nanocomposites with well-dispersed NPs.
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    IL-modified MOF-177 filler boosts the CO2/N2 selectivity of Pebax membrane
    (Elsevier, 2024) Department of Chemical and Biological Engineering; Department of Chemical and Biological Engineering; Habib, Nitasha; Tarhanlı, İlayda; Şenses, Erkan; Keskin, Seda; Uzun, Alper; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Koç University Boron and Advanced Materials Application and Research Center (KUBAM) / Koç Üniversitesi Bor ve İleri Malzemeler Uygulama ve Araştırma Merkezi (KUBAM); Graduate School of Sciences and Engineering; College of Engineering
    Mixed matrix membranes (MMMs) having ionic liquid (IL) modified metal-organic frameworks (MOF) as fillers present a broad potential for enhancing the separation properties of the polymers. Here, we incorporated an IL, 1butyl-1-methyl-pyrrolidinium tricyanomethanide [BMPyr][TCM], into MOF-177 and used the corresponding composite as filler in Pebax polymer to fabricate IL/MOF-177/Pebax MMMs at different filler loadings. These MMMs along with those prepared by using pristine MOF-177 as a filler were then tested for CO2/N2 separation by measuring their CO2 and N2 permeabilities at 35 degrees C and 1 bar. The [BMPyr][TCM]/MOF-177/Pebax MMM having 10 wt.% filler loading showed remarkable improvements in both CO2 permeability (137 f 2.0 Barrer) and CO2/N2 selectivity (622 f 105) compared to the neat Pebax membrane having corresponding performance values of 98.0 f 2.0 Barrer and 64.5 f 6.0, respectively. This simultaneous improvement in both CO2 permeability and CO2/N2 selectivity breaks the trade-off limitation of polymer membranes. Besides, the MMMs having 10 and 15 wt.% loadings of fillers were located well above the updated Robeson's upper bound, demonstrating the great promise of [BMPyr][TCM]/MOF-177/Pebax MMMs for CO2/N2 separation.
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    Dynamically bonded cellulose nanocrystal hydrogels: structure, rheology and fire prevention performance
    (Elsevier Ltd, 2024) Kaynak-Uraz, Elif; Department of Chemical and Biological Engineering; Department of Chemical and Biological Engineering; Şenses, Erkan; Koparipek, Nazlınur Arslan; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Koç University Boron and Advanced Materials Application and Research Center (KUBAM) / Koç Üniversitesi Bor ve İleri Malzemeler Uygulama ve Araştırma Merkezi (KUBAM); College of Engineering; Graduate School of Sciences and Engineering
    Flame retardant composite hydrogels offer many advantages over conventional flame retardants, such as high water-retention capacity, enhanced fire resistance, and mechanical tunability. Herein, we developed flame-retardant dynamic covalent hydrogels using wood-derived cellulose nanocrystals (CNCs) crosslinked with boronate ester bonds, addressing environmental and health issues associated with the presence of non-biodegradable synthetic polymer and/or inorganic nanoparticle components in the existing systems. Our rheological investigation shows a liquid-to-soft-solid transition of CNC dispersions with tunable network elasticity ranging between ≈ 0.2 kPa to 3.5 kPa and an immediate self-healing ability. Coating pine wood with these hydrogels delayed ignition by about 30 s compared to native wood, and achieved a remarkable limiting oxygen index of 64.5 %. Also, the increased borax content of the gels was found to decrease and delay the first peak of the heat release rate up to 40 s, causing an increase in the fire retardancy index by 277 %. We correlate the microstructure and rheological behavior with the fire prevention mechanisms for the rational design of sustainable fire-retardant materials, and the results showcased a circular use of plant-based dynamic gels to prevent wood fires, even after drying- a feature lacking in conventional hydrogels.
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    Cellulose nanocrystal and pluronic L121-based thermo-responsive composite hydrogels
    (Elsevier Sci Ltd, 2023) Department of Chemical and Biological Engineering; Department of Chemical and Biological Engineering; Tarhanlı, İlayda; Şenses, Erkan; Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Koç University Boron and Advanced Materials Application and Research Center (KUBAM) / Koç Üniversitesi Bor ve İleri Malzemeler Uygulama ve Araştırma Merkezi (KUBAM); Graduate School of Sciences and Engineering; College of Engineering
    Cellulose nanocrystal (CNC) is a promising sustainable material with its biocompatibility, high aspect ratio, and mechanical strength. CNC-based systems have potential applications in various fields including biosensors, packaging, coating, energy storage, and pharmaceuticals. However, turning CNC into smart systems remains a challenge due to the lack of stimuli-responsiveness, limitation in compatibility with hydrophobic matrices, and their agglomeration tendency. In this work, a thermo-responsive nanocomposite system is constructed with CNCs and polymersome forming Pluronic L121 (L121), and its phase behavior and mechanical properties are investigated in detail. Two different CNC concentration (4 % and 5 %) is studied by changing the L121 concentration (1-20 %) to understand the effect of unimers and polymersomes on the CNC network. At dilute L121 concentrations (1-5 %), the composite system becomes softer but more fragile below the transition temperature. However, it becomes much stronger at higher L121 concentrations (10-20 %), and a gel network is obtained above the transition temperature. Interestingly, the elastically reinforced CNC gels exhibit greater resistance to microstructural breakdown at large strains due to the soft and deformable nature of the large polymersomes. It is also found that the gelation temperature for hydrogels is tunable with increasing L121 concentration, and the nanocomposite hydrogels displayed thermo-reversible rheological behavior.
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    Influence of kosmotrope and chaotrope salts on water structural relaxation
    (American Chemical Society (ACS), 2020) Luo, Peng; Zhai, Yanqin; Mamontov, Eugene; Xu, Guangyong; Faraone, Antonio; Department of Chemical and Biological Engineering; Department of Chemical and Biological Engineering; Şenses, Erkan; Faculty Member; College of Engineering; 280298
    The structural relaxation in water solutions of kosmotrope (structure maker) and chaotrope (structure breaker) salts, namely sodium chloride, potassium chloride, and cesium chloride, were studied through quasielastic neutron scattering measurements. We found that the collective dynamics relaxation time at the structure factor peak obtained using heavy water solutions shows a distinctively different behavior in the kosmotrope as opposed to the chaotrope solutions, increasing with the salt concentration in the former and decreasing in the latter. In both cases the trends are proportional to the concentration dependence of the relative viscosity of the solutions. These results indicate that kosmotropes and chaotropes influence the solutions viscosity by impacting in opposite ways the hydrogen bond network of water, strengthening it in one case and softening it in the other.
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    Multiscale polymer dynamics in hierarchical carbon nanotube grafted glass fiber reinforced composites
    (American Chemical Society (ACS), 2019) Krishnamurthz, Ajay; Tao, Ran; Doshi, Sagar M.; Burni, Faraz Ahmed; Natarajan, Bharath; Hunston, Donald; Thostenson, Erik T.; Faraone, Antonio; Forster, Amanda L.; Forster, Aaron M.; Department of Chemical and Biological Engineering; Department of Chemical and Biological Engineering; Şenses, Erkan; Faculty Member; College of Engineering; 280298
    Carbon nanotube (CNT) grafted glass fiber reinforced epoxy nanocomposites (GFRP) present a range of stiffnesses (MPa to GPa) and length scales (mu m to nm) at the fiber-matrix interface. The contribution of functionalized CNT networks to the local and bulk polymer dynamics is studied here by using a combination of torsion dynamical mechanical thermal analysis (DMTA), positron annihilation lifetime spectroscopy (PALS), and neutron scattering (NS) measurements. DMTA measurements highlight a reduction in the storage modulus (G') in the rubbery region and an asymmetric broadening of the loss modulus (G '') peak in the alpha-transition region. NS measurements show a suppressed hydrogen mean-square displacement (MSD) in the presence of glass fibers but a higher hydrogen MSD after grafting functionalized CNTs onto fiber surfaces. PALS measurements show greater free volume characteristics in the presence of the functionalized CNT modified composites, supporting the view that these interface layers increase polymer mobility. While NS and DMTA are sensitive to different modes of chain dynamics, the localization of functionalized nanotubes at the fiber interface is found to affect the distribution of polymer relaxation modes without significantly altering the thermally activated relaxation processes.
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    Enteric coating of drug loaded aerogel particles in a wurster fluidized bed and its effect on release behaviour
    (Editions de Sante, 2023) Ulker, Zeynep; Demir, Enis; Işık, Murat; Ekmekçiyan, Nadin; Department of Chemical and Biological Engineering; Department of Chemical and Biological Engineering; N/A; N/A; N/A; Department of Chemical and Biological Engineering; Erkey, Can; Şenses, Erkan; Akgün, Işık Sena; Darvishi, Saeid; Karaz, Selcan; Faculty Member; Faculty Member; PhD Student; PhD Student; Master Student; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); College of Engineering; College of Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; 29633; 280298; N/A; N/A; N/A
    Ibuprofen loaded and unloaded alginate aerogel particles were successfully coated with methacrylic acid-ethyl acrylate copolymer in a Wurster fluidized bed. Pores of both aerogels were well-preserved during the coating process. Effects of drug loading, polymer rheology, and atomizing pressure on coating thickness and coating layer surface morphology were investigated. Coatings were conducted at circulatory particle motion regime. Due to low weight of unloaded aerogels, this regime was achieved at lower air flow rates than ibuprofen loaded aerogels. Coatings of ibuprofen loaded aerogels were conducted between 1.3 and 1.5 bar atomizing pressures and at 60 °C. Unloaded aerogels were coated at a constant and high atomizing pressure of 1.7 bar and at 60 °C. At this condition, coating thickness of unloaded aerogels increased linearly from 25.6 μm to 53.4 μm with increasing coating time from 10 to 50 min. For ibuprofen loaded aerogels, coating thickness increased non-linearly from 15.9 μm to 84.1 μm with increasing coating time from 10 to 180 min. Ibuprofen release from aerogels in acidic medium was prevented via coating. In the basic medium, the fastest release was obtained from uncoated aerogels and 57% of ibuprofen was released in 30 min while 44% of crystalline ibuprofen dissolved at the same time. The slowest release rate was achieved via coating and 13% of the drug was released from coated aerogels in 30 min. © 2023 Elsevier B.V.
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    Effect of polymeric viscoelastic environment on multiscale structural dynamics of lipid bilayers
    (Cell Press, 2022) N/A; N/A; Department of Chemical and Biological Engineering; Department of Chemical and Biological Engineering; Karaz, Selcan; Şenses, Erkan; Master Student; Faculty Member; Graduate School of Sciences and Engineering; College of Engineering; N/A; 280298
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    Entangled polymer dynamics in attractive nanocomposite melts
    (American Chemical Society (ACS), 2020) Şenses, Erkan; Tyagi, Madhu Sudan; Faraone, Antonio; Department of Chemical and Biological Engineering; N/A; Department of Chemical and Biological Engineering; Şenses, Erkan; Darvishi, Saeid; Faculty Member; PhD Student; College of Engineering; Graduate School of Sciences and Engineering; 280298; N/A
    We investigate single chain dynamics of an entangled linear poly(ethylene oxide) melt in the presence of well-dispersed attractive nanoparticles using high-resolution neutron spectroscopy at particle volume fractions as high as 0.53. The short-time dynamics shows a decrease of the Rouse rates with particle loading, yet the change remains within a factor of 2, with no evidence of segment immobilization as often hypothesized. The apparent reptation tube diameter shrinks by approximate to 10% from the bulk at a 0.28 particle volume fraction when the face-to-face interparticle distance approaches the single chain size. The tube diameter is remarkably concentration-independent at higher loadings where all chains are essentially bound to particle surfaces. These direct experimental observations on the microscopic chain dynamics in attractive nanocomposites are distinct from their nonattractive counterparts and account for some of the unusual dynamic behaviors of the nanoparticles as well as rheology in the composites.
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    Protective coating of highly porous alginate aerogel particles in a Wurster fluidized bed
    (Elsevier, 2022) Demir, Enis; Işık, Murat; Ekmekciyan, Nadin; N/A; Department of Chemical and Biological Engineering; Department of Chemical and Biological Engineering; Department of Chemical and Biological Engineering; Akgün, Işık Sena; Şenses, Erkan; Erkey, Can; PhD Student; Faculty Member; Faculty Member; Koç University Tüpraş Energy Center (KUTEM) / Koç Üniversitesi Tüpraş Enerji Merkezi (KÜTEM); Graduate School of Sciences and Engineering; College of Engineering; College of Engineering; N/A; 280298; 29633
    Alginate aerogel particles were successfully coated with a copovidone and hydroxypropyl cellulose based polymer in a Wurster fluidized bed. The results indicate that the pores of aerogels were not damaged during the process. Several sets of experiments were conducted at three different temperatures and atomizing air pressures. Coating time for all the runs ranged from 5 min to 40 min and the coating thickness ranged from 12.4 +/- 4.6 mu m to 170.6 +/- 43.3 mu m.Changing bed temperature led to significant changes in coating thickness whereas both bed temperature and atomizing pressure affected coating layer surface morphology. The smoothest coating layer surface and the highest coating efficiency which was 69.2 +/- 0.4% were achieved at 50 degrees C with 1.7 bar atomizing pressure. At this condition, the coating layer thickness increased linearly with coating time.(c) 2022 Elsevier B.V. All rights reserved.