Researcher: Darvishi, Saeid
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Darvishi, Saeid
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Publication Metadata only 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; Erkey, Can; Şenses, Erkan; Akgün, Işık Sena; Darvishi, Saeid; Karaz, Selcan; Faculty Member; Faculty Member; PhD Student; PhD Student; Master Student; Department of Chemical and Biological Engineering; 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/AIbuprofen 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.Publication Metadata only 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; Şenses, Erkan; Darvishi, Saeid; Faculty Member; PhD Student; Department of Chemical and Biological Engineering; College of Engineering; Graduate School of Sciences and Engineering; 280298; N/AWe 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.Publication Metadata only Enhanced ionic conductivity and mechanical strength in nanocomposite electrolytes with nonlinear polymer architectures(TÜBİTAK, 2023) N/A; Department of Chemical and Biological Engineering; N/A; Bakar, Recep; Şenses, Erkan; Darvishi, Saeid; PhD Student; Faculty Member; PhD Student; Department of Chemical and Biological Engineering; Koç University Boron and Advanced Materials Application and Research Center (KUBAM) / Koç Üniversitesi Bor ve İleri Malzemeler Uygulama ve Araştırma Merkezi (KUBAM); Koç University Surface Science and Technology Center (KUYTAM) / Koç Üniversitesi Yüzey Teknolojileri Araştırmaları Merkezi (KUYTAM); Graduate School of Sciences and Engineering; College of Engineering; Graduate School of Sciences and Engineering; N/A; 280298; N/ASolvent-free polymer-based electrolytes (SPEs) have gained significant attention to realize safer and flexible lithium-ion batteries. Among all polymers used for preparing SPEs electrolytes, poly(ethylene oxide), a biocompatible and biodegradable polymer, has been the most prevalent one mainly because of its high ionic conductivity in the molten state, the capability for the dissolution of a wide range of different lithium salts as well as its potential for the environmental health and safety. However, linear PEO is highly semicrystalline at room temperature and thus exhibits weak mechanical performance. Addition of nanoparticles enhances the mechanical strength and effectively decreases the crystallization of linear PEO, yet enhancement in mechanical performance often results in decreased ionic conductivity when compared to the neat linear PEO-based electrolytes; new strategies for decoupling ionic conductivity from mechanical reinforcement are urgently needed. Herein, we used lithium bis(trifluoromethane-sulfonyl)-imide (LiTFSI) salts dissolved in various nonlinear PEO architectures, including stars (4-arms and 8-arms) and hyperbranched matrices, and SiO2 nanoparticles (approximately equal to 50 nm diameter) as fillers. Compared to the linear PEO chains, the room temperature crystallinity was eliminated in the branched PEO architectures. The electrolytes with good dispersion of the nanoparticles in the nonlinear PEOs significantly enhanced ionic conductivity, specifically by approximately equal to 40% for 8-arm star, approximately equal to 28% for 4-arms star, and approximately equal to %16 for hyperbranched matrices, with respect to the composite electrolyte with the linear matrix. Additionally, the rheological results of the SPEs with branched architectures show more than three orders of magnitude enhancement in the low-frequency moduli compared to the neat linear PEO/Li systems. The obtained results demonstrate that the solvent-free composite electrolytes made of branched PEO architectures can be quite promising especially for irregularly shaped and environmentally benign battery applications suitable for medical implants, wearable devices, and stretchable electronics, which require biodegradability and biocompatibility. © TÜBİTAK.Publication Metadata only Effect of polymer topology on microstructure, segmental dynamics, and ionic conductivity in PEO/PMMA-based solid polymer electrolytes(American Chemical Society (ACS), 2022) Bakar, Recep; Li, Tianyu; Hong, Kunlun; Department of Chemistry; Department of Electrical and Electronics Engineering; N/A; Department of Chemical and Biological Engineering; N/A; N/A; Aydemir, Umut; Nizamoğlu, Sedat; Han, Mertcan; Şenses, Erkan; Darvishi, Saeid; Bakar, Recep; Faculty Member; Faculty Member; Master Student; Faculty Member; PhD Student; PhD Student; Department of Chemistry; Department of Electrical and Electronics Engineering; Department of Chemical and Biological Engineering; College of Sciences; College of Engineering; Graduate School of Sciences and Engineering; College of Engineering; Graduate School of Sciences and Engineering; Graduate School of Sciences and Engineering; 58403; 130295; N/A; 280298; N/A; N/APoly(ethylene oxide) (PEO)-based solid polymer electrolytes (SPEs) have attracted much interest due to their high ionic conductivity resulting from inherently fast segmental dynamics and high salt solubility, yet they lack mechanical stability in their neat form. Blending PEO with another rigid, or high glass transition temperature, polymer is a versatile way to improve the mechanical stability; however, the ionic conductivity is strongly reduced due to slower segmental dynamics of highly interpenetrating linear polymer chains. In this work, we used model PEO/PMMA blend systems prepared with various well-defined PEO architectures (linear, stars, hyperbranched, and bottlebrushes) doped with lithium bis(trifluoromethane-sulfonyl)-imide (LiTFSI) and investigated, for the first time, the role of macromolecular architecture of PEO on crystallization, segmental dynamics, and ionic conductivity in the blends and electrolytes. The results suggest that room-temperature miscibility of these polymers can be dramatically extended by using nonlinear PEO in the blends instead of linear chains, which crystallize above 35 wt %. The broadband dielectric spectroscopy results revealed enhanced decoupling of PMMA and PEO segmental dynamics in compact branched architectures, which helps to achieve faster segmental motion of star PEO in glassy PMMA. This manifests as nearly three-fold higher ionic conductivity in these nonlinear blends compared to the conventional linear PEO/PMMA system. Regardless of the PEO architectures, the temperature dependence of ionic conductivity blends with PMMA and LiTFSI is well defined using the Vogel-Fulcher-Tammann mechanism, suggesting that ion transport is mainly affected by the segmental motion. The activation energy values decrease with the increasing ionic conductivity. Overall, our results show that macromolecular architecture can be a tool to decouple segmental dynamics and ion mobility to rationally design SPEs with improved performance.Publication Metadata only Nonlinear architectures can alter the dynamics of polymer-nanoparticle composites(American Chemical Society (ACS), 2021) Tyagi, Madhusudan; Zhang, Qingteng; Narayanan, Suresh; N/A; N/A; Department of Chemical and Biological Engineering; Department of Chemical and Biological Engineering; Darvishi, Saeid; Nazeer, Muhammad Anwaar; Kızılel, Seda; Şenses, Erkan; Master Student; Researcher; Faculty Member; Faculty Member; Department of Chemical and Biological Engineering; Graduate School of Sciences and Engineering; N/A; College of Engineering; College of Engineering; N/A; N/A; 28376; 280298Polymer nanocomposites exhibit remarkable physical properties that are attractive for many applications. These systems have been so far investigated using linear polymer chains; the role of polymer matrix architecture in local dynamics, bulk rheology, and nanoparticle (NP) motion remains unexplored. Here, using quasi-elastic neutron scattering, bulk rheology, and X-ray photon correlation spectroscopy, we investigated nano-composites with spherical silica nanopartides well dispersed in poly(ethylene oxide) matrices having different architectures (specifically linear, stars, and hyperbranched). The results reveal that the mechanical reinforcement of the nanocomposites with the nonlinear polymers can be altered by orders of magnitude with respect to the conventional nanocomposite with the linear polymer. Polymer compactness and interpenetrability are found to play crucial roles in determining their bulk rheology. At the microscopic level, average segmental dynamics is remarkably slowed down by the attractive NPs in the matrices of high degree of branching, whereas no significant effect is observed in the linear polymer matrix at the same NP loading. In addition, the nanoscale dynamics of particles in the compact nonlinear matrices exhibits strong decoupling from the bulk viscoelasticity, allowing their fast relaxation even at approximate to 30% by volume. These results provide an experimental evidence that macromolecular architecture is a powerful new tool for tuning the bulk theological properties as well as the nanoscale dynamics of polymer nanocomposites (PNCs) without the need for changing polymer molecular weight, nanoparticle size, shape, loading, or dispersion state.