Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Molecular Modelling of the Effect of Alkali Promoters on Co Adsorption and Dissociation on the Co(111) Surface(2023) Kızılkaya, Ali Can; Kızılkaya, Ali Can; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyFischer-Tropsch Synthesis (FTS) is a surface polymerization process that has been industrially used to convert non-petroleum feedstocks to synthetic transportation fuels. Modification with an alkali promoter of the Co-based catalysts provided promising results to obtain hydrocarbons with enhanced olefin content in FTS. Activation of CO is the key factor to achieve desired end products in FTS, yet the mechanism related to the CO dissociation behavior on alkali promoted cobalt surfaces remains unknown. This study aims to examine the impact of alkali promoters (Li, Na, K) on the adsorption and dissociation characteristics of CO on the Co(111) surface using Density Functional Theory (DFT). Our results revealed that CO adsorption energy increased by 32-37% with alkali addition, yet H adsorption energy remained relatively unchanged. The effect of alkali addition on CO dissociation routes were also examined. The high activation barrier (>200 kJ/mol) makes it improbable for direct CO dissociation to occur on alkali promoted Co(111) surfaces under FTS conditions. For H-assisted pathways, alkali addition increased the activation barrier for HCO and H2CO dissociation, overall reducing the H-assisted CO dissociation rate. It was found that alkali addition makes the surface more carbophilic since the C adsorption energy increased by 7-11% upon alkali addition. Also, with increasing C concentration on the Co(111) surface, subsurface carbon geometries became more stable. Ultimately, it is concluded that alkali promoters of Li, Na and K have similar effects on CO adsorption and dissociation on the Co(111) surface.Master Thesis Fabrication of Polymeric Nano-Coatings Via Chemical Vapor Deposition(Izmir Institute of Technology, 2016) Kırköse, Sema; Ebil, Özgenç; Ebil, Özgenç; 03.02. Department of Chemical Engineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThin film coatings are used to provide protection to the substrate of interest against physical and chemical elements. Coating can also be applied to modify the surface properties of the substrate. One of the most important aspects of coating processes is controlling the thickness of coating material over the substrate. As a subset of a family of chemical vapor deposition methods, iCVD relies on vapor-to-surface reactions to form solid ultrathin polymer films. Unlike other CVD methods, iCVD is unique in that a polymerization reaction is induced by a thermally or chemically activated initiator molecule, much like in liquid-based thermal polymerization except without the use of a liquid solvent medium. The aim of the study is to fabricate polymeric protective nano-coatings via iCVD on flat surfaces at low or ambient temperatures. A variety of polymers, including homopolymers of glycidyl methacrylate (GMA), cyclo hexyl methacrylate (CHMA) and 1H, 1H, 2H, 2H,-Perfluorodecyl acrylate (PFDA) and P(GMA-PFDA) copolymers were fabricated via iCVD. The surface roughness and contact angle values were measured. Smooth hydrophobic surfaces having high contact angle (approximately 130˚) were obtained with PPFDA and PGMA-co-PPFDA thin films. Chemical compositions of the homo and co-polymer films were also evaluated confirming the retention of functional groups during polymerization, thus opening possibility of using iCVD produced films in various sensor applications.Master Thesis Development of Arginine-Containing Well-Defined Polymers(Izmir Institute of Technology, 2014) Taykoz, Damla; Bulmuş Zareie, Volga; Bulmuş Zareie, Esma Volga; 03.01. Department of Bioengineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThe aim of this work is to synthesize arginine-containing well-defined polymers via reversible addition-fragmentation chain transfer (RAFT) polymerization and perform preliminary investigation on the use of these polymers in nucleic acid complexation for potential gene therapy applications. Pentafluorophenyl methacrylate (PFMA) was chosen as an active ester monomer to produce polymers having functional groups available for further modification. RAFT polymerization of PFMA was performed varying polymerization conditions such as feed composition and polymerization temperature. Polymers (PPFMA) were characterized using nuclear magnetic resonance (NMR) spectroscopy and gel permeation chromatography. Linear increase in ln[M]0/[M] with polymerization time, and number average molecular weight (Mn) with monomer conversion indicated RAFT controlled polymerization of PFMA under the conditions tested. Furthermore, block copolymers of PFMA with poly(ethylene glycol) methacrylate (PEGMA) as a biocompatible component were prepared. Copolymerization was studied using both P(PFMA) and P(PEGMA) as macro RAFT agent. Copolymerization kinetic studies indicated that chain extension block copolymerizations were successfully performed using both macroRAFT agents. P(PFMA) was reacted with arginine methylester (AME) in the presence of triethylamine (TEA). 100% of P(PFMA) active ester groups could be modified with AME at a polymer/AME/TEA mole ratio of 1/1/3, as determined by 1H-NMR spectroscopy. The AME modified polymers were complexed with a 681-bp DNA fragment through electrostatic interactions at varying nitrogen/phosphate (N/P) ratios. Gel electrophoresis experiments revealed that AME-modified P(PFMA) was able to complex with DNA at a N/P ratio of 200. Furthermore, the hydrodynamic diameter (Dh) of polymer/DNA complexes in phosphate buffer saline was found to be 58 nm, while the free DNA displayed a Dh of 109 nm, indicating the complexation of DNA by AME-modified P(PFMA).Master Thesis Synthesis of Amine Containing Well-Defined Polymers Via Reversible Addition-Fragmentation Chain Transfer (raft) Polymerization and Their Characterization(Izmir Institute of Technology, 2013) Kurtuluş, Işıl; Bulmuş Zareie, Volga; Bulmuş Zareie, Esma Volga; 03.01. Department of Bioengineering; 03. Faculty of Engineering; 01. Izmir Institute of TechnologyThe aim of the study is to synthesize well-defined, spermine-like, amine containing polymers via reversible addition fragmentation chain transfer (RAFT) polymerization as a potential endosomal escaping agent for intracellular drug delivery applications. Tert-butyl (2-((tert-butoxycarbonyl) amino) ethyl)(2-hydroxyethyl)carbamate was first synthesized and then methacrylated to yield 2-((tert-butoxycarbonyl) (2- ((tert-butoxycarbonyl) amino) ethyl) amino) ethyl methacrylate, (BocAEAEMA). BocAEAEMA was then polymerized via RAFT polymerization. A series of RAFT polymerization kinetics experiments were performed in order to investigate the RAFTcontrolled character of polymerizations. The effect of [M]/[R] ratio at constant monomer (0.36 M, 0.72 M and 1.44 M) and initiator concentrations (3.6x10-3 M) on polymerization kinetics was first investigated. Linear proportionality between ln [M]0/[M] and polymerization time, and Mn and conversion, indicated the RAFTcontrolled polymerization of BocAEAEMA monomer under the conditions tested. Boc-AEAEMA polymers were deprotected to yield AEAEMA polymers prior to assays performed to determine cytotoxicity and proton sponge capacity of polymers. Proton sponge capacity of AEAEMA polymers (5.5 kDa and 8 kDa) and PEI (25 kDa and 60 kDa) was investigated via potentiometric titration using constant polymer (2.2 x10-5 M) or repeating unit (2.9 x10-5 M) concentrations. The proton sponge capacity of p(AEAEMA)was found to be comparable to those of PEIs at the same repeating unit concentration. AEAEMA polymers did not show cytotoxic effect on NIH 3T3 cells up to 1.6 M concentration, tested via a cell viability assay for 24h and 72 h.