Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Studying Dopa Adhesion on Polystyrene Under Water(Izmir Institute of Technology, 2021) Yıldız, Remziye; Akdoğan, Yaşar; Emrullahoğlu, MustafaMussels wet adhesive performance has been arousing curiosity for a long time. It is found that 3,4-dihydroxyphenylalanine (DOPA) is responsible for adhesive properties of mussels. Despite a large body of research characterizing the interactions DOPA with hydrophilic surfaces, relatively few works have addressed the mechanism of interactions with hydrophobic surfaces. The benzene ring of DOPA is the main attributor to the adhesion on hydrophobic polystyrene (PS) surface. However, here we showed that two hydroxyl groups of catechol have also effects on wet adhesion. We studied wet adhesive properties of DOPA, tyrosine and phenylalanine functionalized PEG polymers, PEG-(N-Boc-L-DOPA)4, PEG-(N-Boc-L-Tyrosine)4, PEG-(N-Boc-L-Phenylalanine)4, on spin labeled PS nanobeads (SL-PS) by electron paramagnetic resonance (EPR) spectroscopy. Surface coverage ratio of SL-PS upon additions of PEG-(N-Boc-L-DOPA)4, PEG-(N-Boc-L-Tyrosine)4 and PEG-(N-Boc-L-Phenylalanine)4 showed that SL-PS was covered with 70%, 50% and 0%, respectively. This showed that spontaneous wet adhesion on PS increases with the number of amino acids hydroxyl groups. This is also supported with the density functional theory (DFT) energy calculations and ab-initio molecular dynamics (AIMD) simulations. In water, interactions between water molecules and hydroxyl groups on the catechol induce catechol adhesion via π-π stacking between the catechol and double styrene rings which were already tilted out with water.Master Thesis Quasi-Static Axial Compression Behavior of Empty and Polystyrene Foam Filled Aluminum Tubes(Izmir Institute of Technology, 2003) Toksoy, Ahmet Kaan; Güden, MustafaThe strengthening effect of foam filling and the effect of foam filling on the crushing properties of the light weight foam filled circular tubes were investigated through the polystyrene foam filled thin-walled Al tubes of 16 and 25 mm in diameter. The empty tubes crushed progressively in asymmetric (diamond) mode. The foam filling however turned the deformation mode into progressive axisymmetric (concertina) mode in 25 mm Al tube, while the deformation mode in foam filled 16 mm Al tube remained to be the same with that of the empty tube. The strengthening coefficients of foam-filling defined as the ratio between the increase in the average crushing load of the filled tube with respect to empty tube and plateau load (load corresponding to the plateau stress of the foam) were found to be 1.8 and 3.2 for the concertina and diamond mode of deformation, respectively. The higher value of strengthening in diamond mode of deformation was attributed to the filler deformation beyond the densification region. This was also confirmed by the microscopic observation of the partially crushed sections of the filled tubes. The interaction effect between tube and filler was assessed by the compression testing of the partially foam filled tubes. The effects of filler density, deformation rate (in the range between 0.001-0.04 s-1) and the use of adhesive between the tube wall and filler on the average crushing load, stroke efficiency and specific absorbed energy of the tubes were determined. The specific absorbed energy of the filled tube was compared with that of the empty tubes of wall thickening on the equal mass basis. Finally, two modes of deformation modes were proposed for the crushing behavior of the foam filled thin-walled Al tubes.