Master Degree / Yüksek Lisans Tezleri
Permanent URI for this collectionhttps://hdl.handle.net/11147/3008
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Master Thesis Preparation and Characterization of Antifouling Nanofiltration Membranes From a Responsive Pentablock Copolymer(Izmir Institute of Technology, 2018) Çağlar, Nağahan; Alsoy Altınkaya, SacideThe most substantial factor restricting the extensive application of membrane processes is the fouling problem resulting from the deposition of solutes in water on the surface or within the pores of membranes. The frequently used chemical washing procedure to eliminate the fouling issue causes environmental pollution and shortens the membrane life. In order to overcome these disadvantages, the development of membranes possessing low fouling potential is needed. In recent years, the stimuliresponsive polymers have received attention for developing membranes possessing low fouling potential. The antifouling property of these membranes is controlled through the change in their conformation and hydrophilic/hydrophobic characteristics as a response to change in external stimuli such as pH, temperature and ionic strength. The aim of this study was to design antifouling nanofiltration membranes (NF) using a pentablock copolymer which consists of temperature responsive Pluronic F127 (PEO-b-PPO-b- PEO) in the middle block and pH responsive poly(N,N-(diethylamino)ethyl methacrylate) (PDEAEM) in the end blocks. Effects of pH and temperature responsiveness on the membrane fouling were investigated. Fouling tendencies of the membranes were evaluated by using Bovine Serum Albumin (BSA), Alginate (ALG) as organic foulant and Escherichia coli (E.coli) as biological foulant. NF membranes were characterized by scanning electron microscope (SEM), contact angle and zeta potential measurements. It was demonstrated that pentablock copolymer coated membranes displayed antifouling resistance by changing filtration pH and temperature.Master Thesis Fabrication of Thin Layer Polymer-Based Biointerphase for Biosensing Application(İzmir Institute of Technology, 2016) Yücel, Müge; Yıldız, Ümit HakanThis study aims to fabricate polymer-carbon nanotube composite as a bioelectronic interface for sensing volatile organic compounds (VOCs) in exhaled breath. Sensor platform is made of two layers i) polymeric membranes and ii) conducting layer. Poly(vinylidene fluoride) (PVDF), polystyrene (PS), and poly(methyl methacrylate) (PMMA) are selected as model polymers that are processed by electrospinning to utilize polymeric membranes. Multi-walled carbon nanotubes (MWCNTs) are used to fabricate conducting layer on top of PVDF, PS, PMMA polymer membranes. Aqueous solution of well-dispersed MWCNTs are obtained by several purification and filtration steps and conductivity of working MWCNT solution is adjusted about 120 μS/cm for whole study. This solution is further used to impregnate PVDF, PS, PMMA membrane. The PVDF-MWCNT, PS-MWCNT and PMMA-MWCNT sensor platforms are tested by electrochemical station that recording electrical resistivity change by time. All sensors platforms, made of three polymeric membranes-MWCNT, are found to be a responsive upon applying the toluene and acetone vapor. The sensing mechanism is hypothesized as the adsorption of VOCs onto the conducting CNT layer blocking electron stream on CNT network and causing resistivity change. The sensitivity of PVDF-MWCNT sensing platform is exceedingly higher with respect to other two candidates due to solvent vapor- polymeric membrane interactions. This contribution changes sensor platform characteristics and make them quite sensitive to trace amount of VOCs. Acetone and toluene are detected from ppm to ppb range and reproducible responses are recorded. As a result, acetone and toluene, biomarkers of diabetes and lung cancer, can be differentiated with produced sensor.