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 Hydroxyopatite and Polymer Composite Biomaterials(Izmir Institute of Technology, 2002) Gültekin, Naz; Tıhmınlıoğlu, FundaIn the thesis, the preparation and characterization of polylactide-Hydroxyapatite(HA) composite films for biomaterial applications have been studied. The effects of number of parameters such as polymer type, HA loading, surface modification and its concentration on the mechanical, thermal microstructural and hydrolytic degradation properties of the composites were investigated. Four different types of polymers, Poly (L-lactide)(PLA1), 96/4 L-lactide,D-Lactide Copolymer (PDLA1), Poly (L-Lactide)(PLA2), and 67/23 Poly (L-Lactide-co-D,L-Lactide)(PDLA2), have been used. In this study, PolyLactide-HA composite films have been prepared by solvent-casting technique. The HA powder was synthesized by precipitation technique. Interfacial interactions between HA and polylactide polymer were modified to improve filler compatibility and mechanical properties of the composites by surface treatment of the HA with two different silane coupling agents; 3-aminopropyltriethoxysilane (AMPTES) and 3-mercaptopropyltrimethoxysilane (MPTMS) at three different concentration. Silane treatment indicated better dispersion of HA particles in the polymer matrix and improvements in the mechanical properties of the composites compared to the untreated HA loaded polylactide composites. Tensile test results showed that the maximum improvement in the mechanical properties of the composites was obtained for the PLA composites containing 1 wt % aminofunctional silane treated HA and 0.5 wt % mercaptopropyltrimethoxy silane treated HA for PDLA composites. Scanning electron microscopy studies also revealed better dispersion of silane treated HA particles in the polymer matrix. Thermal degradation kinetics of the composites was investigated and it was found that addition of HA into polymer matrix decreased the thermal degradation temperature and also slowed down the degradation rate. In this study, the hydrolytic degradation of poly (L-Lactide)(PLA), poly (L-Lactide-co-D-Lactide) (PDLA) and their hydroxyapatite (HA) loaded composites (10-50-w/w %) were investigated in simulated body fluid (SBF) at 37 0C and at pH 7.4 by in vitro static testing. Using different techniques, namely weighting to quantify water absorption monitored the hydrolytic degradation and weight loss, scanning electron microscopy (SEM) to observe morphological changes occurred at the surface of the films over time. At the end of the 150 days, only 12.5 wt % and 9.5 wt % of weight PLA1 and PLA2 were lost respectively. Degradation of the copolymers was faster than PLA1 and PLA2 and weight loss data of PDLA1 and PDLA2 were found to be nearly same with 17.5 wt % and 17 wt %, respectively. The changes of pH on all polymer were stable at 7.4, because of simulated body fluid indicates buffer solution properties. Degradation rate of PLA and PDLA composites containing 10 wt % HA decreased, and also water absorption of these samples increased. Weight loss decreased approximately from 12 wt % to 5 wt % and water absorption increased from 10 wt % to 13 wt % for PLA composites containing 10 wt % HA. The change of microstructural properties of obtained composites has been determined in simulated body fluid as a function of time. It was found that the surface of polymer composite films was coated with the calcium phosphate layer. This coating was increased with HA loading and ageing time.Master Thesis Synthesis of Well-Defined Fatty Acid Polymers as Potential Membrane Destabilizing Agents(Izmir Institute of Technology, 2014) Aydınlıoğlu, Esra; Bulmuş Zareie, Esma VolgaThe aim of this thesis is to synthesize well-defined, fatty acid polymers via reversible addition fragmentation chain transfer (RAFT) polymerization, as potential membrane destabilizing agents which can be used for intracellular drug delivery applications. A new methacrylate monomer, derived from an unsaturated fatty acid, 11-[2-(2-methyl-acryloyloxy)-ethylsulfanyl] undecanoic acid (UDAMA), was synthesized using 10-undecenoic acid as a starting compound. Monomer synthesis was composed of two steps: In the first step, thiol-ene thermal addition of 2-mercaptoethanol to 10-undecenoic acid was performed. The yield of the reaction was 85 %. In the second step, the addition product was reacted with methacryoyl chloride to yield a new monomer, UDAMA. The yield of the second synthetic step was 92%, calculated from 1H NMR spectroscopy. UDAMA was polymerized via both conventional free radical and RAFT polymerization techniques. Polymers were characterized using 1H-NMR spectroscopy and gel permeation chromatography (GPC). Linear increase in ln [M]0/[M] with polymerization time, and Mn with monomer conversion indicated the RAFT-controlled polymerization of UDAMA monomer under the conditions tested. The new monomer, UDAMA was also copolymerized with methacrylic acid (MAA) via RAFT polymerization to obtain water-soluble, pH-responsive polymers. Random copolymers of MAA and UDAMA were synthesized using two different polymerization feed composition having 20 mol% or 50 mol% UDAMA content. Copolymerizations were also found to be controlled by RAFT mechanism, as evidenced by measurements via 1H-NMR spectroscopy and GPC. The pH-responsive behavior of copolymers was demonstrated via UV−visible spectroscopy and dynamic light scattering measurements. Hemolysis assays revealed that the copolymers with 20 mol% UDAMA content demonstrated pH-dependent hemolytic activity.