GCRIS

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Characterization of Conjugated Polyelectrolytes for Nucleic Acid Sensing, Gene Delivery and Imaging
(01. Izmir Institute of Technology, 2022) Yücel, Müge; Yıldız, Ümit Hakan; Yıldız, Ümit Hakan
In this thesis, cationic derivatives of poly(3-alkylmethoxythiophene) (PT) which are a class of conjugated polyelectrolytes (CPE), have been synthesized. PT has been polymerized via FeCl3 oxidative polymerization, were treated in a set of solvents to elaborate coil conformation of polymer chain in different physicochemical environment. Spectroscopic and scattering techniques have ascertained that ethylene glycol is a good solvent for PT regarding Flory-Huggins theory. The smaller interaction parameter of PT with respect to ethylene glycol than water drives a thermodynamically driven ultra-small particle (Pdot) formation in aqueous phase by a rapid nanophase separation between PTrich ethylene glycol and PT-poor water phase. All CPEs have been then employed to prepare single polymer chain polymer dots (Pdot) by “nanophase separation” method. As a next step, Pdots have been characterized in terms of optical and colloidal properties that they possess in the backbone conformations altered by solvation effect. Regarding their colloidal characteristic, translocation of Pdot into cancerous cells was analyzed compared to healthy cells by 2D cell culture and co-culture studies. It has reported that Pdots have ability to penetrate through nuclear envelope in hepatocellular carcinoma whereas accumulate around nucleus of healthy liver cells in cytoplasm. Additionally, Pdots were studied in breast cancer cell lines to understand the behavior of Pdot staining in 2D cell culture of invasive and non-invasive breast cancer types. The findings suggest that Pdots are prone to penetrate into the invasive cancerous cells attributed to the greater deformations on nucleus membrane of triple negative breast cancer cells. In a next application, the enhanced photophysical property of PT exhibited in ethylene glycol media allows PT to be utilized as a fluorescent probe for determination of single nucleotide polymorphism by a non-amplification-based protocol. Fluorescence emission at specific wavelengths resulted from very distinct conformations of PT chain is the key elements for the SNP detection assay. The evaluation of optical data obtained from the probe with principal component analysis proves the separation of healthy individuals from patients with an overall 96% accuracy.
Synthesis and Chracterization of Polyimide Derivative Adhesives
(Izmir Institute of Technology, 2018) Acar, Oktay; Demir, Mustafa Muammer; Tirkeş, Seha
While the rapid advancement of technology is pushing the limits, today need for special advanced materials has been increased in order to obtain high-tech products with desired performance. Lightweight materials that can operate at high temperatures have critical importance in aerospace field. Between those materials, polyimides come front with their unique mechanical properties and high thermo-oxidative stabilities. They are commonly used in defense and aerospace industries as adhesives, coatings and resins in composites operating at high temperatures. PMR-15 (Polymerization of Monomeric Reactants) is considered as a state-ofthe-art high temperature resistant structural adhesive, due to its low cost, exceptional thermo-mechanical strength and thermo-oxidative resistance, up to 300 °C. However, PMR-15 has both limited processing and flexibility properties. LARC-RP46 (Langley Research Center) was developed as an alternative to PMR-15 resin. It has a higher melt flow rate to some extent. In this thesis, MDA-BTDA-ODA copolyimide adhesives with nadic end caps were synthesized. The chemical structures of the synthesized resins were verified by FTIR and 1H NMR analysis. The copolymers have thermal stabilities as high as 500 °C and Tg at around 400 °C. They showed superior adhesion performance up to 16.3 MPa. Compared to both commercial PMR-15 and LARC RP-46 polyimides, copolyimide resins showed significant processability. Kinetics of curing process of the resins was investigated by using the autocatalytic kinetic model of Kamal – Sourour. The experimental data are well-fitted with the model. The activation energies were calculated by kinetic constants derived from the model.

Phd Degree / Doktora

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