In this study three polymers, namely poly(carbonate urethane), poly(bisphenol-a-epichlorohydrin) and poly(methyl methacrylate), were selected and change of properties with gamma treatment were studied. Two different dose rates were used for irradiations and the properties of the irradiated polymers exposed to same total absorbed dose were compared. In addition, long irradiations of up to about six months with high dose rate were done in order to understand the radiation stability of the polymers, which may be possible candidates for embedding media for low and intermediate level radioactive (nuclear) waste before their final disposal. Tensile, DSC, DMA, TGA, FTIR-ATR, FTIR tests were completed to understand the degradation of the polymers as a function of dose rate and total absorbed dose. The DSC and FTIR results showed that there was not much structural chemical changes in polymer chains with irradiation. However, the changes in mechanical properties were recorded. It was concluded that poly(carbonate urethane) and poly(bisphenol-aepichlorohydrin) can possibly be used in conditioning of radioactive waste, as they are radiation stable polymers. However, due to the moderate resistance of poly(methyl methacrylate) to ionizing radiation, it can be used for low level radioactive waste conditioning.

In recent years, biodegradable polymeric systems have gained importance for design of surgical devices, artificial organs, drug delivery systems with different routes of administration, carriers of immobilized enzymes and cells, biosensors, ocular inserts, and materials for orthopedic applications. Polysaccharide-based polymers represent a major class of biomaterials, which includes agarose, alginate, dextran, and chitosan. Chitosan has found many biomedical applications, including tissue engineering, owing to its biocompatibility, low toxicity, and degradation in the body, which has opened up avenues for modulating drug release in vivo in the treatment of various diseases. These chitosan-based delivery systems range from microparticles to nanoparticles and from gels to films. In this study, chitosan (CH) and chitosan-polyethylene glycol (CH-PEG) microspheres with different compositions were prepared by oil/water emulsion method and crosslinked with gluteraldehyde. Some microspheres were loaded with a model chemotherapeutic drug, methotrexate (MTX). SEM, particle size and in vitro release analysis were performed. In vitro drug release studies showed that the release of MTX from CH-PEG microspheres was faster compared to CH microspheres. In the second part, CH-PEG microspheres were conjugated with a monoclonal antibody which is immunoglobulin G (IgG). The cytotoxicity efficiencies of entrapped drug were determined by using MCF-7 and MCF-7/MDA-MB breast cancer cell lines. In the third part, CHF-PEG films with the same compositions as in microspheres were prepared by solvent casting method. IR, DSC, mechanical and surface analysis were performed. The mechanical properties of films were improved by the presence of proper amount of PEG but higher amounts of PEG caused the deteriotion in the properties.

In this work, EPDM rubber was compounded with increasing amount of filler (FEF N 550 type carbon black), process oil (saturated mineral oil), vulcanizing agent [di (t-butylperoxy) diisopropyl benzene, i.e., BBPIB] and diene [5-ethylidenebicyclo(2.2.1)-hept-2-ene, i.e., ENB] in order to investigate mechanical and rheological properties. Effect of Increasing amount of filler was investigated by using FEF N 550 type carbon black in 35, 70, 87.5, 105 phr. Decrease in scorch times of vulcanization reactions, ts2 (25, 21, 19, and 18 s, respectively) and slight increase in rate constants for vulcanization reactions (0.0270, 0.0274, 0.0301 and 0.0302 s-1, respectively) were explained in terms of nature of semi-active filler. Effect of increasing amount of process oil was investigated by using saturated mineral oil (TUDALEN 3909) in 15, 30, 45 phr. Scorch time for vulcanization reaction and rate constants were measured as 95, 103, 97 s and 0.0277, 0.0274, 0.0291 s-1, respectively. Effect of increasing amount of vulcanizing agent was investigated by using BBPIB (PERKADOX 14/40 MB-gr) in 2.5, 5, 7.5, 10 phr. The compound with 5 phr vulcanizing agent gave optimum rheometer data, crosslink density,, ultimate tensile strength, hardness, deflection and damping. Vulcanization reaction rate constant reached 0.0335 s-1 with 7.5 phr vulcanizing agent. Effect of increasing ENB ratio was investigated by using 4 different EPDM with ENB ratios 5.0, 5.6, 7.5, 8.9%. With two different cure systems, compounds with 5.6 and 7.5% ENB ratio gave optimum results. Vulcanization cure time, reaction rate constant and compression set properties changed in irregular manner.

SELENOPHENE DERIVATIVES FOR ELECTROCHROMIC APPLICATIONS Aydemir, Kadir M.S., Department of Chemistry Supervisor: Prof. Dr. Levent Toppare February 2008, 60 pages A novel selenophene-based monomer / 1,4-di(selenophen-2-yl) benzene (DSB), synthesized via Stille coupling reaction of 1,4 dibromobenzene and tributyl (2-selenophenyl) stannane and corresponding conducting homopolymer (Poly (DSB)) was electrochemically synthesized in the presence of tetrabutylammoniumhexafluorophosphate (TBAPF6) as the supporting electrolyte in dichloromethane. The resulting conducting polymer was characterized by Cyclic Voltammetry (CV), Fourier Transform Infra Red Spectrometry (FTIR) and Ultraviolet&ndash / Visible Spectrometry (UV-Vis Spectrometry). Spectroelectrochemistry analysis and kinetic studies of Poly (DSB) revealed &ndash / * transition (max) at 340 nm with almost zero percent transmittance (T%) concurrently with striking and rapid (0.6 s) absorbance change at near infrared region (1250 nm) with 35% percent transmittance, indicating that Poly (DSB) is a very suitable near infrared electrochromic material. Copolymer of selenophene with ethylenedioxythiophene (EDOT) was potentiostatically synthesized. Poly (selenophene-co-EDOT) was characterized by Cyclic Voltammetry, FTIR and UV-Vis Spectrometry. During spectroelectrochemistry studies, &ndash / * transition (max) was observed at 555 nm with a switching time of 1.4 s and 39% transmittance. Polaron and bipolaron bands were observed at 851 nm and 1299 nm, respectively. Switching time at 1299 nm was 1.8 s with a percent transmittance of 72. Copolymer of DSB with EDOT (Poly (DSB-co-EDOT)) was synthesized and characterized. max, polaron and bipolaron bands were observed at 457 nm, 696 nm and 1251 nm, respectively. A rapid switching time (0.2 s) with 12% transmittance was observed at 696 nm. At the near infrared region (1251 nm), satisfactory percent transmittance (35%) and a moderate switching time (1.75 s) were observed.

ABSTRACT A GLOW IN THE DARK: SYNTHESIS AND ELECTROPOLYMERIZATION OF CHEMILUMINESCENT THIOPHENE DERIVATIVES Asil, Demet M.Sc., Department of Chemistry Supervisor : Prof. Dr. Ahmet M. &Ouml / nal Co-Supervisor: Assist. Prof. Dr. Atilla Cihaner September 2008, 63 Pages Two novel chemiluminescent monomers, 2,3-dihydrothieno(3,4-d)pyridazine-1,4-dione (T-Lum) and 5,7-di-thiophen-2-yl-2,3-dihydro-thieno[3,4-d]pyridazine-1,4-dione (TTT-Lum), were synthesized. The reaction between T-Lum and TTT-Lum in alkaline solution with H2O2 gave chemiluminescence which can be catalyzed using Fe(III) ion. Owing to its sensitivitiy towards Fe(III) ion / T-Lum and TTT-Lum can be promising materials to detect bloodstains in the application of forensic science instead of luminol which gave response to a large family of metallic cations beside Fe(III). Also, TTT-Lum, which is based on a terthienyl system, was electropolymerized and its corresponding polymer (PTTT-Lum) was obtained via repetitive cycling or constant potential electrolysis in both 0.1 M LiClO4 dissolved in acetonitrile containing 5% of BF3-Et2O by volume and neat BF3- Et2O solution. In addition, PTTT-Lum, soluble in alkaline water, was synthesized successfully without breaking the pyridazinedione unit (chemiluminescent unit), as proved by Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR) and Electrochemical Luminescence (ECL) measurements. Thus, PTTT-Lum, bearing chemiluminescent unit, can be a good candidate to be used as a sensor in near future. Furthermore, the PTTT-Lum film has a very stable and well-defined reversible redox couple as well as electrochromic behavior during p-doping process. The polymer film has also a band gap of 1.74 eV with an absorption band in its neutral state at 536 nm. Finally, PTTT-Lum film was found to be electrochemiluminescence active, maintaining its activitiy over 1000 cycles.

Conducting polypyrrole (PPy) nanoparticles were synthesized via microemulsion polymerization system. The characterization of PPy nanoparticles was done by Fourier transform infrared spectrometer (FTIR) and scanning electron microscope (SEM). Nanocomposites were prepared by melt-mixing of polypyrrole with polypropylene (PP) and processed with injection molding. The amount of PPy in nanocomposites varied in the range of 1-20% by weight. The effect of PPy nanoparticles on mechanical, electrical properties and thermal stability of nanocomposites were investigated. Tensile test has revealed that increasing amount of PPy increased the strength and the stiffness of the nanocomposite while limiting the elongation of PP. Thermal gravimetric analysis has showed that incorporation of PPy nanoparticles has improved the thermal stability of the nanocomposites. Four probe conductivity measurement has exhibited that increasing amount of PPy nanoparticles increases the conductivity of nonconductive PP up to 2,4.10-4 Scm-1. In order to improve the dispersion of PPy in PP, sodium dodecylsulphate was used as dispersant. The same techniques were used to characterize nanocomposites containing 2% by weight dispersant. Composites prepared with dispersant have exhibited improvement in some mechanical and thermal properties and involved smaller dimension PPy nanoparticles.

This thesis aims to investigate the effects of gamma radiation on the properties of polycarbonate, an engineering thermoplastic which has a wide range of applications. A commercial grade polycarbonate resin, after being shaped into the required specimen forms by injection molding, was irradiated with different doses up to 180 kGy. Tensile strength was found to decrease with increasing dose. The lowest values of tensile modulus, flexural modulus and flexural strength were obtained at 96 kGy, which is also the dose at which molecular weight values showed a minimum. No remarkable changes in Shore D hardness values and NMR spectra were observed. The ATR-FTIR spectra showed that irradiation was effective on carbonyl groups in the structure. The glass transition temperatures of the specimens irradiated up to the maximum dose were lower than those of the non-irradiated specimens. The onset of weight loss at lower temperatures and steeper weight loss behavior in the TGA curves indicated decreasing thermal stability of the polymer with increasing dose.

This study was undertaken to prepare polystyrene (PS)/montmorillonite (MMT) nanocomposites by different methods, including melt intercalation, in-situ polymerization and masterbatch methods. The in-situ polymerization method consisted of dispersing the styrene monomer into the galleries of MMT followed by subsequent polymerization. The PS/MMT nanocomposites formed by melt intercalation method were prepared on a twin-screw extruder. The masterbatch method was in fact a two-step process. As the first step, a high clay content composite of polystyrene (masterbatch) was prepared by in-situ polymerization, and then the prepared masterbatch was diluted to desired compositions with commercial polystyrene in a twin-screw extruder.The structural, thermal and mechanical properties of the nanocomposites were examined. X-Ray diffraction (XRD) analysis showed that the d-spacing of the in-situ formed nanocomposites containing 0.73 and 1.6 wt. %organoclay increased from 32.9 &amp / #506 / to 36.3 and 36.8 &amp / #506 / respectively, indicating intercalation while the dspacing of the other prepared materials remained nearly unchanged compared to pure organoclay. At low clay content, (&lt / 1 wt.%), in-situ formed nanocomposites showed the best improvement in mechanical properties including tensile, flexural, impact strength and Young&rsquo / s modulus. In all the three methods, the addition of organoclay increased the Young&rsquo / s modulus compared to neat resin, but the maximum improvement was 88.5 %, obtained at 0.73 wt. % organoclay in the in-situ formed material. In-situ polymerization method did not prove to be efficient at high clay loadings in terms of mechanical properties. At high clay loadings, the effects of the three methods on promoting mechanical properties were not significantly different from each other. The glass transition temperature increased from 105.5 oC in the pure polystyrene to 108.4 oC in the in-situ formed nanocomposite at 0.73 wt % organoclay due to the restricted mobility of the polymer chains within the organoclay layers.

The synthesis and optoelectronic properties of biphenyl based conjugated copolymers with varying acceptor units in the polymer backbone were investigated. The well known Donor-Acceptor Theory was used to establish the synthetic pathway for the structural modifications. Solubility issues regarding biphenyl polymer was solved by copolymerizing with soluble units. For this purpose / poly 4-(biphenyl-4-yl)- 4&rsquo / -tert butylspiro[benzo[d]imidazole-2,1&rsquo / -cyclohexane] (P1), poly 4-(biphenyl-4-yl)- 2- dodecyl-2H-benzo[d][1,2,3]triazole (P2) and poly(4-(5-(biphenyl-4-yl)-4-hexylthiophen- 2-yl)-2-dodecyl-7-(4-hexylthiophen-2-yl)-2H-benzo[d][1,2,3]triazole (P3) were synthetized using Suzuki coupling process. Electrochemical properties of these polymers were examined by cyclic voltammetry, spectroelectrochemistry and kinetic studies. Polymers P2 and P3 showed both p- and n-doping behaviors and multicolored electrochromic states. Optical studies revealed that emission color of biphenyl is tuned from blue to orange and the polymers are good candidates for light emitting diode applications. OLED application of P3 was established and outputs of the device were increased by energy transfer studies. The preliminary investigation indicated that P3 possesses promising efficiencies.

Tissue engineering is a multidisciplinary field that is rapidly emerging as a promising new approach in the restoration and reconstruction of tissues. In this approach, three dimensional (3D) scaffolds are of great importance. Scaffolds function both as supports for cell growth and depot for sustained release of required active agents (e.g. enzymes, genes, antibiotics, growth factors). Scaffolds should possess certain properties in accordance with usage conditions. Wet-spinning is a simple technique that has been widely used for the fabrication of porous scaffolds for tissue engineering applications. Natural polymers can effectively be used in scaffold fabrication due to their biocharacteristics. Among natural polymers, chitosan and alginate are two of the most studied ones in tissue engineering and drug delivery fields because of being biologically renewable, biodegradable, biocompatible, non-antigenic, non-toxic and biofunctional. In this study, two kinds of porous scaffolds were produced as chitosan and alginate coated chitosan fibrous scaffolds by wet-spinning technique In order to investigate the delivery characteristics of the scaffolds, loading of gentamicin as a model antibiotic and bovine serum albumin (BSA) as a model protein was carried out in different loading models. Resultant scaffolds were characterized in terms of their structural formation, biodegradation, biomineralization, water uptake and retention ability and mechanical properties. Additionally, release kinetics of gentamicin and BSA were examined. Efficiency of gentamicin on Escherichia coli (E.coli) was examined. Characterization of scaffolds revealed their adequacy to be used in bone tissue engineering applications and capability to be employed as bioactive agent delivery systems.