In the present work, anatase and rutile titanium dioxide (TiO2) coated lustrous mica pigments were prepared by heterogeneous nucleation method. Anatase-rutile phase transformation of the TiO2 on mica substrate was achieved by coating very thin layers of tin (IV) oxide on mica surfaces prior to TiO2 deposition. Muscovite mica, which was used in the experiments was sieved, pre-treated with sodium bicarbonate and decantated before coating process. The surface morphology of mica titania pigments and anatase-rutile phase transformation were investigated by SEM and XRD analyse, respectively. Also, microwave-assisted synthesis of copper phthalocyanine and tetracarboxamide copper phthalocyanine pigments were carried out with phthalic anhydride and trimellitic anhydride precursors, respectively. Molecular structures of these pigments were confirmed by FT-IR and UV-visible spectroscopy analyse. Furthermore, combination pigments were obtained by the process of deposition of copper phthalocyanine pigments on mica-titania pigment substrate in dimethyl formamide solvent. FT-IR analysis and XRD analyse were performed to observe the transformations in the crystal forms of copper phthalocyanines on the substrate. The surface morphologies of copper phthalocyanines on the mica titania pigments were investigated by SEM analysis. Varying amounts of copper phthalocyanines were deposited on the mica surfaces, and nitrogen elemental analysis was performed to determine the amount of copper phthalocyanines. The resulting pigments were incorporated into alkyd based resin to prepare paint samples. L*a*b* values, gloss property, and hardness of the paint samples were determined by color measuring device, gloss meter and hardness measuring device, respectively. The resulting combination pigments obtained in this study showed improved luster, hue, and color intensity. Furthermore, in literature it was reported that these pigments have very high bleed resistance. This can be attributed to large macromolecular structure of copper phthalocyanine on the surface of mica titania pigment that prevents bleeding of the pigment from the paint. Moreover, the paint samples obtained from combination pigments showed higher hardness with respect to the paint sample of the mica titania pigment.

Cholesterol and ethanol biosensors based on conducting polypyrrole (PPy), poly(3,4-ethylenedioxythiophene) (PEDOT) and poly(3,4-ethylenedioxypyrrole) (PEDOP) were constructed. Cholesterol oxidase (ChOx, from Pseudomonas fluorescens) and alcohol oxidase (AlcOx, from Pichia pastoris) were physically entrapped during electropolymerization of the monomers (Py, EDOT, EDOP) in phosphate buffer containing sodium dodecylsulfate (SDS) as the supporting electrolyte. The amperometric responses of the enzyme electrodes were measured monitoring oxidation current of H2O2 at +0.7 V in the absence of a mediator. Kinetic parameters, such as Km and Imax, operational and storage stabilities, effects of pH and temperature were determined for all entrapment supports. Based on Michaelis-Menten (Km) constants, it can be interpreted that both enzymes immobilized in PEDOT showed the highest affinities towards their substrates. Before testing the alcohol biosensors on alcoholic beverages, effects of interferents (glucose, acetic acid, citric acid, L-ascorbic acid) which might be present in beverages were determined. The alcohol content of the distilled beverages (vodka, dry cin, whisky, raki) was measured with these biosensors. A good match with the chromatography results (done by the companies) was observed.

A new class of &amp / #960 / -conjugated monomers was synthesized with combination of electron donating and electron-withdrawing heterocyclics to understand the effects of structural differences on electrochemical and optoelectronic properties of the resulting polymers. The use of this alternating donor-acceptor-donor strategy allows the synthesis of low band gap polymers in which the redox, electronic, and optical properties are controlled through easily approachable synthetic modification of the polymer backbone. This control allows fine-tuning of the band gap to values between 1.0 and 1.8 eV by making structural changes. These structural manipulations yield varied electronic absorption energies for a range of colors in the neutral polymer films, multi-colored electrochromism, and accessible states for reduction leading to n-type doping. The polymers prepared were characterized using cyclic voltammetry, colorimetry, and UV-Vis-NIR spectroscopy demonstrating that the polymers can undergo both p- and n-type doping and color changes in both redox states.

Bismaleimide resins are important in aerospace applications as matrix component of composite materials due to their high thermal and mechanical properties. 4,4&rsquo / -bismaleimidodiphenylmethane (BMI) which is the most widely used bismaleimide, was synthesized starting from maleic anhydride and 4,4&rsquo / -diaminodiphenylmethane (MDA). N,N&rsquo / -diallylaminodiphenyl methane (ADM), N,N&rsquo / -diallylaminodiphenyl sulfone (ADS) and N,N&rsquo / -diallyl p-phenyl diamine (PDA) were synthesized by allylating primary aromatic diamines. Nine different prepolymers with 1:1, 1.5:1 and 2:1 molar ratios of BMI/diallyl compound were prepared and cured. The effect of increase in BMI ratio on thermal properties of the resin systems were investigated via Differential Scanning Calorimetry (DSC) and Thermal Gravimetric Analyzer (TGA). DSC results showed that the curing temperature of the resins increased due to the increase in BMI ratio in the resins. Thermal gravimetric analysis showed that incorporation of BMI monomer improved the thermal stability of the resins. BMI/ADM resin system showed better thermal stability compared to BMI/ADS and BMI/PDA resins. Processing characteristics of resins having 1:1 and 1.5:1 mole ratio of BMI/ADM were investigated by viscosity measurements and these resins were found to be suitable for composite production with Resin Transfer Molding (RTM). Composites were manufactured by RTM technique using two different mole ratios of BMI/ADM resins as matrix component. The effect of different matrix composition on thermal and mechanical properties of the composites were investigated. The concept of this thesis work was arised from the requirements of some projects carried out in T&uuml / bitak-SAGE. Keywords: Bismaleimide resins, composite, thermal properties, resin transfer molding.

Long bone fractures are fixed with bone plates to restrain movement of bone fragments. Fracture site must experience some pressure for proper healing. Bone plates are mostly made up of metals having 5 - 10 times higher elastic modulus than bones and most of the load is carried by them, leading to stress shielding and a bony tissue with low mineral density and strength. To avoid these problems, biodegradable polymer-based composite plates were designed and tested in this study. Poly(L-lactide) and Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) biodegradable polymer composite fibers containing hydroxyapatite (HAP) nanoparticles were produced by extrusion and spinning techniques to reinforce the polymeric bone plates. The composite fibers were expected to mimic the natural organization of bone so that HAP nanorods aligned parallel to the loading axis of bone plate. Also, lactic acid was grafted on HAP surfaces and had a positive effect on the mechanical properties of the PLLA composites. A 50% (w/w) HAP nanoparticle content was found to increase tensile modulus value (4.12 GPa) ca. 2.35 times compared to the pure polymeric fiber with a reduction to one third of the original UTS (to 50.4 MPa). The fibers prepared were introduced to polymeric plates with their long axes parallel. Fiber reinforced bone plates were compression tested longitudinally and up to a 4% increase in the Young&rsquo / s Modulus was observed. Although this increase was not high was not high probably due to the low fiber content in the final plates, this approach was found to be promising for the production of biodegradable polymeric bone plates with mechanical values closer to that of cortical bones. Biological compatibility of fibers was validated with in vitro testing. The osteoblasts attached and spread on the fibers indicating that bone fractures fixed with these could attract of bone forming osteoblasts into defect area and help speed up healing.

5,8-Bis(2,3-dihydrothieno[3,4b][1,4]dioxin-5-yl)-2-(naphthalen-2-yl)-3-ferrocenyl-4a,8a-dihydroquinoxaline (DEFNQ), 5,8-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-2-(phenyl)-3 ferrocenylquinoxaline (DEFPQ) and 5,8-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-2,3-di(naphthalen-2-yl)quinoxaline (DEDNQ) were synthesized, electrochemically polymerized and electrochromic properties of resultant polymers were investigated. For the characterization of the monomers Nuclear Magnetic Resonance (1H-NMR, 13C-NMR) were used. Cyclic Voltammetry (CV) and Ultraviolet&ndash / Visible Spectroscopy were used to investigate electrochemical behavior of the monomers and redox reactions of conducting polymers. After electrochemical polymerizations, the electrochromic properties of the conducting polymers were investigated via spectroelectrochemistry, kinetic and colorimetry studies to explore the one of most important property of conducting polymers, the ability to switch reversibly between the two states of different optical properties, &lsquo / electrochromism&rsquo / . Cyclic Voltammetry and Spectroelectrochemistry studies for PDEFNQ, PDEFPQ and PDEDNQ showed that ferrocenyl (Fc) group containing derivatives are multichromic green to transmissive polymer with high tendency to be both p and n doped. PDEDNQ which was not functionalized with ferrocenyl group does not show multichromism. According to the electrochemical and spectroscopic results each polymer is a potential candidate for optoelectronic applications.

Boron nitride nanotubes (BNNTs), firstly synthesized in 1995, are structural analogues of carbon nanotubes (CNTs) with alternating boron and nitrogen atoms instead of carbon atoms. Besides their structure, mechanical and thermal properties of BNNTs are very similar to the remarkable properties of CNTs. However, BNNTs have higher resistance to oxidation than CNTs. Also, BNNTs are electrically isolating. Therefore, they are envisioned as suitable fillers for the fabrication of mechanically and thermally enhanced polymeric composites, while preserving the electrical isolation of the polymer matrix. In this study, polypropylene (PP) &ndash / boron nitride nanotube (BNNT) composites were prepared using a twin-screw extruder. Mechanical and thermal properties of PP&ndash / BNNT composites were investigated as a function of nanotube loading. The nanotubes used in the composites were synthesized from the reaction of ammonia gas with a powder mixture of elemental boron and iron oxide. X-ray diffraction (XRD) analysis revealed the predominant hexagonal boron nitride in the synthesized product. Multi-wall nanotubes with outer diameters ranging from 40 to 130 nm were observed with SEM and TEM analyses. Tensile testing of PP&ndash / BNNT composites revealed slight increases in the Young&rsquo / s modulus and yield strength of neat PP with 0.5 and 1 wt% of the as-synthesized BNNT additions. On the other hand, due to the agglomeration of BNNTs, elongation at break and tensile strength values of composites decreased with increasing nanotube content. In the case of using 0.5 wt% loading of purified and then surface modified BNNTs, slight improvement in all mechanical properties of neat PP was achieved. Differential scanning calorimetry (DSC) analysis revealed a noticeable increase in the crystallization temperature of BNNT&ndash / added composites. Coefficient of linear thermal expansion (CLTE) of polymeric composites were studied and no significant change in the CLTE of neat PP was observed with the addition of BNNTs. Results of thermal gravimetric analysis (TGA) indicated improvements in the thermal stability of neat PP with BNNT additions.

The objectives of this study are to synthesize sub-micron sized zinc borate and to use them with other flame retardant additives in poly(ethylene terephthalate) (PET) based composites. The study can be divided into two parts. In the first part, it was aimed to synthesize sub-micron sized zinc borate (2ZnO.3B2O3.3.5H2O) with the reaction of zinc oxide and boric acid. For this purpose, low molecular weight additives or surfactants were used in the syntheses to prevent the agglomeration and to decrease particle size. Effect of type of surfactant and its concentration / effect of using nano-sized zinc oxide as reactant on the synthesis, properties and morphology of 2ZnO.3B2O3.3.5H2O were investigated. Synthesized zinc borates were characterized by X-Ray diffraction (XRD), Scanning Electron Microscope (SEM) and Thermogravimetric Analysis (TGA). The results were compared with a commercial zinc borate, Firebrake (FB). Characterization results showed that at least in one dimension sub-micron size was obtained and synthesized zinc borates did not lose their hydration water until the process temperature of the composites. In the second part of the study, PET based composites, which mainly included synthesized sub-micron sized zinc borates were prepared by using a co-rotating twin screw extruder and injection molding machine. Synergist materials such as boron phosphate (BP) and triphenyl phosphate (TPP) were also used in the composite preparation. The composites were characterized in terms of flammability and mechanical properties. Flammability of composites was determined by using a Limiting Oxygen Index (LOI) test. Mechanical properties such as tensile strength, elastic modulus, elongation at break and impact strength were also studied. According to LOI and impact tests, the composites containing 3 wt. % BP and 2 wt. % zinc borate which was modified with poly(styrene-co-maleic anhydride), 2PSMA05/3BP and 2PSMA1/3BP have higher LOI and impact values when compared to neat PET.

Acrylonitrile were copolymerized with 2-ethylhexyl acrylate and hexyl acrylate via one step emulsion polymerization using ammonium persulfate (initiator), 1-dodecanthiol (chain transfer agent) and DOWFAX 8390 (surfactant) in the presence of water at about 68 0C. Poly (acrylonitrile-2ethylhexyl acrylate) and poly (acrylonitrile-hexyl acrylate) copolymers with three different comonomer composition (8, 12 and 16 molar percent) were prepared. FTIR and 1H-NMR were used in order to clarify the chemical structure of copolymers. The comonomer amount incorporated into copolymers was determined by using 1H-NMR spectra. The thermal behavior of copolymers was determined by DSC and TGA. Molecular weights of copolymers were determined by intrinsic viscosity (IV) measurements. IV measurements revealed that both poly (acrylonitrile-2ethylhexyl acrylate) and poly (acrylonitrile-hexyl acrylate) have sufficient molecular weight to form nanoporous filtration membranes. Nanoporous filtration membranes were prepared and tested for chromium (IV) removal. It was observed that chromium (VI) rejections of nanoporous filtration membrane were highly dependent on the concentration and the pH of the solutions. Almost complete removal (99, 9 percent Cr (VI)) rejection was achieved at pHs 2, 5 and 7 for solution containing 50 ppm, chromium (VI) with permeate flux within a range from 177 to 150 L/m2h at 689.5 kPa. Also, chemical structure, swelling ratios, sheet resistivity and fracture morphologies of the nanoporous filtration membrane were studied. It should be noted that the nanoporous filtration membranes were fouling resistant.

In this study, shelf life of three different crosslinked double base (XLDB) propellants stabilized with 2-nitrodiphenylamine (2-NDPA) and n-methyl-4-nitroaniline (MNA) were determined by using the stabilizer depletion method. Depletions of the stabilizers were monitored at different aging temperatures using High Performance Liquid Chromatography (HPLC). Kinetic models of pseudo zero, pseudo first, pseudo second and shifting order were used to find the best model equation that fits the experimental data. The rates of depletion of stabilizers were calculated at 45, 55 and 65&deg / C based on the best fit kinetic models. Using the rate constants at different temperatures, rate constants at room temperature were calculated by Arrhenius equation. The activation energies and frequency factors for the depletion of 2-NDPA and MNA were obtained for all XLDB propellants. Moreover, the results were evaluated based on the NATO standard / STANAG 4117 and the propellants were found stable according to the standard. Vacuum thermal stability (VTS) tests were also conducted to evaluate the stability of XLDB propellants. The propellant that includes the stabilizer mixture of MNA and 2-NDPA was found to have less stability than the propellants that include 2-NDPA only. However, there were rejection (puking) and migration of stabilizer derivatives for the aged samples of propellants that were stabilized with only 2-NDPA. Moreover, formation of voids and cracks were observed in block propellant samples due to excess gas generation.