Different substituted thiophene and pyrrole monomers namely hexamethylene (bis-3-thiopheneacetamide) (HMTA), N-(4-(3-thienylmethylene)-oxycarbonylphenyl)maleimide (MBThi), 2,4,6-Tris-(4-pyrrol-1-yl-phenoxy)-[1,3,5]triazine (TriaPy), 2,4,6-Tris-(thiophen-3-ylmethoxy)-[1,3,5] triazine (TriaTh), and N-(2-(thiophen-3-yl)methylcarbonyloxyethyl) maleimide (NMT) were synthesized. The chemical structures of the monomers were characterized by Nuclear Magnetic Resonance (1H-NMR and 13C-NMR) and Fourier Transform Infrared (FTIR) Spectroscopies. Electrochemical behavior of the monomers in the presence and absence of comonomers were studied by cyclic voltammetry. Subsequently, monomers were homopolymerized and copolymerized via electrochemical methods and the resultant polymers were characterized by FTIR, Scanning Electron Microscopy (SEM) and conductivity measurements. Second part of the study was devoted to investigate one of most interesting property of conducting polymers, the ability to switch reversibly between the two states of different optical properties, &ldquo / electrochromism&rdquo / . In recent years there has been a growing interest in application of conducting polymers in electrochromic devices. Thus, electrochromic properties of the synthesized conducting polymers were investigated by several methods like spectroelectrochemistry, kinetic and colorimetry studies. Spectroelectrochemistry experiments were performed in order to investigate key properties of conjugated polymers such as band gap, maximum absorption wavelength, the intergap states that appear upon doping and evolution of polaron and bipolaron bands. Switching time and optical contrast of the homopolymers and copolymers were evaluated via kinetic studies. Results implied the possible use of these materials in electrochromic devices due to their good electrochromic properties.

The effects of melt state compounding and addition order of ethylene-butyl acrylate-maleic anhydride (E-BA-MAH), ethylene-glycidyl methacrylate (E-GMA), ethylene-methyl acrylate-glycidyl methacrylate (E-MA-GMA) terpolymer and/or three types of organoclays (Cloisite&reg / 15A, 25A and 30B) on morphology, thermal, mechanical and dynamic mechanical properties of polyamide-6 are investigated. XRD patterns show that the interlayer spacing for Cloisite&reg / 15A remained unchanged / however it increased for the organoclays Cloisite&reg / 25A and Cloisite&reg / 30B in both polyamide-6/organoclay binary nanocomposites and in polyamide-6/organoclay/impact modifier ternary systems. TEM analyses indicate that exfoliated-intercalated nanocomposites are formed. Sizes of elastomeric domains in nanocomposites are larger than the domains in their corresponding blends. The MFI results show that incorporation of elastomer reduces the MFI, due to the formation of graft copolymer. Both storage and loss moduli and complex viscosity of polyamide-6 increase with organoclay addition. In DMA measurements, in rubbery region, all nanocomposites show higher storage modulus than the unfilled counterparts. In general, the organoclays increase tensile and flexural strength, Young&amp / #8217 / s and flexural modulus and elongation at break, but decrease the impact strength, on the contrary, the addition of elastomer has the opposite effect. Generally, Cloisite&reg / 15A containing ternary nanocomposites have higher tensile, flexural and impact strength and Young&amp / #8217 / s and flexural modulus than the ternary nanocomposites prepared with Cloisite&reg / 25A and Cloisite&reg / 30B. In general, nanocomposites processed by adding all the ingredients simultaneously give higher tensile and flexural strength and modulus than the nanocomposites produced by other mixing sequences.

In this study, effect of injection molding process parameters on fiber length and on mechanical properties of Polyamide-6 / glass fiber composite were investigated to produce higher performance composites. Polyamide-6 was first compounded with an E-grade glass fiber in a co-rotating intermeshing twin screw extruder. Then, by using this composite, twenty-five types of experiments were performed by injection molding by changing the barrel temperature, injection pressure, hold pressure, mold temperature, cooling time and screw speed. Izod notched impact, tensile, viscosity, heat deflection temperature, differential scanning calorimetry tests were performed on injection molded samples. By performing these tests, the effects of process parameters on mechanical properties and on fiber length were observed. In order to understand the variation in mechanical properties, thermal tests were also conducted. Also, fiber length distributions of the samples were measured.Experimental data show that fiber breakage decreases with increasing screw speed, injection pressure, however, fiber length increases with increasing barrel temperature, mold temperature and cooling time. Fiber length is almost not affected with the hold pressure. It is assumed in this study that crystallinity is not affected with injection pressure, hold pressure and screw speed. As barrel temperature and cooling time increase, crystallinity increases, however, as mold temperature increases, crystallinity decreases. Impact strength, tensile modulus and tensile strength increase, whereas elongation at break decreases with the average fiber length. Crystallinity affects the tensile strength and modulus positively. The tensile strength and modulus increase with increasing crystallinity.

The variation in properties of Polypropylene (PP) / Ethylene Vinyl Acetate (EVA) blends upon EVA content, temperature, and light stability were followed by using tensile testing, impact testing, and differential scanning calorimetry (DSC). Young&rsquo / s modulus of the blends decreased with increasing drawing temperature and EVA content. The stress at break values of the blends slightly increased with EVA whereas decreased with drawing temperature. The percent strain at break values of the blends were found to increase abruptly by increasing EVA content and drawing temperature. These changes in the mechanical properties are the indication of compatibility. The impact tests were performed only at 0&deg / C, 25&deg / C and the impact strength increased with the temperature and EVA content, but none of the samples were broken at higher testing temperatures. The effect of stabilizer was very obvious because stabilizer-free samples failed after 400 hours whereas, the samples with stabilizer resisted up to 750 hours. Elongation values of the samples decreased because of increasing brittleness by UV irradiation. We also observed chain stiffening effect by crosslinking in all samples upon UV irradiation. Thermal analysis of the blends of the drawn samples showed an increasing trend of crsytallinity with increasing drawing temperature. Increasing drawing temperature made polymer chains more flexible because of the increasing chain mobility. These flexible chains were then oriented in one direction during tensile testing and therefore uniaxial crystallization occurred. The morphology of impact and tensile tests samples were also analyzed by scanning electron microscope (SEM). The fibrillation of pure PP is higher than the fibrillation of the blends.

In this study, organo-montmorillonite (OMMT) nanocomposites containing 1%, 5%, 10% and 15% OMMT were prepared by in situ intercalative oxidative polymerization of pyrrole in the presence of OMMT. Thermal and morphological properties of the Polypyrrole(PPy)/OMMT nanocomposites were investigated by Thermal Gravimetric Analysis (TGA), X-ray Diffraction Analysis (XRD) and Scanning Electron Microscope (SEM). Electrical conductivities of composites were measured by four probe technique. Formation of PPy and its incorporation in PPy/OMMT composites were confirmed by FTIR analysis. TGA results showed that PPy/OMMT composites have outstanding thermal stability compared to that of PPy. XRD analysis revealed intercalation of PPy in the OMMT lamelles. Scanning electron micrographs demonstrated that the morphology of the PPy/OMMT nanocomposites differ slightly from that of the clay, since the modification of PPy was not significant in flaky structure of OMMT nanoparticles. Conductivity values of PPy/OMMT composites were found in the order of 10-3S/cm. Since PPy has poor processibility, Polypropylene(PP)/PPy composites were prepared in the composition range of 2-20 % PPy. Mechanical properties were investigated by tensile tests. Electrical conductivities were measured by four probe technique. Morphological characterizations were made by SEM. Young&amp / #8217 / s Modulus of PPy/PP composites increased with increasing PPy content, and addition of 2 wt % PPy to PP resulted in a dramatic decrease in the tensile strain at break of the material. Also by addition of 2 wt % PPy to PP, the tensile strength of material decreased and further increase in PPy content, tensile strength increased. Furthermore, an increase in the PPy content in PPy/PP composites resulted in an increase in conductivity. SEM micrographs revealed that as the PPy loading increases from 10% to 20% in composite system, adhered PPy particles by PP matrix were driven out of PP matrix while PP matrix oriented along the draw direction during tensile test.

Polymers having one of the three complementary colors (red, green, and blue) in the reduced state and high transmissivity in the oxidized state are key materials towards use in electrochromic devices and displays. Although many neutral state red and blue polymers were reported up to date, neutral state green polymeric materials appear to be limited. For potential application of electrochromic materials in display technologies, one should have to create the entire color spectrum and this can be only achieved by having materials with additive or subtractive primary colors in their neutral states. To obtain a green color there should be at least two simultaneous absorption bands. Although the neutral state color is of great importance, the transmittance in the oxidized state is crucial too. The materials having one of the three primary colors should also possess highly transmissive oxidized states in order to be used in commercial electrochromic device applications. Donor-acceptor molecules lead to lower band gap due to resonances that enable a stronger double bond character between the donor and acceptor units. The materials with low band-gaps produce cathodically coloring polymers due to the lower energy transition in the doped state. Moreover, donor-acceptor type materials commonly show two absorption maxima. Since donor-acceptor approach seems to be the key to the complex nature of producing these materials, novel donor-acceptor type polymers were synthesized, and electrochromic properties were investigated in detail.Additionally a solution-processable donor-acceptor type polymer was realized using method of introducing alkyl side chains in the polymer structures.

Polypropylene films are widely used in industry, especially for packaging purposes. However, these films become statically charged when they are subject to friction. The accumulation of charges in some applications can be harmful, especially for the electronic devices and can cause undesirable appearance due to the attraction of dusts. Furthermore, minimum susceptibility to mechanically induced surface damage is a desired property since scratches reduce the mechanical strength and the bright texture of the film in packaging of commercial items and limit the applications of the material. This study aims to provide antistatic character to polypropylene films by the utilization of conductive fillers which function independent of humidity and enhance their scratch resistance by means of aromatic based additives. Polypyrrole-polypropylene composites including 2%, 5%, 7% and 9% pyrrole were synthesized by chemical modification. 2% of pyrrole was adequate to provide antistatic character to the films. Moreover, they attained conductive property when the pyrrole content exceeds 7%. Polypropylene based materials containing four different compositions of 1,7-dihydroxynaphthalene, 2,3-dihydroxynaphthalene, 2,7-dihydroxynaphthalene, pphenylene diamine and hydroquinone were prepared by mechanical mixing. Scratch resistance of polypropylene films increased significantly with the insertion of additives. The material containing 2% 1,7-dihydroxynaphthalene introduced the highest enhancement by more than 60%. Moreover, mechanical analysis results showed that insertion of the additives except hydroquinone increased Young&amp / #8217 / s modulus of the polypropylene films. In addition, tensile strength and elongation at break of polypropylene films were enhanced significantly with insertion of the additives regardless of the additive type.

Poly(N-isopropylacrylamide) (PNIPAM) is a smart polymer exhibiting an inverse temperature-solubility relationship with a sharp transition at 32&deg / C in its aqueous solution. Due to its reversible thermo-responsive phase transition behavior at around body temperature, PNIPAM promise a potential for a variety of novel applications especially in biotechnology and medicine. PNIPAM can be produced by conventional polymerization methods, as well as by use of ionizing radiation, primarily by gamma which leads mainly to a residual-free crosslinked polymer. In this study, RF plasma (glow discharge) technique is used as a novel synthesis method in solid state leading to higher proportions of linear polymer. Since plasma method is an additive-/initiator-free process, a residual-free polymer is expected. To obtain a better understanding of the plasma induced solid state polymerization mechanism of NIPAM, X-ray data are used. It is found that crystalline structures of Acrylamide (AAm) and NIPAM are isomorphous. Plasma and post plasma aging effects on crystalline structure of NIPAM are followed. From the Electron Paramagnetic Resonance (EPR) investigations it is observed that post plasma polymerization of NIPAM in solid state proceed by radicalic mechanism. After determination of temperature range in which the radical formed by plasma treatment of NIPAM is highly stable, decay kinetics of the propagating radical in solid state after plasma treatment has been studied in detail.

ABSTRACT BIOSENSOR BASED ON INTERPENETRATED POLYMER NETWORK OF ALGINIC ACID AND POLY (1-VINYLIMIDAZOLE) Kartal, M&uuml / jgan M.S., Department of Chemistry Supervisor : Prof. Dr. Levent Toppare January 2008, 63 pages A new proton conductor polymer was prepared using alginic acid (AA) and poly (1-vinylimidazole) (PVI). The polymer network was obtained by mixing AA and PVI at various stoichiometric ratios, x (molar ratio of the monomer repeat units). The AA/PVI network was characterized by elemental analysis (EA) and FT-IR spectroscopy. Potential use of this network in enzyme immobilization was studied. Enzyme entrapped polymer networks (EEPN) were produced by immobilizing invertase and tyrosinase (PPO) in the AA/PVI network. Additionally, the maximum reaction rate (Vmax) and Michaelis-Menten constant (Km) were investigated for the immobilized invertase and enzymes. Also, temperature and pH optimization, operational stability and shelf life of the polymer network were examined.

Tissue engineering is an interdisciplinary field that seeks to address the needs by applying the principles of chemistry, biology and engineering for the development of viable substitutes that restore and maintain the function of human bone and cartilage tissues. In tissue engineering, scaffolds play an important role as temporary supports for the transplantation of specific cells and tissues. In this study, poly(ester-urethane)urea (PEUU) and poly(caprolactone) (PCL) scaffolds were fabricated. Scaffolds were characterized by SEM. Porosities of scaffolds vary from 67 % to 80 %. Controlled drug delivery systems release drugs at predetermined rates for extended periods. In this study / firstly poly(lactic-co-glycolicolide/tricalcium phosphate) (PLGA/TCP) and poly(L-lactide)/tricalcium phosphate (PLLA/TCP) composites loaded with Gentamicin or Vancomycin were prepared as controlled drug delivery systems for the local treatment of osteomyelitis. The release behavior of drugs were monitored by UV-VIS spectrometer. It was shown that, Vancomycin loaded samples released higher amounts of drug than the samples loaded with Gentamicin. Secondly, porous ceramic samples were coated with PLGA and PLLA and they were loaded with dexamethasone. The release behavior of samples were monitored by UV-VIS spectrometer.The cubic ceramics released higher amounts of dexamethasone than cylindrical ceramics. When the mechanical properties of porous ceramic samples were concerned, PLLA coated samples had better mechanical properties.