ABSTRACT CHARACTERIZATION OF SERPENTINE FILLED POLYPROPYLENE Can, Semra Ph.D., Department of Polymer Science and Technology Supervisor: Prof. Dr. Teoman Tin&ccedil / er March 2008, 158 pages In this study, the aim is to prepare polypropylene (PP)/serpentine composites and study their mechanical, thermal and morphological properties. Another objective is to explore whether it is possible to have PP/serpentine nanocomposites with melt intercalation method by using the advantage of the layer silicate structure of serpentine. The most widely used fillers in PP are talc and mica which belong to the phyllosilicates group of silicate minerals. So far, there has been almost no study employing serpentine as filler in either any polymers or PP, although it also belongs to the same group of minerals as talc and mica. Accordingly, it was planned to divide the work into the study of two groups. In group 1, for the compositions with 2, 5, 10 and 20 wt% serpentine, the particulate filler effects of serpentine both alone and in the presence of surface treatments with hydrochloric acid (HCl) and silane coupling agent (SCA) were investigated. The most impressive results in terms of static and dynamic mechanical properties were achieved with SCA rather than HCl. When the effect of serpentine without any treatment is considered, reinforcing effect of it can easily be observed without deteriorating the composite properties even at high filler loadings. In group 2, the nanofiller effects of serpentine in 2 and 5 wt% filled compositions by modification of both the filler and the matrix were aimed to be examined with melt intercalation method. In addition to HCl and SCA treatments, maleic anhydride grafted polypropylene (PP-g-MA) and quaternary ammonium salt (QAS) of cetyl-trimethyl-ammonium bromide were used as compatibilizer and intercalating agent, respectively. While the amount of QAS was kept constant, different percentages of compatibilizer were employed. The presence of QAS and PP-g-MA further improved the properties with respect to group 1 members. Interestingly, the percentage strain at break values did not decrease as much as group 1 compositions with the same filler content. It can be concluded that partial intercalation of group 2 compositions was achieved, according to the X-ray and TEM results. Keywords: Serpentine, PP/serpentine composites, SCA, PP-g-MA, serpentine nanocomposites

The aim of this study was to improve electrical properties of conductive polymer composites. For this purpose, various studies were performed using different materials in this dissertation. In order to investigate the effect of alternative composite preparation methods on electrical conductivity, nylon 6/carbon black systems were prepared by both in-situ polymerization and melt-compounding techniques. When compared with melt compounding, in-situ polymerization method provided enhancement in electrical conductivity of nylon 6 composites. Furthermore, it was aimed to improve electrical conductivity of polymer composites by modifying surface chemistry of carbon black. 1 wt. % solutions of 3-Aminopropyltriethoxysilane and formamide were tried as chemical modifier, and treated carbon black was melt mixed with low-density polyethylene (LDPE) and nylon 6. According to electron spectroscopy for chemical analysis (ESCA), chemicals used for surface treatment may have acted as doping agent and improved electrical conductivity of polymer composites more than untreated carbon black did. Formamide was more effective as dopant compared to the silane coupling agent. In order to investigate electromagnetic interference (EMI) shielding effectiveness and dielectric properties of conductive polymer composites, 1, 2 and 3 wt. % solutions of formamide were tried as chemical modifier and treated carbon black was melt mixed with poly(ethylene terephthalate) (PET). Composites containing formamide treated carbon black exhibited enhancement in electrical conductivity, EMI shielding effectiveness and dielectric constant values compared to composites with untreated carbon black. In order to enhance electrical conductivity of polymer composites, the selective localization of conductive particles in multiphase polymeric materials was aimed. For this purpose, carbon nanotubes (CNT) were melt mixed with polypropylene (PP)/PET. Grinding, a type of solid state processing technique, was applied to PP/PET/CNT systems to reduce the average domain size of blend phases and to improve interfacial adhesion between these phases. Grinding technique exhibited improvement in electrical conductivity and mechanical properties of PP/PET/CNT systems at low PET compositions. To investigate application potential of conductive polymer composites, polyaniline (Pani)/carbon nanotubes (CNT) composites were synthesized and electrochemical capacitance performances of these systems, as electrode material in electrochemical capacitors, were studied. Polyaniline/carbon nanotubes composites resulted in a higher specific capacitance than that of the composite constituents. Pseudocapacitance behavior of Pani might contribute to the double layer capacitance behavior of nanotubes. Additionally, as an alternative to Pani/CNT systems, polyaniline films were deposited on treated current collectors and electrochemical capacitance performances of these electrode systems were investigated. The highest specific capacitance of polyaniline/carbon nanotubes composites was 20 F/g and this value increased to 35.5 F/g with polyaniline film deposited on treated current collector.

A novel electrically conducting polymer, poly(2-dodecyl-4,7-di(selenophen-2-yl)benzotriazole) (Poly(SBT)), containing selenophene as a strong donor and benzotriazole as a strong acceptor group was synthesized by electrochemical polymerization. Homopolymerization and copolymerization ( in the presence of 3,4-ethylenedioxythiophene (EDOT) ) was achieved in acetonitrile/ dichloromethane(95/5 v/v) with 0.1M tetrabutylammonium hexafluorophosphate (TBAPF6). The electrochemical and optical properties of homopolymer and copolymer were investigated by Cyclic voltammetry, UV-Vis, near IR Spectroscopy. Cyclic voltammetry and spectroelectrochemistry studies demonstrated that homopolymer can be reversibly reduced and oxidized (both n- and p-doped) between -1.9 V and 1.4 V, at a scan rate of 100 mV/s. Optical contrast was calculated as 32% and 56% with a switching time of 2.4 s and 0.4 s at 511 and 1200 nm respectively. Poly(SBT) exhibits a &amp / #955 / max value of 511nm and a band gap of 1.67eV.

The synthesis of black conducting polymer (CP) and/or crosslinked polymers (CLP) and/or radical ion polymer (RIP) and/or white polymers (WP) and/or orange polymer (OP) were achieved by using KOH with TCP, pyrrole and thiophene via microwave energy in a very short time interval. Polymerizations were carried out by constant microwave energy with different time intervals varying from 1 to 25 min / or at constant time intervals with variation of microwave energy from 90 to 900 watt / or varying the water content from 0, 0.5 to 5 ml at constant time intervals and microwave energy, or at constant time interval, water content, microwave energy with variation of amount of KOH 0.03 mol to 6x10-4 mol. The effects of heating time, microwave energy, water content and amount of KOH on the percent conversion and the polymer synthesis were also investigated.White, orange polymers and radical ion polymers were characterized by FTIR (Fourier Transform Infrared), 1H-NMR (Proton Nuclear Magnetic Resonance), 13C-NMR (Carbon-13 Nuclear Magnetic Resonance), TGA/ FTIR (Thermal Gravimetric Analysis / Fourier Transform Infrared), DSC (Differential Scanning Calorimeter), SEM (Scanning Electron Microscope), ESR (Electron Spin Resonance), GPC (Gel Permeation Chromatography), UV-Vis (UV-Visible Spectroscopy) and Light Scattering. Conducting and crosslinked polymers were characterized by FTIR, TGA/ FTIR, DSC, SEM, ESR, XRD (Powder Diffraction X-Ray) and conductivity.

Thrombus formation and blood coagulation is a major problem associated with blood contacting products such as catheters, vascular grafts and artificial hearts. An intense research is being conducted towards the synthesis of new hemocompatible materials and mdifications of surfaces with biological molecules. In this study, polyurethane (PU) films were synthesized in medical purity from diisocyanate and polyol without using any other ingredients and the chemical, thermal and mechanical properties were characterized by solid state NMR, FTIR, GPC, mechanical tests, DMA and TGA. The surfaces of PU films were modified by covalent immobilization of different molecular weight heparins / low molecular weight heparin (LMWH) and unfractionated heparin (UFH) and these surfaces were examined by ESCA, ATR-FTIR, AFM and contact angle goniometer. Cell adhesion studies were conducted with whole human blood and examined by SEM. The effects of different types of heparins on blood protein adsorption and on platelet adhesion were analyzed by electrophresis and SEM, respectively. The surfaces of the UFH immobilized polyurethane films (PU-UFH) resulted in lesser red blood cell adhesion in comparison to LMWH immobilized polyurethane film surfaces (PU-LMWH). When the PU films were treated with blood plasma, the surfaces modified with two different heparin types showed a clearly different protein adsorption behavior especially in the early stage of blood plasma interaction. PU-LMWH samples showed about three times less protein adsorption compared to PU-UFH samples. The morphologies of platelets adhered on material surfaces demonstrated differences / such as PU-UFH had clusters with some pseudopodia extensions, while PU-LMWH had round shaped platelets with little clustering. PU surfaces modified by immobilization of LMWH and UFH, demonstrated promising results for the improvement of non-thrombogenic devices and surfaces.

ABSTRACT DESIGN, SYNTHESIS AND ELECTROPOLYMERIZATION OF A NEW CHEMILUMINESCENT TERTHIENYL SYSTEM Atilgan, Nurdan M.Sc. Department of Chemistry Supervisor: Prof. Dr. Ahmet M. &Ouml / nal Co-Supervisor: Assist. Prof. Dr. Atilla Cihaner September 2008, 57 pages A novel monomer, possessing chemiluminescence properties, 5,7-di-ethylenedioxythiophen-2-yl-2,3-dihydro-thieno[3,4-d]pyridazine-1,4-dione (ETE-Lum) was synthesized. Chemiluminescence properties of ETE-Lum were investigated in alkaline water solution in the presence of H2O2 and this reaction was catalyzed by Fe+3 ion and blood. This study submits a new opportunity to investigate forensic and analytical application instead of 5-amino-2,3-dihydro-1,4-phthalazine-dione (luminol). Response of other metalic cations was also investigated under the same reaction conditions. Electrochemical properties of ETE-Lum were studied in 0.1 M acetonitrile/tetrabutylammonium perchlorate solvent system containing BF3-Et2O and also in neat BF3-Et2O solution. In addition, the corresponding polymer film of ETE-Lum (PETE-Lum) was synthesized successfully via repetitive cycling by cyclic voltammetry and its electrochemical properties were investigated in a monomer-free electrolyte solution. Spectroelectrochemical behavior of the polymer film on indium tin oxide working electrode was also investigated by recording the electronic absorption spectra, in-situ, in monomer-free electrolyte solution at different potentials. Furthermore, spectroelectrochemical studies revealed that PETE-Lum had an electronic band gap of 1.66 eV. The results of electrochemical and electroluminesence measurements indicated that chemiluminecent unit of monomer was protected during polymerization. In addition, PETE-Lum film was found to be electrochemiluminescence active, maintaining its activitiy over 1000 cycles.

In the first part of this dissertation, poly(methylsilyne) was produced both in small and large-scales. In the small-scale, the aim was to synthesize the polymer by electrochemical polymerization of methyltrichlorosilane at a constant potential of -6 V supplied by batteries, using sodium dodecyl sulfate (SDS) as the supporting electrolyte. The polymer was characterized by 1H-NMR, FTIR, UV-Visible Spectroscopy and GPC in addition to its distinctive yellow color. The yellow color and the 1H-NMR, FTIR, UV-Visible and GPC results proved that poly(methylsilyne) was produced successfully in small-scale. In the second part of the synthesis, the objective was to scale-up the electrochemical synthesis of poly(methylsilyne) while investigating the effects of the parameters like the electrode, solvent and supporting electrolyte types, monomer/solvent ratio and reaction time on the synthesis. Although successful results were obtained in large-scale synthesis with acetonitrile and SDS, the problems with the reproducibility of the synthesis were solved using a system containing 1.2-dimethoxyethane (DME) and tetrabutylammonium perchlorate (TBAP). In the second part of the dissertation, the aim was to prepare polypropylene/silicon-based preceramic polymer blends and to characterize them in terms of flammability, thermal and mechanical properties and morphologies. In order to investigate the effect of the silicon-based preceramic polymers, two different polymers were used: poly(methylsilyne) (PMSy) and allylhydridopolycarbosilane (SMP-10) where the latter was a commercially available silicon carbide precursor. Triphenylphosphate (TPP) and a metal complex were also used in polypropylene based composites to gain a synergy with the silicon containing polymers. The polymer composites were prepared using a twin-screw extruder and molded in an injection molding machine. As a result of the flammability tests, it was seen that in order to achieve a significant decrease in the flammability of polypropylene, at least 20 wt% additive was needed. Furthermore, it was observed that the most significant improvement in flame retardancy was obtained in PP/10SMP/5TPP/5M sample containing 10 wt% SMP-10, 5 wt% TPP and 5 wt% metal complex with a limiting oxygen index (LOI) value of 23.5%. This was explained by the synergy obtained by SMP-10, TPP and the metal complex. With the addition of these silicon containing polymers, thermal properties of the composites increased to a great extent. For the mechanical properties, it was seen that impact strength of the composites significantly increased with the addition of SMP-10, PMSy and TPP.

Poly(N-vinylcaprolactam), PNVCL, is a nonionic, nontoxic, water soluble, thermally sensitive and biocompatible polymer. It contains hydrophilic carboxylic and amide groups with hydrophobic carbon-carbon backbone chain so its hydrolysis does not produce small amide compounds which are often not desired for biomedical applications. Moreover PNVCL possesses lower critical solution temperature, (LCST) in the range of physiological temperature (32-34 oC). These properties make the polymer suitable for use in some biotechnology applications such as implantation of artificial organs and tissues, purification of enzymes, proteins and living cells, and in drug release systems. In this study PNVCL was synthesized by free radical polymerization with solution technique. Polymerization was done at different temperatures for different time periods in an oil bath. The activation energy for polymerization was found from Arrhenius plot as 108.4 kJ/mol. Polymer was characterized by FT-IR, 1H-NMR and 13C-NMR, DSC, TGA and XRD techniques. FT-IR and NMR measurements confirmed that the polymerization proceeded through the vinyl group.

This study was aimed to synthesize low molecular weight hydroxyl terminated polyurethane acrylate polymers that can be used in biomedical applications. Acrylate end capping via inter-esterification reaction was successfully achieved with the methacryloyl chloride addition to the hydroxyl ends of the polyurethane at low temperatures. Isocyanate terminated polyurethane acrylates were also synthesized for the sake of comparison. TDI, HDI and MDI were used as diisocyanates for urethane synthesis and they were end capped with MMA and HEMA. Nature of the monomers used had an effect on thermal, morphological, and rheological properties that were interpreted in terms of the level of hydrogen bonding and degree of phase separation. Synthesized polymers were characterized by NMR, FTIR-ATR, DSC, TGA, GPC, Mass Spectroscopy, SEM and rheometry. In the literature, polyurethane acrylate polymers have been synthesized from the isocyanate terminated polyurethanes in which the urethane chains were ended with isocyanate groups. However, the toxicity of the isocyanate groups limited their biomedical applications especially in prosthetic dentistry as a soft lining material. Therefore, it is inevitable to explore the cytotoxicity of polyurethane acrylate polymers. For this purpose, silver nanoparticles that have an average particle size of 40 nm, were incorporated to the synthesized polymers. This addition, which intends to improve the degree of cytotoxicity, was successful to a certain extent.

Vinylesters are termosets resins that have reactive double bond at the chain ends. They are produced by the reaction of various epoxies and acrylic acids by step growth polymerization. Vinylester chains are oligomers with molecular weight from 600 to 1200 g/mol. The resin viscosity is very high / therefore, diluent is used for easy application. The generally used diluent is styrene with, reactive double bonds to form a crosslink between the chains. The diluted resin viscosities are between 200 &amp / #8211 / 2000 cps. Peroxide initiators are used for network formation. The mechanical properties of vinylester resin are enhanced with reinforcements such as glass fiber, carbon fiber, Kevlar or nanoparticules to make composites. Various molecular weights of vinylester resins were synthesized and the samples were prepared with different styrene contents. The effects of the styrene content, temperature and molecular weight on the viscosity were measured and examined. The main effects were determined as styrene content and temperature, while the effect of molecular weight is negligible. The resins were characterized with IR and NMR spectroscopy. The molecular weights were determined by theoretical calculations, titration and H-NMR spectroscopy. Peroxide initiators were used to cure the resins with the cobalt complex accelerator. The resins were post-cured at different temperatures. The completion of the curing was monitored by the disappearance of the carbon-carbon double bonds of methacrylate (943 cm-1) and styrene (910 cm-1), by FT-IR spectrum. The effects of styrene content, post-cure conditions, and molecular weight on the mechanical properties were discussed. The glass transition temperatures were determined by DSC and DMA. The crosslink densities and rheological properties were determined by creep test. The important properties of vinylester resins, which are modulus, tensile and flexural strength, shrinkage, water absorption, glass transition temperature, HDT values and impact strength were investigated.