A new analytical technique to measure the chemical composition distribution (CCD) of polyolefins, crystallization elution fractionation (CEF), was introduced in 2006 during the First International Conference on Polyolefin Characterization. CEF is a faster and higher resolution alternative to the previous polyolefin CCD analytical techniques such as temperature rising elution fractionation (TREF) and crystallization elution fractionation (CRYSTAF) (Monrabal et al., 2007). Crystallization elution fractionation is a liquid chromatography technique used to determine the CCD of polyolefins by combining a new separation procedure, dynamic crystallization, and TREF. In a typical CEF experiment, a polymer solution is loaded in the CEF column at high temperature, the polymer is allowed to crystallize by lowering the solution temperature, and then the precipitated polymer is eluted by a solvent flowing through the column as the temperature is raised. CEF needs to be calibrated to provide quantitative CCD results. A CEF calibration curve consists of a mathematical relationship between elution temperature determined by CEF and comonomer fraction in the copolymer that could be estimated by Fourier transform infrared spectroscopy (FTIR) and carbon-13 nuclear magnetic resonance (13C NMR). Different comonomer types in ethylene/α-olefin copolymers will have distinct calibration curves. The main objective of this thesis is to obtain CEF calibration curves for several different ethylene/α-olefin copolymers and to investigate which factors influence these calibration curves. A series of homogeneous ethylene/α-olefin copolymers (1-hexene, 1-octene and 1-dodecene) with different comonomer fractions were synthesized under controlled conditions to create CEF calibration standards. Their average chemical compositions were determined by 13C NMR and FTIR and then used to establish CEF calibration curves relating elution temperature and comonomer molar fraction in the copolymer.

A series of pyrene end-labeled monodisperse poly(ethylene oxide)s (PEO(X)-Py2 where X represents the number average molecular weight (Mn) of the PEOs and equals 2, 5, 10 and 16.5 K) and one pyrene mono-labeled PEO (PEO(2K)-Py1) were synthesized and characterized in solution using fluorescence. First, the end-to-end cyclization (EEC) of PEO(X)-Py2 was investigated in seven organic solvents with viscosities (η) ranging from 0.32 to 1.92 mPa•s. The classical Birks scheme was used to globally fit the pyrene monomer and excimer fluorescence decays. The fraction of pyrenes that did not form excimer (ffree) was found to increase with increasing η and Mn. This result was contrary to the assumptions made by Birks’ scheme. To account for this, ffree was assumed to represent the fraction of PEO chains other than the monolabeled polymer impurities that cannot accomplish EEC. A fluorescence blob model (FBM) was applied to handle this assumption in the process of excimer formation for the PEO(X)-Py2 samples in solution. The radius of a blob, Rblob, in organic solvents was determined according to the results retrieved from the FBM. To quantitatively account for the existence of pyrene impurity in pyrene-labeled macromolecules, known amounts of PEO(2K)-Py1 were added into a PEO(2K)-Py2 solution and the fluorescence decays were fitted globally according to the Birks scheme and “model free” (MF) analysis to verify the validation of the MF analysis. The MF analysis was then applied to determine the amounts of 1-pyrenebutyric acid (PyBA) that had been added to a solution of pyrene end-labeled fourth generation dendritic hybrid (Py16-G4-PS). The results demonstrated that the contribution from unwanted fluorescent species could be isolated and quantitatively accounted for by fitting the fluorescence decays of the pyrene monomer and excimer globally with the MF analysis. Since the PEO(X)-Py2 samples form hydrophobic pyrene aggregates in aqueous solution, a sequential model (SM) was proposed to characterize the pyrene excimer formation of PEO(X)-Py2 in water at different polymer concentration (CP). The capture distance over which the pyrenyl end-groups experience hydrophobic forces in water was determined by assuming that the end-to-end distances of the PEO(X)-Py2 samples adopt a Gaussian distribution and that the fraction of pyrenes that are aggregated (fE0) determined by the sequential model corresponds to the fraction of PEO(X)-Py2 chains whose end-to-end distance is smaller than the hydrophobic capture distance. Since a surfactant can interact with a hydrophobically modified water-soluble polymer in aqueous solution, the interactions taking place between PEO(X)-Py2 and sodium dodecyl sulfate (SDS) were investigated at a low PEO(X)-Py2 concentration. The pyrene monomer and excimer fluorescence decays of the PEO(X)-Py2 and SDS solutions were acquired at various SDS concentrations and globally fitted according to the MF analysis to retrieve the parameters that described the kinetics of pyrene excimer formation. At high SDS concentrations above the critical micelle concentration (CMC), the pyrene end-groups of the short-chain samples (PEO(2K)-Py2 and PEO(5K)-Py2) were incorporated inside the same micelle and excimer was formed intramolecularly, while most pyrene groups of the long-chain samples (PEO(10K)-Py2 and PEO(16.5K)-Py2) were isolated into different micelles. Lastly, both the rheological properties and fluorescence behavior of a pyrene-labeled hydrophobically-modified alkali-swellable emulsion (Py-HASE) polymer in basic aqueous solution with SDS were studied. Furthermore, a joint experimental setup that combined a rheometer and a steady-state fluorometer was applied to investigate at the molecular level the effect that a shearing force had on the polymeric network. However, despite the dramatic decrease in solution viscosity with increasing shear rate, no change in the fluorescence spectra was detected, suggesting that changes in the polymeric network that affected the balance of intra- versus intermolecular pyrene associations did not impact the process of excimer formation. Together the experiments described in this thesis represent the broadest set of examples found in the scientific literature where information on the dynamics and level of association of pyrene-labeled polymers has been retrieved through the quantitative analysis of the fluorescence decays acquired with pyrene-labeled polymers in solution.

This study was conducted to investigate the effects of component concentrations and addition order of the components, on the final properties of ternary nanocomposites composed of poly(ethylene terephthalate), organoclay, and an ethylene/methyl acrylate/glycidyl methacrylate (E-MA-GMA) terpolymer acting as an impact modifier for PET. In this context, first, the optimum amount of the impact modifier was determined by melt compounding binary PET-terpolymer blends in a corotating twin-screw extruder. The amount of the impact modifier (5 wt. %) resulting in the highest Young&rsquo / s modulus and reasonable elongation at break was selected owing to its balanced mechanical properties. Thereafter, by using 5 wt. % terpolymer content, the effects of organically modified clay concentration and addition order of the components on ternary nanocomposites were systematically investigated. Mechanical testing revealed that different addition orders of the materials significantly affected mechanical properties. Among the investigated addition orders, the best sequence of component addition (PI-C) was the one in which poly(ethylene terephthalate) was first compounded with E-MA-GMA. Later, this mixture was compounded with the organoclay in the subsequent run. Young&#039 / s modulus of not extruded pure PET increased by 67% in samples with 5 wt. % E-MA-GMA plus 5 wt. % clay loading. The highest percent elongation at break was obtained as 300%, for the addition order of PI-C, with 1 wt. % clay content, which is nearly 50 fold higher than that obtained for pure PET. In X-ray diffraction analysis, extensive layer separation associated with delamination of the original clay structure occurred in PI-C and CI-P sequences with both 1 and 3 wt. % clay contents. X-ray diffraction patterns showed that, at these conditions exfoliated structures resulted as indicated by the disappearence of any peaks due to the diffraction within the consecutive clay layers.

Polymeric composites are any of the combinations or compositions that comprise two or more materials as separate phases, at least one of which is a polymer. By mixing a polymer with another material, such as glass, carbon, or another polymer, it is often possible to improve the desired properties of the polymer. In this study, ternary composites were prepared by using recycled poly(ethylene terephthalate), PET as the matrix material, short glass fiber (SGF) as the reinforcing filler and thermoplastic elastomer as the impact modifier. Bottle grade recycled PET was mixed in a twin screw extruder with a thermoplastic elastomer which is a terpolymer of ethylene/methyl acrylate/glycidyl methacrylate (E-MA-GMA), and E type short glass fiber is fed to the extruder from a side feeder. During this study, recycled PET was mixed with from 10 to 50 wt. % elastomer, and SGF was added to the system in the range from 10 to 40 % by weight. Processing parameters were kept constant during extrusion. The composites were then compression molded for characterization experiments. The produced composites were characterized in terms of their mechanical and thermal properties and morphologies. Melt behavior and fiber length distribution of the composites were also determined for selected composites. In ternary systems with 10 % elastomer, highest tensile strength values were observed. High tensile and flexural moduli values were obtained for the composites containing 20 % elastomer. Results of impact tests designated that impact strength increased significantly after 30 % elastomer content. Thermal analyses of the composites were done by using a DSC (Differential Scanning Calorimeter). Degree of crystallinity of ternary system decreased with increasing elastomer content, but melting points of the composites were not affected significantly. SEM micrographs showed that the adhesion between the matrix and fiber increased considerably with elastomer addition.

Ethylene (C2H4) is a very simple molecule, a gas, and has numerous effects on the growth, development and storage life of many fruits, vegetables and ornamental crops. In higher plants, ethylene is produced from L-methionine in essentially all tissues and ACC Synthase and ACC Oxidase are the two key enzymes in the biosynthesis of ethylene. The objective of the present study was to transform tobacco (Nicotiana tabacum L. cv. Samsun) plant with partial sequence of torenia acc oxidase gene in antisense and sense orientations via Agrobacterium-mediated gene transfer system, and to analyze its effect on ethylene production in transgenic plants. Six antisense and seven sense T0 putative transgenic lines were obtained and were further analyzed with several assays. Leaf disc assay and chlorophenol red assay under selection (75 mg/L kanamycin) revealed positive results compared to the non-transformed plant. T1 generations were obtained from all putative transgenic lines. PCR analysis and Northern Blot Hybridization results confirmed the transgenic nature of T1 progeny. Furthermore, ethylene amount produced by flowers were measured with gas chromatography, which resulted in an average of 77% reduction in S7 line and 72% reduction in A1 line compared with the control flowers. These results indicated that, transgenic tobacco plants carrying torenia acc oxidase transgene both in antisense and sense orientations showed reduced ethylene production thus a possibility of flower life extension.

In this research, oxidative dehydrogenation of ethane to ethylene was studied over Cr-O and Cr-V-O mixed oxide catalysts through steady-state and dynamic experiments. The catalysts were prepared by the complexation method. By XRD, presence of Cr2O3 phase in Cr-O / and the small Cr2O3 and V2O4 phases of Cr-V-O were revealed. In H2-TPR, both catalysts showed reduction behaviour. From XPS the likely presence of Cr+6 on fresh Cr-O was found. On Cr-V-O, the possible reduction of V+5 and Cr+6 forms of the fresh sample to V+4, V+3 and Cr+3 states by TPR was discovered through XPS. With an O2/C2H6 feed ratio of 0.17, Cr-O exhibited the highest total conversion value of about 0.20 at 447&deg / C with an ethylene selectivity of 0.82. Maximum ethylene selectivity with Cr-O was obtained as 0.91 at 250&deg / C. An ethylene selectivity of 0.93 was reached with the Cr-V-O at 400&deg / C. In the experiments performed by using CO2 as the mild oxidant, a yield value of 0.15 was achieved at 449&deg / C on Cr-O catalyst. In dynamic experiments performed over Cr-O, with C2H6 pulses injected into O2-He flow, the possible occurrence of two reaction sites for the formation of CO2 and H2O was detected. By Gaussian fits to H2O curves, the presence of at least three production ways was thought to be probable. Different from Cr-O, no CO2 formation was observed on Cr-V-O during pulsing C2H6 to O2-He flow. In the runs performed by O2 pulses into C2H6-He flow over Cr-V-O, formation of CO rather than C2H4 was favored.

Ethylene hydrogenation on Ni(111) / equilibrium geometry calculations for Ni2 dimer, Ni13 and Ni55 nanoclusters / and ethylene adsorption on Ni(100), Ni(111), Ni2, and Ni13 were studied quantum mechanically by means of energetic and kinetic differences. Ethylene hydrogenation on Ni(111) was simulated by use of DFT/B3LYP/6-31G** formalism. The reaction mechanism was mainly composed of three elementary steps. Firstly, ethylene adsorption on bare Ni(111) surface was performed. Second step and third step were the formation of ethane from adsorbed ethylene by use of two types of hydrogen atom, bulk and surface. During the hydrogenation reaction of ethylene on Ni(111), bulk hydrogen atom, representing for hydrogen atoms emerging from the bulk of Ni metal, was determined to be rather reactive than surface hydrogen atom, as suggested by experimental findings. Small Ni clusters, Ni2 and Ni13, were investigated by means of DFT/B3LYP/modified-6-31G**. Equilibrium geometry calculations resulted in Ni2 binding energy of 1.078eV/atom, showing good agreement with experimental value. Ni13 was found to have a structure of icosahedral, suggested experimentally, and binding energy of 2.70eV/atom. Ni55 was, also, studied by semi-empirical PM3 formalism, resulting in expected icosahedral structure. Finally, DFT/B3LYP/6-31G** investigation of ethylene adsorption was performed on Ni(111), Ni(100) and Ni13 surfaces which were selected according to their nickel atom coordination numbers of 9, 8 and 6, respectively. Comparison of adsorption energies of -18.00kcal/mol, -31.4kcal/mol and -43.42kcal/mol, respectively, indicated that the change in energies for ethylene adsorption on different nickel surfaces was directly proportional to coordination number of the nickel atoms constructing the surfaces.

Semiconductor quantum dots (QDs) and gold nanoparticles (AuNPs) have gained tremendous attention in the last decade as a result of their size-dependent spectroscopic properties. These nanoparticles have been a subject of intense study to bridge the gap between macroscopic and atomic behavior, as well as to generate new materials for novel applications in therapeutics, biological sensing, light emitting devices, microelectronics, lasers, and solar cells. One of the most promising areas for the use of these nanoparticles is in biotechnology, where their size-dependent optical properties are harnessed for imaging and sensing applications. However, these nanoparticles, as synthesized, are often not stable in aqueous media and lack simple and reliable means of covalently linking to biomolecules. The focus of this work is to advance the progress of these nanomaterials for biotechnology by synthesizing them, characterizing their optical properties and rendering them water-soluble and functional while maintaining their coveted optical properties. QDs were synthesized by an organometallic chemical procedure that utilizes coordinating solvents to provide brightly luminescent nanoparticles. The optical interactions of these QDs were studied as a function of concentration to identify particle size-dependent optimal concentrations, where scattering and indirection excitation are minimized and the amount light observed per particle is maximized. Both QDs and AuNPs were rendered water-soluble and stable in a broad range of biologically relevant conditions by using a series of ligands composed of dihydrolipoic acid (DHLA) appended to poly(ethylene glycol) methyl ether. By studying the stability of the surface modified AuNPs, we revealed some interesting information regarding the role of the surface ligand on the nanoparticle stability (i.e. solubility in high salt concentration, resistance to dithiothreitol competition and cyanide decomposition). Furthermore, the nanoparticles were functionalized using a series of bifunctional ligands that contain a dithiol group (DHLA) for surface binding, a PEG segment to instill water-solubility and a terminal functional group for easy bioconjugation (i.e. NH 2 , COOH, or biotin). Finally, a sensing application was demonstrated to detect the presence of microbial DNA (unmethlylated CpG) by using Toll-like receptor 9 proteins as the recognition components and the QDs as the transduction elements via Förster Resonance Energy Transfer.

Diss. (sammanfattning) Umeå : Sveriges lantbruksuniversitet, 2005. / Härtill 4 uppsatser.

Thesis (M. Sc.)--Carleton University, 2004. / Includes bibliographical references (p. 127-130). Also available in electronic format on the Internet.