Thesis (Ph. D.)--Virginia Polytechnic Institute and State University, 1986. / Vita. Abstract. Includes bibliographical references (leaves 204-209). Also available via the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 2000. / Typescript. Vita. Includes bibliographical references. Also available on the Internet.

Thesis (Ph. D.)--Lehigh University, 2000. / Includes vita. Includes bibliographical references (leaves 36-43, 88-90, 139-140, 187, 238-241, 282-285, 323).

Στην παρούσα διατριβή θα παρουσιαστούν αποτελέσµατα πειραµατικών µετρήσεων που πραγµατοποιήθηκαν στο Εργαστήριο Τεχνολογίας Πλάσµατος του Πανεπιστηµίου Πατρών, ενώ συµπεριλαµβάνονται και αποτελέσµατα από την εξάµηνη παραµονή στο Istituto di Metodologie Inorganiche e Plasmi (IMIP) του Πανεπιστηµίου του Bari. Στο πρώτο κεφάλαιο (Ι) παρουσιάζονται κάποιες βασικές έννοιες του πλάσµατος και η θεωρητική ερµηνεία της συµπεριφοράς του απέναντι σε µια επιφάνεια τοποθετηµένη µέσα σε αυτό. Στην συνέχεια, στο κεφάλαιο ΙΙ θα παρουσιαστούν οι πειραµατικές διατάξεις και οι τεχνικές που χρησιµοποιήθηκαν για την πειραµατική µελέτη της αλληλεπίδρασης πλάσµατος-επιφάνειας αλλά και για τον χαρακτηρισµό του επεξεργασµένου πολυµερούς. Το επόµενο κεφάλαιο (ΙΙΙ) αναφέρεται στην σύγκριση των χαρακτηριστικών των εκκενώσεων αίγλης ηλίου µε ή χωρίς την τοποθέτηση πολυµερικού υλικού στον χώρο της εκκένωσης. Στο κεφάλαιο ΙV θα εξετασθεί ο ρόλος της συνολικής πίεσης, δηλαδή πως αλλάζουν οι οπτικές ιδιότητες της εκκένωσης σε συνθήκες διαφορετικής πίεσης, ενώ ακόµα θα παρουσιαστούν πειραµατικά αποτελέσµατα που αφορούν σε περιπτώσεις που το ηλεκτρόδιο στήριξης πολώνεται εξωτερικά ή βρίσκεται σε δυναµικό επίπλευσης. Στο πέµπτο κεφάλαιο (V) παρουσιάζεται η µελέτη του πλάσµατος µίγµατος ηλίου – οξυγόνου και αργού-οξυγόνου. Η µελέτη των ιδιοτήτων του υλικού υπό αυτές τις συνθήκες και επίσης οι επαγόµενες µεταβολές στο πλάσµα είναι ένα βήµα πιο µπροστά από την επεξεργασία µε καθαρό ήλιο, που αναπτύχθηκε στα προηγούµενα κεφάλαια καθώς συντελείται χηµική αλληλεπίδραση της αέριας φάσης µε το δείγµα. Θα αποδειχτεί ότι ο ρυθµός εγχάραξης του Πολυτερεφθαλικού Αιθυλενεστέρα είναι µεγαλύτερος σε αυτό το µίγµα και τα δείγµατα παρουσιάζουν ενισχυµένη διαβρεξιµότητα. Στο κεφάλαιο VI θα παρατεθούν συµπεράσµατα από την µελέτη των πολυµερικών επιφανειών Πολυαιθυλενίου και Πολυτερεφθαλικού Αιθυλενεστέρα µετά την επεξεργασία σε εκκενώσεις αίγλης ραδιοσυχνότητας αδρανών αερίων (Ηe, Ar) αλλά και δραστικών αερίων (ΝΗ3, Ο2). Επιχειρείται η επιβράδυνση του φαινοµένου γήρανσης των πολυµερών και η βελτίωση του υδρόφιλου χαρακτήρα τους µε την επιλογή των κατάλληλων παραµέτρων της διεργασίας. Τέλος στο Κεφάλαιο VII θα παρουσιαστούν τα συµπεράσµατα όλης της µελέτης καθώς και προτάσεις για µελλοντική έρευνα. / -

Seven β-triketimine nickel complexes C1-C7 with composition [L1-7Ni(μ-Br)2NiL1- 7][BArF4]2, where L1 = HC{C(Me)=N(2,4,6-Me3C6H2)}3, L2 = HC{C(Me)=N(2,6- Me2C6H3)}3, L3 = HC{C(Me)=N(2,4-Me2C6H3)}3, L4 = HC{C(Me)=N(2-MeC6H4)}3, L5 = HC{C(Me)=N(2,4,6-Me3C6H2)}2{C(Me)=N(2,6-Me2C6H3)}, L6 = HC{C(Me)=N(2,4,6-Me3C6H2)}{C(Me)=N(2,6-Me2C6H3)}2, and L7 = HC{C(Me)=N(2,4,6-Me3C6H2)}{C(Me)=N(2,6-iPr2C6H3)}2 were synthesized from the interaction of nickel(II) bromide with L1-7 in the presence of NaBArF (BArF = [(3,5- (CF3)2C6H3)4B]−). These complexes were then fully characterized by single-crystal X- ray diffraction (XRD), MALDI-MS and elemental analysis. From XRD results, they were found to be five-coordinated dimeric bromide-bridged species [LNi(μ- Br)2NiL][BArF]2. The geometry at nickel was distorted square pyramidal, with the τ parameter in the range 0.05 to 0.28. In addition, an enamine-diimine nickel complex C8: (L2-NiBr2) was synthesized from triketimine ligand L2 and nickel dibromide in THF, thus lacking the weakly co-ordinating BArF anion. This complex was found to be pseudotetrahedral, where only two of the three imine nitrogen atoms co-ordinated. These two nitrogen atoms and two bromine atoms formed the coordination shell of Ni(II). The six-membered ring [Co-N1-C2-C3-C4-N2] adopted a boat conformation. These complexes (C1-C7) were screened in the polymerization of ethylene monomer using methylaluminoxane (MAO) as cocatalyst in toluene as solvent at 30°C. It was observed that the steric and electronic variations conferred on the complexes by ligands L1-7 had a strong influence on the activity and also on the properties of the produced polyethylene. The catalytic activity decreased in the order C2 > C1 > C6 > C5 > C7 in the range 3229 to 271 kg PE (mol Ni)-1 h-1 for a standard set of conditions (3 bar ethylene, 30 ̊C, Al:Ni 2000), while the catalysts C3 and C4, bearing only a single ortho substituents, were inactive under identical conditions. Those conditions also had strong influences on catalyst activity and polymer properties: Al:Ni ratio in the range 500 to 3000 maximized activity at 2000. For the polymerization temperature in the range 20 to 50 °C, the activity was maximized at 30 °C, while the number of branches increased with temperature while Mn decreased due to increased chain transfer. Increasing the polymerization pressure resulted in fewer branches while the molecular weight increased because of high concentration of ethylene monomer. The effect of the nature of the counterion on polymerization activity and on the polymer properties was investigated when ethylene was polymerized by C8 (N,N-Ni) and C2 (N,N,N-Ni). It was found that polyethylene produced by C8 had significantly greater crystallinity (Tm 59 ̊C, 35 branches per 1000 carbons) than that produced by C2 (Tm 36 ̊C, 53 branches per 1000 carbons). The presence of the weakly nucleophilic counterion (BArF) as in C2, may have facilitated chain walking, resulting in a branched polymer, whereas [MeMAO]- (C8) was a slightly more nucleophilic counterion impeding chain walking. Furthermore, activity was also much greater for C2 than for C8. This is the first report of an anion effect on branching.

M.Sc. / An annual production of approximately 46 million metric tons of polyolefins worldwide, emphasizes the industrial importance of this product and the polymerisation process. Olefins are the basic building block of the petrochemical industry and are therefore readily available and cheap. Reactivity of olefins decreases from ethylene to propylene to 1-octene and makes the study of polymerisation catalysts more complex, seeing that the activity of a catalyst differs from monomer to monomer. In this study zirconocene complexes with bridged cyclopentadienyl ligands have been prepared and investigated as , possible catalysts for the polymerisation of higher aolefins. Fulvenes have been reductively coupled and used as ligands for zirconium complexes. Steric bulk of the substituents on the ligand have been increased and changes in the polymeric products have been studied. The tacticty, endgroups and chain lengths of the polyolefins have been investigated. There is currently a considerable interest in the development of 'non-metallocene' catalysts as alternatives for the polymerisation and oligomerisation of a-olefins. Chelating diamide complexes of Group 4 metals have been the focus of much attention and these compounds have shown moderate to high reactivity. However, only a few examples of the corresponding chelating alkoxides are known. In this study, alkoxide complexes of zirconium and titanium have been prepared with Schiff bases as ligands. These complexes have been evaluated as polymerisation catalysts and the products have been studied. The titanium complexes were more active than the zirconium analogues. The narrow molecular weight distribution of the polyolefins gave evidence that these catalysts are single-sited catalysts.

The inverse scattering problem is based on the scattering theory in physics, where measured data such as radiation from an object is used to determine the unique structure of the object in question. This approach has been widely successful in fields ranging from geophysics and medical imaging, to quantum field theory. In 1996 Henrik Flyvbjerg suggested that a similar approach could be used to study a reaction far from equilibrium of the self-assembly of a nucleation dependent biopolymer and, under certain conditions, uniquely determine the kinetics of the assembly. Here we use this approach to elucidate the unique structure of human islet amyloid polypeptide, also known as amylin, in-vitro. We use a systematic phenomenological analysis of the amount of monomer in fibril, of amylin, for various initial concentrations from an unstructured monomer pool. Using the assumption that nucleation is the rate-limiting step in fibril formation, we invoke mass action to develop our model. We find that the fibrillogenesis of amylin is well described by a nucleation dependent polymerization event that is characteristic of the sigmoidal shape of the reaction profile generated by our data. Furthermore, we find a second nucleation event is needed to accurately match model predictions to the observed data for the kinetic profiles of fibril formation, and the experimental length distributions of mature fibrils from in-vitro assays. This analysis allows for the theoretical determination of each step of assembly in the nucleation process. Specifically, we find the number of steps to nucleation, the size of each oligomer formed in the nucleation process, the nucleus size, and the elongation kinetics of fibrils. The secondary nucleation process is found to be a fibril dependent surface mediated nucleation event and is similar in reaction order to the primary nucleation step. Model predictions are found to be congruent with experimental assay results of oligomer populations and monomer concentration. We demonstrate that, a persistent oligomer formation is a natural and necessary consequence of nucleated fibril formation, given certain qualitative features of the kinetic profile of fibril formation. Furthermore, the modeling assumptions about monomer and fibril mass are in agreement with experiment. / Science, Faculty of / Mathematics, Department of / Graduate

This research project focuses on the synthesis of fluorescent polymers with pendant triazole-substituted coumarin side chain units. Copper(I)-catalyzed Huisgen’s 1,3-dipolar cycloaddition of alkynes with azides to form a 1,2,3-triazole ring, a typical example of “click” reaction, has been utilized for the synthesis of a novel vinyl monomer, 2-oxo-3-(4- vinyl-1H-1,2,3-triazol-1-yl)-2H-chromen-7-yl acetate 62. The monomer and its precursors were synthesised and characterized using 1D- and 2D-NMR and FT-IR. Coumarin-containing triazole polymers were synthesised using free radical polymerization. Reversible Addition-Fragmentation Chain Transfer (RAFT)-mediated polymerization was used to synthesise well defined coumarin-containing triazole polymers with moderate PDI values. The polymers were characterised using 1H-NMR and FT-IR. Modelling of the monomer precursor 61 and the monomer 62 at DFT level of approximation provided useful insights into possible conformations adopted by the monomer precursor 61 and the monomer 62. The photophysical properties of the novel monomer and the synthesised polymers were investigated in a polar solvent.

Certain aromatically substituted phenyl vinyl ethers were prepared by means of a two-step synthesis involving first, the synthesis of the corresponding beta-chlorophenetole derivative and subsequently treating this compound with flake potassium hydroxide to yield the vinyl ether. The beta-chlorophenetole derivatives prepared were: ortho-methyl-, meta-methyl-, para-methyl-, ortho-methoxy-, para-methoxy-, ortho-chloro-, and ortho-phenyl-beta-chlorophenetole. The vinyl ethers prepared were: phenyl, ortho-methyl-, meta-methyl-, and para-methyl-phenyl vinyl ether. Allyl phenyl ether was also prepared. The polymeric properties of these ethers were investigated. 2-aminovanillin was prepared from vanillin and its condensations with anthranilic acid, ortho-toluidine, ortho-phenylenediamine, and ortho-aminophenol were attempted. Diagnostic derivatives of 2-aminovanillin were also prepared: 2-acetaminovanillin, 2-aminovanillin phenylhydrazone, 2-aminovanillin 2,4-dinitrophenylhydrazone. / Science, Faculty of / Chemistry, Department of / Graduate

In order to investigate the relative merits of a selective oxidant for the degradation of natural polymers, humic acid extracts from three Alberta soil sites and three British Columbia soil sites, and two Kraft's prepared wood lignins were oxidized with 1.6 N NaOCl at room temperature (23°C) for 5 days. The oxidation products included CO₂, highly volatile acids and organic solvent soluble (OSS) products with the relative size of each fraction determined by carbon content. OSS products were characterized by Infrared (IR), Thin Layer Chromatography (TLC) and Nuclear Magnetic Resonance (NMR) techniques and identified after methylation and separation by Gas Liquid Chromatography (GLC) methods involving co-injecting authentic compounds and matching elution time and temperature of some of the components with that of the authentic compounds. Proceeding from the known chemistry of the NaOCl reaction, the CO₂ and highly volatile acid products could only be derived from the aliphatic chain or saturated ring components of humic acids or lignin and represented 66 to 82% of the products assuming no destruction of aromatic structure. Benzene carboxylic acid products were derived from the aromatic component of the starting materials. Estimates of the degree of aromaticity of the starting materials, using GLC and potentiometric titration data, were substantially less than those calculated from proposed model humic acid and lignin structures in the soils literature. An unidentified oily component was found in the oxidation products of two of the humic acid preparations. The results of this study indicated humic acid and lignin are composed of a mixed aliphatic-aromatic compound system. The relatively more mature humic acid preparations were found to be of greater aromaticity than the less mature samples. It was found 2 that NaOCl was not totally selective in differentiating Sp² from Sp³ carbon hybrids; as a result the total discrimination between aliphatic and aromatic structures was not a safe assumption. It is postulated that aromatic ring opening may occur at sites of hydroxyl group substitution on the ring structures resulting in an apparent less aromaticity and the generation / Land and Food Systems, Faculty of / Graduate