Polymer chemistry has primarily been a main chain carbon-based science, but recently the usage of inorganic polymeric materials has increased with polyphosphazene research leading the way. The credit for the increased interest in the field of phosphazene chemistry arises from the unique physical properties these materials possess. Depending upon the rigidity of the side group, the morphology of these materials is controllable. A high degree of chain mobility is exhibited by this class of polymers resulting in low glass transitions. The industrial applications of these materials are quite divergent as a result of the various morphologies and glass transitions. Possible sealant applications of these materials are apparent and have yet to be realized. These will be the focus of this thesis. The objective of this research was to characterize polyphenoxy-ethylphenoxy-phosphazene in terms of three bulk properties to determine the possibility of favorable sealant application. Investigation of the solubility parameter through solvent ingression experiments determined the solvent resistive abilities of the material. Thermogravimetric analysis set an upper temperature limit of application by determining the thermal stability of the polymer. The study of polyphenoxy-ethylphenoxy-phospazene through dynamic mechanical analysis provided insight into the vibrational damping characteristics of the material as well as establishing a lower temperature limit of possible use. Combination of the results from these various experiments enables one to make qualitative conclusions regarding favorable sealant application. / Master of Science

The use of plasma-sprayed coatings as surface pretreatments for adhesive bonding has been investigated. Increased pressure by the Environmental Protection Agency and other environmental groups has prompted the search for environmentally safe methods of pretreating metals before bonding. Plasma spraying techniques may offer an appropriate non-chemical-solution method to prepare metal surfaces for adhesive bonding. The technique has the capability of coating an adherend with almost any chemical compound. Plasma spraying techniques allow for optimization of coating characteristics such as thickness, porosity, and uniformity. Both the chemical and the physical properties of an adherend surface coating influence the durability performance in a bonded sample. Polymer and inorganic powders were plasma-sprayed on aluminum and titanium. Polymer powders included an epoxy, a polyester, a bismaleimide/cyanate ester mixture, and a bismaleimide/LARC TPI 1500 mixture. Inorganic powders, Al₂O₃, AIPO₄, MgO, and SiO₂ were sprayed on aluminum adherends, and TiO₂, TiSi₂, MgO, and SiO₂ were sprayed on titanium adherends. Inorganic coatings were sprayed at two different coating thicknesses. Surface analytical techniques, X-ray Photoelectron Spectroscopy (XPS) and Scanning Electron Microscopy/Energy Dispersive X-ray analysis (SEM/EDX), were used for the surface characterization of the plasma-sprayed adherends and failure surfaces. XPS results suggest that the chemical state of an element is sometimes altered during the plasma spraying process. SEM photomicrographs reveal various topographical differences in the sprayed coatings. All polymer powders were smooth with the exception of the bismaleimide/polyimde samples. The inorganic specimens exhibited differences in coating uniformity and surface morphology. The strength and durability of samples where the plasma-sprayed coatings were used as surface pretreatments for adhesive bonding were evaluated by loading the bonded specimens with either a peel or a shear stress and cycling the specimens through an environmental cycle that would simulate use conditions. The durability tests suggest that many of the samples prepared using thin plasma-sprayed coatings had crack growths and failure modes equivalent to reference specimens, phosphoric acid anodized aluminum and Turco 5578 treated titanium. / Master of Science

Podophyllotoxin, a naturally occurring lignan isolated from several species of Podophyllum, is used as a precursor to the clinical chemotherapeutic agents teniposide and etoposide. The biosynthesis of podophyllotoxin is not fully understood, but its optical activity, like that of most lignans, is suggestive of enzyme-mediated processes. It has been proposed that the formation of podophyllotoxin begins with stereo-controlled coupling of a hydroxy cinnamyl alcohol derivative and a substituted hydroxy Cinnamic acid, although no "coupling" enzyme has been isolated to date. Further biosynthetic modifications of the coupled compound could lead to matairesinol and/or yatein, which have been proposed as potential biological precursors of podophyllotoxin. Although no firm evidence has been obtained to date, conversion of matairesinol to yatein has been postulated. This conversion would, however, involve biosynthetic steps which, though common for hydroxycinnamates, are unprecedented at the dimeric level. Conversion of yatein to podophyllotoxin has been demonstrated, with the conversion involving a stereo-controlled cyclization and subsequent stereospecific hydroxylation. In order to investigate the biosynthesis of podophyllotoxin, leading from the postulated precursors matairesinol and yatein, a series of stereospecific deuterium-labelled matairesinol and yatein derivatives was proposed and the synthetic methodology for each compound developed. The methodology used to obtain deuterium-labelled compounds can be extended to generating tritium-labelled compounds as well. With sufficient quantities of a number of the deuterium-labelled compounds, feeding studies can now be carried out in Podophyllum plants. Isolation and analysis of podophyllotoxin, from plants fed with labelled yatein, will allow determination of the stereochemical nature of yatein cyclization. Isolation and analysis of yatein, from plants fed with labelled matairesinol, will indicate whether matairesinol is indeed a precursor to yatein (and, hence, podophyllotoxin). The information obtained from the synthesis and incorporation of such labelled compounds should then provide a clearer understanding of some interesting but, as yet, unestablished biotransformations. / Master of Science

In this thesis, the miscibility behavior of blends of polypropylene (PP) and poly(l-butene) (PB1) will be reexamined. The driving force for this study is the fact that contradictory conclusions on this subject exist in the literature. In this thesis, the glass transition behavior, morphology, spherulite growth rate and melting behavior of PP/PB1 blends with different molecular weights and tacticities have been investigated. Dynamic mechanical analysis on the melt blends of isotactic polypropylene and poly(1-butene) (it-PP/it-PB1), made of commercial high molecular weight materials, indicates a single but broad, composition dependent glass transition temperature. Crystallization studies of the a phase of it-PP in these blends show that the spherulitic growth rate of it-PP decreases with increasing it-PBl content. The melting behavior of the it-PP also depends on blend composition. However, polarizing optical microscopy reveals morphologies strongly indicating phase separation in these blends. These seemingly conflicting results are explained by further studies performed on the blends of the same it-PP with an atactic poly(i-butene) of lower molecular weight and blends of the atactic poly(1-butene) with an atactic polypropylene. From studies of the glass transition behavior, morphology and growth rate, it was found that the it-PP and the at-PP are definitely miscible with the low molecular weight at-PB1. Since commercial isotactic polypropylene and isotactic poly(1-butene) always contain a certain amount of low molecular weight fractions, it can be concluded that the single composition-dependent T _g, the growth rate depression and the changes in the melting behavior of the it-PP/it-PB1 blends arise from the miscibility of the low molecular weight fractions (both isotactic and atactic) of the it-PB1 and it-PP. Theoretical calculations utilizing the Flory-Huggins-Hildebrand theory (7) supports the above conclusions and suggests the phase separation phenomena in the it-PP/it-PB1 blends is caused by the high molecular weight it-PB1. / Master of Science

The importance of taxol as an anticancer drug lies not only in its activity in antitumor assays but also in its unique mechanism of action. Unfortunately, taxol is not water-soluble and therefore must be given in conjunction with emulsifying agents. Modifications of taxol were carried out in order to prepare water-soluble taxol derivatives. The C-2’ hydroxyl group of taxol was substituted with various groups to increase water solubility. The synthesized taxol derivatives, 2’-((3-sulfo-1-oxopropyl)oxy)taxol sodium salt, 2’-((4-((2-sulfoethyl)amino)-1,4-dioxobutyl)oxy)taxol sodium salt, and 2’-((4-((3-sulfopropyl)amino)-1,4-dioxobutyl)oxy)taxol sodium salt were more water-soluble than taxol. The synthetic pathways to these compounds are compared and discussed. / Master of Science

The generality of the [4+1] cyclopentene annulation was demonstrated by the total synthesis of (±)-pentalenene and its C-9 epimer which were prepared in a stereocontrolled manner in analogy with the synthesis of (±)-isocomene, (±)-hirsutene and (±)-pentalenic acid. The key features of this synthesis involved preparation of acid 161, its conversion to diazoketone 148, intramolecular cyclopropanation of this substance to vinylcyclopropane 163 and the vinylcyclopropane-cyclo pentene rearrangement of several derivatives of 195 to triquinanes 147, 146, 197, and 204. A detailed study of temperature, conformation, and electronic effects on the diradical scission of vinylcyclopropanes of type 195 was carried out under pyrolytic conditions. Conclusive results regarding conformational stability at C-9 were also attained and exploited in the context of stereocontrol at this center. As a result of this synthesis, several new methods of functional transformations emerged, such as the selective reduction of conjugated esters and a new method of preparation of enolethers from carboxylic acids. / Master of Science / incomplete_metadata

The polyamide poly(ε-caprolactam) or "nylon 6" is a very important fiber forming polymer which finds many applications in the carpet industry and elsewhere due to the very high strength of this fiber. However, a major drawback is its hydrophilicity. This feature influences both the surface and bulk mechanical behavior. Siloxane based macromolecules are hydrophobic, thermally stable and exhibit dimensional stability over a wide temperature range. Unlike the polyamide nylon 6, these hydrophobic materials display relatively low surface free energy. Thus, they can be used for the surface modification of nylon 6, provided a suitable adhesion or "anchoring" method is feasible. Polyamide-polydimethylsiloxane segmented or block copolymers were found to be suitable "interfacial" agents. They were synthesized by reacting aminopropyl-terminated polydimethylsiloxane (PDMS) oligomers with sebacyl chloride via an interfacial polymerization in which methylene chloride was used as the solvent or organic phase. A second diamine "chain extender" was also utilized, if desired. By varying the mole ratio of soft segment to the chain extender p-aminocyclohexylmethane (PACM-20), copolymers with various percentages of hard segments can be synthesized. Weight fractions of 2, 5, or 10% of the polyamide-poly-dimethylsiloxane block copolymers were physically melt mixed with nylon 6 in an extruder. The presence of polydimethylsiloxane on the surface of the blend was detected by determining the critical surface tensions of wetting using water as the contact angle test liquid. Such modified polyamides were successfully melt spun into fibers which displayed good mechanical properties and enhanced soil resistance. Fibers spun from these modified nylon 6 blends showed surface hydrophobicity. These modified polyamides or related materials may become technologically important in carpeting applications. Additional studies involving attempts at directly polymerizing ε-caprolactam via hydrolytic ring opening polymerization from functional polysiloxanes are also reported. In general, the structural integrity of these copolymers is less well defined. Certain procedures utilizing the aminopropyl polydimethylsiloxane initiated lactam oligomerization, followed by adipic acid chain extension produced interesting materials and should be further examined. / Master of Science / incomplete_metadata

Although Particle Beam Liquid Chromatography/Mass Spectrometry (PB LC/MS) has been shown to be useful for the identification and confirmation of nonvolatile and thermally labile compounds, evidence has been reported of response nonlinearity at low concentrations. Addition of a mobile phase additive to the HPLC mobile phase improves the linearity via a so-called "carrier effect.” A study has been done to characterize the physical and chemical phenomena involved in this carrier effect. A matrix of probes and additives were combined at 9 levels (2-1000ng) while Single Ion Monitoring (SIM) monitored the effectiveness of each additive on linearity and sensitivity. Next, the pH and concentration of the additive were varied for the 24 sample probes, ranging from pharmaceutical to environmental samples. Data is provided demonstrating the statistical effect on quantitative performance for each study. Analytical examples are shown. A mathematical model has been applied to account for the nonlinearity of PB LC/MS. For a given droplet distribution, reducing the concentration of the analyte results in reduced particle size. Application of a high pass filter to a particle distribution replicates response factor and signal obtained by PB LC/MS. In addition, a mathematical model representing the linear response upon addition of a nonvolatile buffer has been successfully applied. Graphs are presented showing the feasibility of this model. / Master of Science

The addition of the lithium dienolate of ethyl crotonate to 2-cyclopentenone was studied to determine the stereochemical outcome of this Michael addition. Proof of the stereochemistry was provided via the unambiguous synthesis and comparison of ketone 73 from norcamphor 85. / Master of Science

The mechanical performance of composite materials depends not only on the matrix and the reinforcing fiber, but also to a great extent on the fiber/matrix interfacial adhesion. The focus of this work was to study carbon fiber surface chemical and physical properties and their effects on fiber/matrix adhesion. Untreated, commercially surface treated and oxygen plasma treated PAN based carbon fibers were used for study. XPS was used to determine fiber surface chemistry. A two-liquid tensiometric method was conducted to determine fiber surface energy and its dispersion and polar components. SEM was used to examine the fiber surface topography. Commercial surface treatment increased the carbon fiber surface oxygen content and fiber surface energy primarily in the polar component. An even higher level of fiber surface oxygen functionality and polar surface energy were achieved by oxygen plasma treatment. Oxygen plasma treatment also resulted in etching and pitting of AU-4 carbon fiber surface. Carbon fibers with varying surface properties were incorporated into epoxy matrices. Single fiber fragmentation tests were carried out to evaluate the strength as well as the temperature dependence and humidity durability of interfacial adhesion. Commercially treated carbon fibers which having a higher surface oxygen content and higher surface energy clearly produced superior interfacial adhesion, relative to untreated fibers. An even greater level of adhesion was achieved with oxygen plasma treated fibers. Fiber surface roughness improved durability under elevated temperature and relative humidity conditions. The presence of sodium on the fiber surface dramatically decreased durability at high relative humidity. / Master of Science