In the study of the cyclodehydrogenation of 12-(3-methylphenyl)benz[a]anthracene, Zajac pointed out that the hydrocarbon might undergo ring closure at either of the ortho positions of the phenyl ring. These positions are not equivalent with respect to the methyl group and ring closure might yield either 2-methyl dibenzo[a,l]pyrene or 4-methyldibenzo[a,l]- pyrene or a mixture of both isomers. When the compound, 12-(J-methylphenyl)benz[a]-anthracene, was dehydrogenated only one isomer was isolated. The isomer which was isolated could be either of the two possibilities. Therefore, it was decided to synthesize 2-methyldibenzo[a,l]pyrene unequivocally. By comparing the physical properties of the compound synthesized unequivocally with those of the compound from the cyclodehydrogenation of 12-(3-methylphenyl)benz[a]anthracene it can be determined which isomer was isolated by Zajac. Therefore, 12-{ 2-chloro-5-methylphenyl)benz[a]-anthracene was synthesized; this compound could then be cyclodehydrohalogenated to the corresponding 2-methyldibenzo[a,l]]pyrene. Using potassium hydroxide-quinoline and alkoxides led only to the recovery of starting material or to the destruction of it, depending on whether the reaction conditions were mild or drastic. Aluminum chloride destroyed the starting material in reaction time as short as five minutes. Stannic chloride destroyed only part of the starting material. An aluminum chloride-stannic chloride mixture also destroyed the starting material. In none of the experiments mentioned could the presence of 2-methyldibenzo[a,l]pyrene be detected. Although the right conditions for the cyclodehydrohalogenation were not found, the data obtained during the gas chromatographic studies are very valuable because it can be used for the other phases of the work being done in This Laboratory. / Master of Science

no abstract provided by author / Master of Science

The diversity of adhesive/adherend pairs has created innumerable unique combinations of thermodynamic, kinetic, chemical, physical and rheological contributions with which to explain adhesion processes. So complex are the interrelationships of these contributions to the overall composite system that little information can be extracted about the role of the adhesive properties themselves. This study attempts to simplify the number of variables influencing the strength of adhesive joints by employing a series of styrene-isoprene-styrene linear triblock copolymers as model hot-melt adhesives for titanium 6-4 alloy substrates. The block copolymer samples have narrow molecular weight distributions and styrene contents ranging from 20 to 60% by weight. For these systems a finite number of "dominant" variables are defined including 1) adherend wettabf lity, 2) mechanical properties, 3) rheology, 4) adhesive and adherend contamination, and 5) temperature-pressure cycles for joint formation. Characterization of the block copolymer series in each of these areas is presented. Copolymer morphology emerges as an important variable affecting the material and adhesive properties of these systems. The adhesive joints prepared from these samples are simple lap shear specimens. Comparative joint strengths and joint fracture energies of the series of copolymer adhesives are rationalized in terms of styrene content, styrene domain connectivity and domain orientation. Scanning electron microscopy is employed to examine the surface characteristics of the fractured adhesives. Distinctive failure features are associated with the styrene content and dissipative capacities of the adhesives. / Master of Science

In this study the applicability of Carbon-13 NMR and XPS to the detection of chemical changes in a solid composite rocket propellant was studied. Storage at elevated temperatures was used to simulate the propellant ageing process. In the XPS analysis, changes in the sources for the N(1s) and Cl(2p) photopeaks were investigated. The propellant loses "organic" nitrogen as it ages. Changes in the amount of Cl⁻ present are in doubt due to instrumental considerations. Carbon-13 NMR analysis showed that with increasing age of a sample there is a corresponding loss of vinylic groups from the binder. This loss of vinylic character is preferential in the order pendant>>cis>trans. Due to the long scan times involved this method is of limited utility for ageing analysis. / Master of Science

The use of water based adhesive primers in enhancing the durability of aluminum adhesively bonded with epoxy was studied. The effects of the thickness of both the aluminum oxide surface layer and the primer layer on bond durability were established. 5052 aluminum alloy was oxidized by phosphoric acid anodization prior to primer coating. The oxide layer thickness was controlled mainly by changing anodization voltage and directly measured using a HR-SEM (high resolution scanning electron microscope). The oxide layer was also examined by AES (Auger electron spectroscopy) and XPS (X ray photoelectron spectroscopy). The surface oxide layer was porous and the thickness varied from 0.2 to 2.2 μm. The anodized aluminum substrates contained 3 atomic % of phosphorus and were coated with several solid concentrations of water based adhesive primers. These primers contained non-reactive polyurethane emulsions, and were dried at room temperature. The primer thicknesses were measured by ellipsometry. The primer penetrated into the aluminum oxide pores, confirmed by observing the primer surface after the aluminum oxide was removed by dissolving in dilute NaOH aqueous solution. All adhesive bonding was done using the wedge test configuration with a structural epoxy adhesive, Naviloc® XY 0210, which was cured for 30 min. at 180°C. The wedge samples were immersed in 80°C water and crack lengths were monitored as a function of time. Both the initial crack length and crack propagation were minimized when the primer thickness was a little less than the aluminum oxide thickness. In a separate study, the aluminum oxide surfaces were aged in hot water or hot humid environment before bonding. The crack lengths of the aged samples for both 60°C water immersion and 70°C ≥95 %R.H. conditions were similar to those of non-aged sample. On the other hand, when the samples were aged in 80°C water, the oxide was hydrated and the crack length increased. The locus of failure also changed from cohesive failure in the adhesive for the lower temperature aged samples to a mixed mode of cohesive failure and aluminum oxide-primer interfacial failure for the 80°C aged samples. / Master of Science

Polyrotaxanes, a new class of polymer architectures, so called molecular composites, are comprised of macrocycles threaded by linear backbones with no covalent bond between them. By using poly(1,4-phenylenevinylene) (PPV), one of the most promising conductive polymers, as the linear backbone and different sizes of crown ethers (42C14, 60C20) as macrocycles, molecular composites of the conducting polymer were generated To compare with the PPV rotaxanes, PPV was synthesized and characterized by NMR, IR, UV-vis, photoluminescence spectroscopy, and TGA. The molecular weight of this polymer was measured by low angle laser light scattering. The poly(1,4-phenylenevinylene) rotaxanes were isolated by dialysis and solid-liquid extraction. They were also characterized by TGA, IR, UV-vis, photoluminescence spectroscopy, and solid state ¹³C NMR from which the mass contents of the crown ethers were calculated. The conductivities of the PPV rotaxanes were measured by the four-probe method. The conductivities of PPV42C14 rotaxane and PPV60C20 rotaxane were found to be 1.06x10⁻⁵ S/cm and 2.0x10⁻⁹ S/cm, respectively, after doping with concentrated sulfuric acid. The photoluminescence spectra of PPV rotaxanes showed different chemical shift and intensity from that of the PPV. / Master of Science

A series of perfectly alternating polyimide/ poly(dimethylsiloxane) microphase separated block copolymers ranging from 0-50 wgt. % poly(dimethylsiloxane) have been measured for permeability characteristics. The polyimide segment of the copolymers was based on oxydiphthalicdianhydride (ODPA) and 1,4-Bis(4-amino-1,1- dimethylbenzyl)benzene (Bis P). The polysiloxane was an aminopropyl terminated poly(dimethylsiloxane). Randomly segmented block copolymers of =20 wet. % poly(dimethylsiloxane) with different segment lengths were also studied, based on the same materials for the sake of comparison with the perfectly alternating versions of the same block copolymers. Permeability measurements were performed on tough, microphase separated, transparent films with O₂, N₂, CH₄, and CO₂ gases in that order. The effects of the chemical composition and block lengths on permeability coefficients and selectivity values were evaluated. The permeability of copolymer films to gases was found to be highly sensitive to the morphology of the copolymer. The morphology was found to be controlled by varying the amount and the segment length of each component and this allowed for fine control of the permeability characteristics. Conversely, the measurement of permeability characteristics can lead to more information about the morphology of complicated microphase separated block copolymers. / Master of Science

The hydrogenation of unsaturated carbon-carbon bonds catalyzed by transition metal hydrido complexes has received considerable attention in the literature. Environmental interests have placed considerable emphasis on switching these processes into aqueous media. The dimeric complex [Ir(COD)Cl]₂ (COD = 1,5-cyclooctadiene) has been found to undergo bridge-splitting reactions with bidentate phosphine ligands to produce coordinatively unsaturated, 16 electron complexes of the form [Ir(COD)(P-P)]Cl (P-P = bidentate phosphine). Two bidentate ligands were examined: 1,2-bis(dimethylphosphino)ethane [DMPE] and 1,2-bis(diethylphosphino)ethane [DEPE]}. These compounds have been found to be both water soluble and reactive towards molecular hydrogen at room temperature, qualities that make them ideal for serving as catalysts for the aqueous hydrogenation of unsaturates. Water-soluble ligands were also allowed to react with [Ir(COD)Cl]₂. In these cases, the product was analogous to the [Ir(COD)(PMe₃)₃]Cl complex. Two water-soluble phosphines were examined: 1,3,5-triaza-7-phosphaadamantane [PTA] and tris(hydroxy-methyl)phosphine [THP]. When these complexes were hydrogenated in water, the PTA complex underwent an oxidative addition of molecular hydrogen with the loss of COD to form the facial isomer of Ir(H)₂(PTA)₃Cl. However, the THP made both meridional and facial isomers of Ir(H)₂(THP)₃Cl upon hydrogenation. The facial was determined to be the kinetically favored product while the meridional was the thermodynamically favored product. The complexes Ir(COD)(DMPE)Cl, Ir(COD)(DEPE)Cl, and Ir(H)₂(PTA)₃Cl were determined to be excellent aqueous hydrogenation catalysts. They catalyzed the reduction allyl alcohol to n-propanol under relative mild conditions. / Master of Science

A monolayer film of methyl stearate was compressed until catastrophic film collapse took place. Surface pressure relaxation was then followed as a function of time. Investigation involving the effects of film compression beyond the collapse pressure revealed an important process involved in the surface pressure relaxation mechanism. When the monolayer is compressed beyond the collapse pressure and then held at a constant area, the surface pressure relaxation, in a plot of surface pressure vs time, was delayed during the initial stage of the process. A similar delay in the surface pressure relaxation was also observed for a monolayer film of methyl stearate when it was compressed and held at 40 mN/m, below the collapse pressure, for some time before allowing it to relax under a constant area condition. A relaxation mechanism has been proposed to explain the delay phenomenon observed during the surface pressure relaxation at constant area: At collapse, the monolayer film buckles and folds over to form bilayer molecular channels (ridges and ribbons). The ridges and ribbons act as a reservoir for monolayer material to make up for lost molecules at the air/water interface due to the growth of a bulk (crystalline) phase under a constant area condition. The results from temperature dependence studies as well as from the area-relaxation experiments strongly support the proposed relaxation mechanism. The Langmuir-Blodgett films of methyl stearate, deposited before and after the catastrophic film collapse, revealed interesting structural features of the collapsed film. The experimental results from the pressure-time, area-time, and pressure-area isotherms strongly suggest that the methyl stearate monolayer film undergoes an organized film collapse. This work helps to better understand the relaxation mechanism in monolayer films at the air/water interface. / Master of Science

Polyrotaxanes are new polymers. Macrocyclic molecules, such as crown ethers, are threaded by linear or branched polymer chains. There is no covalent bond between the crown ethers and the polymer backbone. After the crown ethers are threaded onto the polymer backbone, both ends of the polymer can be blocked by large end groups. Polyrotaxanes are the topological isomers of blends of crown ethers and polymers. This architectural modification will produce interesting chemical and physical property changes in the polymer such as T_g and T_m, solubility, tensile strength, flexibility of the polymer. The study include crown ethers, blocking groups, poly(azomethine)s A and B, poly(azomethine)rotaxanes A and B synthesis, characterization, and property research. Crown ethers, 21-crown-7, 30-crown-10, 42-crown-14, and 60-crown-20, were synthesized from oligo(ethylene glycol)s and oligo(ethylene glycol) ditosylates with 22-40% yield. The high temperature synthetic method was developed so that the percentage yield of large crown and the small crowns in the same reaction could be controlled. A new purification method, low temperature recrystallization method was developed. The crown ethers properties included melting points, decomposition temperature, chemical shift on NMR spectra were studied. A series of blocking groups were synthesized and characterized. Several synthetic routes were studied, and the best route was the Grignard synthesis. The purification method was improved by recrystallization in cyclohexane or carbon tetrachloride. A by-product, bis(p-t-butylphenyl)methanol, was obtained. The new compounds, p-tri(p-t-butylphenyl)methylaniline and p-tri{(p-t-butylphenyl)methylphenol, were identified by ¹H NMR, FTIR, and elemental analysis. Poly(azomethine)s A and B are liquid crystalline polymers. They are rigid and strong. They have high T_m's and do not dissolve in general solvents. To check the reported information, the synthesis and characterization of these polymers were repeated. They precipitated from the reaction solution when their degree of polymerization reached 3-5. They were not thermally stable and were easily hydrolyzed in strong acids and in GPC column. In order to establish the effectiveness of the blocking groups, a monomeric rotaxane, a di(azomethine)rotaxane, was designed and synthesized. The compound was successfully isolated by multiple reprecipitations and recrystallizations. A 12% yield of this compound was obtained. The largest crown ether that the blocking group could block was 42-crown-14. / Master of Science