The interphase region at modified polymer surfaces or at polymer\ metal interfaces may be critical in determining the strength and durability in adhesive applications. Methods to investigate these regions are limited however and this research has focused on the use of infrared reflection absorption spectroscopy (IRRAS) and x-ray photoelectron spectroscopy (XPS) to investigate the molecular structure of both modified and unmodified thin films. The optical constants of polyphenylene sulfide (PPS) were determined and exact optical theory was utilized to simulate spectra for a variety of reflectance techniques. This method was also utilized to confirm the ordered state of thin spin coated PPS films. The surface modification of polystyrene, polyphenylene sulfide, and poly(arylene ether) phosphine oxides was also examined by these techniques and optical theory used to optimize experimental conditions. Results after plasma treatment indicated a very thin modified surface layer (< 10 nm) where the thickness and specific surface chemistry depended on the polymer and plasma gas used. The interaction of an epoxy resin with a surface modified PPS film showed that while most of the modified surface layer is removed after this treatment, a remaining amount can serve to cross-link a thin adsorbed epoxy film. Results for the oxygen plasma treatment of poly(arylene ether) phosphine oxides showed the formation of a surface phosphate layer that inhibited further plasma etching. The kinetics of formation and the particular chemistry involved were examined in detail. A new technique, variable temperature reflection absorption spectroscopy (VTRAS) was developed as a method to investigate the reorganization of thin PPS films on a variety of substrates. Both the crystallization and melting temperatures could be determined for quenched coatings on a variety of substrates. While degradation under vacuum was not observed on chromium and aluminum surfaces, PPS films on copper surfaces showed a loss in crystallizability, and did not return to the original ordered state after exposure to temperatures near 300°C. Loss of cuprous oxide was also observed, and chain scission mechanisms were postulated. Additional measurements on thin sputtered cuprous oxide films showed less degradation for the same temperature treatments, emphasizing the role of the underlying metal in the degradation process. Spin coated films of polyetherimide were shown to be oriented after spin coating, and the relaxation to a more random state could also be observed by the VTRAS technique. Degradation of PPS films in air was examined and the diffusion of copper species into the bulk of the film with the formation of copper carboxylates was observed. The use of the VTRAS technique in air also was useful in determining the temperature needed for the onset of degradation. Bonded PPS/copper laminates were investigated and results showed that the particular surface chemistry was crucial in determining the peel strength observed. After a simple thermal! oxidation pretreatment for copper foil, an increase in the peel strength of almost one order of magnitude was observed over non-oxidized foils. Chemical oxidation with alkaline persulfate solutions resulted in a needle-like surface oxide morphology, and bond strengths were also increased by this pretreatment method. Failure surface analysis and model interaction studies with PPS tetramer showed that the formation of excess cuprous sulfide at the interface was the most probable cause of poor adhesion in these systems. Foil pretreatment by thermal oxidation gave the highest peel strength, and also exhibited the lowest amount of interfacial cuprous sulfide. / Ph. D.

Electronic structure calculation is an essential approach for determining the structure and function of molecules and is therefore of critical interest to physics, chemistry, and materials science. Of the various algorithms for calculating electronic structure, the pseudospectral method is among the fastest. However, the trade-off for its speed is more up-front programming and testing, and as a result, applications using the pseudospectral method currently lag behind those using other methods. In Part I of this dissertation, we first advance the pseudospectral method by optimizing it for an important application, polarized Raman spectroscopy, which is a well-established tool used to characterize molecular properties. This is an application of particular importance because often the easiest and most economical way to obtain the polarized Raman spectrum of a material is to simulate it; thus, utilization of the pseudospectral method for this purpose will accelerate progress in the determination of molecular properties. We demonstrate that our implementation of Raman spectroscopy using the pseudospectral method results in spectra that are just as accurate as those calculated using the traditional analytic method, and in the process, we derive the most comprehensive formulation to date of polarized Raman intensity formulas, applicable to both crystalline and isotropic systems. Next, we apply our implementation to determine the orientations of crystalline oligothiophenes --- a class of materials important in the field of organic electronics --- achieving excellent agreement with experiment and demonstrating the general utility of polarized Raman spectroscopy for the determination of crystal orientation. In addition, we derive from first-principles a method for using polarized Raman spectra to establish unambiguously whether a uniform region of a material is crystalline or isotropic. Finally, we introduce free, open-source software that allows a user to determine any of a number of polarized Raman properties of a sample given common output from electronic structure calculations. In Part II, we apply the pseudospectral method to other areas of scientific importance requiring a deeper understanding of molecular structure and function. First, we use it to accurately determine the frequencies of vibrational tags on biomolecules that can be detected in real-time using stimulated Raman spectroscopy. Next, we evaluate the performance of the pseudospectral method for calculating excited-state energies and energy gradients of large molecules --- another new application of the pseudospectral method --- showing that the calculations run much more quickly than those using the analytic method. Finally, we use the pseudospectral method to simulate the bottleneck process of a solar cell used for water splitting, a promising technology for converting the sun's energy into hydrogen fuel. We apply the speed of the pseudospectral method by modeling the relevant part of the system as a large, explicitly passivated titanium dioxide nanoparticle and simulating it realistically using hybrid density functional theory with an implicit solvent model, yielding insight into the physical nature of the rate-limiting step of water splitting. These results further validate the particularly fast and accurate simulation methodologies used, opening the door to efficient and realistic cluster-based, fully quantum-mechanical simulations of the bottleneck process of a promising technology for clean solar energy conversion. Taken together, we show how both polarized Raman spectroscopy and the pseudospectral method are effective tools for analyzing the structure and function of important molecular systems.

Thesis (M.Tech.: Chemistry)-Dept. of Chemistry, Durban Institute of Technology, 2003 ix, 70 leaves + 1 computer laser optical disc / The purpose of this study is to utilize computational techniques in the determination of the mechanistic pathways for the one-pot conversion of a pentacyclo-undecane (PCU) dione 1.1 to a pentacyclo-undecane cage lactam 1.2.

Thesis (M.Tech.: Chemistry)-Dept. of Chemistry, Durban Institute of Technology, 2003 ix, 70 leaves + 1 computer laser optical disc / The purpose of this study is to utilize computational techniques in the determination of the mechanistic pathways for the one-pot conversion of a pentacyclo-undecane (PCU) dione 1.1 to a pentacyclo-undecane cage lactam 1.2.

Call number: LD2668 .T4 1985 J665 / Master of Science

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy

No description available.

No description available.

This thesis is concerned with the synthesis and characterisation of novel TCNQ (7,7,8,8-tetracyanoquinodimethane), TMTCNQ (2,3,5,6-tetramethyl-7,7,8,8-tetracyanoquinodimethane) and TCNQF4 (2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane) based zwitterionic D-1t-A materials (where D and A are electron donors and acceptors respectively) of which the methylated Z-~-(N-methyl-4-quinolinium)-a-cyano-4( 2,3,5,6-tetrafluoro)styryldicyanomethanide [CH3(4)Q3CNQF4] is a typical example. Synthetic modification of the donor moiety was also undertaken, resulting in a diverse range of pyridinium, quinolinium and benzothiazolium-based materials, which may have use in nonlinear optical research. For the quinolinium system an extensive range of both 2- and 4-substituted analogues have been prepared and their properties compared and contrasted. The solvatochromic behaviour of these zwitterions was investigated in detail by dissolution in a range of organic solvents and measurement of their longest wavelength charge-transfer absorption bands using UV/Visible spectroscopy, which revealed that the substituents have a marked effect upon their solvatochromic properties. Most of the adducts studied display highly negative solvatochromism as the solvent polarity increases, in which their absorption maxima are linearly related with the normalised ENT values for the Reichardt dye. However the fluorinated quinolinium and pyridinium derivatives exhibit an unusual aggregation-induced reverse solvatochromism effect. The negative halochromic behaviour of selected zwitterions has also been investigated, with a hypsochromic shift of the longest wavelength CT absorption band being observed upon addition of electrolytes. Increased polarisation within the fluorinated R(4)Q3CNQF4 and R(2)Q3CNQF4 adducts has been indicated by solution state dipole moment measurements indicating greater nonlinear optical potential. However this increased polarisation has also been shown to be a major cause of the limited stability of these materials to photo-oxidation. The behaviour of the R(4)Q3CNQF4 and R(2)Q3CNQF4 zwitterions on the subphase and their resultant Langmuir-Blodgett film forming ability was also studied. However unlike the TCNQ-based materials the fluorinated adducts have been shown to be poor LB film forming materials.

No description available.