The focus of this thesis has been on the effects of segregation in mixtures of amphiphilic molecules. Two different systems were investigated: fluorocarbon-hydrocarbon surfactant mixtures and lipid-surfactant mixtures. In fluorocarbon-hydrocarbon surfactant mixtures the repulsive interactions between the chains can lead to a demixing into different types of coexisting micelles, fluorocarbon rich and hydrocarbon rich. From NMR self-diffusion measurements such a demixing was found to occur in the mixture of the partially fluorinated surfactant HFDePC and C16TAC. We furthermore suggested a demixing also within the micelles to explain 19F-NMR line width data and results from neutron scattering. In lipid-surfactant mixtures, a segregation of the molecules may instead be caused by a difference in the preferred curvature of the lipid and the surfactant residing within the same aggregate. Using a surfactant selective electrode, binding isoterms of four different cationic surfactants (C12TAC, C14TAC, C16TAC and HFDePC) to preformed lipid (GMO) vesicles were determined. Perforated vesicles were observed by cryo-TEM in the mixture with C16TAC. To explain the results from the binding isoterms, the formation of pores in the bilayer was regarded as a cooperative process, similar to micelle formation. The surfactant accumulates at the edges of the pores, and increasing the surfactant concentration results in an increased number of pores with a constant surfactant/lipid ratio at the edges. The lipid-surfactant mixtures were also studied at the solid/solution interface using AFM. An adsorbed mesh structure, a counterpart to the bulk perforated lamellar phase, was observed for the first time.

The phase separation of mixed Langmuir-Blodgett (LB) monolayers was investigated using a combination of atomic force microscopy (AFM), X-ray photoelectron emission microscopy (X-PEEM) and confocal fluorescent microscopy measurements. Shapes of phase-separated domains that formed on solid substrate surfaces depended on a competition between line tension and dipole-dipole interactions. In the mixed LB film of arachidic acid (C19H39COOH) (C20) and perfluorotetradecanoic acid (C13F27COOH) (F14), the components phase separated into elevated hexagonal domains of C20 surrounded by a continuous domain primarily consisting of F14. The underlying molecular arrangement of C20 was found to be an oblique packing. The domains in this system grew via Ostwald ripening and the kinetics of their growth was modeled by twodimensional LifshitzSlyozov equation. In the stearic acid (C17H35COOH) (C18) and F14 mixed films, the C18 domains formed a linear pattern where the F14 molecules filled the areas in between the lines occupied by C18. For the mixed film of palmitic acid (C15H31COOH) (C16) and perfluorooctadecanoic acid (C17F35COOH) (F18), the surfactants phaseseparated into elevated hexagonal domains with hairy extensions radiating from them. These domains were composed of F18 and surrounded by C16. Ostwald ripening was found to be the mechanism of domain growth. Phase separation was controlled by different forces such as line tension and dipole interactions, as well as the diffusion of the molecules, solubility of the surfactant in the sub-phase, temperature and surface pressure. Simple mechanisms regarding phase separation and pattern formation were discussed in these mixed systems. It was observed that all fatty acid / F14 systems in this study were immiscible at all molar fractions examined. The fatty acid / F18 systems were immiscible at short chains of fatty acids (myristic acid (C13H27COOH) C14, C16, C18), whereas at longer fatty acid chains (C20, C22 behenic acid (C21H43COOH)) the components of the mixed system became miscible. When perfluorocarboxylic acid chain combined with fatty acids, the domains changed from large hexagonal domains into narrow lines as the fatty acid chain decreased in length.

The phase separation of mixed Langmuir-Blodgett (LB) monolayers was investigated using a combination of atomic force microscopy (AFM), X-ray photoelectron emission microscopy (X-PEEM) and confocal fluorescent microscopy measurements. Shapes of phase-separated domains that formed on solid substrate surfaces depended on a competition between line tension and dipole-dipole interactions. In the mixed LB film of arachidic acid (C19H39COOH) (C20) and perfluorotetradecanoic acid (C13F27COOH) (F14), the components phase separated into elevated hexagonal domains of C20 surrounded by a continuous domain primarily consisting of F14. The underlying molecular arrangement of C20 was found to be an oblique packing. The domains in this system grew via Ostwald ripening and the kinetics of their growth was modeled by twodimensional LifshitzSlyozov equation. In the stearic acid (C17H35COOH) (C18) and F14 mixed films, the C18 domains formed a linear pattern where the F14 molecules filled the areas in between the lines occupied by C18. For the mixed film of palmitic acid (C15H31COOH) (C16) and perfluorooctadecanoic acid (C17F35COOH) (F18), the surfactants phaseseparated into elevated hexagonal domains with hairy extensions radiating from them. These domains were composed of F18 and surrounded by C16. Ostwald ripening was found to be the mechanism of domain growth. Phase separation was controlled by different forces such as line tension and dipole interactions, as well as the diffusion of the molecules, solubility of the surfactant in the sub-phase, temperature and surface pressure. Simple mechanisms regarding phase separation and pattern formation were discussed in these mixed systems. It was observed that all fatty acid / F14 systems in this study were immiscible at all molar fractions examined. The fatty acid / F18 systems were immiscible at short chains of fatty acids (myristic acid (C13H27COOH) C14, C16, C18), whereas at longer fatty acid chains (C20, C22 behenic acid (C21H43COOH)) the components of the mixed system became miscible. When perfluorocarboxylic acid chain combined with fatty acids, the domains changed from large hexagonal domains into narrow lines as the fatty acid chain decreased in length.

As feature sizes in semiconductor devices become smaller and newer materials are incorporated, current methods for photoresist and post plasma etch residue removal face several challenges. A cleaning process should be environmentally benign, compatible with dielectric materials and copper, and provide residue removal from narrow and high aspect ratio features. In this work, sub-critical CO2 based mixtures have been developed to remove the etch residues; these mixtures satisfy the above requirements and can potentially replace the two step residue removal process currently used in the integrated circuit (IC) industry. Based on the chemical nature of the residue being removed, additives or co-solvents to CO2 have been identified that can remove the residues without damaging the dielectric layers. Using the phase behavior of these additives as a guide, the composition of the co-solvent was altered to achieve a single liquid phase at moderate pressures without compromising cleaning ability. The extent of residue removal has been analyzed primarily by x-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Various techniques such as attenuated total reflection - Fourier transform infrared (ATR-FTIR) spectroscopy, angle-resolved XPS (ARXPS), and interferometry were used to probe the interaction of cleaning fluids with residues. Model films of photoresists and plasma deposited residues were used to assist in understanding the mechanism of residue removal. From these studies, it was concluded that residue removal takes place primarily by attack of the interface between the residue and the substrate; a solvent rinse then lifts these residues from the wafer. It has been shown that transport of the additives to the interface is enhanced in the presence of CO2. From positronium annihilation lifetime spectroscopy (PALS) studies on a porous dielectric film, it has been shown that these high pressure fluids do not cause significant changes to the pore sizes or the bonding structure of the film. Hence, this method can be used to remove post etch residues from low-k dielectric films.

Paper and cellulosic materials hold a good promise of being candidates for flexible packaging materials provided suitable barrier properties such as water repellence and grease resistance are imparted to them. One of the methods to achieve these objectives is to surface modify paper/cellulose by applying thin fluorocarbon coatings on the surface. Fluorocarbon thin films produced by plasma enhanced chemical vapor deposition (PECVD) offer several advantages over the films produced by conventional polymerization means. Plasma deposited films are pinhole-free, chemically inert, insoluble, mechanically tough, thermally stable and highly coherent and adherent to variety of substrates. In this work, we investigate the use of PECVD technique to produce barrier films on paper and cellulosic materials. These films, with composition and properties not much different from PTFE, repel water and act as a good barrier to lipophilic materials. Two different monomers, pentafluoroethane (PFE; CF3CHF2) and octafluorocyclobutane (OFCB; C4F8), were investigated and compared in terms of deposition rates and final film properties. Various analytical techniques (XPS, FT-IR, SEM, Ellipsometry, Contact Angle Goniometry, etc.) were used to characterize the fluorocarbon films. The fluorocarbon coated paper exhibited hydrophobic character as evidenced by high water contact angles. Although the films allow water vapor diffusion, the films are hydrophobic and are not wetted when liquid water contacts these layers. Based on various thickness of these films deposited on surface of cellulose, there was a minimum PFE film thickness required to achieve a stable hydrophobic behavior. The fluorocarbon films investigated in this work also exhibited good resistance to lipophilic materials (e.g. oils, fatty acids, etc.). While techniques such as oleic acid penetration and TAPPI "oil-kit" test are commonly used in paper industry to qualitatively test the grease barrier properties of paper/cellulose, this work attempts to quantify the grease barrier properties of fluorocarbon coated paper using techniques such as magnetic resonance imaging (MRI) and quartz crystal microbalance (QCM). Finally, the feasibility of deposition of dual layer films by PECVD was investigated using PFE and n-isopropylacrylamide (NIPAAM) as precursors for applications in barrier packaging and printing.

Smooth fluorocarbon plasma polymer films have been for a long time considered for fabrication of hydrophobic and slippery coatings. Interest in fluorocarbon materials was also supported by their excellent self-lubricant, dielectric properties and chemical inertness. This thesis is focused on development of new methods for fabrication of fluorocarbon plasma polymes, which could combine the chemical composition and the physical structure necessary for reaching superhydrophobic character of coatings. Poly(tetrafluoroethylene) was the subject material. RF magnetron sputtering using gas aggregation cluster source was the method adapted to fabricate fluorocarbon nanostructured films with chemical composition close to conventional bulk PTFE, but with high degree of cross- linking and branched structure. A model of growth of such plasma polymer nanostructures was discussed.

Fluorkemi används på varselkläder i syfte för att skydda textilen mot smuts, vatten, fett och olja. Kemikalierna är skadliga för människor och miljö, de är dessutom mycket svårnedbrutna eller så bryts de inte ner överhuvudtaget. Kemikalierna är utvecklade av människor och delas upp i perfluorerade och polyfluorerade ämnen (PFAS). PFAS klassificeras också som PBT-ämnen, vilket står för att de är persistenta, bioackumulerande och toxiska. Studien är utförd i ett samarbete med Tranemo Textil AB, där behovet av fluorkarbonberedning på varselkläder undersökts. Syftet med studien är att undersöka utifrån användning och tvättprocess om fluorkarbonberedning är essentiell på varselkläder. Genom intervjuer med experter och tvätterier har studien fått fram information om fluorkemi och hur tvättprocessen ser ut. Resultatet från intervjuerna har kombinerats med tester på tyger och på ett bärprov med ett byxben med fluorkarbonberedning och ett byxben utan. Bärprovet har testats av en person i dennes dagliga arbete under sex månader. Studien har sammanställt resultatet och kan konstatera att fluorkemin har negativ påverkan på människa och miljö, vilket ligger till grund för en diskussion kring vad som är nödvändig användning. Vidare kan det konstateras att fluorkarbonberedningens effekt försämras över tid, genom användning, tvätt och annan yttre påverkan. Slitaget sker ojämnt och vissa delar av ett plagg kan ha god avvisande effekt medan andra delar är så kallade öppna friytor. Smuts kan då gå in under beredningen och kapslas in. I resultatet har det också framkommit att rätt skötsel av den här typen av plagg är viktigt och att återaktivering genom värme är väsentlig. Samtidigt belyser respondenterna återkommande en mentalitet hos arbetare att de vill att plaggen ska visa att de arbetar och därför vara smutsiga, vilket medför att många plagg sällan tvättas. Genom utförda intervjuer och tester har studien kommit till slutsatsen att fluorkemi inte är nödvändig på varselkläder. Den yttre påverkan som relativt snabb sliter på beredningen genom användning och tvätt i kombination med att fluorkemin inte fyller någon långvarig avvisande funktion är aspekter som tagits i hänsyn för slutsatsen. / Fluor chemistry is used on high visibility workwear to protect the textile from dirt, water, grease, and oil. The chemicals are harmful to people and the environment, they are also very degraded, or they do not break down at all. The chemicals are developed by humans and divided into perfluorinated and polyfluorinated substances (PFAS). PFAS is also classified as PBT substances, which means that they are persistent, bioaccumulate, and toxic. The study was in collaboration with Tranemo Textil AB, where the need for fluorocarbon finish for high visibility workwear was explored. The purpose of the study is to investigate if a fluorocarbon finish is essential on high visibility workwear, based on the use phase and washing process. Through interviews with experts and laundries, the study has obtained information about fluor chemistry and how the washing process works. The results of the interviews have been combined with tests on fabrics and on a wear test that has been tested in the person’s daily work for six months. The wear test is trousers with one leg with fluorocarbon finish and the other leg without. The study has compiled the results and can find that fluor chemistry has a negative impact on humans and the environment, which forms the basis for a discussion about what is essential use. Furthermore, it can be found that the effect of the fluorocarbon finish impairs over time, through use, washing, and other external impacts. The abrasion is uneven, and some parts of the garment can still have a good repellent effect, while other parts have so-called open surfaces. On the open surfaces, dirt can enter during the fluorocarbon finish and be encapsulated. The study has also emerged that proper care of this type of garment is important and that reactivation through heat is essential. At the same time, respondents repeatedly highlight workers' mentality that the garment should show and reflect high work ethics. This causes that many garments are rarely washed and become very dirty. Through interviews and tests, the study has concluded that fluor chemistry is not necessary for high visibility workwear. The external effects with relatively quickly abrasion on the finish through use and washing, this in combination with that fluor chemistry does not fulfil any long-lasting function are aspects that have been considered in the conclusion.

No description available.

Pelchem, a commercial subsidiary of Necsa (South African Nuclear Energy Corporation), produces a range of commercial fluorocarbon products while driving research and development initiatives to support the fluorine product portfolio. One such initiative is to develop improved analytical techniques to analyse product composition during development and to quality assure produce. Generally the C–F type products produced by Necsa are in a solution of anhydrous HF, and cannot be directly analyzed with traditional techniques without derivatisation. A technique such as vibrational spectroscopy, that can analyze these products directly without further preparation, will have a distinct advantage. However, spectra of mixtures of similar compounds are complex and not suitable for traditional quantitative regression analysis. Multivariate data analysis (MVA) can be used in such instances to exploit the complex nature of spectra to extract quantitative information on the composition of mixtures. A selection of fluorocarbon alcohols was made to act as representatives for fluorocarbon compounds. Experimental design theory was used to create a calibration range of mixtures of these compounds. Raman and infrared (NIR and ATR–IR) spectroscopy were used to generate spectral data of the mixtures and this data was analyzed with MVA techniques by the construction of regression and prediction models. Selected samples from the mixture range were chosen to test the predictive ability of the models. Analysis and regression models (PCR, PLS2 and PLS1) gave good model fits (R2 values larger than 0.9). Raman spectroscopy was the most efficient technique and gave a high prediction accuracy (at 10% accepted standard deviation), provided the minimum mass of a component exceeded 16% of the total sample. The infrared techniques also performed well in terms of fit and prediction. The NIR spectra were subjected to signal saturation as a result of using long path length sample cells. This was shown to be the main reason for the loss in efficiency of this technique compared to Raman and ATR–IR spectroscopy. It was shown that multivariate data analysis of spectroscopic data of the selected fluorocarbon compounds could be used to quantitatively analyse mixtures with the possibility of further optimization of the method. The study was a representative study indicating that the combination of MVA and spectroscopy can be used successfully in the quantitative analysis of other fluorocarbon compound mixtures. / Thesis (M.Sc. (Chemistry))--North-West University, Potchefstroom Campus, 2012.

Pelchem, a commercial subsidiary of Necsa (South African Nuclear Energy Corporation), produces a range of commercial fluorocarbon products while driving research and development initiatives to support the fluorine product portfolio. One such initiative is to develop improved analytical techniques to analyse product composition during development and to quality assure produce. Generally the C–F type products produced by Necsa are in a solution of anhydrous HF, and cannot be directly analyzed with traditional techniques without derivatisation. A technique such as vibrational spectroscopy, that can analyze these products directly without further preparation, will have a distinct advantage. However, spectra of mixtures of similar compounds are complex and not suitable for traditional quantitative regression analysis. Multivariate data analysis (MVA) can be used in such instances to exploit the complex nature of spectra to extract quantitative information on the composition of mixtures. A selection of fluorocarbon alcohols was made to act as representatives for fluorocarbon compounds. Experimental design theory was used to create a calibration range of mixtures of these compounds. Raman and infrared (NIR and ATR–IR) spectroscopy were used to generate spectral data of the mixtures and this data was analyzed with MVA techniques by the construction of regression and prediction models. Selected samples from the mixture range were chosen to test the predictive ability of the models. Analysis and regression models (PCR, PLS2 and PLS1) gave good model fits (R2 values larger than 0.9). Raman spectroscopy was the most efficient technique and gave a high prediction accuracy (at 10% accepted standard deviation), provided the minimum mass of a component exceeded 16% of the total sample. The infrared techniques also performed well in terms of fit and prediction. The NIR spectra were subjected to signal saturation as a result of using long path length sample cells. This was shown to be the main reason for the loss in efficiency of this technique compared to Raman and ATR–IR spectroscopy. It was shown that multivariate data analysis of spectroscopic data of the selected fluorocarbon compounds could be used to quantitatively analyse mixtures with the possibility of further optimization of the method. The study was a representative study indicating that the combination of MVA and spectroscopy can be used successfully in the quantitative analysis of other fluorocarbon compound mixtures. / Thesis (M.Sc. (Chemistry))--North-West University, Potchefstroom Campus, 2012.