Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: In the modern, fast moving society of today, there is a strong focus in research placed on the elimination of lengthy invasive medical procedures. Target specific, and chemo selective treatments are of great interest. Various advantages of this include patient comfort and over and above all cost reduction of invasive procedures. This project focused on the development of an injectable gel system with the use of biocompatible polymers. A system is regarded as injectable if the functional polymers are in solution before administration, but gels when added together. In order to design this system, one has to make use of polymers with complimentary functional groups. Telechelic amino-functionalized PVP with narrow molecular weight distribution was synthesized via RAFT-mediated polymerization. The polymer was thoroughly characterized and cross-linked with Poly(styrene-alt-maleic anhydride) to form a three dimensional polymeric network capable of absorbing and retaining large amounts of water and or biological fluid. Unfortunately the cross-linking needed to be performed in non-aqueous solution due to hydrolysis of maleic anhydride as a competing reaction in water. The gel was used in two model studies. The first model study focused on the attachment of a synthetic polypeptide onto the gel. The second model study evaluated the cytotoxicity effects of these gels when placed in direct contact with rodent cardiac myoblast and myocyte cells. These studies rendered promising results for future biological applications. / AFRIKAANSE OPSOMMING: In die moderne, vinnig bewegende samelewing van vandag, word daar in navorsing, 'n sterk fokus geplaas op die uitskakeling van lang indringende mediese prosedures. Doel spesifieke, en chemo selektiewe behandelings is van groot belang. Verskeie voordele van hierdie is die toename in gemak van die pasiënt en die verlaging van kostes verbonde aan hierdie indringende prosedures. Hierdie projek het gefokus op die ontwikkeling van 'n inspuitbare gel stelsel deur gebruik te maak van biologiese aanvaarbare polimere. ‘n Stelsel word beskou as inspuitbaar, indien die funksionele polimere in oplossing is voor toediening, maar wel kan gel wanneer bymekaar gevoeg word. Om hierdie tipe stelsel te kan ontwerp moet daar gebruik gemaak word van polimere met beskikbare funksionele groepe. Telecheliese amino-funksionele Poly(N-vinielpirollideen) met 'n smal molekulêre gewig verspreiding is gesintetiseer deur middel van RAFT-bemiddelde polimerisasie. Die polimeer is deeglik gekarakteriseer en daarna gekruis-koppel met P(STY-alt-MAnh) om 'n driedimensionele polimeriese netwerk te vorm. Hierdie netwerk is dan ook in staat om groot hoeveelhede water en/of biologiese vloeistof te absorbeer en te behou. Ongelukkig was hierdie reaksie uitgevoer in ʼn nie-waterige oplossing as gevolg van die hidrolise van Maleïne anhydride as 'n mededingende reaksie in water. Die gel is in twee model studies gebruik. Die eerste model-studie het gefokus op die beslaglegging van 'n sintetiese polipeptied op die gel. Die tweede model studie het die sitotoksiese uitwerking van hierdie gels in direkte kontak met knaagdier hart myoblast en lymfocyten selle geëvalueer. Hierdie studies het dan ook belowende resultate vir toekomstige biologiese toepassings gelewer.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2009. / In papermaking, the addition of filler can be detrimental to the properties of the resulting paper hence the use of additives that enhance paper properties are of paramount importance. Syndiotacticity rich poly(vinyl alcohol) (PVA) microfibrils were prepared for use as filler retention aids. They were prepared via in situ fibrillation during the saponification of high molecular weight poly(vinyl pivalate). The resulting fibers had high thermal stability and crystalline melting temperature. They were not fully soluble in water even at 100 oC. In order to make them less water resistant the syndiotacticity of the PVA microfibrils was varied by copolymerizing vinyl pivalate with vinyl acetate and saponifying the resultant copolymer. It was observed that changes in syndiotacticity had a significant effect on the crystallinity, morphology and thermal properties of the resultant PVA. The surfaces of the fibers were modified by first crosslinking using glyoxal (a dialdehyde), and then attaching cationic and anionic groups by grafting and by carboxymethylation. Crosslinking prior to modification was beneficial in minimizing the solubility of the fibers in the aqueous media in which they were modified. Heterogeneous modification techniques were employed so that fiber properties could be preserved. Carboxymethylation was carried out using the two step Williamson’s ether synthesis. The first step involves the formation of a highly reactive alkoxide by the reaction of PVA with a strong base and the second its etherification using a functional alkyl halide. Poly(methacryloyloxy ethyl trimethyl ammonium chloride) and poly(acrylic acid) were grafted from the PVA microfibrils using the KPS/Na2S2O3 redox initiation system. Grafting was confirmed by FTIR and NMR spectroscopy. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were carried out on both modified and unmodified PVA microfibrils. The results showed that crosslinking resulted in an enhancement of the thermal properties of the microfibrils. A decline in the onset temperature for thermal degradation and crystalline melting temperature were observed, and were attributed to the modification of the PVA microfibrils.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2006. / Dyeing has an influence on the characteristic properties of wool fibres. This can result in changes in the final properties of the fibre including fibre elasticity, fibre strength and breaking elongation of the wool fibres, especially in the case of dark colours. Damage that occurs to the fibre surface due to the action of acid, alkali, dyestuff, water, heat, and mechanical stress during the dyeing process can thus have an affect on the fibre breaking elongation and the fibre strength. The aim of this project was to assess the effect of dyeing with different colours (ranging from light to dark) on the surface of wool fibres using atomic force microscopy (AFM). The results indicated that four different types of surface damage can be discerned: scale raising, scale chipping, fluting and pitting. The findings also indicate that the surface damage to the fibres was greater and more noticeable (especially the scale raising) on fibres dyed with dark colours than to fibres dyed with light colours. The same applied to the fibre strength and elongation, where generally the fibre breaking extension and the breaking load was smaller in the case of darker colours. The effect of dyeing with different colour shades on the fibre surface was observed with AFM. Several characteristic scale parameters of a statistical significant number of dyed and undyed fibres were measured in order to determine the surface damage caused by dyeing. The correlation between the surface damage, observed by AFM, and the loss in tensile strength and fibre elongation, determined by tensile tests, were investigated. This was done in order to determine the effect of the cuticle damage on the tensile stress/strain behaviour. The results show that AFM is a viable tool to study the effects of different dyes on the fibre surface and for detecting surface modifications with great accuracy. It was found that dyeing with dark colours caused greater damage to the surface than light colours, and it was possible to distinguish different lightness areas, which could be regarded as light and dark colours.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Impact polypropylene copolymers (IPPC) are important commercial materials, but their morphology and molecular architecture are not yet fully understood. In this study the focus was on selectively removing specific fractions from the original IPPC, recombining the remaining fractions, and studying the properties of these recombined polymers. It was found that some properties of the samples changed remarkably, depending on the fraction of material that was removed before recombination. For example, the degree of phase separation and the crystalline morphology of the recombined materials varied noticeably. During the study an effective way of staining samples for transmission electron microscopy (TEM) was developed. Furthermore, a comparison of fourier transform infrared spectroscopy (FTIR), with TEM and scanning electron microscopy (SEM) results, revealed a hitherto unreported relationship between phase separation. Absorption bands appeared at 1100 cm-1 and 1080 cm-1 in the FTIR spectra and appear to be an indication of phase separation. It was further established that specific copolymer fractions present in the original polymer affect not only the morphology of the final polymer, but also the hardness and impact resistance. / AFRIKAANSE OPSOMMING: Impak polipropileen kopolimere (IPPK) is belangrike kommersïele materiale, maar die kennis met betrekking tot die morfologie en molekulere argitektuur van die materiale is nog gebrekkig. Tydens hierdie studie was die fokus op die selektiewe verwydering van spesifieke fraksies van die oorspronklike IPPK, herkombinering van die oorblywende fraksies, en die studie van die eienskappe van hierdie herkombineerde polimeriese materiale. Daar is gevind dat sommige van die eienskappe van die herkombineerde materiale daadwerklik verskil van die oorspronklike materiaal, en dat die verskille direk verband hou met die spesifieke fraksie wat uit die oorspronklike materiaal verwyder is. Die mate van fase-skeiding asook die kristal-morfologie van die herkombineerde materiaal het opmerklik verskil van die oorspronklike. Tydens die studie is n effektiewe manier ontwikkel om die materiale te vlek vir transmissie elektron-mikroskopie (TEM). Verder is daar ‘n verband tussen die resultate verkry deur Fourier Transform infrarooi spektroskopie (FTIS) en die verkry met TEM en skandeer elektron mikroskopie (SEM) vasgestel. Die verwantskap tussen FTIS en fase-skeiding is tot dusver nie in die wetenskaplike literatuur vermeld nie. Meer spesifiek is daar gevind dat absorbsie-bande sigbaar by 1100 cm-1 en 1080 cm-1 in die FTIS spektra ‘n aanduiding van fase skeiding kan wees. Dit was verder vasgestel dat spesifieke kopolimeer fraksies wat teenwoordig is in die oorspronklike IPPK, nie alleen die morfologie van die materiaal beinvloed nie, maar ook die hardheid en impak-weerstand van die materiaal.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2007. / This study comprises the synthesis, functionalization, and characterization of 1-butene oligomers, as well as the synthesis of oligobutene-based macro-RAFT agent. The directed oligomerization of 1-butene was carried out with a Cp2ZrCl2 as a catalyst, activated with MAO as a co-catalyst (10% in toluene), in the ratio Al/Zr =1000/1. Oligomers possessing vinylidene double bonds, with low molecular weight (Mw), ranging between 800 and 2000 g.mol-1 as confirmed by gel permeation chromatography, were obtained. The oligomers were successfully functionalized by adding hydroxyl functionality to the vinylidene double bond using oxymercuration-demercuration reaction, and as a result hydroxy-terminated oligobutenes were obtained. Characterization techniques such as 1H NMR, 13C NMR, GC-MS and FTIR confirmed the successful synthesis and functionalization of 1-butene oligomers. The hydroxy-terminated oligobutenes were used to prepare an oligobutene-based macro-RAFT agent. The synthesis of the macro-RAFT agent was carried out with an esterification reaction between the hydroxy-terminated oligobutenes and an acid functionalized RAFT agent. The successful synthesis of the macro-RAFT agent was confirmed by 1H NMR, 13C NMR, FTIR, and UV spectroscopy. The chain transfer ability of the macro-RAFT agent to induce living characteristics in free radical styrene polymerization was investigated with respect to molecular weight control and kinetic behaviour. The macro-RAFT agent was identified as suitable RAFT agent, yielding polystyrene-b-oligobutnes with low polydispersities and molecular weight ranging from 3000 to 40000 g/mol.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2006. / Cellulose, one of the most abundant organic substances on earth, is a linear polymer of D-glucose units joined through 1,4-β-linkages. Cellulose is however not easily processed without chemical modification. A number of techniques exist for the modification of cellulose, of which the viscose process is one of the most widely applied. Grafting of synthetic polymeric chains onto or from cellulosic materials is an useful technique that can be used to combine the strengths of synthetic and natural polymers dramatically, so changing the properties of cellulosic materials (pulp, regenerated cellulose, cellulose derivatives). In this study five model xanthate (Reversible Addition-Fragmentation chain Transfer (RAFT)/Macromolecular Design through Interchange of Xanthates (MADIX)) agents, namely, monofunctional, difunctional, trifunctional and tetrafunctional species of the form S=C(O-Z)-S-R, with different leaving groups and different activating moieties, were prepared and then studied to determine the feasibility of cellulose modification via addition fragmentation processes. These agents were characterized by Nuclear Magnetic Resonance spectroscopy (NMR), Fourier Transform Infrared spectroscopy (FT-IR) and Ultraviolet spectroscopy (UV). Polyvinyl acetates (PVAc) in the form of linear, three armed and four armed star shaped polymers were then successfully synthesized in reactions mediated by these xanthate RAFT/MADIX agents Xanthates were applied to polysaccharide materials using the viscose process (xanthate esters were formed directly on a cellulosic substrate, with subsequent alkylation) Grafting reactions were then conducted with the polysaccharides; cellulose was modified with vinyl acetate, [this is an example of a surface modification of natural polymers that is of interest in various industries, such as textiles and paper manufacture]. Analysis of the graft copolymers was conducted via Size Exclusion Chromatography (SEC), Liquid Adsorption Chromatography (LAC), Thermogravimetric Analysis (TGA), and FT-IR. Polyvinyl acetate was successfully grafted onto three polysaccharides (cellulosic materials), namely Hydroxyl Propyl Cellulose (HPC), Methyl Cellulose (MC) and cellulose. The study showed that the modification of cellulosic substrates with defined grafts of vinyl acetate can be easily achieved through minor modifications to existing industrial techniques.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2006. / Hydrophobic core/shell latex particles were synthesized for use in barrier coatings using the miniemulsion polymerization process. Particles with liquid or with hard cores were successfully synthesized using miniemulsion as a one-step nanoencapsulation technique. Different materials, including an oil (hexadecane, HD) and two different waxes (paraffin and microcrystalline wax), were used as the core of the particles. The shell of the particles was mainly made from a copolymer containing three relatively hydrophobic monomers, namely methyl methacrylate (MMA), butyl acrylate (BA) and vinyl neodecanoate (Veova-10). Before any further investigations could be carried out, it was important to determine the morphology of the synthesized core/shell particles at the nanometer level. Particle morphology was mainly determined by two different techniques: transmission electron microscopy (TEM) and atomic force microscopy (AFM). TEM was used to directly visualize the morphology of the investigated core/shell particles at the nanometer level, while AFM was used to confirm the formation of these core/shell particles. AFM was a powerful technique with which to study the particle morphology of the core/shell latices during the film formation process. As a second part of the study, the effect of various factors on the hydrophobicity and barrier properties of the resulting films produced from the synthesized core/shell latices to water and water vapour was investigated. This included the effect of: (i) the surfactant concentration, (ii) the wax/polymer ratio for both waxes, (iii) the molecular weight of the polymeric shell, (iv) the amount of the most hydrophobic monomer used (Veova-10), and (v) the degree of crosslinking in the polymeric shell. Results showed that all the above-mentioned factors had a significant impact on the water sensitivity of the resultant films prepared from the synthesized core/shell latices. It was found that the presence of wax materials as the cosurfactant, instead of HD, in the miniemulsion formulation could significantly improve the hydrophobicity and barrier properties of the final films to water and water vapour. In addition, increasing the amount of wax, Veova-10, and the molecular weight of the resultant polymeric shell, led to a significant increase in the hydrophobicity and barrier properties of the resultant latex films. In contrast, hydrophobicity and water barrier properties decreased drastically as the quantity of surfactant and degree of crosslinking increased in the final latex films.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2006. / Co-crystallization is the phenomenon by which chains of different crystallizabilities crystallize at the same temperature. Co-crystallization is frequently observed in the blends of different types of polyethylene. It is believed that co-crystallization can occur due to the thermodynamically miscible parts of two components in the blends having similar crystallization rate. The study focused on the phenomenon of co-crystallization in polyethylene blends and how by varying the crystallization conditions the co-crystallization region will change. Three techniques have been used in this study. TREF was used to fractionate the polymers and blends. Each of the TREF fractions was studied using both DSC and CRYSTAF to determine whether the fraction contained both types of materials. It is shown that the difference in the crystallization fractionation mechanisms between TREF, CRYSTAF and DSC can be utilize to study co-crystallization effects in polyethylene blends. Results also shows that by varying the heating and cooling rate profiles in DSC and CRYSTAF the co-crystallization fractions will appeared as a single fraction or as two separate fractions. Further, it was demonstrated how the co-crystallization area could be illustrated using a unique 3-dimensional plot where the data from the prep-TREF fractionation, and the DSC and CRYSTAF, were combined to give the “crystallization map” of the blend. These plots give a quiche visual illustration of any co-crystallization regions in the blends as well as how much the crystallization conditions effect the blend crystallization.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2007. / The synthesis of complex architectures, namely block copolymers with tailored enduse properties, is currently an important research area in academia and industry. The challenge is finding a versatile polymerization technique capable of controlling the molecular properties of the formed copolymers, which in turn determines their macroscopic properties. Reversible addition-fragmentation chain transfer (RAFT)- mediated living polymerization is a robust technique capable of producing controlled polymer products. With the great advances in living polymerization techniques and the environmental awareness of society there is an increasing demand to produce these polymer products via the RAFT living technique in heterogeneous media. Conventional emulsion and miniemulsion polymerization present various problems when used to produce polymers mediated by the RAFT process. There is an inherent need to find cost effective and flexible operating conditions to conduct RAFT polymerization in heterogeneous media with the ability to produce well-defined block copolymers. In this study the use of three novel trithiocarbonate RAFT agents to produce welldefined AB-type, ABA-type and star block copolymers via the RAFT process was investigated. Optimal operating conditions for the production of living block copolymers in homogenous and heterogeneous media were determined. The main focus was on the development of the RAFT process in heterogeneous media to efficiently produce block copolymer latex products. The RAFT-mediated miniemulsion polymerization system stabilized with non-ionic surfactants was thoroughly investigated. The ability of the ab initio and in situ RAFT-mediated emulsion polymerization systems to produce controlled latexes was demonstrated. Controlled block copolymer products were successfully synthesized in homogenous and heterogeneous media via the RAFT process when the optimum reaction conditions were chosen.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2006. / This study concerns the investigation of the isomerization of different metallocene catalysts in solution, and the effects thereof on the microstructure of polypropylenes prepared with these catalysts. Two C2 symmetric ansa metallocenes, ethylene-bis(indenyl) zirconium dichloride (EI) and dimethylsilyl-bis(2-methyl benzoindenyl) zirconium dichloride (MBI) were exposed, in solution, to both sunlight and UV radiation. The rac-meso isomerization of these catalysts were followed by 1H NMR spectroscopy. The reaching of a photostationary state is described, as well as the effect of isomerization of these catalysts in solution on the polymerization of propylene. Results show that metallocene structure has an effect on the isomerization rate and photostationary state. Results also show that the wavelength of light plays a role in the isomerization process. Effects on stereochemistry and molecular weight of the formed polymer as well as the catalyst activity is described and discussed. In addition the effect of activating the catalysts with MAO before exposure to light is discussed.