Thesis (PhD)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Hierarchical information transfer is investigated as a tool to prepare well‐defined nanostructures with high aspect ratios, via the self‐assembly of helically folding poly(paraaryltriazole) (P(p‐AT)) foldamers. A novel ‘helicity codon’ based on the 1,4‐linkage geometry in 1,4‐aryl‐disubstituted‐1,2,3‐ triazoles is developed. Helical folding is induced exclusively by directing all triazole moieties into a cisoid configuration. By linking the triazole rings in a para fashion about the aryl moiety, this helicity codon codes for a helix with a large internal cavity of ~ 3 nm. One turn of the putative helical conformation requires 14 repeat units and the helical pitch is ~ 0.38 nm. The aryltriazole backbone is appended with amphiphilic oligo(ethylene glycol) (oEG) units which have the dual roles of imparting solubility as well as instigating a solvophobic helical folding in solvents which poorly solvate the hydrophobic arytriazole backbone but, solvate the side chains fully. The helix interior is hydrophobic and the exterior is amphiphilic. A true polymer synthesis approach to the foldamer synthesis, based on the copper catalysed azide‐alkyne cycloaddition (CuAAC) AB step growth polymerization system, is developed. This is preceded by a facile synthetic protocol for the AB monomers. The subsequent P(p‐ AT)s have high molecular weights ensuring several turns in the helical foldamer. A DMF/H2O good solvent/bad solvent system is established. Twist sense bias in the helical foldamers is successfully imparted by installing enantiopure chiral oEG side chains. Spectroscopic signatures for the solvent dependent coil to helix transition are established enabling the tracking of the conformational transitions from primary to secondary and finally tertiary structure. Conclusive evidence for the formation of stable, long stacked helical columns, in the solution state, is provided via cryo‐TEM. The helical stacks are several microns long, but of random lengths and do not intertwine but rather run parallel to each other. The helical stacks, however, have indeterminate lengths. Control over the length and chirality of the self‐assembled helical stacks is successfully imparted by using a template which mimics the role of ribonucleic acid (RNA) in tobacco mosaic virus (TMV). The template used is the hydrophobic α‐helical polypeptide poly(γ‐ benzyl‐L‐glutamate) (PBLG). Self‐assembly is driven by solvophobicity in a DMF/H2O system, the PBLG template being encapsulated inside the hydrophobic cavities of the stacked/selfassembled helical foldamers. Information from the template, i.e. length and chirality, is used to control the length and the chirality of the stacked/self‐assembled construct. The templated self‐assembly process is solvent dependent. When carried out in the solvent regime at the coil to helix transition mid‐point of the foldamer host, system operates under a dynamic equilibrium. Under these conditions, the self‐assembly process is shown to take place between two distinct states, the foldamer helices and the helical template, the template threading through the foldamer helices. The resulting self‐assembled construct has a pseudo‐rotaxane architecture. Under dynamic equilibrium conditions, temperature induced dis‐assembly of the templated assembled construct, is shown to be a cooperative process, whilst re‐assembly is characterized by a large hysteresis. By increasing the volume fraction of water, the solvophobic character of the system is increased and template assembled construct is better stabilised. The assembly system, however, loses its dynamic equilibrium character and falls into kinetic traps. Temperature induced de‐threading, of the foldamer helices, becomes less favourable and loses its cooperative character although the hysteresis loop is reduced. / AFRIKAANSE OPSOMMING: Hiërargiese inligtingsoordrag is bestudeer as ‘n hulpmiddel om goed gedefinieerde nanostrukture met ‘n goeie beeldverhouding voor te berei. Die nanostrukture word voorberei deur middel van self‐samestelling van heliese vouing van poli(para‐arieltriasool) (P(p‐AT)) ‘foldamers’. ‘n Nuwe heliese‐kodon gebaseer op die 1,4 koppelingsgeometrie in 1,4 arieldigesubstitueerde‐ 1,2,3‐triasool is ontwikkel. Heliese vouing word uitsluitlik geïnduseer as al die triasole in die sis konfigurasie is. Deur die triasole in ‘n para konfigurasie te bind, kodeer die heliese kodon vir ‘n heliks met ‘n groot interne kanaal van ~ 3 nm. Een draai van die heliks benodig 14 herhalende eenhede en die heliese gradiënt ~ 0.38 nm. Amfifiliese oligo(etileen glikol) (oEG) eenhede is aan die arieltriasoolruggraat aangeheg. Hierdie aanhegting van oEG eenhede bevorder oplosbaarheid en dit induseer ‘n solvofobiese heliese vouing in oplosmiddels wat nie die hidrofobiese arieltriasoolruggraat oplos nie, maar wel die sy‐kettings volledig oplos. Die binnekant van die heliks is hidrofobies en die buitekant is amfifilies. ‘n Polimeersintese benadering tot die ‘foldamer’ sintese (gebaseer op die koper gekataliseerde siklo‐addisie reaksie tussen ‘n asied en ‘n alkyn) AB stapsgewyse groei polimerisasiestelsel, is ontwikkel. Dit is voorafgegaan deur ‘n geskikte sintetiese protokol vir die AB monomere. Die daaropvolgende P(p‐AT) het ‘n hoë molekulêre massa wat verseker dat daar ‘n hele paar draaie in die heliese ‘foldamer’ is. ‘n DMF/H2O goeie oplosmiddel/ swak oplosmiddel sisteem is vasgestel. Draaiing van die heliks na ‘n spesifieke kant alleenlik is suksesvol geïnduseer deur die toevoeging van suiwer enantiomere van die chirale oEG sykettings. Spektroskopiese handtekeninge van die oplosmiddel‐afhanklike ketting tot heliks transformasie word vasgestel sodat die oorgangstoestande gevolg kan word vanaf primêre tot sekondêre en uiteindelik tesiêre struktuur. Beslissende bewyse vir die formasie van stabiele, lang gestapelde heliese kolomme in die opgeloste toestand is bewys met cryo‐TEM. Die heliese stapels is verskeie mikron lank, maar het verskillende lengtes. Die heliese stapels is parallel aan mekaar en oorvleuel nie. Die lengte van die heliese stapels is egter onbepaalbaar. Beheer oor die lengte en chiraliteit van die self‐samestellende heliese stapels is verkry deur gebruik te maak van ‘n templaat wat die rol van ribonukleïensuur (RNS) in die tabakmosaïekvirus (TMV) naboots. Hidrofobiese α‐heliese polipeptied poli(γ‐bensiel‐Lglutamaat) (PBLG) is gebruik as die templaat. Self‐samestelling word gedryf deur solvofobisiteit in ‘n DMF/H2O stelsel, met die PBLG templaat wat dan geënkapsuleer word binne die hidrofobiese holtes van die gestapelde/ self‐saamgestelde heliese ‘foldamers’. Die lengte en die chiraliteit van die templaat word gebruik om die lengte en chiraliteit van die gestapelde helikse te beheer. Die templaatbemiddelde self‐samestellende proses is afhanklik van die oplosmiddel. Die stelsel is by ‘n dinamiese ewewig wanneer, uitgevoer in ‘n oplosmiddel, die ketting na heliks oorgang die middelpunt van die ‘foldamer’ gasheer bereik het. By hierdie omstandighede vind die self‐samestellende proses plaas tussen twee afsonderlike toestande nl. die ‘foldamer’ helikse en die heliese templaat, en die templaat wat vleg deur die ‘foldamer’ helikse vleg. Die gevolglike struktuur het ‘n pseudo‐rotaxane argitektuur. By dinamiese ewewigstoestande veroorsaak temperatuur dat die self‐samestellende templaatstrukture weer disintegreer. Hierdie is ‘n koöperatiewe proses terwyl die hersamestelling gekarakteriseer word deur ‘n sloerende proses. Deur die waterfraksie te vermeerder, word die solvofobiese karakter van die sisteem verhoog en die templaat selfsamestellende struktuur beter gestabiliseer. Die samestellingsproses verloor egter sy dinamiese ewewigkarakter en val in kinetiese slaggate. Temperatuur geïnduseerde disintegrasie van die foldamer helikse word minder gunstig en dit verloor die koöperatiewe karakter alhoewel die sloering verminder is.

Thesis (PhD)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: Density functional theory (DFT) has been used to investigate the effect of the surrounding molecules on the structure of selected boron-nitrogen compounds. It was found that a very limited number of molecules, orientated according to the experimental crystal structure, are needed to successfully reproduce the large changes in structure witnessed when HCN–BF3 and CH3CN–BF3 crystallises. Specifically, the addition of seven molecules shortens the B–N distance by 0.735 °A in (HCN–BF3)8 and 0.654A° in (CH3CN– BF3)8. Accompanying the large changes in B–N bond length are equally large changes in the N–B–F angle. Investigation of the structure of these complexes in terms of localised electron pairs shows that the availability of lone pairs, in close proximity to the B–N bond axis, plays an important role in the bond change. Through delocalisation of the fluorine lone pairs the antibonding σ ∗(B–N) orbital becomes increasingly occupied as the N–B–F angle lessens and vice versa. Further, an investigation of the specific effects of dipole-dipole interactions was performed by applying uniform electric fields of varying strength along the donor-acceptor bond axis of a series of compounds of the form X–Y; X=H3N, HCN, CH3CN; Y = BF3, BH3, SO3. All complexes investigated show sensitivity to the external electric field, however, only the compounds having nitrile donors and acceptors with fluorine atoms produce large changes, which in turn are dominated by a very sudden large change in B–N bond length occurring in a very narrow range of changing field strength. Analysis of the changes in bond character reveals that HCN–BF3 and CH3CN–BF3 have long bonds in the gas phase, formed primarily through electrostatic interaction between the donor and acceptor. In the short bond in the condensed phase the bond character changes considerably through the introduction of strong electron sharing interactions, i.e. covalent or orbital interactions. Fundamental changes in the nature of the bond, catalysed by surrounding molecules, thus lie at the heart of the large phase-dependent changes in these species. / AFRIKAANSE OPSOMMING: ’n Kohn-Sham elektrondigtheidsteorie (DFT) studie is gedoen op die effek van die omliggende molekules in die kristalstruktuur van sekere molekules wat boor-stikstof bindings bevat. Daar is gevind dat ’n klein aantal molekules, georienteer soos in die eksperimentele kristalstruktuur, benodig word om die groot veranderinge in stuktuur te veroorsaak wat eksperimenteel waargeneem word wanneer HCN–BF3 en CH3CN–BF3 kristaliseer. Spesifiek, die byvoeging van sewe molekules verminder die B–N bindingslengte met 0.735 °A in (HCN–BF3)8 en 0.654 A° in (CH3CN–BF3)8. Die groot veranderinge in B–N bindingslengte gaan saam met ewe groot veranderinge in die N–B–F hoek. ’n Ondersoek van die struktuur van die molekules in terme van gelokaliseerde elektronpare wys dat die beskikbaarheid van alleenpare, wat naby die B–N bindingsas lˆe, ’n belangrike rol speel in the verandering in bindingslengte. Deur delokalisasie van die fluoor alleenpare word die antibindende σ ∗(B–N) orbitaal toenemend beset soos die N–B–F hoek afneem en omgekeerd. Verder is die spesifieke effek van dipool-dipool interaksies ondersoek deur uniforme elektriese velde aan te lˆe langs the donor-akseptor bindingsas van ’n reeks komplekse van die vorm X–Y; X = H3N, HCN, CH3CN; Y = BF3, BH3, SO3. Al die komplekse toon sensitiwiteit teenoor die eksterne elektriese veld, maar net die verbindings wat nitriel akseptore en fluoor atome aan the donor fragmente het, toon groot veranderinge, wat op hulle beurt weer oorskadu word deur ’n skielike verandering in the B–N bindingslengte in ’n nou band van veranderende veldsterkte. Analise van die veranderinge in bindingskarakter toon dat HCN–BF3 en CH3CN–BF3 lang bindings in die gasfase het, wat hoofsaaklik gevorm word deur elektrostatiese interaksies tussen die donor en akseptor fragmente. In die kort binding in die kristalfase is daar ’n aansienlike verandering in the karakter as gevolg van die intrede van sterk elektrondelingsinteraksies, m.a.w. kovalente of orbitaalinteraksies. Fundamentele veranderinge in the manier wat die binding saamgestel word, wat gekataliseer word deur omliggende molekules, is dus die oorsaak van die groot faseafhanklike veranderinge.

Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Polymethacrylates are well known adhesives and can carry specific functionality, but have the disadvantage that their flexible backbones impart limited thermal stability and mechanical strength. Polyurethanes (PUs) are finding increasing application and use in many industries due to their advantageous properties, such as a wide range of flexibility combined with toughness, high chemical resistance and excellent weatherability. PUs do however have some disadvantages, for instance, PU is considered an expensive polymer, especially when considered for solvent based adhesives. the focus of this study was to consider a largely unstudied area of PU chemistry, namely combining PUs with polymethacrylates. Two types of linear urethane macromers (UMs) UM1 and UM2 were synthesized by the polyaddition polymerization of 4,4'-methylenediphenyl diisocyanate (MDI) with ethylene glycol (EG), and MDI with neopentylglycol (NPG), via a pre-polymer method, followed by termination with 2-hydroxy ethylacrylate (2-HEA) and methanol (MeOH) to yield UMs having specific urethane chain lengths, and which have to be predominantly monofunctional. Structural identification of the UMs was verified by MALDI-TOF-MS, FTIR, 13C-NMR and 1HNMR spectroscopy.Various percentages of the respective UMs (0_55 wt % of methacrylate monomers) were then incorporated into polymethyl methacrylate (PMMA) and poly n-butyl methacrylate (PnBMA) backbones via solution free-radical copolymerization. The resulting methyl methacrylate-g-urethane and n-butyl methacrylate-g-urethane copolymers were characterized by 1H-NMR,13C-NMR, FTIR, SEC with double detectors (UV and RI), light scattering, UV-Vis, HPLC, TGA, DSC, DMA and TEM. Weight percentages of UM incorporated into the methyl methacrylate-g-urethane copolymers were calculated using FTIR, UV-Vis and 1H-NMR techniques. Phase separation which occurred between the urethane segment and methacrylate segment in the graft copolymerization products was investigated by DMA, DSC and TEM analysis. Microphase separation occurred in all PMMA-g-UM1 and PnBMA-g-UM1 copolymers: two glass transitions temperatures corresponding to the PMMA or PnBMA and UM1 fractions, respectively, were observed. On the other hand, DMA and DSC results showed that in most graft copolymer products the two respective component parts PMMA-g-UM2 or PnBMA-g- UM2 were compatible, because only one Tg was observed. Two glass transitions occurred for PMMA or PnBMA and UM2 when the amount of UM was increased to 55 wt % during copolymerization and microphase separation was evident in DSC, DMA and TEM measurements. Thermal stability and storage modulus (stiffness) of all the synthesized PMMA-g-urethane and PnBMA-g-urethane copolymers increased as the concentration of urethane macromonomer in the copolymerization feed increased, as confirmed in TGA and DMA results. The surface and adhesive properties of the synthesized graft copolymer were studied by measuring the static contact angle and peel strength. Adhesion increased as the content of UMs increased in the graft copolymer. The graft copolymers prepared using a high UM2 feed for both PMMA and PnBMA showed improved in adhesion compared to the pure methacrylate polymers. The adhesion was better for both leather and for vinyl. / AFRIKAANSE OPSOMMING: Polimetakrilate is bekende kleefstowwe. Hulle het egter die tekortkoming dat hulle buigbare ruggraat beperkte termiese en meganiese stabliteit besit. Poliuretane (PUs) word deesdae al hoe meer gebruik in baie nywerhede as gevolg van hulle baie voordele, insluitend hul wye buigsaamheid tesame met sterkte, hoë chemiese weerstand en uitstekende weerbaarheid. PUs het egter ’n paar nadele: hulle is baie duur, veral wanneer hulle gebruik word in oplosmiddel-gebaseerde kleefstowwe. Die doel van hierdie studie is om die kombinering van PUs met polimetakrilate te bestudeer, 'n onderwerp wat tot dusver baie min aandag-getrek het. Twee tipes liniêre uretaanmakromere (UMs), UM1 en UM2, is gesintetiseer deur gebruik te maak van poliaddisiepolimerisasie van 4,4'-metileendifeniel diisosianaat (MDI) met etileenglikol (EG), en MDI met neopentielglikol (NPG), via ‘n prepolimeermetode, gevolg deur terminering met 2-hidroksiëtielakrilaat (2-HEA) en metanol (MeOH). Die produk hiervan is UMs met spesifieke kettinglengtes (hoofsaaklik monofunksioneel). Die samestelling van die UMs is met behulp van die volgende gevorderde analitiese tegnieke bepaal: MALDI-TOFMS, FTIR, 13C-NMR en 1H-NMR. Verskillende hoeveelhede van die UMs (0_55 gewIing% metakrilaatmonomere) is dan in die polimetielmetakrilaat (PMMA) en poli-n-butielmetakrilaat (PnBMA) ruggrate geïnkorporeer deur middel van oplossing-vryradikaalpolimerisasie. Die samestelling van die kopolimeerprodukte, metiel-metakrilaat-g-uretaan en n-butiel-metakrilaat-g-uretaan, is met behulp van die volgende gevorderde analitiese tegnieke bepaal: 1H-NMR, 13C-NMR, FTIR, SEC met dubbele detektors (UV en RI), ligverstrooiing UV-Vis, HPLC, TGA, DSC, DMA en TEM. Die hoeveelheid UM geïnkorporeer in die metielmetakrilaat-g-uretaan kopolimere is bereken deur gebruik te maak van FTIR, UV-Vis en 1H-NMR data. Die faseskeiding wat plaasgevind het tussen die uretaansegment en die metakrilaatsegment in die produkte van die entpolimerisasie is met behulp van DMA, DSC en TEM ondersoek. In alle PMMA-g-UM1 en PnBMA-g-UM1 kopolimere het mikrofaseskeiding plaasgevind: twee verskillende glasoorgangstemperature vir die PMMA of PnBMA en UM1 fraksies is waargeneem. Hierteenoor het DMA en DSC resultate getoon dat in die meeste entkopolimeerprodukte (PMMA-g-UM2 of PnBMA-g-UM2) was die twee komponente verenigbaar, aangesien net een Tg waargeneem is. In die geval van die kopolimere waar die hoeveelheid UM in die kopolimerisasiereaksies tot 55 gew% verhoog is, is twee glasoorgangstemperature vir PMMA of PnBMA, en UM2 waargeneem. Mikrofaseskeiding is met behulp van DSC, DMA en TEM bewys. Termiese stabiliteit en stoormodulus (styfheid) van alle gesintetiseerde PMMA-g uretaan en PnBMA-g-uretaan kopolimere het toegeneem namate die uretaankonsentrasie in die kopolimerisasiereaksie toegeneem het soos deur middel van TGA en DMA resultate bewys is. Die oppervlakte- en kleefeienskappe van die bereide entkopolimere is bestudeer deur die statiese-kontakhoek en skilkrag te meet. Adhesie het toegeneem namate die UMinhoud toegeneem het. Die entkopolimere berei met hoë PMMA en PnBMA inhoud het uiteindelik beter adhesie getoon as die suiwer metakrilaatpolimere. Die adhesie was beter vir beide leer en viniel.

Thesis (PhD)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: To comply with the ever growing demands for materials with better properties and complex architectures, polymer chemistry has resorted to the use of living free radical polymerization techniques. Despite the structural control some of these techniques offer, major disadvantages do exist. For example, most require ultra-pure reagents, hence only a small fraction of the monomers used in industry can be polymerized in this way. This rendered these new living techniques less advantageous from a commercial point of view. Recently, a revolutionary new living free radical process, namely the reversible addition-fragmentation chain transfer process, or RAFT process, was developed that combines the control over the polymer produced with the robustness and versatility of a free radical process. However, the RAFT process is not without its problems. In some dithioester mediated polymerizations, significant inhibition and rate retardation effects have been observed. Two main opposing opinions have been proposed in recent literature to explain these phenomena observed. The main point of difference between these two groups is the fate of the formed intermediate RAFT radicals, i.e., slow fragmentation of the formed intermediate radicals together with possible reversible intermediate RAFT radical termination, or fast fragmentation of the formed intermediate radicals together with possible irreversible intermediate RAFT radical termination. Between these opposing two groups, there is a difference of six orders of magnitude for the rate of fragmentation of the formed intermediate RAFT radicals. The work presented in this thesis is an attempt to clarify some of the mysteries, i.e., inhibition and rate retardation observed in some RAFT polymerizations. Experimental evidence to support or contradict the theories of the above mentioned two opposing groups was investigated. The concentration-time evolution of the intermediate radical concentration (cy), for styrene and butyl acrylate polymerizations mediated by cumyl dithiobenzoate (COB) at 70°C and 90 °C, was followed via in situ electron spin resonance spectroscopy (ESR). The concentration-time evolution profiles observed were ascribed to the formation of very short chains during the early stages of the reaction. It was also found that the RAFT process is not particularly sensitive to oxygen. The intermediate and propagating radical (cp) concentrations (and their ratio) for the cumyl dithiobenzoate mediated styrene polymerizations were examined by ESR spectroscopy and kinetics. The system showed strong chain length effects in kinetics, assuming all chains were of similar number average molar mass (Mn). However, unusual behavior with respect to existing mechanistic knowledge was observed in other aspects of the system. The central equilibrium "constant" (Keq) was found to be dependent on both temperature and initial reactant concentrations. The observed intermediate radical concentrations were not consistent with predictions based on existing literature models. It was also found that the time dependence of the intermediate radical concentration varies significantly with the type of RAFT agent used. Unexpectedly, intermediate radicals were detected at very long reaction times in the virtual absence of initiator, enhancing the belief of possible reversible termination reactions involving the intermediate radicals. An extra radical (nonpropagating or intermediate) species was observed (via ESR spectroscopy) to form during some reactions. Its concentration increased with time. The combination of data from several analytical techniques provided evidence for the formation of dead chains by the termination of intermediate radicals in the free radical polymerization of styrene, mediated by a cumyl dithiobenzoate RAFT agent, at 84°C. Experiments done focused on the early stages of the reactions, targeting very low final number average molar mass values, with high initiator concentrations. The formation of these terminated chains did not occur to a significant extent until a large fraction of the chains reached a degree of polymerization greater than unity. This corresponded to the occurrence of a maximum in intermediate radical concentration. In situ 1H nuclear magnetic resonance (NMR) and electron spin resonance spectroscopy was used to directly investigate the processes that occur during the early stages (typically the first few monomer addition steps) of an AIBN-initiated reversible addition fragmentation chain transfer polymerization of styrene, in the presence of a cyanoisopropyl dithiobenzoate and cumyl dithiobenzoate RAFT agent, at 70°C and 84 °C respectively. 1H NMR spectroscopy allowed the investigation of the change in concentration of important dithiobenzoate species as a function of time. Identification and concentrations of the radicals present in the system could be inferred from corresponding ESR spectroscopy data. An apparent "inhibition" effect was observed in both the cyanoisopropyl and cumyl dithiobenzoate mediated polymerizations. This effect could be reduced by increasing the reaction temperature to 84 °C. However, the use of cumyl dithiobenzoate as RAFT agent prolonged this effect. This apparent "inhibition" effect was attributed to selective fragmentation of the formed intermediate radicals during the early stages of the reaction, and to different propagation rate coefficients (kp) of the resulting (different) radicals. A change in the equilibrium coefficient for the systems investigated was ascribed to possible progressively decreasing addition and fragmentation rate coefficients of propagating and intermediate radicals formed during the reaction. The increase in intermediate radical concentration, and thus possible intermediate radical termination, was shown to also be a probable cause of the rate retardation observed in the RAFT mediated systems investigated. To conclude, probable causes of the observed inhibition and rate retardation in some dithiobenzoate mediated systems were investigated. It was found that intermediate RAFT radical termination does occurs, albeit reversibly or irreversibly. A maximum in the intermediate radical concentration, and thus possible intermediate radical termination, was seen to occur during the observed rate retardation. An apparent inhibition effect observed was ascribed to a possible change in termination kinetics, the formation of terminated intermediate radical products and a rapidly changing kp of the propagating radicals. / AFRIKAANSE OPSOMMING: Om te voldoen aan die ewig groeiende aanvraag vir materiale met beter eienskappe en komplekse samestellings, is in die polimeerchemie lewende vry-radikaal polimerisasietegnieke ontwikkel. Ten spyte van die feit dat party van die polimerisasie tegnieke die strukuur van die gevormende polimere kan beheer, bestaan daar tog nadele. Die meeste polimerisasie tegnieke benodig ultra suiwer reagense, dus kan net 'n klein fraksie van die monomere wat deur die industrie gebruik word op so 'n manier gepolimeriseer word. Dus, vanuit 'n komersieële oogpunt, is die nuwe lewende polimerisasietegnieke minder voordelig. Onlangs is 'n revolusionere nuwe lewende vry-radikaal polimerisasieproses, naamlike die RAFT-(eng. reversible addition-fragmentation chain transfer process) proses ontwikkel, wat die beheer oor die geproduseerde polimere, kombineer met die robuustheid en veelsydigheid van 'n vry-radikaalproses. Die RAFT proses is egter nie sonder probleme nie. Beduidende inhibisie en vertraging van die polimerisasie tempo is in sommige dithioester-bemiddelde polimerisasies opgemerk. Daar is hoofsaaklik twee opponerende opinies oor die redes vir die inhibisie en vertragings effekte. Die grootste verskil tussen die twee groepe lê in die lot van die gevormde intermediêre radikaal, m.a.w. stadige fragmentasie van die gevormende intermediêre radikale tesame met moontlike onveranderlike intermediêre radikaalterminasie, of vinnige fragmentasie tesame met moontlike omkeerbare intermediêre radikaalterminasie. Tussen die twee groepe, is daar 'n verskil van ses ordegrotes vir die groote van die tempo van fragmentasie van die gevormende intermediêre radikaal. Die werk wat in die tesis weergee word, is 'n poging om sommige van die geheime van die RAFT proses, m.a.w. inhibisie en vertraging van die polimerisasietempo, op te los. Die ondersoek was gerig op eksperimetele bewyse om die teorieë van die twee opponerede groepe of te bevestig of teen te spreek. Die konsentrasie tyd-verandering van die intermediêre radikaal konsentrasie vir stireen- en butielakrilaatpolimerisasie, bemiddeled deur CDB (eng cumyl dithiobenzoate) by 70 oe and 90 oe, is gevolg deur middel van in situ (lat. vir in die oorspronklike plek, m.a.w. binne-in die ESR masjien) elektronspin-resonans (ESR) spektroskopie. Die vorm van die konsentrasie tyd-profiele is toegeskryf aan die vorming van baie kort polimeerkettings gedurende die vroeë reaksietye. Dit is ook bepaal dat die RAFT-proses nie besonder sensitief was vir suurstof nie. Die intermediêre en die propagerende radikaalkonsentrasie (en hulle verhouding) vir die CDB bemiddelde stireen polimerisasies, is bepaal deur middel van elektronspin-resonans spektroskopie en die kinetika van die sisteem. Die kinetika van die sisteem toon 'n sterk afhanklikheid teenoor die lengte van die polimeerkettings, as aanvaar word dat al die kettings dieselfde numeriese gemiddelde molêre massa het. Des nieteenstaande, is egter onverwagte gedrag in ander aspekte van die sisteem opgemerk. Dit was ook gevind dat die sentrale ewewigs-"konstante" (Keq) afhanklik was van die temperatuur en die oorspronklike reaktant konsentrasie. Die bepaalde intermediêre radikaalkonsentrasie het verskil van voorspelde waardes gebaseer op literatuur modelle. Dit is ook gevind dat die intermediêre radikaalkonsentrasie afhanklik is van die tipe RAFT agent wat in die polimerisasie reaksies gebruik word. Intermediêre radikale is onverwags gevind na baie lang reaksietye, wanner verwag is dat die konsentrasie van die afsetter, en dus ook die intermediêre radikale, baie klein sou wees. Dit het die verwagting dat omkeerbare intermediêre radikaalterminasie kan plaasving, versterk. 'n Ekstra radikale spesie, wat gedurende die reaksie vorm en waarvan die konsentrasie groter word met tyd, is ook deur ESR-spektroskopie geidentifiseer. 'n Kombinasie van verskillende skeikundige tegnieke is gebruik om bewyse te kry vir die vorming van dooie kettings wat ontstaan deur middel van intermediêre radikale terminasiereaksies, in die vry-radikaalpolimerisasie van stireen, wat deur 'n CDB RAFT-agent bemiddeled word by 84°C. Eksperimente is gedoen om die reaksie tydens vroeë reaksietye te ondersoek. Baie hoë afsetter konsentrasies is ook gebruik, wat tot uiters lae numeriese gemiddelde molêre massas van die polimeerkettings gelei het. Beduidende konsentrasies van die dooie kettings is eers gevind nadat 'n graad van polimerisasie van groter as een bereik is. Dit het ooreengestem met 'n maksimum in die konsentrasie van die intermediêre radikale. In situ 1H kern magnetiese-resonans (KMR) en electronspin-resonans spektroskopie was gebruik om 'n RAFT proses, wat gedurende die vroeë reaksie tye (tipies gedurende die eerste paar monomeer toevoegingstappe) te bestudeer, wat deur AIBN (eng azo bis(isobutyronitrile)) afgeset word en bestaan uit stireen en CIDB (eng cyanoisopropyl dithiobenzoate) en CDB RAFT agente onderskeidelik, en by 70°C and 84 °C reageer. 1H KMRspektroskopie was gebruik om die veranderinge in die konsentrasie van die belangrike spesies te bepaal. Die identifikasie en konsentrasie van die radikale kon bepaal word deur middel van ESR data. 'n Skynbare 'inhibisie-effek' is waargeneem in die reaksies wat bemiddeled word deur CIDB en CDB. Die effek is verminder toe die reaksietemperatuur verhoog is na 84°C. Die gebruik van CDB as RAFT agent het egter die effek vergroot. Die skynbare 'inhibisie effek' was toegeskryf aan die selektiewe fragmentasie van die intermediêre radikale gedurende die vroeë reaksietye, en aan verskillende propagasie tempokoëffisiënte (kp) van die verskillende radikale. Die veranderlike sentrale ewewigskoëffisiënte is toegeskryf aan die toevoegings en fragmentasie tempokoëffisiënte van die propagerende en intermediêre radikale wat toenemend afneem. Die is ook getoon dat die toename in die konsentrasie van die intermediêre radikale en dus moontlike intermediêre radikale terminasie, 'n oorsaak kan wees van die vertraging van die polimerisasietempo in die RAFT-bemiddelde reaksies. Ter samevatting, die waarskynlike oorsake vir inhibisie en die polimerisasietempo vertraging opgemerk in sekere dithiobenzoaat-bemiddelde sisteme, is ondersoek. Dit was gevind dat intermediêre radikaalterminasie wel kan gebeur, of dit nou omkeerbaar of onveranderlik gebeur. 'n Maksimum in die konsentrasie van die intermediêre radikale, en dus moontlike intermediêre radikaalterminasie, het voorgekom tesame met 'n vertraging in die polimerisasietempo. Die skynbare inhibisie-effek wat opgemerk was kan toegeskryf word aan 'n moontlike verandering in die terminasie kinetika, die formasie van getermineerde intermediêre radikale en 'n vinnig veranderende propagasie tempokoëffisiënt.

Dissertation (PhD)--Stellenbosch University, 2004 / ENGLISH ABSTRACT: Over the past decade peptide bola-amphiphiles have been the subject of much attention because of their role as potential models of functionalised membranes and as new generation surfactants. In the quest for new surfactants a peptidomimetic-based approach was used to design a library of novel 'hybrid' bola-amphiphilic peptide surfactants derived from sapecin B and a model symmetrical oligo-glycine bola-amphiphile. The library was divided into different series, each one purpose-built; first, to investigate hierarchal supramolecular architecture and, second, to investigate potential antimicrobial activity. The bola-amphiphiles were synthesised using Fmoc-polyamide based solid phase peptide synthesis and purified via high performance liquid chromatography. The peptide hybrids were characterised using electro spray mass spectrometry, nuclear magnetic resonance, different modes of electron microscopy, Fourier-transform infrared spectroscopy and, in some cases, further studies were done using circular dichroism and bioactivity tests. The model bola-amphiphile suberamide(GGh was synthesised using peptide fragment condensation based on solid phase peptide synthesis. The synthesis is bi-directional (N~C and C~N) and versatile, making it possible to synthesis new dicarboxylic oligopeptide bola-amphiphiles and other analogous compounds. The product, suberarnide(GG)2, was purified using its inherent ability to self-assemble in an acidic solution. Novel asymmetrical bola-amphiphiles composed of dipeptide head groups linked via an aliphatic (I)-amino acid, serving as a hydrocarbon spacer, were also synthesized. Two small libraries of bola-amphiphiles were established - the first involved variation in to-amino acid length and the other variation in the C-terminal amino acid. The bolaamphiphiles were self-assembled in either 0.1% trif1uoroacetic acid or 0.1% triethylamine. Electron microscopy revealed the formation of a variety of higher order supramolecular architectures based on ~-sheet self-assembly. FT-IR spectrometry indicated that interlayer and intralayer hydrogen bond networks, together with strong selfassociation, promoted by the hydrophobic effect and, in certain instances, electrostatic interactions, are responsible for the variety of supramolecular architectures. Variations in the higher order structures can be attributed to amino acid composition, specifically length of m-amino acid, nature of the C-terminal amino acid and the optimised solvent conditions used for the self-assembly process. A third library of novel 'hybrid' bola-amphiphilic peptide surfactants, in which a cationic tripeptide motif from antimicrobial peptides was combined in a hybrid molecule containing a oi-amino acid residue, was established. These bola-amphiphiles displayed potent antimicrobial activity against both Gram-positive and Gram-negative bacteria; the analogues were as active or more active than the leader peptides yet, remarkably, displayed little or no appreciable haemolytic activity. These organopeptide bolaamphiphiles thus demonstrated selective toxicity towards bacteria. The hydrophobicity imparted by the co-amino acid has contrasting effects on haemolysis and antimicrobial activity of the peptide analogues. The other unique feature of these peptides and their analogues is the fact they self-assembled into complex supramolecular architectures, composed primarily of ~-sheets. Their self-assembly is primarily governed by hydrophobic interactions together with inter and intralayer hydrogen bonding. Electron microscopy clearly revealed higher order structures for both peptides and analogues. The generation of higher order supramolecular architecture is dependent on optimisation of ~- sheet self-assembly whereas antimicrobial activity is dependent on the balance between net positive charge and optimum hydrophobicity of the peptide hybrids. This study has demonstrated that it is possible to design hybrid peptide surfactants capable of producing higher order supramolecular architecture and improving the antimicrobial activity whilst reducing the haemolytic effect. The study and design of these versatile 'purpose-built' bio-inspired surfactants heralds a novel approach, one that shows tremendous potential. / AFRIKAANSE OPSOMMING: Die afgelope dekade het bola-amfifiliese peptiede baie aandag geniet weens hulle rolle as potensiële modelle van gefunksionaliseerde membrane en as 'n nuwe generasie surfaktante. In die soeke na nuwe surfaktante is 'n peptiedornimetiese benadering gevolg om 'n biblioteek van nuwe "hibried" bola-amfifiliese peptiedsurfaktante van sapesien B en 'n simmetriese oligoglisien bola-amfifil af te lei. Die biblioteek is in verskillende reekse onderverdeel. Elke reeks is doelmatig vervaardig om ondersoek in te stel na twee aspekte, nl. die rangorde van die supramolekulêre strukture en die potensiële antirnikrobiese aktiwiteit. Fmoc-poliamied gebaseerde soliedefase-peptied-sin-tese is aangewend vir die sintese van die bola-amfifile en hulle is met behulp van hoë doeltreffendheid vloeistofchromatografie gesuiwer. Die peptiedhibriede is gekarakteriseer met behulp van elekrosproei massaspektrometrie, kern-magnetiese resonansie, verskillende modusse elektronrnikroskopie, Fourier-transform infrarooispektrometrie en, in sommige gevalle is verdere studies met sirkulêre dichroïsme en bioaktiwiteitstoetsing uitgevoer. Die bola-amfifilsuberamiedtflfij--model is met behulp van peptiedfragment-konden-sasie gesintetiseer gegrond op soliedefase-peptiedsintese. Dit sintese vind in twee rigtings plaas (N~C en C~N) en is veelsydig aangesien dit die sintese van sowel nuwe dikar-boksielbola- amfifile as ander analoë verbindings moontlik maak. Die produk, suber-arnied(GG)2, is gesuiwer met behulp van die verbinding se inherente vermoë tot self-montering in suur oplossings. Nuwe assimetriese bola-amfifile, saamgestel uit dipeptiedkopgroepe, gekoppel via 'n alifatiese ro-aminosuur, wat as koolwaterstofspasieerder dien, is ook gesintetiseer. Twee klein bola-amfifilbiblioteke is saamgestel - die een het variasies in die ro-aminosuur se lengte omvat en die ander een variasies in die C-terrninale aminosuur. Selfmontering van die bola-amfifile het plaasgevind in of 0,1 % trifluorasynsuur Of 0,1 % trietielamien. Elektronrnikroskopie het die bestaan van 'n verskeidenheid hoërorde supramolekulêre strukture, gegrond op p-plaatselfmontering, aangetoon. Uit FT-IR-spektrometrie blyk dit dat inter - en intralaag waterstofbinbdingsnetwerke en sterk selfassosiasie, 19. word bevorder deur die hidrofobiese effek en, in sekere gevalle, elektrostatiese interaksies, is verantwoordelik vir die verskeidenheid supramolekulêre strukture. Variasies in die hoërorde strukture kan toegeskryf word aan aminosuursamestelling, in besonder die lengte van die ro-aminosuur, die aard van die C-terminale aminosuur en die geoptimiseerde oplosmiddelkondisies wat gebruik is vir die selfmonteringsproses. 'n Derde biblioteek nuwe "hibried" bola-amfifiliese peptiedsurfaktante, waarin 'n kationiese tripeptiedmotief uit antimikrobiale peptiede gekombineer is met 'n m-aminosuurresidu, is geskep. Sommige van hierdie bola-amfifile het 'n kragtige antimikrobiese aktiwiteit teenoor sowel Gram-positiewe as Gram-negatiewe bakterieë gertoon. Die analoë strukture was aktief, of selfs meer aktief as die voorste peptiede maar het, verbasend genoeg, nie 'n beduidende hemolitiese aktiwiteit vertoon nie. Hierdie organopeptied bola-amfifil het dus 'n selektiewe toksisiteit teenoor bakterieë vertoon. Die hidrofo-bisiteit, as gevolg van die ui-aminosuur, het 'n resiproke effek op hemolise en die antimikrobiese aktiwiteit van die peptiedanaloë. Die ander uitstaande kenmerk van die peptiede en hulle analoë is die vermoë om te selfmonteer en komplekse supramolekulêre strukture, bestaande hoofsaaklik uit ~-plate, te vorm. Hierdie selfmontering word in hoofsaak beheer deur hidrofobiese interaksies asook inter - en intralaagwaterstofbinding. Elektronmikroskopie het duidelik hoërorde strukture getoon by sowel dié peptiede as hulle analoë. Die ontwikkeling van hoërorde supramolekulêre struktuurvorms is afhanklik van die optimalisering van die ~-plaatselfmontering. Daarteenoor is die antimikro-biese aktiwiteit afhanklik van die balans tussen die netto positiewe lading en die opti-male hidrofobisiteit van die peptiedhibriede. Hierdie studie het getoon dat dit moontlik is om hibriedsurfaktante te ontwerp wat hoërorde supramolekulêre strukture te produseer en om die antimikrobiese aktiwiteit te verbeter terwyl die hemolitiese effek verminder word. Die studie en ontwerp van hier-die veeldoelige, "doelmatig-gesintetiseerde" biogeïnspireerde surfakante stel 'n unieke benadering daar, wat oor groot potensiaal beskik.

Thesis (PhD)--Stellenbosch University, 2005. / ENGLISH ABSTRACT: See fulltext for abstract / AFRIKAANSE OPSOMMING: Sien volteks vir opsomming

Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: Please refer to full text for abstract

Thesis (PhD)--Stellenbosch University, 2001. / ENGLISH ABSTRACT: Please refer to fulltext for abstract. / AFRIKAANSE OPSOMMING: Sien volteks vir opsomming.

Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The distribution of different free chemical functional groups on wood and pulp fibres was determined by means of atomic force microscopy (AFM) with chemically modified tips. Because these functional groups show a higher affinity to similar groups on the substrate surface during scanning, AFM images were recorded using an additional digital pulsed-force mode (DPFM) controller. This allowed the distribution of the chemical components to be imaged and to a degree, also to be quantified. The investigated tip coatings showed different sensitivities towards the major chemical components present in wood fibres. These components were determined on spin-coated films as well as wood fibres. It was possible to make a clear distinction between cellulose and lignin in both cases. This technique could therefore be used to differentiate between cellulose and lignin present on pulp fibre surfaces and to confirm the successful removal of lignin by pulping. The chemical composition of wood fibres and fibre surfaces of several acacia and eucalyptus species, and hybrids originating from various growth sites in South Africa, are compared. The objective was to determine the differences in chemical surface composition due to genetics or site. The motivation for this was to eventually facilitate a tailor-made supply of wood for pulping which results in an optimal blend of fibres that can be pulped together with similar yields. This, however, first requires a sound knowledge of the fibre properties. The surface functionality on the single fibre level is a key property because it determines how good inter-fibre bonding will be when paper is formed, which in turn depends to a large degree on the amount of free hydroxyl groups that are available and therefore on the cellulose content on the fibre surface. The cellulose and lignin contents on the fibre surface were determined with chemical force microscopy (CFM), a variation of AFM. CFM involves the use of chemically modified tip using selected functional groups. Since, the general bulk composition of the fibre and the surface composition differ, both parameters were determined. Significant differences in the cellulose and lignin content on fibre surfaces were found, with regard to genotype and site, respectively. In some, but not all, cases the surface composition of wood fibres followed the bulk composition and differences were generally more pronounced. Differences due to genotype were significant, especially with regards to the surface lignin content - but variation due to site was also distinctly recognisable. This variation in surface functionality could be the reason why some pulpwood blends result in a lower pulp yield and different quality. / AFRIKAANSE OPSOMMING: Die verspreiding van verskillende vrye chemiese funksionele groepe op hout en pulpvesels is bepaal deur middel van atoomkragmikroskopie (AFM), met chemies-gemodifiseerde punte (tips). Omdat hierdie funksionele groepe 'n hoër verwantskap tot soortgelyke groepe op die substraat se oppervlak gedurende skandering toon, kan AFM-beelde wat met 'n addisionele digitalepulskragmodusbeheerstel bepaal word dit moontlik maak om die verspreiding van die chemiese komponente uit te beeld en tot op ‘n sekere vlak te kwantifiseer. Die ondersoekte punt-oppervlakmiddels het verskillende sensitiwiteite teenoor die hoof chemiese komponente in die houtvesels en spin-bestrykte films getoon. 'n Duidelike onderskeid kon in beide gevalle tussen sellulose en lignien gemaak word. Hierdie tegniek kon dus gebruik word om te onderskei tussen sellulose en lignien wat op die pulpveseloppervlak teenwoordig was en om die suksesvolle verwydering van lignien gedurende die pulpproses (pulping) te bevestig. In hierdie studie is die chemiese samestelling van houtvesels en die veseloppervlaktes van verskeie akasia en eucalyptus spesies, asook dié van gekruisde spesies wat van verskeie werfliggings in Suid-Afrika afkomstig is, vergelyk. Die doel was om te toets vir verskille in chemiese oppervlaksamestellings, wat veroorsaak kan word deur genetika of werf verskille, met die uiteindelike mikpunt om ‘n spesiaal-gemaakte voorraad van hout vir pulping te fasiliteer, wat kan lei tot 'n optimale mengsel van vesels wat saam gepulp kan word met soortgelyke opbrengs. Dit vereis natuurlik 'n goeie kennis van die veseleienskappe. Die oppervlakfunksionering van enkel vesels is ‘n kritiese eienskap omdat dit bepaal hoe goed interveselverbindings sal wees wanneer papier gevorm word. Dit hang tot ‘n groot mate af van die hoeveelheid vry hydroksielgroepe wat beskikbaar is en dus ook van die sellulose inhoud op die veseloppervlak. Die sellulose- en lignieninhoud op die veseloppervlak is bepaal met chemiese kragmikroskopie – 'n variasie van atoomkragmikroskopie. Omdat die algemene grootmaat samestelling van die vesel en die oppervlaksamestelling mag verskil, is altwee parameters bepaal. Beduidende verskille in die sellulose- en lignieninhoud, met betrekking tot genotipe en werfligging, op veseloppervlaktes is gevind. In sommige, maar nie alle, gevalle het die oppervlaksamestelling van houtvesels ooreengestem met die grootmaatsamestelling, en verskille was oor die algemeen meer beduidend. Verskille as gevolg van genotipe was beduidend, veral met betrekking tot die oppervlak lignieninhoud, maar variasie as gevolg van werfligging was ook duidelik herkenbaar. Hierdie variasie in oppervlakfunksionering kan die rede wees hoekom sommige pulp–hout mengsels lei tot 'n laer pulpopbrengs en verskille in kwaliteit.

Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch, 2010. / ENGLISH ABSTRACT: The properties of polymer nanocomposites depend greatly on the chemistry of the polymer matrices, the nature of the nanofillers, and the way in which they are prepared. Understanding the synthesis–structure–property relationship of nanocomposites is vital for the development of advanced polymer nanocomposites with enhanced mechanical strength, stiffness and toughness for structural engineering applications. To this end, the primary aim of this study was to determine the impact that the preparation methods have on the properties of PP/filler nanocomposites, with specific focus on the in situ polymerization of propylene via the methylaluminoxane (MAO) activated metallocene catalyst technique. Two different fillers (Silica and Calcium carbonate) were used as support for the metallocene catalysts. Different supporting methodologies for the synthesis of the supported catalyst were examined. A C2 symmetric metallocene catalyst ansa dimethylsilylbis(2-methyl benzoindenyl) zirconium dichloride (MBI) was used in this study. The catalyst systems were then evaluated for propylene polymerization. The early observation shows that a direct adsorption of the metallocene onto the filler has a diminishing effect on the catalyst productivity and the fillers had to be treated with MAO in order to avoid catalyst deactivation by the filler surface. Due to the low productivity of the supported active species, the presence of soluble catalyst active species, besides the supported active species is required in the synthesis of PP nanocomposites via in situ polymerizations. The syntheses of PP nanocomposites were carried out via in situ polymerization in which different quantities of MAO treated fillers were reacted with pre-activated catalyst solution. The effect of the addition of MAO-filler on the polymerization kinetics and consequently on PP matrix microstructure was investigated. Changes in the in situ polymerization kinetics, compared to kinetics of homogeneous polymerization, were observed. Therefore, the microstructure of the polymer matrix was also influenced by the presence of nanofillers in the polymerization media. The influence of the different synthesis methods on the performance of the nanocomposites was investigated using melt-mixed PP/filler nanocomposites obtained using PP homopolymer. The dispersed phase morphologies of the different nanocomposites were investigated by transmission electron microscopy (TEM). Results show that PP nanocomposites with improved filler dispersion were achieved by in situ polymerization compared to melt-mixed nanocomposites. The influence of the synthesis method on the crystallization behaviour of PP nanocomposites was also investigated. It was found that, for the in situ prepared nanocomposites the tacticity of the PP matrix plays the major role in determining the degree of crystallinity. Results also show that when nanocomposites with comparable PP matrices are compared, the overall crystallization rate of the in situ polymerized nanocomposites is higher than that of the melt mixed nanocomposites. The mechanical properties of in situ polymerized PP and melt mixed PP nanocomposite were also investigated and compared. Due to improved nanoparticle dispersion in the PP matrix, in situ polymerized nanocomposites show enhanced mechanical properties, especially tensile and impact properties, compared to pure PP and melt mixed prepared nanocomposites when a PP matrix of equivalent microstructure was used. Finally, the melt compounding method was further investigated using different fillers and commercial PP as a matrix. The effect of filler type, size and applied surface coating on the flow and mechanical properties of PP nanocomposites was studied. The aim of this part of this study is to obtain a good trade-off between the processability and the mechanical properties and to gain insight into the cause of the emergence of different properties for nanocomposites prepared by melt compounding. / AFRIKAANSE OPSOMMING: Die eienskappe van polimeer nanokomposiete hang grotendeels af van die chemie van die polimeer matriks, die wese van die nano-vullers, en die manier waarop hierdie materiale berei word. Om die sintese-struktuureienskap verwantskap te verstaan is noodsaaklik vir die ontwikkeling van gevorderde nanokomposiete met beter meganiese eienskappe, styfheid en taaiheid vir strukturele ingenieurstoepassings Die primêre doelstelling van hierdie studie was dus om die impak van voorbereidingsmetodes op die eienskappe van PP/vuller nanokomposiete te bestudeer, met spesifieke fokus op die in-situ polimerisasie van propileen met metiel alumoksaan-geativeerde metalloseen kataliste. Twee verskillende vullers (silika en kalsium karbonaat) is gebruik as ondersteuning vir die metalloseen kataliste. Verskillende metodiek is gebruik om die ondersteunde kataliste te berei. ‘n C2 simmetriese metalloseen katalis ansa-dimetielsiliel(2-metiel bensoindeniel) sirkonium dichloride (MBI) is in die studie gebruik. Die katalissisteme is daarna evalueer vir propileen polimerisasie. Daar is oorspronklik vasgestel dat direkte adsorpsie van die metalloseen op die vuller ‘n negatiewe effek op die katalis aktiwiteit gehad het, en dat die vuller oppervlak eers met MAO behandel moes word om deaktivering van die katalis deur die vuller-oppervlak te vermy. As gevolg van die lae aktiwiteit van die ondersteunde aktiwe katalisspesies, is die teenwoordigheid van opgeloste aktiewe katalis nodig vir die voorbereiding van PP nanokomposiete via in situ polimerisasie-reaksies. Die sintese van PP nanokomposiete is uitgevoer deur in –situ polimersiasie waartydens verskillende hoeveelhede MAO-behandelde vullers gereageer is met vooraf-geaktiveerde katalis oplossings. Die effek van die byvoeging van MAO-vuller op die polimerisasie-kinetika en gevolglik op die PP matriks mikrostruktuur is ondersoek. Dit is gevind dat die mikrostruktuur van die polimeer-matriks beinvloed word deur die teenwoordigheid van nanovullers in die polimerisasie-medium. Die invloed van verskillende bereidingsmetodes op die eienskappe van die nanokomposiete is ondersoek deur smelt-vermengde PP/vuller nanokomposiete te maak. Die dispersie-fase morfologie van verskillende nanokomposiete is ondersoek deur transmissie elektron mikroskopie (TEM). Resultate wys dat PP nanokomposiete met verbeterde vuller-dispersie berkry is deur in situ polimerisasie in vergelyking met die smelt-vermengde materiale. Die effek van die sintese-metode op die kristallisasie van die PP nanokomposiete is ook ondersoek. Daar is gevind dat, vir die in situ bereide nanokomposiete, die taktisiteit van die PP matriks die grootste rol speel in die bepaling van die persentasie kristalliniteit. Resultate het ook gewys dat, wanneer nanokomposiete met soortgelyke PP matrikse vergelyk word met die in situ nanokomposiete, die laasgenoemde se tempo van kristallisasie hoer is as vir die smelt-vermengde nanokomposiete. Die meganiese eienskappe van die in situ bereide en smelt-vermengde PP nanokomposiete is ook ondersoek en vergelyk. As gevolg van verbeterde nano-partikel dispersie in die PP matriks, het die in situ bereide nanokomposiete beter meganiese eienskappe openbaar, in vergelyking met die smelt-vermenge nanokomposiete, veral trek- en slagsterkte. . Laastens is die smelt-vermengings metode verder ondersoek deur gebruik te maak van verskillende vullers en kommersiële PP as matriks. Die effek van die tipe vuller, die grootte en die oppervlakbedekking van die vullerpartikels op die vloei en meganiese eienskappe van die PP nanokomposiete is ondersoek. Die doel van hierdie studie was om ‘n balans te kry tussen prosesseerbaarheid en meganiese eienskappe en om insig te verkry oor die verskille in eienskappe wat openbaar word wanneer smeltvermengde nanokomposiete bereie word.