Thesis (PhD)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Novel silicone nanocomposites were prepared using poly(acrylonitrile) (PAN) based reinforcing fibres as well as multi-walled carbon nanotubes (MWCNTs). Compatibility of the fibre fillers with the silicone matrix required the synthesis of novel amphiphilic, organic–inorganic graft copolymers of PAN and poly(dimethylsiloxane) (PAN-g-PDMS). These fibre precursor materials were synthesised via the “grafting through” technique using conventional free radical copolymerisation. The PDMS macromonomer content in the feed was varied from 5 wt% to 25 wt% and the molecular weights of the macromonomer were 1000 g.mol-1 and 5000 g.mol-1. The solvent medium of the precipitation reaction was optimised at a volume ratio of 98% benzene to 2% dimethylformamide (DMF). Successful incorporation of PDMS yielded graft copolymer blend materials of PAN-g-PDMS, blended with PAN homopolymer and unreacted PDMS macromonomer. A gradient elution profile was developed to track the successful removal of the PDMS macromonomer via hexane extraction. The gradient profile showed that as the PDMS content in the feed increased, the number of graft molecules in the blend increased relative to the number of PAN homopolymer molecules. The crystallisability of the PAN segments was shown to decrease as the PDMS content increased. The synthesised polymer was used as precursor material for the electrospinning of fibre fillers. The electrospinning of the precursor material was successfully achieved using 100% DMF as electrospinning solution medium. The amphiphilic nature of the precursor material in DMF resulted in self-assembled aggregate structures in the electrospinning solution. An increasing PDMS content was shown to affect the aggregation of the precursor material, and resulted in an increase in the solution viscosity. The “gel-like” solutions limited the achievable fibre morphological control when altering conventional electrospinning parameters such as voltage, tip-to-collector distance, and solution concentrations. The rapid evaporation and stretching of the solution during electrospinning, combined with the phase segregated amphiphilic molecules in solution and the crystallisation of the PAN segments resulted in (non-equilibrium morphology) fully porous fibres. The crystallinity was shown to decrease after electrospinning of the fibre precursor materials. Successful incorporation of surface oxidised MWCNTs into the electrospun fibres was achieved. The content of nanotubes was varied from 2 wt% to 32 wt%. The MWCNTs reduced the mean fibre diameters by acting as cross-linkers between the PAN segments and increasing the solution conductivity. The nanotubes dispersed well throughout the porous structure of the fibres and aligned in the direction of the fibre axis. Fabrication of silicone composites containing nonwoven and aligned fibre mats (with 8 wt% MWCNTs in the fibres, and without) was successfully achieved. The compatibilisation of the PDMS surface segregated domains allowed excellent dispersion and interaction of the PAN based fibre fillers with the silicone matrix. Mechanical analysis showed improved properties as the PDMS content in the fibre increased. The highest PDMS content fibres did, however, exhibit decreased properties. This was ascribed to increased PDMS (soft and weak) content, decreased crystallinity and increased fibre diameter (lower interfacial area). Dramatic improvements in strength, stiffness, strain and toughness were achieved. The most significant result was an increase in strain of 470%. The mechanical results correlated with results of SEM analysis of the fracture surfaces. The dramatic improvements in properties were a result of the fibre strength and ductility, as well as the mechanism of composite failure. / AFRIKAANSE OPSOMMING: Nuwe silikonnanosamestellings is berei deur gebruik te maak van poli(akrilonitriel) (PAN) gebaseerde versterkende vesels wat multi-ommuurde koolstof nanobuisies bevat het. Versoenbaarheid van die vesels met die silikonmatriks het die sintese van nuwe amfifiliese, organies–anorganiese ent-kopolimere van PAN en poli(dimetielsiloksaan) (PAN-g-PDMS) benodig. Die vesel voorlopermateriaal is deur middel van ‘n “ent-deur” vryeradikaalkopolimerisasie gesintetiseer. Die inhoud van die PDMS makromonomeer in die reaksie het gewissel vanaf 5% tot 25%. Die gebruik van twee verskillende molekulêre massas makromonomere is bestudeer (1000 en 5000 g.mol-1). Die optimale oplosmiddelmengsel vir die neerslagreaksie was 'n volume verhouding van 98% benseen tot 2% dimetielformamied (DMF). Suksesvolle insluiting van PDMS het versnitmateriale van PAN-g-PDMS kopolimere gemeng met PAN homopolimere en ongereageerde PDMS makromonomere gelewer. 'n Gradiënteluering- chromatografiese profiel is ontwikkel om die suksesvolle verwydering van die PDMS makromonomere via heksaanekstraksie te bepaal. Die gradiëntprofiel het aangetoon dat indien die PDMS inhoud in die reagense verhoog is, die aantal entmolekules relatief tot PAN homopolimeermolekules ook verhoog het. 'n Toename in PDMS inhoud het egter 'n afname in kristallisasie van die PAN segmente tot gevolg gehad. Die gesintetiseerde polimeer is gebruik as die beginmateriaal vir die elektrospin van veselvullers. Die elektrospin van die beginmateriaal was suksesvol wanneer 100% DMF as elektrospinoplosmiddel gebruik is. Die amfifiliese aard van die beginmateriaal in DMF lei tot outokonstruksie van aggregaatstrukture in die elektrospinoplossing. Toenemende PDMS inhoud beïnvloed die outokonstruksie van die molekules in oplossing en het gelei tot 'n toename in die oplossings se viskositeit. Die "gelagtige" oplossings beperk die haalbare vesel se morfologiese beheerbaarheid wanneer konvensionele elektrospin parameters soos elektriese spanning, punt-tot-versamelaar afstand, en oplossingkonsentrasies gewysig word. Die vinnige verdamping en strek van die oplossing tydens elektrospin, gekombineer met die fase-geskeide amfifiliese molekules in oplossing en die kristallisasie van die PAN segmente, het gelei tot (nie-ewewig morfologie) volledige poreuse vesels. Die kristalliniteit van die veselbeginmaterial het afgeneem nadat elektrospin toegepas is. Die insluiting van die oppervlak-geoksideerde multi-ommuurde koolstof nanobuisies in die elektrogespinde vesels was suksesvol. Die inhoud van die nanobuisies het gewissel van 2 wt% tot 32 wt%. Die MWCNTs het die gemiddelde veseldeursnit verminder deur op te tree as kruisbinders tussen die PAN segmente van die molekules. Die nanobuisies was goed versprei deur die poreuse struktuur van die vesels en dit was gerig in die rigting van die vesel-as. Bereiding van die silikonsamestellings bestaande uit nie-geweefde en gerigte veseloppervlakke (met en sonder 8 wt% multi-ommuurde koolstof nanobuisies in die vesel) was suksesvol. Die versoenbaarheid tussen die oppervlak van die PDMS-geskeide gebiede en die silikonmatriks laat uitstekende verspreiding en interaksie van die PAN-gebaseerde veselvullers met die silikonmatriks toe. Meganiese analise het aangetoon dat die fisiese eienskappe verbeter het namate die PDMS inhoud in die vesel vermeerder het. Die vesels met die hoogste PDMS inhoud het egter verswakte eienskappe getoon. Dit is toegeskryf aan ‘n verhoogde PDMS inhoud (sag en swak), ‘n afname in kristalliniteit en ‘n verhoogde veseldeursnit (laer grensoppervlakke). Dramatiese verbeterings in sterkte, styfheid, verlengbaarheid, vervorming en taaiheid is bereik. Die mees betekenisvolle gevolg was 'n toename in die verrekking van 470%. Die meganiese resultate is gekorreleer met SEM ontleding van die brekingsoppervlakke. Die veselkrag en vervormbaarheid, sowel as die meganisme van die splyting van die samestellings, het tot die dramatiese verbeterings in die meganiese eienskappe gelei.

Thesis (PhD)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: The main objective of this study was to develop electrospun nanofibres with both antimicrobial and antibiofouling properties for possible application in water filtration. To do this, two routes were investigated: firstly, the use of biocides and bactericidal copper salts to introduce bactericidal properties on electrospun nanofibres. Secondly, the modification of polymers using furanone compounds to obtain nanofibres with the ability to repel microbial attachment. Fabrication of biocide-containing PVA nanofibres was successful. This was achieved through direct doping of PVA solutions with AquaQure which is an aqueous biocide comprising of mainly Cu2+ and Zn2+, prior to the electrospinning process coupled with chemical crosslinking using glyoxal. The conventional needle based electrospinning technique was used to fabricate these nanofibrous mats. The presence of the constituents of AquaQure on surfaces of PVA/AquaQure nanofibrous mats was confirmed using energy dispersive x-ray analysis (EDX). ATR/FTIR, XRD, TGA, DSC and SEM techniques were used to do chemical and thermal analysis of the nanofibres in comparison with pristine PVA nanofibres. These nanofibres demonstrated antimicrobial activity of up to 5 log against the Gram-positive strain S. aureus Xen 36 and Gram-negative strains E. coli Xen 14, S. typhimurium Xen 26, P. aeruginosa Xen 5 and K. pneumoniae Xen 39. Because of crosslinking, these fibres also demonstrated good water stability. Leaching of the ions constituting AquaQure was limited and compared with South African national standards for drinking water, the water filtered through these nanofibress was deemed safe for human consumption. Bioluminescence imaging and fluorescence microscopy were used to confirm antimicrobial activity results obtained from plate counting. These nanofibres demonstrated satisfactory antimicrobial efficiency but did not repel microbial attachment. The second part of this study entailed the investigation of copper-doped PVA and SMA nanofibres for antimicrobial activity. Although bactericidal properties of copper are well documented, its selection was based on the fact that it is the main constituent of the AquaQure. Bubble electrospinning was used instead of needle electrospinning to upscale nanofibre production. Similar techniques as those used in PVA/AquaQure nanofibres were used to characterize the copper functionalized nanofibres. Even though these nanofibres demonstrated exceptional antimicrobial efficacy (up to 5 log) for all the strains, bioluminescence imaging indicated a trend for these cells to enter a dormant state on contact with the copper containing-nanofibres. The last part of this project involved testing of free furanone compounds as well as surface-tethered furanone-modified nanofibres for their antibiofouling potentials. To do this, blends of 2,5-dimethyl-4-hydroxy-3(2H)furanone (DMHF) (5% wt/vol) with PVA (10% wt/vol) were prepared and electrospun to produce PVA/DMHF nanofibres. The free furanones and furanone-modified nanofibres demonstrated not only antibiofouling properties but also antimicrobial activity. Other furanone compounds with 3(2H) and 2(5H) cores were synthesized. The synthesis of these furanone compounds (5-(2-(2-aminoethoxy)ethoxy)methyl)-2(5H)furanone and 4-(2-(2-aminoethoxy)-2,5-dimethyl-3(2H)-furanone) was successful. Their structures and molar masses were confirmed using 1H NMR and ES mass spectroscopy. These furanones were then covalently immobilized on the SMA backbone. To test their antimicrobial and antibiofouling activity, the furanone-modified polymer was dissolved in an ethanol and methanol mixture (1:1) and electrospun to produce nanofibres. The free furanone and furanone-modified SMA nanofibres derived from 4-(2-(2-aminoethoxy)-2,5-dimethyl-3(2H)-furanone demonstrated high antibiofouling and antimicrobial efficiency against the Gram-positive strain S. aureus Xen 36 and Gram-negative strains E. coli Xen 14, S. typhimurium Xen 26, P. aeruginosa Xen 5 and K. pneumoniae Xen 39. The 2(5H) furanone on the other hand had limited activity against the strains. These nanofibres were also characterized and compared with their pristine polymer counterparts and leaching experiments were conducted using GC-MS. / AFRIKAANSE OPSOMMING: Die hoofdoel van hierdie studie was om nanovesel filtrasie nanofibre met beide antimikrobiese en aanpakwerende eienskappe te ontwikkel. Twee verskillende metodes is ondersoek. Eerstens is biosiede en bakteriee-dodende koper soute gebruik om antimikrobiese nanovesels te lewer. Tweedens is nanovesels met furanoon samestellings gemodifiseer om nanovesels te lewer wat mikrobiese aanhegting voorkom. Die fabrisering van biosied-bevattende PVA nanovesel nanofibre was suksesvol. AquaQure, ‟n biosied wat hoofsaaklik uit Cu2+ en Zn2+ bestaan, is direk by PVA oplossings gevoeg voor die elektrospin proses, en is gevolg deur chemiese kruisbinding deur middel van “glyoxal”. Die nanovesels is neergele in ‟n ongeweefde mat deur middel van die konvensionele naald-gebasseerde elektrospin proses. Verspreidings X-staal analises (EDX) is gebruik om die teenwoordigheid van AquaQure komponente in en op die oppervlakte van die PVA/aquaqure nanovesel matte te bevestig. ATR/FTIR, UV-Vis, XRD, TGA, DSC en SEM tegnieke is gebruik vir chemiese en termiese analises om sodoende PVA/aquacure nanovesels met ongemodifiseerde PVA nanovesels te vergelyk. PVA/aquacure nanovesels het ‟n antimikrobiese aktiwiteit van tot 5 log reduksie getoon teen Gram-positiewe S. aureus Xen 36 en Gram-negatiewe E. coli Xen 14, S. typhimurium Xen 26, P. aeruginosa Xen 5 en K. pneumoniae Xen 39. Die vesels was stabiel in water na kruisbinding. Slegs beperkte uitloging van Aquaqure Cu2+ en Zn2+ ione is waargeneem, en water wat deur die PVA/aquacure nanovesels gefiltreer is, is volgens Suid Afrikaanse Nasionale Standaarde vir drinkwater steeds veilig vir menslike gebruik. Behalwe vir die plaat-tellingsmetode het bio-lumiserende fotos en fluoroserende mikroskopie ook die antimikrobiese aktiwiteit van die vesels bevestig. Die vesels het bevredigende antimikrobiese efektiwiteit getoon, maar kon nie mikrobiese aanhegting voorkom nie. In die tweede gedeelte van die werk is die antimikrobiese aktiwiteit van PVA en SMA vesels wat met koper verreik is, ondersoek. Alhoewel die bakteriee dodende eienskappe van koper reeds goed gedokumenteer is, is hierdie ondersoek gedoen op grond van die feit dat koper een van die hoof komponente van aquaqure is. Nanovesels is uit koper-verreikte oplossings van PVA en SMA deur middel van die borrel-gebasseerde elektrospin tegniek gefabriseer, ten einde die opbrengs van nanovesels te verhoog. Fisiese kruisbinding deur middel van hitte behandeling is toegepas ten einde die stabiliteit van die vesels in water te verbeter. Dieselfde karakteriseringstegnieke wat gebruik is vir die PVA/aquacure vesels is op hierdie vesels toegepas. Alhoewel die vesels uitstekende antimikrobiese aktiwiteit van tot 5 log reduksie gedemonstreer het, het bio-lumiserende beeldvorming getoon dat die selle ‟n dormante stadium binnegaan na kontak met hierdie vesels. In die laaste gedeelte van die projek is vrye furanoon samestellings en nanofibre met oppervlak-gehegde furanone getoets vir aanpakwerende potensiaal. Om dit te bewerkstellig was „n mengsel van 2,5 – dimethyl-4-hydroxy-3(2H) furanone (DMHF) (5% wt/vol) en PVA (10% wt/vol) voorberei en gebruik om PVA/DMHF nanovesel filtrasie nanofibre te produseer deur middel van die elektrospin proses. Die vrye furanone en furanoon-gemodifiseerde nanofibre het nie alleen aanpak weerstandbiedende einskappe gedemonstreer nie maar ook antimikrobiese eienskappe. DMHF was gebruik as die begin material om furanoon samestellings te produseer met 3(2H) en 2(5H) kerne. Die sintesis van hierdie furanone se samestellings (5-(2-(2-aminoethoxy)ethoxy)methyl)-2(5H)furanone en 4-(2-(2-aminoethoxy)-2,5-dimethyl-3(2H)-furanone) was suksesvol. Hulle strukture en molere massas was bevestig met 1H NMR en ES massa spektrometrie. Hierdie furanone is daarna kovalent ge-immobiliseer op die SMA rugbeen. Om hulle antimikrobiese en aanpakwerende aktiwitiet te toets, is die furanoon-gemodifiseerde polimeer opgelos in „n etanol en metanol mengsel (1:1) en ge-elektrospin om nanovesel filtrasie nanofibre te produseer. Die furanone en furanoon-gemodifiseerde nanovesel filtrasie nanofibre afkomstig van 4-(2-(2-aminoethoxy)-2,5-dimethyl-3(2H)-furanone het hoe aanpakwerende en antimibrobiese effektiewitiet getoon teenoor die Gram-positiewe S. aureus Xen 36 en Gram-negatiewe E. coli Xen 14, S. typhimurium Xen 26, P. aeruginosa Xen 5 and K. pneumoniae Xen 39. Hierdie nanovesel filstrasie nanofibre is ook gekarakteriseer en vergelyk met die ongemodifiseerde polimeer. „n Uitlogings eksperiment is uitgevoer deur gebruik te maak van GC-MS.

Thesis (PhD)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The possibility of utilizing the chromium/bis(diphenylphosphino)amine (PNP) type of catalysts in ethylene polymerization processes was investigated. These processes include the production of linear low density polyethylene (LLDPE), the production of polyethylene waxes and the synthesis of special comonomers for ethylene copolymerization. The chromium/Ph2PN{CH(CH3)2}PPh2 tetramerization system was used in combination with a polymerization catalyst to yield ethylene copolymers with controlled branching. Copolymers with bimodal chemical composition distributions were obtained in these tandem reactions. This chromium/PNP-type tetramerization catalyst and metallocene polymerization catalysts are not completely compatible in tandem catalytic systems due to different optimum temperatures for their effective functioning. The oligomerization to polymerization catalyst ratios, the catalyst to cocatalyst ratios and the temperature profile are all factors influencing the amount of -olefins formed and therefore the type of copolymer produced. The activity of the polymerization catalyst decreases in the presence of the oligomerization catalyst, indicating that the two catalysts interfere chemically. The main difference between copolymers produced in conventional or tandem fashion is the presence of a small amount of low molecular weight material produced by the oligomerization catalyst and also the presence of a highly crystalline component. The latter component results from the initial low concentration of a-olefins in the first conversion, but such a component is also independently produced by the oligomerization catalyst. LLDPE with butyl branches is obtained when a selective trimerization catalyst is used in combination with a polymerization catalyst. The chromium/(o-OMeC6H4)2 PN(CH3)P(o-OMeC6H4)2 trimerization system is more suitable than the chromium/Ph2PN{CH(CH3)2}PPh2 tetramerization system for use in tandem reactions with a metallocene catalyst due to its high activity and selectivity at higher temperatures. The chemical composition distribution varies with an increase in reaction time due to the increasing amount of 1-hexene produced. Comparison of CRYSTAF traces of tandem copolymers with conventional copolymers show that the tandem copolymers have a broader chemical composition distribution. Addition of 1- hexene during the course of a conventional copolymerization reaction produces copolymers with similar chemical composition distributions to that of the tandem copolymers. Later addition of the polymerization catalyst to the oligomerization reaction mixture results in copolymers with higher comonomer content, similar to conventional copolymers. Chromium/(o-EtC6H4)2PN(CH3)P(o-EtC6H4)2 is not suitable for LLDPE production in tandem reactions, since it is selective to higher oligomers or polyethylene waxes at higher temperatures. Variation of the MAO cocatalyst and hydrogen concentrations significantly influences the yield, viscosity and crystallization behaviour of the waxlike products. Low MAO concentrations resulted in multiple melting peaks, while higher concentrations display single melting peaks and lower viscosity values. Ethylene co-oligomerization reactions with styrene or p-methylstyrene using the chromium/PNP-type oligomerization technology produce various phenyl-hexene and phenyl-octene isomers either through cotrimerization or cotetramerization. The known ethylene trimerization catalysts show cotrimerization behaviour, while the catalysts with known selectivity for ethylene tetramerization also yield cotetramerization products. Chromium complexes that contain the more bulky ligands display lower selectivity towards co-oligomerization and greater preference for ethylene homotrimerization. These co-oligomerization products can be incorporated into a polyethylene chain by copolymerization in a simultaneous or sequential tandem reaction. The combined co-oligomerization-polymerization reactions yield copolymers with lower crystallinity than obtained from the conventional ethylene-styrene copolymerization reaction due to higher comonomer incorporation. The polymer yields are higher in the cooligomerization- copolymerization reactions. The ability of the different cooligomerization products to incorporate into the polyethylene chain was established: unreacted styrene and the more bulky isomers, 3-phenyl-1-hexene and 3-phenyl-1- octene, are not incorporated readily, while branches resulting from 4-phenyl-1- hexene, 4-phenyl-1-octene, 5-phenyl-1-octene and 6-phenyl-1-octene are detected in the NMR spectrum. / AFRIKAANSE OPSOMMING: Die moontlikheid om die chroom/bis-(difenielfosfino)amien (PNP) tipe katalisatore in etileen-polimerisasie reaksies te gebruik is ondersoek. Hierdie prosesse sluit die produksie van lineêre lae digtheid poliëtileen (LLDPE), die produksie van poliëtileenwasse en die sintese van spesiale komonomere vir etileenkopolimerisasie in. Die chroom/Ph2PN{CH(CH3)2}PPh2 tetramerisasie-sisteem is gebruik in kombinasie met ¢n polimerisasiekatalisator om etileenkopolimere met gekontroleerde vertakkings te vorm. Kopolimere met ‘n bimodale chemiese samestellingsverspreiding word verkry in hierdie tandemreaksies. Hierdie chroom/PNP-tipe tetramerisasiekatalisator en die metalloseenkatalisators is nie heeltemal verenigbaar in die tandemsisteem nie weens verskille in hul optimum reaksietemperature vir effektiewe funksionering. Die oligomerisasie tot polimerisasiekatalisatorverhouding, die katalisator tot kokatalisatorverhouding en die temperatuurprofiel is almal faktore wat die gevormde hoeveelheid -olefiene beinvloed, en dus die tipe kopolimeer wat gevorm word. Die aktiwiteid van die polimerisasiekatalisator verminder in die teenwoordigheid van die oligomerisasiekatalisator, wat aandui dat die twee katalisatore chemies met mekaar inmeng. Die duidelikste verskil tussen die kopolimere wat geproduseer word op die konvensionele of die tandem manier is die teenwoordigheid van ‘n klein hoeveelheid lae molekulere massa materiaal wat gevorm word deur die oligomerisasiekatalisator, asook ‘n komponent met baie hoë kristalliniteit. Die laasgenoemde komponent ontstaan weens die aanvanklike lae konsentrasie van die a-olefiene in die eerste omsetting, maar so ‘n komponent word ook onafhanklik gevorm deur die oligomerisasiekatalisator. LLDPE met butiel-vertakkings word verkry wanneer ‘n selektiewe trimerisasiekatalisator in kombinasie met ‘n polimerisasiekatalisator gebruik word. Die chroom/(o-OMeC6H4)2PN(CH3)P(o-OMeC6H4)2 trimerisasiesisteem is meer geskik as die chroom/Ph2PN{CH(CH3)2}PPh2 tetramerisasiesisteem vir gebruik in tandem met ‘n metalloseenkatalisator weens die katalisator se hoë aktiwiteit en selektiwiteid vir 1-hekseen by hoër reaksietemperature. Die chemiese samestellingsverspreiding verander soos die reaksietyd toeneem weens die toenemende hoeveelheid 1-hekseen wat gevorm word. Vergelyking van die CRYSTAF-diagram van die tandemkopolimere met konvensionele kopolimere toon dat die tandemkopolimere ‘n wyer chemiese samestellingsverspreiding het. Geleidelike byvoeging van 1-hekseen gedurende die loop van ‘n konvensionele reaksie, vorm kopolimere met ‘n soortgelyke chemiese samestelingsverspreiding as die tandemkopolimere. Latere byvoeging van die polimerisasiekatalisator lei tot die vorming van kopolimere met ‘n hoër komonomeerinhoud, soortgelyk aan die konvensionele kopolimere. Chroom/(o-EtPC6H4)2PN(CH3)P(o-EtC6H4)2 is nie geskik om LLDPE in tandemreaksies te vorm nie, aangesien dit selektief is vir hoër oligomere of poliëtileenwasse by hoër reaksietemperature. Variasie van die MAO-kokatalisator en die waterstofkonsentrasies beinvloed die hoeveelheid produk wat gevorm word, asook die viskositeit en kristallisasiegedrag daarvan. Lae MAO konsentrasies lei tot meer as een smeltpiek, terwyl hoër konsentraises ‘n enkelpiek vertoon. Die viskositeit van die produkmengsel is ook laer. Die gebruik van die chroom/PNP-tipe oligomerisasietegnologie in etileenkooligomerisasiereaksies met stireen, lei tot die vorming van verskeie feniel-hekseenen fieniel-okteenisomere deur of kotrimeriasie, of kotetramerisasie. Katilisatore met bekende etileentrimerisasieligande vertoon kotrimerisasiegedrag terwyl die ligande wat bekend is vir selektiwiteit in etileentetramerisasie, kotetramerisasieprodukte vorm. Die chroomkomplekse met die meer bonkige ligande het laer selektiwiteit vir ko-oligomerisasie en vertoon ‘n groter voorkeur vir etileenhomo-trimerisasie. Die ko-oligomerisasieprodukte kan in ‘n poliëtileenketting ingebou word deur kopolimerisasie in ‘n gelyktydige of opeenvolgende tandemreaksie. Die gekombineerde ko-oligomerisasie-polimerisasiereaksie vorm kopolimere van ‘n laer kristalliniteit as wat gevind word met die konvensionele etileen-stireen kopolimerisasie reaksie weens hoer komonomeerinkorporasie. Meer polimeer word gevorm in die ko-oligomerisasie-kopolimerisasie reaksie. Die vermoë van die verskillende ko-oligomerisasieprodukte om in die poliëtileenketting ingesluit te word is bepaal. Ongereageerde stireen en die meer bonkige isomere, 3-feniel-1-hekseen en 3-feniel-1-okteen, word nie maklik ingevoeg nie. Vertakkings as gevolg van die inkorporasie van 4-feniel-1-hekseen, 4-feniel-1-okteen, 5-feniel-1-okteen and 6- feniel-1-okteen kan waargeneem word in die KMR spektrum.

Thesis (PhD)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Antimicrobial fibers are very useful in various fields such as air and water purification, wound dressings and protective bandages, where sterile environments are essential. The nonwoven nanofiber mats or membranes are able to filter out microorganisms and potentially kill several threatening pathogenic bacteria. In this thesis, a variety of styrene-maleimide copolymer derivatives were prepared based on the modification of poly(styrene-co-maleic anhydride with various primary amine compounds. All prepared copolymer derivatives were electrospun to nanofiber mats using the needle electrospinning technique. For the characterization, differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were used to study the thermal properties of the electrospun fiber mats. Scanning electron microscopy (SEM) was carried out to observe fiber dimensions and morphology. The antibacterial activity of electrospun fiber mats was evaluated against different bacteria including Staphylococcus aureus (Gram-positive), Escherichia coli and Pseudomonas aeruginosa (Gram-negative). The evaluation study utilized different tools to test for antibacterial activity and mode of cell death, including bioluminescent imaging, fluorescence imaging and the viable cell counting method. Excellent antimicrobial activity was obtained against the different strains especially against Staphylococcus aureus. Fiber mats containing tertiary amino groups, phenol or quaternary ammonium groups had the strongest antimicrobial properties. / AFRIKAANSE OPSOMMING: Antimikrobiese vesels is baie nuttig in verskeie toepassingsgebiede, soos lug- en watersuiwering, wondbedekkings en beskermende verbande, waar ‘n steriele omgewing noodsaaklik is. Die ongeweefde nanovesel matte of membrane is in staat om mikroorganismes te verwyder deur filtrasie, maar kan ook verskeie patogeniese bakterieë doodmaak. In hierdie proefskrif is ‘n verskeidenheid stireen-maleimied kopolimeer afgeleides gesintetiseer, gebaseer op die modifikasie van poli(stireen-ko-maleïne anhidried) met verskeie primêre amien verbindings. Nanovesel matte van al die gesintetiseerde kopolimeer afgeleides is gemaak deur gebruik te maak van die naald-elektrospin tegniek. Die termiese eienskappe van hierdie nanovesel matte is bestudeer deur gebruik te maak van differensiële skandeer kalorimetrie (DSK) en termogravitasie analiese (TGA) as karakteriseringsmetodes. Die vesel dimensies en morfologie is bestudeer deur skandeer elektronmikroskopie as karakteriseringsmetode te gebruik. Die antibakteriële aktiwiteit van die gespinde vesel matte is geëvalueer teen verskillende bakterieë, naamlik Staphylococcus aureus (Gram-positief), Escherichia coli en Pseudomonas aeruginosa (Gram-negatief). Die evalueringstudie het verskillende instrumente gebruik om vir antibakteriële aktiwiteit en meganisme van seldood te toets, insluitend bioluminiserings beelding, fluoressensie beelding en die lewensvatbare sel tellingsmetode. Uitstekende antimikrobiese aktiwiteit is verkry teen die verskillende rasse, veral teen Staphylococcus aureus. Vesel matte met tersiêre aminogroepe, fenol of kwaternêre ammoniumgroepe het die sterkste antimikrobiese eienskappe gehad.

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

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.

Thesis (PhD)--University of Stellenbosch, 2011. / Please refer to full text to view abstract.

Thesis (PhD (Chemistry and Polymer Science))--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: Positron annihilation lifetime spectroscopy (PALS) is well established as a novel method currently available for the study of polymers at a molecular level because of its sensitivity to the microstructural changes in the polymer matrix. The technique provides unique, but limited, information of the solid state structure – primarily on the nature of the free volume (or unoccupied space) in the polymer due to the less dense packing of polymer chains relative to in other solid materials. In the case of completely homogeneous polymer materials the measurement and interpretation of the positron annihilation parameters is relatively simple. However, in the case of polymers with more complex morphologies the situation becomes less clear. This is due to the possibility of the formation, localization and subsequent annihilation of o-Ps (ortho-positronium) within different areas of the complex morphology. This can result in more than one o-Ps lifetime component being present, and each of the different components corresponds to areas with differing types and amounts of 'open spaces'. In this study a detailed and systematic approach was taken to study the positron annihilation parameters in various semi-crystalline polymers and to correlate these to the chain structure and morphology of the materials. The study focused specifically on polyolefin polymers as these are the most widely used semi-crystalline materials, but more importantly, they offer the possibility to produce a variety of morphological complexity by simple manipulation of the chain structure – while there is essentially no difference in the chemical composition of the materials. The copolymers were selected to study the influence of short-chain branching (amount and length), short-chain branching distribution and tacticity on the morphology, and subsequent positron annihilation lifetime parameters. Three separate topics were addressed. First, preparative temperature rising elution fractionation was used to isolate polymer samples that are homogeneously crystallisable and to produce a series of polymers with differing chain structure and resultant morphologies. Second, additional series were produced by removing specific crystallisable fractions from the bulk materials. Third, the temperature variation of the samples as they approach and go through the crystalline melting point was studied. All the raw positron data were found to be best fitted with a four-component positron annihilation lifetime analysis. The longest lifetime (which is attributed to annihilation of o-Ps in the amorphous phase of the materials) showed systematic variations with the degree and nature of the short-chain branding, tacticity variation, a combination of both short-chain branching and tacticity, and changes in the amorphous phase as a result of heating. The third lifetime component (which is attributed to o-Ps annihilation in or around the crystalline areas of the materials) showed less variation across the sample series. Typically, greater variations were observed in the propylene copolymers than in the ethylene copolymers, which are reflective of the more complex chain structure and corresponding morphology in the propylene copolymer series. Direct evidence for a contribution from the nature of the amorphous phase to the bulk microhardness of the sample was also found. / AFRIKAANSE OPSOMMING: Positronvernietigingsleeftydspektroskopie (PALS) is goed gevestig as ‘n nuwe metode vir die studie van polimere op molekulêrevlak agv die sensitiwiteit van die metode vir mikrostrukturele veranderings in die polimeermatriks. Hierdie tegniek verskaf unieke, maar beperkte, inligting aangaande die vastetoestandstruktuur – veral aangaande die aard van die vryevolume (of onbesette spasie) in die polimeer as gevolg van die minder digte verpakking van polimeerkettings relatief tot in ander vastestowwe. In die geval van volledig homogene polimeriese materiale is die meet en interpretasie van die positronvernietigingsparameters relatief eenvoudig. Maar in die geval van polimere met meer komplekse morfologieë is die situasie minder duidelik. Die rede hiervoor is die moontlikheid vir die formasie, lokalisering en gevolglike vernietiging van o-Ps (orto-positronium) in die verskillende areas van die komplekse morfologie. Dit kan tot gevolg hê dat meer as een o-Ps komponent teenwoordig is en waar elk van die verskillende komponente ooreenstem met areas met verskillende tipes en hoeveelhede 'oop spasies'. In hierdie studie is ‘n sistematiese, in-diepte benadering gebruik om die positronvernietigingsparameters in verskeie semikristallyne polimere te bestudeer en hulle te korreleer met dié van die kettingstruktuur en die morfologieë van die materiale. Hierdie studie het spesifiek gefokus op poliolefiene aangesien hulle die mees algemene semikristallyne materiale is wat gebruik word en, nog meer belangrik, hulle bied die geleentheid om verskeie komplekse morfologieë te lewer dmv eenvoudige manipulasie van die kettingstrukture – terwyl daar basies geen verandering in die chemiesesamestelling van die materiale is nie. Die kopolimere is gekies om die invloed van kort-ketting vertakking (lengte en hoeveelheid), kort-ketting vertakking verspreiding en taktisiteit op die morfologie en vervolgens die positronvernietigingsleeftyd parameters te bestudeer. Drie onderwerpe is aangespreek. Eerstens, preparatiewe temperatuurstygingelueringsfraksionering (prep-TREF) is gebruik om polimeermonsters wat homogeenkristalliseerbaar is te isoleer om sodoende 'n reeks polimere met verskillende kettingstrukture, en gevolglike morfologieë, te lewer. Tweedens, 'n addisionele reekse monsters is berei deur die verwydering van spesifieke kristalliseerbare fraksies vanaf die grootmaatmonsters. Derdens, die temperatuurverandering van die monsters wanneer die monsters naby aan die kristallyne smeltpunt is en wanneer hulle deur die kristallyne smeltpunt gaan is bestudeer. Daar is bevind dat alle rou positrondata ten beste gepas het in 'n vier-komponent positronvernietigingsleeftydanalise. Die langste leeftyd (wat toegeskryf is aan vernietiging van o-Ps in die amorfe fase van die materiaal) het sistematiese variasies getoon met die volgende: hoeveelheid en aard van die kort-kettingvertaking, verandering in taktisiteit, 'n kombinasie van beide kort-kettingvertakking en taktisiteit en veranderings in die amorfiesefase as gevolg van verhitting. Die derde leeftyd komponent (wat toegeskryf is aan die o-Ps vernietiging in of rondom die kristallyne areas van die materiale) het minder variasie in hierdie reeks monsters getoon. Daar is tipies meer variasie waargeneem in die propileenkopolimere as in die etileenkopolimere, wat ’n weerspieëling is van die meer komplekse kettingstruktuur en ooreenstemmende morfologie in die propileenkopolomeerreeks. Direkte bewys vir 'n bydrag van die aard van die amorfe fase tot die grootmaat mikrohardheid van monsters is ook bevind.