Thesis (PhD)--University of Stellenbosch, 2011. / ENGLISH ABSTRACT: The crystallization of polyolefins is an important parameter in determining the properties of such materials. The crystallization phenomenon generally depends on the molecular symmetry (tacticity) and molecular weight of the material. In this study, a series of polypropylenes was prepared using heterogeneous MgCl2-supported Ziegler catalysts with two different external donors, diphenyldimethoxysilane (DPDMS) and methyl-phenyldimethoxysilane (MPDMS), and two different homogeneous metallocene catalysts, racethylene- bis(indenyl) zirconium dichloride, Et(Ind)2ZrCl2 (EI), and rac-ethylene-bis(4,5,6,7- tetrahydro-1-indenyl) zirconium dichloride, Et(H4Ind)2ZrCl2 (EI(4H)). Molecular hydrogen was used as terminating agent. In order to establish a correlation between the molecular weight and the crystallization of these polymers, fractionation of the materials according to crystallizability was performed by means of temperature rising elution fractionation (TREF). This affords the opportunity of blending materials of different molecular weights but similar symmetry. These materials were characterized using various analytical techniques: differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), 13C nuclear magnetic resonance spectroscopy (13C-NMR), high temperature gel permeation chromatography (HT-GPC) and Fourier-transform infrared spectroscopy (FT-IR). DSC was used to study the bulk crystallization of different polypropylene blends, most of which showed only one melting peak. The latter is usually associated with a high degree of cocrystallization. Turbidity analysis of the different polypropylene polymers, obtained using solution crystallization analysis by laser light scattering (SCALLS), provided good crystallization information – similar to that provided by crystallization analysis fractionation (CRYSTAF) and TREF. It was also possible to differentiate between polypropylenes with similar chemical structure but different tacticity and molecular weight. SCALLS results also showed that the blends of different isotactic polypropylene polymers were miscible and cocrystallization had occurred, whereas, the blends of syndiotactic polypropylene and different isotactic polypropylenes were not miscible and some interaction between phases had occurred. Optical microcopy (OM) and scanning electronic microscopy (SEM) were used to study the morphological properties of different isotactic polypropylenes. Results revealed a welldefined and large spherulitic morphology of mixed a1 (disordered) and a2 (ordered) crystal form structures. OM and SEM images also clearly showed an effect of molecular weight and tacticity on the crystal structure of the different polypropylene samples. Finally, various homopolymers and blends were studied to investigate the effect of molecular weight on the mechanical properties of these materials. This was done using microhardness testing and dynamic mechanical analysis. / AFRIKAANSE OPSOMMING: Die kristallisasie van poliolefiene is ‘n belangrike faktor wat die eienskappe van hierdie tipe materiale bepaal. In die algemeen hang kristallisasie af van die molekulêre simmetrie (taktisiteit) en molekulêre massa van die materiaal. ‘n Reeks polipropilene is berei deur gebruik te maak van heterogene MgCl2-ondersteunde Ziegler-kataliste met twee verskillende elektron donors, difenieldimetoksisilaan (DPDMS) en metielfenieldimetoksisilaan (MPDMS), en twee verskillende homogene metalloseenkataliste, rac-etileen-bis(indeniel) sirkoniumdichloried, Et(Ind)2ZrCl2 (EI), en rac-etileen-bis(4,5,6,7-tetrahidro-1-indeniel) sirkoniumdichloried, Et(H4Ind)2ZrCl2 (EI(4H)). Molekulêre waterstof is gebruik as termineringssagent. Ten einde ‘n verband te bepaal tussen die molekulêre massa en kristallisasie van hierdie polimere is hulle gefraksioneer op die basis van hulle kristallisseerbaarheid deur gebruik te maak van temperatuurstyging-elueringsfraksionering (TREF). Deur hierdie tegniek verkry ons materiale van verskillende molekulêre massa maar met dieselfde taktisiteit wat ons kan vermeng. Verskeie tegnieke is gebruik om hierdie materiale te karakteriseer: differensiële skandeerkalorometrie (DSC), wyehoek X-straal diffraksie (WAXS), 13C-kernmagnetiese resonansspektroskopie (13C-KMR), hoë-temperatuur gelpermeasiechromotagrafie (HT-GPC) en Fourier-transform-infrarooispektroskopie (FT-IR). DSC is gebruik om die vaste-toestand kristallisasie van verskeie vermengde polipropilene te bestudeer., en net een smeltpunt is in meeste gevalle waargeneem. Laasgenoemde word gewoonlik verbind met ‘n hoë mate van kokristallisasie. Oplossingkristallisasie analise, dmv laserligverstrooiing (SCALLS), is gebruik om die turbiditeit van die verskillende polipropileen kopolimeervermengings te bepaal. Goeie inligting aangaande die kristallisasie in oplossing – soortgelyk aan dié wat dmv die kristallisasie-analise-fraksioneringstegniek (CRYSTAF) en TREF bepaal is, is verkry. Dit was ook moontlik om te onderskei tussen polipropilene met soortgelyke chemiese strukture maar verskillende taktisiteit en molekulêre massas. SCALLS data het ook getoon dat die vermengings van verskeie isotaktiese polipropileen polimere versoenbaar was en dat kokristallisasie plaasgevind het, terwyl vermengings van sindiotaktiese polipropileen en verskeie isotaktiese polipropilene nie versoenbaar was nie en dat ‘n mate van fase-skeiding plaasgevind het. Optiese mikroskopie (OM) en skandeer-elektronmikroskopie (SEM) is gebruik om die morfologiese eienskappe van verskillende isotaktiese polipropilene te bepaal. Goed gedefineerde en groot sferulitiese morfologie van gemengde a1 (onordelike struktuur) en a2 (ordelike struktuur) kristal-strukture is waargeneem. OM en SEM beelde het ook gewys dat molekulêre massa en taktisiteit ‘n effek het op die kristalstruktuur van die verskillende polipropileenmonsters. Laastens is die meganiese eienskappe van ‘n verskeidenheid homopolimere en vermengde materiale bestudeer, deur gebruik te maak van mikro-hardheid metings en dinamiesmeganiese analise (DMA).

Thesis (PhD)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Tuberculosis (TB) is a major cause of morbidity and mortality across the world, affecting adults and children. Children infected with TB differ from adults, as their immunological and patho-physiological response to the disease is different. Although there are a variety of tests available for TB diagnosis, they have limitations when used to diagnose paediatric TB. Children are also unable to generate sputum spontaneously when required for the use in culture or microscopy as diagnostic method. Children however do produce sputum, containing the TB bacilli, which they swallow. If the TB bacilli can therefore be retrieved from the stomach and tested, TB can be diagnosed using gastric samples. In this thesis, a variety of styrene maleimide copolymer (SMI) derivatives were prepared as potential M. tuberculosis-capturing platforms. This was done by modifying poly(styrene-co-maleic anhydride) (SMA) with a variety of primary amine compounds, selected based on possible chemical interactions with the M. tuberculosis cell wall. All the prepared copolymer derivatives were electrospun into nanofibrous mats using the single needle electrospinning technique to yield SMI nanofibers, functionalized with different compounds. Some of the functionalized SMI nanofibers were prepared by surface-functionalization of the polymer nanofibers after electrospinning and some by modification of the polymer before electrospinning. Affinity studies were conducted at neutral and low pH between the different functionalized SMI nanofibers and two mycobacterium strains, namely the bacillus Calmette-Guérin strain of Mycobacterium bovis (BCG) and M. tuberculosis, to evaluate the surfaces of the modified SMI nanofibers as mycobacterium-capturing platforms. The successful capture of BCG onto the surfaces of the various functionalized nanofibers was confirmed by SEM and fluorescence microscopy (FM). Analysis of the SEM and FM images indicated that the SMI nanofibers, functionalized with a C12 aliphatic quaternary ammonium moiety (SMI-qC12), captured BCG the most effectively through a combination of ionic and hydrophobic interaction. Concentration and time studies revealed that the extent of this interaction was dependent on incubation time and concentration of BCG. The affinity studies with BCG also concluded that the polymer used for the nanofibrous-capturing platform should not be too hydrophobic in character as this caused poor wetting of the functionalized nanofibers, thus preventing close contact with the mycobacteria and a reduction in the capture effectivity of the polymer nanofibers. The successful capture of M. tuberculosis onto the SMI-qC12 nanofibrous surface was confirmed by FM, light microscopy (LM) and polymerase chain reaction (PCR). The extent of this interaction was dependent on the concentration of M. tuberculosis. The detection of M. tuberculosis using FM and LM as detection methods was simplified by the tendency of M. tuberculosis to clump together in clusters on the hydrophobic surface of the SMI-qC12 nanofibers. As a result of this clustering, FM and LM were therefore regarded as feasible detection methods to image M. tuberculosis on the surface of the SMI-qC12 nanofibers, even at relatively low concentration of M. tuberculosis. / AFRIKAANSE OPSOMMING: Tuberkulose (TB) is 'n groot oorsaak van morbiditeit en mortaliteit regoor die wêreld en affekteer volwassenes en kinders. Kinders wat met TB geïnfekteer is, se immunologiese en patofisiologiese reaksie op die siekte verskil van die van volwassenes en dit het belangrike implikasies vir die diagnose van TB in kinders. Alhoewel daar 'n verskeidenheid van toetse beskikbaar is vir die diagnose van TB, het hulle beperkings wanneer dit gebruik word om pediatriese TB te diagnoseer. Kinders kan ook nie spontaan sputum produseer as dit nodig is vir die gebruik in kultuur of mikroskopie as diagnostiese metode. Kinders produseer egter wel sputum, wat die TB basille bevat, wat hulle dan insluk. As die TB basille uit die maag versamel kan word en getoets kan word, kan TB gediagnoseer word met behulp van maag monsters. In hierdie tesis is 'n verskeidenheid van stireen maleimied kopolimeer (SMI) afgeleides voorberei as potensiële Mycobacterium tuberkulose (Mtb)-vaslegging platforms. Dit is gedoen deur die modifikasie van poli(stireen-ko-maleïen anhidried) (SMA) met 'n verskeidenheid primêre amien verbindings as oppervlak-funksionaliseringsagente. Hierdie primêre amien verbindings is gekies op grond van moontlike chemiese interaksies met die Mtb selwand. Al die voorbereide kopolimeer afgeleides is elektrogespin in nanoveselagtige matte met behulp van die enkel-naald elektrospin tegniek om SMI nanovesels te lewer wat gefunksionaliseer is met verskillende verbindings. Sommige van die gefunksionaliseerde SMI nanovesels is berei deur oppervlak-funksionalisering van die polimeer nanovesels na elektrospin, en sommige deur die modifikasie van die polimeer voor elektrospin. Affiniteitstudies is uitgevoer, by neutrale en lae pH, tussen die verskillende gefunksionaliseerde SMI nanovesels en twee mikobakterium rasse, naamlik die basillus Calmette-Guérin ras van Mycobacterium bovis (BCG) en M. tuberculosis, om die oppervlaktes van die gewysigde SMI nanovesels te evalueer as mikobakterium-vaslegging platforms. Ontleding van die SEM en FM beelde het aangedui dat die SMI nanovesels, gefunksionaliseer met 'n C12 alifatiese kwaternêre ammonium groep (SMI-qC12), BCG die doeltreffendste vasgevang het deur 'n kombinasie van ioniese en hidrofobiese interaksie. Konsentrasie- en tydstudies tussen BCG en SMI-qC12 het aangedui dat die omvang van hierdie interaksie afhanklik is van inkubasietyd en konsentrasie van BCG. Die affiniteitstudies met BCG het ook aangedui dat die polimeer wat gebruik word vir die nanoveselagtige-vaslegging platform nie te hidrofobiese moet wees nie, aangesien dit swak benatting van die gefunksionaliseerde nanovesels veroorsaak, en dus noue kontak met die mikobakterieë voorkom met ʼn gevolglike vermindering in die vasvang-effektiwiteit van die polimeer nanovesels. Die suksesvolle vasvang van M. tuberculosis op die SMI-qC12 nanovesels is bevestig deur FM, lig mikroskopie (LM) en polimerase kettingreaksie (PKR). Die opsporing van Mtb deur die gebruik van FM en LM as opsporingmetodes is vergemaklik deur die tendens van Mtb om in groepies saam te pak op die hidrofobiese oppervlak van die SMI-qC12 nanovesels. As gevolg van hierdie groepering, is FM en LM dus haalbare opsporingmetodes om M. tuberculosis op die oppervlak van die SMI-qC12 nanovesels waar te neem, selfs by relatief lae konsentrasie van M. tuberculosis.

Thesis (MSc)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: A comparative study of the chemical composition of linear low density polyethylene polymers, synthesised with 1 - hexene as comonomer was conducted. Catalyst trials were conducted on the linear low density 1 - hexene polymer grade material to evaluate alternative catalysts. A comparative analysis was performed in order to investigate if the samples synthesised under catalyst trial conditions showed any significant differences in terms of crystallinity and mechanical properties with the reference sample that was synthesised using the reference catalyst. The results showed that the macro product properties, namely melt flow Index, density, and level of hexene extractables are different for the trial samples in comparison with the reference sample. The differences observed implied that the trial samples were synthesised with differences on a molecular level. The differences in the chemical composition between the reference sample and the comparative samples were fully explored using a wide range of analytical techniques, namely crystallisation analysis by fractionation (CRYSTAF), temperature rising elution fractionation (TREF), differential scanning calorimetry (DSC), Carbon 13 nuclear magnetic resonance (13C NMR), Size exclusion chromatography (SEC), Positron analysis lifetime spectroscopy (PALS) and micro hardness analysis. The results of the characterisation studies indicated the following: - Crystallinity and hardness analysis of the reference sample, catalyst trial sample 1 and catalyst trial sample 2 indicate that the catalyst trial sample 2 having a low cocatalyst concentration is the most crystalline of all the samples. - The reference sample, catalyst trial sample 1 and catalyst trial sample 2 were further fractionated using TREF at fractionation temperature intervals of 10°C. TREF analysis indicates that the bulk of the material is observed to elute between 70°C - 10°C. - 13C NMR analyses of the TREF fractions identified four populations of fractions that could be selectively removed, allowing the bulk of the material to be recombined. As these highly crystalline fractions were removed, there was an observed decrease in the total crystallinity of the bulk recombined material. This trend was further verified by the free volume analysis. - Free volume analysis indicated of the bulk recombined material indicated a general increase in the T3 lifetime and T4 lifetime intervals. Free volume analysis further confirmed a decrease in crystallinity of the bulk recombined material as highly crystalline material was removed. - Micro hardness analysis of the polymers further verified the crystallinity trends observed. As the molecular composition of the polymer changed due to removal of highly crystalline fractions, the total mechanical strength of the material indicated by the hardness value decreased. The study showed that by changing the chemical composition of the polymer by removing highly crystalline fractions, there was an observed change in the mechanical properties of the polymer. It can be concluded that the samples synthesised under catalyst trial conditions show significant differences in terms of crystallinity and mechanical properties in comparison with the sample that was synthesised using the standard reference catalyst. / AFRIKAANSE OPSOMMING: ‘n Vergelykende analise studie is onderneem van die chemiese samestellings van lineêre lae digtheid poliëtileen polimere, gesintetiseer met 1-hekseen as ko-monomeer. Alternatiewe kataliste is ge-evavuleer ten opsigte van lineêre lae digtheid 1-hekseen Sasol polimeer graad materiaal. Die vergelykende analise is uitgevoer om die monsters onder katalis proef kondisies te evalueer en te merk of enige beduidende verskille in terme van kristalliniteit en meganiese eienskappe met die verwysings monster voorkom. Die resultate toon dat die makro-produk eienskappe, naamlik smelt vloei indeks, digtheid en vlak van hekseen onttrekking, verskillend is vir die proef monsters in vergelyking met die verwysings monster. Die waargenome verskille impliseer dat die proef monsters op molekulêre vlak verskil. Die verskille in chemiese samestelling tussen die verwysings monster en die vergelykende monsters is ten volle ondersoek deur gebruik te maak van 'n wye verskeidenheid van analitiese tegnieke, naamlik kristallisasie analise fraksionering (CRYSTAF), temperatuur stygende eluering fraksionering (TREF), differensiële skandeer kalorimetrie (DSC), koolstof 13 kernmagnetiese resonansie (13C KMR), gelpermeasie chromatografie (SEC), positron analise leeftyd spektroskopie (PALS) en mikro-hardheid analise. Die resultate van die karakterisering studies het die volgende aangedui:- Kristalliniteit en hardheid analises van die verwysings monster en katalis proef monsters 1 en 2 het getoon dat katalis proef monster 2, wat ‘n lae ko-katalis konsentrasie bevat, die mees kristallyn is. - Die verwysings monster en katalis proef monster 1 en 2 is gefraksioneer met behulp van ‘n TREF met temperatuur tussenposes van 10°C. TREF analise toon dat oormaat materiaal ge-elueer word tussen 70°C en 100°C. - 13C KMR analise van die TREF fraksies het 4 verskillende fraksies geidentifiseer wat selektief verwyder kan word. Dit laat ook toe dat die grootste deel van die materiaal weer geherkombineer kan word. Soos die hoogs kristallyne fraksies verwyder is, is ‘n afname in die totale kristalliniteit van die geherkombineerde materiaal waargeneem. Hierdie tendens is bevestig deur vrye volume analises. - Vrye volume analises van die geherkombineerde materiaal toon ‘n algemene toename in die T3en T4 leeftyd aan. Vrye volume analises toon verder dat ‘n afname in die kristalliniteit van die geherkombineerde materiaal plaasvind soos meer kristallyne fraksies verwyder word. - Verdere mikro-hardheid analises van die polimere bevestig die waargenome kristalliniteit tendense. Soos die molekulêre samestelling van die polimere verander as gevolg van die verwydering van die hoogs kristallyne fraksies, so neem die totale meganiese sterkte van die materiaal af; soos aangedui deur die afname in hardheid waarde. Die studie toon dat die verandering van die chemiese samestelling van die polimeer, deur die verwydering van hoogs kristallyne fraksies, 'n waargenome verandering in die meganiese eienskappe van die polimeer laat plaasvind. Daar kan afgelei word dat die monsters, vervaardig onder die katalis proef voorwaardes, beduidende verskille toon in terme van kristalliniteit en meganiese eienskappe in vergelyking met die monster vervaardig deur die huidige verwysings katalis.

Thesis (PhD)--Stellenbosch University, 2008. / ENGLISH ABSTRACT: Electrospinning is a simple yet versatile method used for producing nanofibers from various materials, including natural and synthetic polymers, polymer blends, ceramics and metals. The high specific surface areas, high aspect ratios (length/diameter), and the biomimicking nature of nanofibers make them ideally suited for application in diverse areas, including high-performance filtration, biomedical materials for tissue engineering scaffolds, wound dressings and controlled drug release, fiber-reinforced composites and highly sensitive nano-sensors. Two of the main requirements that need to be met for electrospun nanofiber materials to become commercially viable are: (1) a process for manufacturing continuous aligned nanofiber yarns, and (2) a drastic increase in the fiber production rate of the electrospinning process. The objectives of this study were to develop a scalable process for making continuous yarns of aligned electrospun nanofibers, and to develop a needleless electrospinning method for the high-throughput production of nanofibers. Three novel processes were developed while exploring innovative ways for making yarns from electrospun fibers. Finally, a fourth process, the so-called the NanoCaterpillar process, was developed. This process can be used as a scalable method for obtaining continuous yarns of aligned nanofibers. Advantages of the process include the requirement for relatively simple equipment, the simple process variations required for obtaining yarns of different linear densities, and the fact that, as a 'dry' process, it can be used to manufacture yarns from most materials that can be electrospun. The second goal of this study was to develop a needle-less electrospinning process, capable of making nanofibers at commercially viable throughput rates. The phenomenon of bubble electrospinning was discovered and developed further. Initial exploratory studies showed that bubble electrospinning could be employed to produce nanofibers from polymers in aqueous as well as organic solutions, and that the process follows similar trends to classic electrospinning such as the dependence of fiber diameter on polymer solution concentration and the possibility of including substances in the formed fibers by including them in the spin solution. A second, more in-depth study of the bubble electrospinning process revealed that fibers could be produced at very high rates with estimates, under ideal spinning conditions, reaching 5 kg/h per square meter of bubble bath surface. Furthermore it was found that fiber yield did not depend on the size or the lifetime per bubble. Investigations into several interesting aspects of bubble and jet behaviour during bubble electrospinning, such as child bubble formation and jet-splitting, led to predictive multiple linear regression models being fitted to the experimental data to describe process variables like yield per bubble, number of jets per bubble and fiber diameters. / AFRIKAANSE OPSOMMING: Die elektrospintegniek is 'n eenvoudige, dog veelsydige metode wat gebruik word om nanovesels van verskeie materiale, insluitend natuurlike en sintetiese polimere, polimeermengsels, keramieke, en ook metale te vervaardig. Die hoë spesifieke oppervlakareas, hoë lengte tot deursnee verhoudings en bio-naboodsende eienskappe van nanovesels maak hulle ideaalgeskik vir toepassing in uiteenlopende velde soos filtrasie, biomediese materiale vir weefselingenieurswese, wondbedekkings en beheerde vrystelling van geneesmiddels, veselversterkte saamgestelde materiale en hoogs-sensitiewe nanosensors. Twee van die hoofvereistes waaraan voldoen moet word, voordat elektrogespinde nanovesels kommersieël-lewensvatbaar kan word, is: (1) 'n proses vir die vervaardiging van kontinuë garings van gerigte nanovesels, en (2) 'n drastiese toename in die vervaardigingstempo van die elektrospinproses. Die doelwitte van hierdie studie was om 'n skalleerbare proses te ontwikkel vir die vervaardiging van kontinuë garings van gerigte nanovesels, en om 'n naaldlose elektrospinmetode te ontwikkel vir die hoë-uitset vervaardiging van nanovesels. Drie nuwe prosesse is ontwikkel tydens ondersoeke na innoverende maniere om garings van elektrogespinde nanovesels te vervaardig. Laastelik is 'n vierde proses, die sogenaamde NanoCaterpillar proses ontwikkel. Hierdie proses kan gebruik word as 'n skalleerbare metode vir die vervaardiging van kontinuë garings van gerigte nanovesels. Voordele van die proses sluit in dat relatief eenvoudige toerusting benodig word om die konsep toe te pas, dat slegs eenvoudige veranderinge aan die proses benodig word om garings van verskillende liniêre digthede te verkry, en dat die proses, synde 'n 'droë' proses, gebruik kan word om garings te maak van meeste materiale wat gespin kan word met die elektrospintegniek. Die tweede doelwit van hierdie studie was om 'n naaldlose elektrospinproses te ontwikkel wat nanovesels kon vervaardig teen kommersieël-lewensvatbare tempo's. Die borrelelektrospin verskynsel is ontdek en verder ontwikkel. Aanvanklike ondersoeke het getoon dat die borrelelektrospinproses gebruik kon word om nanovesels te vervaardig van polimere in water- sowel as organiese oplossings. Dit het ook getoon dat die proses soortgelyke tendense toon as die klassieke elektrospintegniek, soos die afhanklikheid van veseldeursnee aan polimeeroplossingkonsentrasie en die moontlikheid om ander stowwe in die gevormde vesels in te sluit deur dit aanvanklik in die spinoplossing in te sluit. 'n Verdere indiepte ondersoek van die borrelelektrospinproses het onthul dat vesels, onder geïdealiseerde omstandighede, vervaardig kon word teen baie hoë tempo's, na beraming 5 kg/h per vierkante meter borrelbadoppervlakarea. Verder is bevind dat die veselopbrengs nie afhanklik was van die borrelgrootte of -lewensduur nie. Ondersoeke na verskillende aspekte van die borrel- en polimeerstraalgedrag tydens die borrelelektrospinproses, soos die vorming van kind-borrels en polimeerstraalsplitsing, het gelei tot die passing van voorspellende meerfoudige liniêre regressiemodelle op die eksperimentele data, ten einde prosesveranderlikes soos opbrengs per borrel, aantal polimeerstrale, en vesels deursnee te kan beskryf.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2009. / Thesis presented in partial fulfilment of the requirements for the degree of Master of Science (polymer science) at the University of Stellenbosch / Embargo date 2010-03-31 plt 2010 / ENGLISH ABSTRACT: A novel method, herein referred to as ‘solvent facilitated coaxial electrospinning’, was used to produce reversibly thermochromic core-shell fibres with poly(methyl methacrylate) (PMMA) as shell and a thermochromic dye composite as core. The thermochromic dye composite consisted of combinations of 1-dodecanol, bisphenol A (BPA) and crystal violet lactone (CVL). In the ‘solvent facilitated coaxial electrospinning’ method, the thermochromic dye composite was dissolved in a suitable ‘facilitating solvent’ prior to spinning, instead of being spun into the fibres from the melt as previously described in literature. A low interfacial tension between the core and shell liquids, which is beneficial to effective core entrainment, was achieved by using a correctly chosen core ‘facilitating solvent’. The PMMA was dissolved to form the shell spinning liquid and by selecting the correct core and shell solvents, spinneret blockage and precipitation due to core and shell liquid interactions were eliminated. High molar mass PMMA was used to produce fibres with diameters in the range of 3–10 μm (larger than typical electrospun fibres) in order to minimize light scattering and subsequently allow visual observation of the thermochromic transitions, unlike the fibres that were produced in literature. The fibres were analyzed using SEM, TEM, TGA and DSC to investigate fibre morphology, dye composite thermal transition and fibre composition. Physical and chemical interactions between the thermochromic dye composite and the PMMA shell were identified as possible causes of differences between the thermochromic transition temperatures of the core-shell fibres and the bulk dyes, as well as of the instability of the colour developed state of certain thermochromic fibres. The spatial confinement of the dye composite inside the fibres and the extensive volume reduction (from bulk dye to small volume inside the fibres) affected the thermochromic behaviour of the thermochromic composite once it was entrained in the fibres. An excess BPA was used in the dye composition to allow the production of reversibly thermochromic fibres with a stable colour developed state. / AFRIKAANSE OPSOMMING: A nuwe metode, hierin beskryf as ‘oplosmiddel gefasiliteerde koaksiale elektrospinnery’, is gebruik om omkeerbare termochromiese kern-skil vesels met polie(metiel metakrilaat) (PMMA) as skil en ‘n saamgestelde termochromiese kleurmiddel as kern te vervaardig. Die saamgestelde termochromiese kleurmiddel het bestaan uit kombinasies van 1-dodekanol, bisfenol A (BPA) en kristal violet laktoon (CVL). Vir die ‘oplosmiddel gefasiliteerde koaksiale elektrospin’-metode, is die saamgestelde termochromiese kleurmiddel opgelos in ‘n gepaste ‘fasiliterende oplosmiddel’ voordat dit geëlektrospin is, eerder as om dit te smelt om dit sodoende in vesels te kan inspin soos beskryf in die literatuur. ‘n Lae raakvlakspanning tussen die kern- en skilspinvloeistowwe, wat voordelig is vir doeltreffende kern insluiting, is bereik deur gebruik te maak van sorgvuldig verkose ‘fasiliterende oplosmiddels’ vir die kern. Die PMMA is opgelos om die skilspinoplossing te vorm en, deur die keuse van die korrekte kern- en skiloplosmiddels, kon spinneret blokkasie en neerslag van die polimeer as gevolg van kern- en skilvloeistofinteraksies elimineer word. Hoë molekulêre massa PMMA is gebruik om vesels te vervaardig met deursnee in die omtrek van 3–10 μm (groter as tipiese elektrogespinde vesels) om sodoende lig-verstrooiing te verminder en daardeur visuele waarneming van die termochromiese oorgange moontlik te maak, in teenstelling met die vesels wat in die literatuur gevorm is. Die vesels is ge-analiseer met SEM, TEM, TGA en DSC om veselmorfologie, termiese omskakelinge van saamgestelde kleurmiddels en veselsamestelling te bestudeer. Fisiese en chemiese interaksies tussen die saamgestelde termochromiese kleurmiddel kern en die PMMA skil is geïdentifiseer as moontlike oorsake van verskille tussen die termochromiese oorgangstemperature van die kern-skil vesels en die kleurmiddels in grootmaat, asook van die onstabiliteit van die gekleurde toestand van sommige termochromiese vesels. Die ruimtelike inperking van die saamgestelde kleurmiddel binne in die vesels asook die beduidende volume verkleining (van grootmaat kleurmiddel tot klein volume binne in die vesels) het die termochromiese gedrag van die saamgestelde kleurmiddel binne die vesels beïnvloed. ‘n Oormaat BPA is in die saamgestelde termochromiese kleurmiddel gebruik om die produksie van omkeerbaar termochromiese vesels met ‘n stabiele gekleurde toestand toe te laat.

Thesis (MSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The presence of mineral oils in dry foodstuff was found to originate from the packaging materials, namely, paperboard manufactured from recovered fibres, and these oils subsequently migrate to the foodstuff via the vapour phase. The presence of mineral oils in food is of concern as it originates from the use of paper products not originally intended for food contact applications, i.e., before the paper is subjected to a suitable recycling process. These mineral oils consist of technical grade compounds which may contain aromatic compounds and other components with unknown toxicological effects. Although the related authorities are currently considering the safe and legal limits of these contaminants in foodstuffs, as well as establishing a standardised test method for monitoring mineral oils in food and packaging materials, paperboard manufacturers wish to ensure that their products are safe for food contact applications. Since recycling is unavoidable, particularly from an ecological and economical point of view, one of the proposed solutions the industry is focussing on is the use of a functional barrier towards mineral oils – be it an inner bag as a direct food-contact surface, or a barrier coating directly applied on the inner side of the paperboard. In this study, a permeation test method was established, and developed, to evaluate the transmission rate of a volatile organic compound, acting as a mineral oil simulant, through model paper and plastic packaging materials. This was correlated to the transmission rate of actual mineral oil through the packaging materials, and therefore used as a highly accelerated tool to characterise packaging materials in relation to their barrier properties. The test method, referred to as the “heptane vapour transmission rate,” was subsequently used to derive the required transport parameters’ characteristics of each of the tested materials, which enabled an evaluation of the potential shelf-life of the packaged product. This research demonstrated that barrier-coated paperboards have the ability to behave in the same way as, and often even better than, commercial plastic films, towards the migration of mineral oil. Detailed information on the interaction between the packaging materials and mineral oil simulant, n-heptane, was acquired from gravimetric sorption. Insight was obtained into a material’s ability to function as a mineral oil barrier. It was established that the quick and easy permeation method was sufficient for evaluating packaging materials as potential mineral oil barriers, and resulted in the determination of transport parameters that were higher than that obtained by sorption. The obtained transport parameters could therefore be considered a worst case scenario when predicting the package content shelf-life. / AFRIKAANSE OPSOMMING: Daar is voorheen bevind dat die teenwoordigheid van mineraalolies in droë voedsel afkomstig is van die verpakkingsmateriaal, naamlik karton, wat vervaardig is van herwonne papierprodukte, en daarna migreer die olies na die voedsel deur die gasfase. Die teenwoordigheid van hierdie mineraalolies in kos wek groot kommer aangesien dit afkomstig is van papierprodukte wat nie oorspronklik bedoel is vir voedselkontak voor die herwinningsproses nie. Die olies bestaan uit industriële graad mineraalolies wat moontlik aromatiese verbindings asook ander komponente bevat waarvan die toksiekologiese effekte onbekend is. Terwyl die betrokke owerhede tans besig is om die veilige en wettige grense van hierdie kontaminante in voedsel te oorweeg, asook die vestigting van 'n gestandaardiseerde toetsmetode vir die kontrole van mineraalolies in die voedsel-verpakkingsmateriaal-kombinasie, wil karton- en papiervervaardigers graag verseker dat hul produkte veilig is vir voedselkontak. Siende dat herwinning onvermydelik is vanuit 'n ekologiese en ekonomiese oogpunt, is een van die voorgestelde oplossings in die bedryf om te fokus op die gebruik van 'n funksionele keerfilm ten opsigte van mineraalolies, wat ‘n sakkie binne-in die karton, wat dien as die direkte kos-kontakoppervlak, of 'n keerlaag, wat direk aangewend word op die binnekant van die karton, kan behels. Hierdie studie ondersoek die daarstel en deursypelingsontwikkeling van 'n toetsmetode om die oordragtempo van 'n vlugtige organiese verbinding, wat optree as 'n mineraalolie simulant, deur middel van model papier- en plastiekverpakkingsmateriale, te evalueer. Dit stem ooreen met die oordragtempo van werklike mineraalolies deur die verpakkingsmateriaal en kan dus gebruik word as 'n hoogs versnelde instrument om verpakkingsmateriale te karakteriseer met betrekking tot hul keereienskappe. Die toetsmetode, die sogenaamde "heptaangasoordragtempo," is vervolgens gebruik om die vereiste oordragparameters af te lei wat kenmerkend is van elk van die geëvalueerde verpakkingsmateriale en wat sodoende gebruik kon word om die potensiële raklewe van die verpakte produk te bepaal. Hierdie navorsing het getoon dat kartonprodukte met ‘n keerlaag die vermoë het om dieselfde op te tree as kommersiële plastiekfilms en dikwels selfs beter, ten opsigte van die migrasie van mineraalolies. Gedetailleerde inligting oor die interaksie tussen die verpakkingsmateriale en mineraalolie simulant, n-heptaan, is verkry vanaf gravimetriese sorpsie. Dit gee insig in 'n materiaal se vermoë om te funksioneer as 'n mineraalolie-keermiddel. Daar is vasgestel dat die vinnige en maklike deurwerking metode voldoende is vir die evaluering van verpakkingsmateriale as potensiële mineraalolie-keermiddels, en verleen oordragparameters wat hoër is as dié verkry deur sorpsie. Hierdie oordragparameters kan dus as 'n ergste scenario vir die voorspelling van die raklewe van ‘n verpakte produk beskou word.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2005. / Two cationic polymerizable surfactants (surfmers), (11-acryloyloxyundecyl)dimethyl-(2-hydroxyethyl)ammonium bromide (Ethanol surfmer) and (11-acryloyloxyundecyl)-dimethylethylammonium bromide (Ethyl surfmer) were synthesized and characterized. Characterization was done using, conductivity, Fourier transform infra-red spectroscopy (FT-IR), electrospray mass spectrometry (ESMS), differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), small angle X-ray scattering (SAXS) and polarized light microscopy with a heating stage. These surfmers and the commercial surfactant cetyltrimethylammonium bromide (CTAB) were used for functionalization of sodium montmorillonite (Na+-MMT), thereby forming organophilic MMT. The functionalization of MMT dispersions was carried out by ion exchange of the sodium ions in Na+-MMT by surfactants in aqueous media. Organophilic MMT clays were then dispersed in styrene and subsequently polymerized by a free radical reaction to yield polystyrene-clay nanocomposites. This in-situ intercalative polymerization process resulted in an exfoliated structure for Ethyl surfmer modified clay, a partially exfoliated structure for Ethanol surfmer modified clay and an intercalated structure for CTAB modified clay. These nanocomposite structures were confirmed by SAXS and transmission electron microscopy (TEM). The nanocomposites exhibited enhanced thermal stability. All the nanocomposites exhibited an inferior storage modulus (GI) at low clay contents relative to polystyrene. At higher clay loadings there was an increase in GI which was dependent on the level of clay dispersion and the clay content. All the nanocomposites showed an increase in glass transition temperature (Tg), regardless of the amount of clay and the level of clay dispersion. There was a shift towards higher temperatures and broadening of the tan δ peak, which was in turn dependent on the amount of clay and level of clay dispersion. Molecular masses of polystyrene-clay nanocomposites were in the range 105 g/mol for bulk polymerization relative to 103 g/mol for solution polymerization as revealed by gel permeation chromatography (GPC).

Thesis (MSc)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: Water-borne coatings often contain multiple additives including pigments, dispersing agents, rheology modifiers, UV stabilizers and biocides. Due to their low molar mass and endocrinedisrupting properties, many of these additives, upon leaching from the substrate film, with time pollute water systems and become hazardous to the environment and to human health. In this study, I aimed to develop a facile method for the production of a polymeric biocide to serve as alternative to low molar mass biocides used in water-borne coatings. A secondary aim was to show that, without additional modification, the polymeric species can be used in surfactant-free ab initio emulsion polymerizations. Using a two-step process, I modified a commercially available copolymer, poly(styrene-alt-maleic anhydride) (SMA 1000), with mixed amines in order to obtain latexes with inherent antimicrobial activity. In the first step, I reacted SMA 1000 with 3-dimethylamino-1-propylamine and aqueous ammonia to confer antimicrobial activity and water-solubility to the SMA copolymer. In the second step, the copolymer was incorporated into a film-forming styrene-butyl acrylate (STY/BuA) latex. The modified SMA was incorporated into a latex in two ways: (1) post-added to the latex, and (2) used as stabilizer in emulsion polymerization. In both cases, the latex remained stable for up to 11 months, and stability was probably due to steric stabilization of the polymer particles. Antimicrobial activity of the latex film was achieved with both methods. When the modified SMA was post-added, antimicrobial activity was restricted to specific areas on the eventual polymer film, and when modified SMA was used as stabilizer, antimicrobial activity was evenly distributed throughout the polymer film. Fluorescence microscopy showed homogeneous distribution of antimicrobial activity upon inoculation in Gram positive bacteria dispersions when the modified copolymer was used as polymeric stabilizer for the synthesis of STY/BuA latexes. No antimicrobial activity against Gram negative bacteria was achieved. The homogeneous distribution of antimicrobial activity throughout the film was a result of adsorption of polymeric biocide/stabilizer to each individual latex particle. With further commercial development, high molar mass copolymers modified for antimicrobial activity may be a feasible, environmentally-friendly and healthy alternative to be used as stabilizers in emulsion polymerizations to produce water-borne coatings. / AFRIKAANSE OPSOMMING: Waterverf bestaan gewoonlik uit ‘n verskeidenheid bestandele, onder andere: pigmente, verspreiding middels, reologie modifiseerders, UV stabiliseerders en biologies aktiewe verbindings. As gevolg van die lae molêre massa en die endokrien ontwrigtende vermoë van baie van die bestandele hou hulle ‘n bedreiging in vir die omgewing in terme van waterbesoedeling en menslike gesondheid, soos hulle die film oor tyd verlaat. In hierdie studie het ek beoog om ‘n eenvoudige metode vir die vervaardiging van ‘n polimeries biologies aktiewe verbindings daar te stel om sodoende as ‘n alternatief vir die lae molêre massa biologies aktiewe verbindings, wat tans in waterverf gebruik word, te dien. ‘n Sekondêre uitkoms van die studie was om te wys dat, sonder enige adissionele omskakelings, dieselfde polimeer gebruik kan word in seep-vrye emulsie polimerisasie. Deur gebruik te maak van ‘n proses, wat uit twee stappe bestaan, het ek ‘n kommersieel beskikbare kopolimeer, poly(stireen-alt-maleinesuuranhidried) (SMA 1000), met gemengde amiene reageer om ‘n sintetiese lateks van stireen en butiel akrilaat (STY/BuA) met inherente antibakteriële aktiwiteit te verkry. In die eerste stap is SMA 1000 met 3-dimetielamien-1-propielamien en waterige ammoniak reageer om ‘n water oplosbare kopolimeer met inherente anti-bakteriële aktiwiteit te verkry. In die tweede stap is hierdie kopolimeer by ‘n sintetiese lateks gevoeg op twee maniere: (1) deur dit nadat die lateks geproduseer is by te voeg, en (2) deur die kopolimeer as stabiliseerder te gebruik in die vervaardiging van die lateks. In albei gevalle is stabiele latekse verkry vir ‘n tydperk van tot 11 maande. Die stabilisering was van steriese geaardheid. Albei die latekse het gevolglik antibakteriële eienskappe getoon. Daar was nie homogene verspreiding van die aktiwiteit in die geval waar die kopolimeer na die tyd bygevoeg is nie en het veroorsaak dat daar sekere areas van die finale film was wat geen aktiwiteit getoon het nie. Fluoresensie mikroskopie het egter homegene verspreiding van die anti-bakteriële aktiwiteit reg deur die film getoon, na inokulasie met Gram positiewe bakterië suspensies wanneer die kopolimeer as polimerisasie stabiliseerder gebruik was. Geen aktiwiteit teen Gram negatiewe bakterië was egter verkry nie. Die homogene verspreiding was as gevolg van die feit dat die kopolimeer sterk adsorbeer op elke individuele lateks partikel wanneer dit as stabiliseerder gebruik word. Verdere ontwikkeling op ‘n kommersiële basis kan daartoe lei dat polimeries biologies aktiewe verbindings as ‘n lewensvatbare en omgewingsvriendelike alternatief vir heidige stabiliseerders in emulsies vir waterverf gebruik kan word.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: In this study, a functional styrene – maleic anhydride copolymer (SMA) was synthesized via reversible addition-fragmentation chain transfer mediated polymerization (RAFT). The obtained copolymer had an alternating structure with well controlled molecular weight. The structure of the copolymer was found to alternating when characterized by NMR and MALDI-Tof-MS. SMA copolymer is functional polymer due to the presence of reactive maleic anhydride moiety in its backbone. The SMA copolymer was used as a starting material for synthesis of other three copolymers with potential anti-viral activity. These three copolymers are referred to as SMA copolymer derivatives because they were synthesized by reacting either maleic anhydride or styrene moieties with certain chemical compounds. The three derived copolymers are; styrene-maleimde copolymer (SMI), styrene sulfonate-maleic anhydride copolymer (SSMA) and styrene sulfonate– maleimide copolymer (SSMI). SMI was synthesized by reacting 4-aminomethylbenzene sulfonamide compound with maleic anhydride moieties on the backbone of SMA copolymer. The reaction proceeded in the presence of co-catalysts triethylamine and dimethylamino pyridine to from amide linkages. The copolymer was characterized by NMR spectroscopy, SEC and FTIR spectroscopy. SSMA copolymer was successfully synthesized by reacting styrene moieties of the SMA copolymers with chlorosulfonic acid. The SSMA copolymer was further reacted with amine compound to synthesize SSMI copolymer. The synthesis of SSMI was achieved by reacting the maleic anhydride moieties in the backbone of the SSMA copolymer with N1,N1- dimethylpropane-1,3-diamine. Both copolymers were successfully characterized by FTIR spectroscopy. / AFRIKAANSE OPSOMMING: 'n Funksionele stireen-maleïensuuranhidried (SMA) kopolimeer is berei d.m.v. omkeerbare addisie-fragmentasie ketting-oordrag-beheerde (OAFO) polimerisasie. Die polimere het 'n wissellende struktuur en goed beheerde molekulêre massa gehad. Die wisselende struktuur is bevestig d.m.v. KMR en MALDI-ToF analise. Die SMA kopolimeer is funksioneel a.g.v. die teenwoordigheid van reaktiewe anhidriedgroepe in die polimeerrugraat. Hierdie SMA kopolimeer is gebruik as uitgangstof vir die bereiding van drie ander kopolimere met potensiele teenvirale-aktiwiteit: stireenmaleïimied kopolimeer (SMI), stireensulfonaat-maleïensuuranhidried kopolimeer (SSMA) en stireensulfonaat-maleïimied kopolimeer (SSMI). Hiedie kopolimere staan bekend as SMA-kopolimeerderivate omdat hulle berei is deur d.m.v. die reaksie van of maleïensuuranhidried of stireengroepe. SMI is suksesvol berei d.m.v. die reaksie van 4-aminobenseensulfonamied met maleïensuuranhidriedeenhede op die polimeerruggraat in die teenwoordigheid van die kokataliste trietielamien of dimetielaminopiridien, om sodoende amiedbindings te vorm. Die kopolimere is gekarakteriseer m.b.v. grootte-uitsluitings-chromatografie (SEC), KMR en FTIR. Die SMMA kopolimeer is suksesvol gesintetiseer d.m.v. die reaksie van die stireeneenhede van die SMMA kopolimeer met chlorosulfoonsuur. Die SSMA kopolimeer is verder gereageer met amienverbindings om die SSMI kopolimeer te lewer. SMMI kopolimere is berei d.m.v. die reaksie van die maleïensuuranhidriedgroepe in die ruggraat van die SSMA kopolimeer met N',N'-dimetielpropaan-1,3-diamien. Albei kopolimere is suksesvol gekarakteriseer m.b.v. KMR en FTIR.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2005. / This thesis begins with the description of the preparation of thirteen dithioesters (of the form Z- (C=S)-S-R) which were characterized via Fourier-transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (NMR) and ultraviolet spectroscopy (UV). The dithioesters were then used as reversible addition-fragmentation chain transfer (RAFT) mediating agents in the bulk polymerization of styrene, in order to observe differences in the kinetic behaviour of the polymerizations and, as a result, the efficiencies of the dithioesters in mediating the polymerizations.