Dissertations / Theses on the topic 'Dissertations – Polymer science'

Thesis (PhD)--Stellenbosch University, 2000.
ENGLISH ABSTRACT: The objective of this research was to produce discrete, nano-shaped polymeric structures on the same length scale as, or one to one copies of, templates, deformable templates or structure-directing hosts. Polymerisation of hydrophobic organic monomers in high concentration surfactant solutions, leads to the formation of shaped particles (rod-like, plank-like and ribbon-like particles) in the micrometer size range. The origin of these regularly shaped particles was investigated. It is proposed that they were not polymeric in nature, but formed by the crystallisation of the surfactant in the presence of electrolytes and ethanol as solvent. The polymeric particles that were formed were found to be of spherical shape, and no directing of the shape was detected. Mesostructured hosts were then investigated for their possible use as structure-directing agents. A series of polyelectrolyte-surfactant complexes of polydiallylammonium chloride with sodium sulphate surfactants (ranging from C10 to C16) were synthesised and characterised in terms of their thermal, mechanical and structural properties. The complex of polydiallylammonium chloride and sodium dodecyl sulphate was selected as an appropriate self-assembled model system for investigations into the structure-directing properties of these new materials. The polymerisation of hydrophobic organic monomers, such as styrene and the di-functional monomer m-diisopropenylbenzene (m-DIB), within the above mesoscopically structured polyelectrolyte-surfactant complex as host, lead to the formation of unconventionally shaped polymeric particles. The influence of the presence of monomers and guest polymers on the phase morphology of the host was investigated by small angle X-ray analyses (SAXS) and dynamic mechanical analyses (DMA). SAXS analyses showed that these new, stable hosts can hold up to 17 % guest polymer before phase disruption is encountered. These findings were supported by changes in the mechanical properties, as determined by DMA. The transmission electron microscopy (TEM) images of particles obtained after polymerisation showed very clearly that the poly-(m-DIB) did not form a continuous copy of the 3D hexagonal structure of the host, but rather colloidal copies of a part of the host structure that swelled the most. The shapes of the polymer mesostructures were dictated by the morphology of the phase of the structure-directing host, to produce nanosized wires (dimensions 4 by 100 nm), cigar-shaped particles (dimensions 8 by 50 nm) and fibrillar bent shapes (larger than 200 nm), as revealed by TEM. According to literature these are the first shaped, polymer nano-particles produced in a soft, selfassembled, organic templating host.
AFRIKAANSE OPSOMMING: Die doel van hierdie navorsing was om diskrete, nano-gevormde polimeriese partikels van dieselfde lengteskaal as, of direkte een tot een kopië van, 'n templaat, 'n vervormbare of struktuur-rigtende gasheersisteem te produseer. Die polimerisasie van hidrofobiese organiese monomere in seep oplossings van hoë konsentrasie, het gelei tot die produksie van gevormde partikels. Die oorsprong van hierdie partikels is ondersoek. Dit word voorgestel dat die partikels nie polimeries van aard is nie, maar gevorm is deur die kristallisasie van die seep in die teenwoordigheid van elekotroliete en etanol as oplosmiddel. Die polimeriese partikels wat wel geproduseer is, was sferies in vorm, en geen rigtende invloed op die vorm van die partikels is waargeneem nie. Meso-gestruktureerde gasheersisteme is ook ondersoek vir moontlike gebruik as struktuur-rigtende agente. 'n Reeks poliëlektroliet-seep komplekse van polidiallielammoniumchloried en natriumsulfaat sepe (van C10 tot C16) is gesintetiseer en gekarakteriseer in terme van hul termiese, meganiese en strukturele eienskappe. Die kompleks van polidiallielammoniumchloried en natrium dodekielsulfaat is gekies as 'n toepaslike self-organiserende modelsisteem vir die ondersoeke na die struktuur-rigtende eienskappe van hierdie nuwe materiale. Polimerisasie van hidrofobiese organiese monomere, soos byvoorbeeld stireen en die di-funksionele monomeer m-di-isopropenielbenseen (m-DIB), in hierdie mesoskopies-gestruktureerde poliëlektroliet-seep kompleks, het gelei tot die vorming van nie-konvensionele gevormde polimeriese partikels. Die invloed van die teenwoordigheid van monomere en gaspolimere op die fasemorfologie van die gasheersisteem is ondersoek d.m.v. kleinhoek X-straal diffraksie (Eng. SAXS) en dinamiese meganiese analise (DMA). SAXS analises het aangetoon dat hierdie nuwe, stabiele gasheersisteem tot 17 % gaspolimeer kan inkorporeer voordat fasevernietiging plaasvind. Hierdie resultate is verder ondersteun deur veranderinge in die meganiese eienskappe soos waargeneem deur DMA. Transmissie elektronmikroskopie (TEM) afbeeldinge van partikels geïsoleer na polimerisasie het baie duidelik gewys dat, in die geval van poli-(m-DIB), die gaspolimeer nie 'n kontinue kopie van die drie dimensionele heksagonale struktuur van die gasheersisteem produseer nie. Daar word eerder 'kolloïdale kopieë' van dele van die gasheersisteem wat die meeste swel gevorm. Die vorms van die polimeer mesostrukture word dus bepaal deur die morfologie van die fase van die struktuur-rigtende gasheer, om nanogrootte draadjies (dimensies 4 x 100 nm), sigaarvormige partikels (8 x 50 nm) en fibrillêre gebuigde vorms (groter as 200 nm) te vorm, soos waargeneem met TEM. Volgens die literatuur is hierdie die eerste geval van gevormde polimeer nanopartikels geproduseer in 'n self-organiserende templaat gasheersisteem.

Thesis (PhD)--Stellenbosch University, 2002.
ENGLISH ABSTRACT: Most polypropylene copolymers commercially available have ethylene, and to a lesser degree t-butene as comonomers. Commercially available higher a-olefins, mostly even-numbered, are seldom used for the production of pp copolymers, probably due to cost. Sasol's Fischer- Tropsch oil-from-coal process produces many linear and branched a-olefins as by-products that can be isolated and purified by a relatively cheap refinery process, including the odd-numbered 1- pentene olefin. Sasol's gas-phase Novolen pp plant at Secunda, South Africa is ideally suited to the manufacture of high quality pp random copolymers. As such an opportunity was identified to research the use of higher a-olefins, and more specifically 1-pentene, in the gas-phase production of pp random copolymers. Different methods to produce propylene / 1-pentene random copolymers in the slurry phase on bench-scale were investigated. A procedure was subsequently developed to produce propylene / 1-pentene random copolymers in the gas-phase in 10 litre autoclaves. It was found that commercially available fourth generation supported catalysts successfully incorporated the bulky 1-pentene monomer into the propylene backbone, both during slurry and gas-phase polymerisations. Software modelling was employed to determine the dew points of selected gas mixtures typically found during the production of pp random copolymers. The results indicated that typical process conditions could be employed during the gas-phase polymerisation of propylene and 1-pentene without the risk of condensation taking place inside the reactor. Propylene / 1-pentene random copolymers were subsequently successfully produced on the 800 litre BASF pilot plant in Germany followed by the first commercial production of the copolymer on Sasol's 50m3 Novolen gas-phase plant at Secunda. Using commercially available software the impact of introducing 1-pentene as comonomer during the production of random copolymers on the condenser cooling capacity was evaluated. Feasible and safe plant operating conditions were established for the production of propylene / 1-pentene random copolymers. The relationship between operating pressure and powder morphology was investigated to optimise process conditions. Operating at higher pressure in the gas-phase increases the monomer concentration in the reactor and as such improves the space/time/yield ratio of the 50m3 reactors. It was shown that higher operating pressures could be employed through the introduction of 1-pentene as comonomer during the production of PP random copolymer. The dramatic increase in catalyst productivity observed during the 800 litre pilot plant trials, up to a comonomer ratio of about 5%, supported the results obtained from a kinetic study carried out in bench-scale autoclaves. A comprehensive study was undertaken to compare the rheological, thermal, crystallisation, physical and mechanical properties of propylene / 1-pentene random copolymers with those of commercially available pp random copolymers. A series of propylene homo- and random copolymers with 1-pentene and ethylene as comonomers respectively, was prepared. NMR and IR techniques were developed to facilitate the determination of copolymer composition for the new family of 1-pentene random copolymers. The effect of comonomer content, molecular weight and temperature on the properties of the series of polymers was investigated. The propylene / 1-pentene random copolymers show unique rheological behaviour associated with the short propyl branches in the polymer backbone with minimum zero shear viscosity at about 2% 1-pentene content. The effect of molecular structure changes with comonomer content were analysed by the calculation of square average end-toend distance, packing length, tube diameter, molecular mass between entanglements and critical molecular mass. The viscosity of the 1-pentene random copolymers shows higher shear and temperature sensitivity compared to propylene homo- and ethylene random copolymers. The thermodynamic melting point of the propylene / 1-pentene random copolymers showed a significant decrease with increasing comonomer content in the 0 to 5% range. A wider melting range and higher peak melting point depression rate was observed compared to ethylene random copolymers at similar and increasing comonomer content measured on a weight % basis. It was found that the crystal structure of the propylene / 1-pentene random copolymers contains both the Q- and the y-modifications with the ratio of the respective crystal forms a function of both comonomer content and crystallisation temperature. The glass temperature decreased slightly with increasing comonomer (1-pentene) content. It is proposed that the short branch (propyl) "defects" in the polymer backbone are .incorporated into the crystal lattice resulting in increased rate of melting point depression with increasing (wt%) comonomer content compared to other random copolymers while maintaining relative high stiffness. The propylene / 1-pentene random copolymers exhibit the lowest haze values compared to all commercially available pp random copolymers at corresponding levels of comonomer content on a wt% basis. The stiffness to haze ratio of propylene / 1-pentene random copolymers are unique for all the members of the pp family. An inverse relationship between comonomer content and the measured tensile yield strength and modulus is observed. Application studies conducted on the propylene / 1-pentene random copolymers highlighted several interesting characteristics. Films produced from these copolymers exhibited very low haze and xylene soluble values while maintaining mechanical integrity. In the BOPP application the combination of processability and premium film properties presents a unique opportunity for the family of propylene / 1-pentene random copolymers. Blow moulding and injection moulding trials highlighted several advantages of product properties manufactured with propylene / 1-pentene random copolymers if compared to other commercially available random copolymers. The 1-pentene randoms presented lower in-mould as well as total shrinkage than ethylene based random copolymers. Stabilisation and nucleation studies conducted on the propylene / 1-pentene random copolymers showed that a typical combination antioxidant package and nucleating agent, at normal loading levels, could be used. In the larger pp random copolymer family 1-pentene imparts a better balance of properties than other comonomers. The combination of low melting point and xylene solubles with high stiffness and clarity is unique to propylene / 1-pentene random copolymers.
AFRIKAANSE OPSOMMING: Die oorgrote meerderheid van kommersieel beskikbare polipropileen (PP) kopolimere het etileen, en tot 'n mindere mate buteen, as komonomeer. Die relatief hoë koste van kommersieel beskikbare hoër alfa-olefiene is moontlik die rede waarom hulle selde gebruik word vir die vervaardiging van PP kopolimere. Die Sasol Fischer-Tropsch proses, waartydens olie uit steenkool vervaardig word, lewer verskeie liniêre en vertakte alfa-olefiene as neweprodukte wat geïsoleer en gesuiwer kan word in 'n relatiewe goedkoop rafineringsproses. Dit sluit ook die onewe-koolstofgetal 1-penteen-olefien in. Sasol se gasfase Novolen PP aanleg in Secunda, Suid-Afrika, is besonder geskik vir die vervaardiging van hoë standaard PP statistiese kopolimere. Voortvloeiend hieruit is die geleentheid geidentifiseer om die gebruik van hoër alfa-olefiene, en meer spesifiek 1-penteen, na te vors tydens die gasfaseproduksie van PP statistiese kopolimere. Verskeie metodes om propeleen / 1-penteen statistiese kopolimere in 'n koolwaterstofoplosmiddel op laboratoriumskaal te produseer, is ondersoek. 'n Prosedure is daarna ontwikkel om propileen / 1-penteen statistiese kopolimere ook in die gasfase te vervaardig in 10-liter drukvate. Die bevinding was dat kommersieel beskikbare vierde-generasie ondersteunde kataliste die swaarder 1-penteenmonomeer suksesvol geïnkorporeer het in die propileenketting tydens beide die koolwaterstof oplosmiddel- en gasfase polimerisasiereaksies. Rekenaargebaseerde modellering is gebruik om die kondensasiekondisies van tipiese gasmengsels, teenwoordig tydens die produksie van PP statistiese kopolimere, te bepaal. Die resultate het aangedui dat normale proseskondisies tydens die gasfasepolimerisasie van propileen en 1-penteengeen risiko van kondensasie in die reaktor inhou nie. Propileen / 1-penteen statistiese kopolimere is gevolglik met groot sukses vervaardig by die 800-liter BASF loodsaanleg in Duitsland, gevolg deur die eerste kommersiële vervaardiging van die kopolimeer op die Sasol50m3 Novolen gasfase-aanleg in Secunda. Deur gebruik te maak van kommersieel beskikbare sagteware, is die impak van 1-penteen as komonomeer tydens die vervaardiging van statistiese kopolimere op die verkoelingskapasiteit van die kondensator bepaal. Veilige en uitvoerbare aanlegkondisies is uitgestip vir die vervaardiging van propileen /1-penteen statistiese kopolimere. Die verhouding tussen die reaktordruk en poeiermorfologie is ondersoek om die prosestoestande te optimiseer. Vervaardiging van kopolimere in die gasfase by hoër drukke lei tot verhoogde monomeerkonsentrasie in die reaktor en gevolglik hoër produksiedeursette. Daar is bewys dat tydens die produksie van PP statistiese kopolimere, met 1-penteen as komonomeer, hoër reaktordruk ingespan kan word. Die dramatiese toename in katalisproduktiwiteit waargeneem tydens die 800- liter loodsaanleg proefloop, tot en met 'n komonomeer inhoud van ongeveer 5%, word ondersteun deur die resultate van 'n kinetiese studie uitgevoer in laboriumskaal drukvate. 'n Omvattende studie, om die reologiese, termiese, kristallyne, fisiese en meganiese eienskappe van propileen / 1-penteen statistiese kopolimere te vergelyk met kommersieel beskikbare PP statistiese kopolimere, is uitgevoer. 'n Reeks propileen homo- en statistiese kopolimere, met 1-penteen en etileen as komonomere onderskeidelik, is berei. KMR- en IR- tegnieke is ontwikkel om die bepaling van komonomeersamestelling vir die nuwe familie van 1- penteen statistiese kopolimere te fasiliteer. Die invloed van komonomeersamestelling, molekulere gewig en temperatuur op die eienskappe van die reeks polimere is ondersoek. Die propoleen / 1- penteen statistiese kopolimere toon unieke reologiese eienskappe wat geassosieer kan word met die propielsykettings in die polimeerruggraat. Die viskositeit van die propileen / 1-penteen statistiese kopolimere toon 'n hoër wrywings- en temperatuursensitiwiteit in vergelyking met propileen homo- en etileen statistiese kopolimere. 'n Drastiese verlaging in die termodinamiese smeltpunt van die propileen / 1- penteen statistiese kopolimere met 'n toename in komonomeerinhoud is waargeneem tot en met 'n 5% komonomeerinhoud. Die propileen / 1-penteen statistiese kopolimere toon 'n breër smeltgebied en 'n hoër tempo in die piek smeltpuntafname in vergelyking met etileen statistiese kopolimere met soortgelyke komonomeer inhoud, gemeet op 'n massabasis. Daar is bewys dat die kristalstruktuur van die propileen / 1-penteen statistiese kopolimere beide die alfa en gamma modifikasies bevat. Die verhouding van die onderskeie kristalvorms is 'n funksie van komonomeerinhoud en kristalisasietemperatuur. 'n Afname in die glastemperatuur met verhoogde komonomeer inhoud is waargeneem. Die aanname dat die kort propielsykettings in die polimeerruggraat in die kristalstruktuur geïnkorporeer word, is gemaak. Dit verklaar die hoë afname in die tempo van die smeltpunt met toenemende komonomeer inhoud relatief tot ander statistiese kopolimere, met die handhawing van hoë moduluswaardes. Die besondere deursigtigheid van die propileen / 1-penteen statistiese kopolimere tesame met relatief hoë modulus waardes is uniek. 'n Omgekeerde verhouding tussen komonomeer inhoud en treksterkte asook moduluswaardes is waargeneem. 'n Toepassingstudie uitgevoer met die propileen / 1-penteen statistiese kopolimere het verskeie interessante resultate gelewer. Films vervaardig van hierdie kopolimere toon besonderse deursigtigheid en lae waarde van xileenoplosbaarheid, terwyl meganiese integriteit gehandhaaf word. Voordele in die vervaardigingsproses van BOPP-films asook bogemiddelde filmeienskappe hou unieke moontlikhede vir propileen / 1-penteen statistiese kopolimere in. Verskeie voordele tydens blaas- en spuitvormingsprosesse is waargeneem relatief tot ander beskikbare statistiese kopolimere. Die 1-penteen statistiese kopolimere toon 'n laer in-vorm sowel as totale krimping relatief tot etileen- gebaseerde kopolimere. 'n Studie het aangetoon dat tipiese bymiddelpakette by normale toevoegingsvlakke geskik is vir propileen / 1-penteen statistiese kopolimere. Gesien in die groter pp statistiese kopolimeer familie toon 1-penteen 'n beter balans van eienskappe as ander komonomere. Die kombinasie van laer smeltpunt en xileen-oplosbares met hoë moduluswaardes en helderheid is uniek aan propileen /1-penteen statistiese kopolimere.

Dissertation (PhD)--Stellenbosch University, 2002.
ENGLISH ABSTRACT: The kinetics of drying and film formation of different polymeric latices were studied. Various theoretical models predict a strong dependency of the film formation characteristics on the particle size and morphology. This could be confirmed by experimental studies. The influence of particle size and morphology of differently structured latices on the film formation process was investigated by Atomic Force Microscopy (AFM) and Ultrasonic shear wave reflection. These two methods allow a comprehensive characterization of the drying and film formation process of emulsions. The studies confirmed the theoretical model, that the film formation behavior is influenced by the particle size and particle morphology. Furthermore the influence of different additives, such as coalescent solvents and rheology modifiers on the film formation behavior was investigated. As a second part of the studies, a novel technique was developed to measure thermal transitions of polymers with the AFM in the non-contact mode, using it as a Dynamic Mechanical Analyzer (DMA) on a local scale. The resonance frequency of the AFM cantilever was measured as a function of the temperature and thermal transitions of a polymer were clearly visible as changes in the resonance frequency / temperature response curve. Using the AFM in this mode allows the determination of the thermal properties of a material at a specific position on a sample, thereof on a macromolecular scale. A simple model was developed to explain the response of the cantilever caused by the transitions in the polymer and the related form of the frequency/temperature curves. This new technique adds a new dimension to standard thermal analysis techniques. It is now possible to resolve the individual thermal transitions of different polymer phases, for example in structured multiphase polymers.
AFRIKAANSE OPSOMMING: Die kinetika van droging en filmvorming van verskeie polimeriese lateksverbindingse is ondersoek. Verskeie teoretiese modelle voorspel 'n sterk afhanklikheid tussen die filmvormingseienskappe, partikelgrootte en morfologie. Hierdie afhanklikhede is eksperimenteel bevestig. Die invloed van partikelgrootte en morfologie van verskillende lateksstrukture op die filmvormingsproses is deur atoominteraksiemikroskopie (Eng: Atomic Force Microscopy, AFM) sowel as ultrasoniese skuifweerstandgolfrefleksie ondersoek. Hierdie twee metodes bied 'n deurslaggewende karakterisering van die droging en filmvormingsproses van emulsies. Resultate bevestig die teoretiese model, nl. dat filmvorming deur partikelgrootte en morfologie beïnvloed word. Die invloed van verskillende bymiddels, insluitend reologie-modifiseerders op filmvorming, is ook ondersoek. Vervolgens is 'n nuwe tegniek ondersoek om die termiese oorgange van polimere met behulp van die AFM in nie-kontak modus (deur dit as 'n dinamiese meganiese analiseerder (DMA) te gebruik) te bestudeer. Die resonansie-frekwensie van die AFM-hefboom is bepaal as 'n funksie van temperatuur. Termiese oorgange van 'npolimeer is duidelik waarneembaar as veranderinge in die resonansfrekwensie/ temperatuur responskurwe. Deur gebruik te maak van die AFM in hierdie modus kan die termiese eienskappe van 'n materiaal by 'n spesifieke posisie op die monster op molekulêre skaal bepaal word. 'n Eenvoudige model is ontwikkel om die oorgange in die polimeer, en gevolglik die vorm van die frekwensie/temperatuur kurwes, dmv. die respons van die hefboom, te verduidelik Hierdie nuwe tegniek gee 'n nuwe dimensie tot die standaard tegnieke van termiese analise tegnieke. Dit is nou moontlik om individuele termiese oorgange van verskeie polimeerfases, byvoorbeeld in gestruktureerde multifase polimere, te ondersoek en op te los

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.

Thesis (MSc)--Stellenbosch University, 2002.
ENGLISH ABSTRACT: Multimedia was the buzzword of the previous decade. Electronic learning is the buzzword of this decade. Both concepts changed, and are still changing the way educators present knowledge and information to students, both locally and worldwide. South Africa, also standing in the midst of these technological changes, has its own unique opportunities regarding the teaching environment. Different factors are currently changing the educational scene in South Africa. With Curriculum 2000 and the Outcome-Based Education concept (OBE) came the opportunity to choose and incorporate relevant science and technology programmes into school curriculums. The introduction of Technology as a subject in junior secondary school, opened the door to bring students in contact with, for example, the vast world of material science. Senior secondary students, on the contrary, have little or no exposure to teaching programmes on modern materials; materials that rule their lives! There is a need for high quality, easily accessible and informative material science programmes. This provided the initiative to create this programme. Depending on the standard of students, "Fun with Polymers" can be used as: • a lecturing tool for teachers and lecturers • an encyclopeadia which students can interactively navigate to learn more about polymer science • a source of information to anyone curious about the interesting world of plastic materials. The name "Fun with Polymers" indicates that learning science can be fun (after ali!). The programme contains easy to use navigation buttons, helpfiles, hypertext, sound, animations and pictures to teach synthetic polymer material science. Content consists of the history of the development of polymer materials, basic polymer chemistry principles, information on the building of macromolecules, facts on synthetic polymer materials, and some questions and answers to test the student's knowledge. Practical experiments, with plastic materials, complement the theoretical information and provide students with hands-on experience.
AFRIKAANSE OPSOMMING: Multimedia was die gonswoord van die vorige dekade. Elektroniese leer is die gonswoord van die nuwe dekade. Beide hierdie konsepte het, en is nog steeds besig, om die wyse hoe kennis en inligting, plaaslik en wêreldwyd, aan studente oorgedra word, te verander. Suid-Afrika, as deel van hierdie tegnologiese veranderinge, bied unieke en uitdagende geleenthede op die gebied van onderwys. Verskillende faktore beïnvloed, op die oomblik, die plaaslike onderwys scenario. Die koms van Kurrikulum 2000 en Uitkomsgebaseerde Onderwys het die deur vir toepaslike wetenskap- en tegnologie programme, as deel van skoolleerplanne, geopen. Die toevoeging van Tegnologie, as vakgebied, tot die junior sekondêre fase, skep die geleentheid om studente in aanraking te bring met, byvoorbeeld, die enorme wêreld van materiaalkunde. Senior sekondêre studente het egter min tot geen blootstelling aan materiaalkunde leerprogramme ten spyte van die feit dat hul lewens daagliks deur moderne materiale beïnvloed en beheer word! Daar bestaan 'n behoefte aan hoë kwaliteit, maklik bekombare inligting oor moderne materiale en vandaar die dryfveer om hierdie program te skep. Afhangende van die standaard van die studente, kan hierdie program gebruik word as: • 'n onderrigprogram vir onderwysers en lektore • 'n bron van inligting wat studente interaktief kan navigeer om meer van polimeeerchemie te wete te kom • 'n bron van inligting vir enigiemand wat nuuskierig is oor die interessante wêreld van plastieke. Die naam van hierdie program: "Fun with Polymers" dui daarop dat die wetenskapleerproses pret kan wees! Die program bestaan uit maklik navigeerbare instruksies, hulplêers, hiperteks, klank, animasies, en foto's om lig te werp op die onderwerp van plastiek. Die inhoud beslaan die geskiedenis van die ontwikkeling van plastiek= materiale, basiese polimeerchemie beginsels, inligting oor die vorming van makro= molekules, feite oor sintetiese polimeermateriale, en vrae en antwoorde om die gebruiker te toets oor sy/haar kennis. Maklik uitvoerbare en toepaslike praktiese eksperimente komplimenteer die teoretiese inhoud van die multimedia program.

Thesis (PhD (Chemistry and Polymer Science))--Stellenbosch University, 2008.
The research presented in this dissertation was concerned with the living radical polymerization (LRP) of an amphiphilic, water-soluble, bi-substituted and biologically compatible acrylamide derivative, namely n-acryloylmorpholine (NAM). The primary objective of this research was the synthesis of novel block copolymers containing poly(dimethylsiloxane) (PDMS) and various chain lengths of poly(acryloylmorpholine) (polyNAM) using a LRP technique, namely reversibleaddition fragmentation chain transfer (RAFT) polymerization. This is the first report on the synthesis of these block copolymers using RAFT polymerization. These novel siloxane block copolymers were synthesized using a monohydroxyterminated PDMS material which had to first be modified into a thiocarbonylthiocontaining moiety in order for it to be used as macromolecular chain transfer agent (macroCTA) in the RAFT copolymerization with NAM. Suitable reaction conditions for the synthesis of these novel block copolymers had to, firstly, be determined, and secondly, optimized. In order to determine suitable reaction conditions, a series of homopolymerizations with NAM were first performed in order to compare which chain transfer agent (CTA), solvent, temperature etc. could possibly be best suited for the block copolymerizations of PDMS-b-polyNAM. Reported in this work is the first account of the homopolymerization of NAM and 2-(dodecylsulfanyl)thiocarbonylsulfanyl-2-methyl propionic acid (DMP) as CTA using RAFT polymerization. The resulting novel siloxane block copolymers are amphiphilic in nature and the existence of these structures was confirmed by size exclusion chromatography/multiangle light scattering (SEC/MALS), proton nuclear magnetic resonance (1H-NMR) spectroscopy, gel elution chromatography (GEC) and transmission electron microscopy (TEM). Interesting phase behaviour was observed in the latter technique.

Thesis (MSc)--Stellenbosch University, 2000.
ENGLISH ABSTRACT: This work involves the study of the effects of Reversible Addition-Fragmentation Chain Transfer (RAFT) agents on the emulsion polymerization of styrene. The feasibility of RAFT as a method for obtaining controlled radical polymerizations in emulsion systems is also investigated. Both seeded and ab initio systems were studied with three RAFT agents of varying structure. Inhibition and retardation effects on addition of various amounts of the RAFT agents to the emulsion systems were observed and the trends noticed. The effect of the RAFT agents on the average number of radicals per latex particle was calculated from reaction rates. The effect of the RAFT agent on the molecular weight and the molecular weight distribution was monitored by gel permeation chromatography. Exit of free radicals from the latex particles proves to be a major feature in the studied RAFT emulsion systems. Fragmentation of the RAFT agent in the latex particles, gives rise to free radical species that can exit from the particle and enter other particles where they can either terminate instantaneously or propagate. The exit and termination processes presumably result in both the inhibition and retardation of the emulsion polymerizations. A linear increase in Mn with conversion is observed, however the low concentration of RAFT agent in the latex particles is responsible for the obtained number average molecular weights being much higher than predicted. The low concentrations of RAFT agents in the latex particles is also responsible for the broad molecular weight distributions that are obtained. Reaction conditions for RAFT experiments should to be chosen so that the effects of exit processes are minimized and that the RAFT agent is primarily situated in the latex particles. These conditions must be met if the RAFT process is to be successful as a method of controlled radical polymerization in emulsions.
AFRIKAANSE OPSOMMING: Hierdie navorsing behels die studie van die effek van In bygevoegde addisie-fragmentasie kettingsoordragsreagent (RAFT1) op die emulsie polimerisasie van stireen. Die uitvoerbaarheid van RAFT as 'n metode om gekontroleerde radikale polimerisasies in emulsiesisteme te verkry is ook ondersoek. Eksperimente met drie RAFTkettingoordragsreagente van gevarieerde strukture is uitgevoer in beide seeded en ab initia sisteme. Die effek van die RAFT-reagent op die inhibisie en vertraging van die emulsie polimerisasie is waargeneem en die invloed van RAFT op die gemiddelde aantal radikale per partikel is bepaal. Die ontwikkeling van die molekulêre massa en die molekulêre massadistribusie is waargeneem deur middel van gel permeasie- kromatografiese tegnieke. Die ontsnapping van vrye radikale vanuit die partikels was 'n belangrike faktor in RAFT emulsiesisteme wat ondersoek is. Hierdie radikale is gegenereer deur die fragmentasie van die oorspronklike RAFT-reagent. Fragmentasie van die RAFT-reagent in die lateks partikels lei tot die vorming van vrye radikale spesies wat uit een partikel kan ontsnap en ander partikels kan binnedring waar dit onmiddellik kan termineer of propageer. Die ontsnappings- en terminasieprosesse van vrye radikale lei oënskynlik tot die inhibering en vertraging van die emulsie polimerisasie. 'n Lineêre verhoging in die gemiddelde molekulêre massa tydens konversie is waargeneem, alhoewel die Mn-waardes baie hoër was as wat verwag is. Die verskil kan toegeskryf word aan die klein hoeveelhede van die RAFT-reagent wat in die partikels teenwoordig is. Hierdie lae RAFT-konsentrasies is ook verantwoordelik vir die breë molekulêre massa distribusie wat waargeneem is. Vir die RAFT-proses om suksesvol te wees in gekontroleerde radikale polimerisasies in emulsies, moet reaksie kondisies so gekies word dat die ontsnapping van vrye radikale tot 'n minimum beperk word en die RAFT-reagent hoofsaaklik in die lateks partikels teenwoordig is.

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)--Stellenbosch University, 2012.
ENGLISH ABSTRACT: The primary aim of this study was to investigate the feasibility of the amphiphilic block copolymer poly((vinylpyrrolidone)-b-poly(vinyl acetate)) (PVP-b-PVAc) as a vehicle for hydrophobic anti-cancer drugs. PVP-b-PVAc block copolymers of constant hydrophilic PVP block length and varying hydrophobic PVAc block lengths were synthesized via xanthate-mediated controlled radical polymerization (CRP). The methodology consisted of growing the PVAc chain from a xanthate end-functional PVP. In an aqueous environment the amphiphilic block copolymers selfassembled into spherical vesicle-like structures consisting of a hydrophobic PVAc bilayer membrane, a hydrophilic PVP corona and an aqueous core. The self-assembly behaviour and the physicochemical properties of the self-assembled structures were investigated by 1H NMR spectroscopy, fluorescence spectroscopy, transmission electron microscopy (TEM) and dynamic and static light scattering. Drug loading studies were performed using a model hydrophobic drug, clofazimine, and a common anti-cancer drug paclitaxel (PTX) to evaluate the potential of the PVP-b-PVAc block copolymers for drug delivery,. Clofazimine and PTX were physically entrapped into the hydrophobic domain of the self-assembled PVP-b-PVAc block copolymers via the dialysis method. The drug-loaded PVP-b-PVAc block copolymers were characterized regarding particle size, morphology, stability and drug loading capacity in order to assess their feasibility as a drug vehicle. The polymer vesicles had a relatively high drug loading capacity of 20 wt %. The effect of the hydrophobic PVAc block length on the drug loading capacity and encapsulation efficiency were also studied. Drug loading increased with increasing the hydrophobic PVAc block length. The effect of the drug feed ratio of clofazimine and PTX on the drug loading capacity and encapsulation efficiency were also investigated. The optimal formulation for the drug-loaded PVP-b-PVAc was determined and further investigated in vitro. The size stability of the drugloaded PVP-b-PVAc block copolymers was also assessed under physiological conditions (PBS, pH 7.4, 37 °C) and were stable in the absence and presence of serum. PVP-b-PVAc block copolymers were tested in vitro on MDA-MB-231 multi-drug-resistant human breast epithelial cancer cells and normal MCF12A breast epithelial cells to provide evidence of their antitumor efficacy. In vitro cell culture studies revealed that the PVP-b-PVAc drug carrier exhibited no cytotoxicity towards MDA-MB-231 and MCF12A cells, confirming the biocompatibility of the PVP-b-PVAc carrier. In vitro cytotoxicity assays using clofazimine-PVPb- PVAc formulations showed that when MDA-MB-231 cells were exposed to the formulations, an enhanced therapeutic effect was observed compared to the free drug. Cellular internalization of the PVP-b-PVAc drug carrier was demonstrated by fluorescent labeling of the PVP-b-PVAc carrier. Fluorescence microscopy results showed that the carrier was internalized by the MDAMB- 231 cells after 3 hours and localized in the cytoplasm and the perinuclear region. Overall, it was demonstrated that PVP-b-PVAc block copolymers appear to be promising candidates for the delivery of hydrophobic anti-cancer drugs.
AFRIKAANSE OPSOMMING: Die studie is gebaseer op die gebruik van amfifieliese blokkopolimere van poli((Nvinielpirolidoon)- b-poli(vinielasetaat)) (PVP-b-PVAc) as potensiële geneesmiddeldraers. PVP-b-PVAc blokkopolimere van konstante hydrofiliese bloklengte en verskillende hydrofobiese bloklengte is voorberei via die RAFT/MADIX-proses. Blokkopolimere met vinielasetaat is vanaf poli(N-vinielpirolidoon) met ‘n xantaatendfunksie voorberei. In ‘n wateromgewing vorm die PVP-b-PVAc blokkopolimere vesikel strukture met ‘n hydrofobiese membraan en ‘n hydrofiliese mantel. Die fisies-chemiese eienskappe van die PVP-b-PVAc blokkopolimere is gekarakteriseerd met gebruik van KMR spektroskopie, fluoresent spektroskopie, transmissie elektronmikroskopie (TEM) en dinamiese en statiese lig verstrooiing. Die potensiaal van PVP-b-PVAc as ‘n geneesmiddeldraer is ondersoek deur gebruik te maak van die hydrofobiese geneesmiddel, clofazimine, en ‘n anti-kanker geneesmiddel, paclitaxel. Clofazimine en paclitaxel is ge-inkapsuleer in die hydrofobiese gedeelte van die blokkopolimere via die dialise-metode. Clofazimine-PVP-b-PVAc en paclitaxel-PVPb- PVAc blokkopolimere is gekarakteriseerd met betrekking tot die partikel grootte, morfologie, stabiliteit en laai kapasitiet om die PVP-b-PVAc blokkopolimere as geneesmiddeldraers te evalueer. Die PVP-b-PVAc geneesmiddeldraer het ‘n relatiewe hoë laai kapsiteit van 20 gew % aangetoon. Die invloed van die bloklengte op die laai kapasitiet is ook ondersoek en beskryf. ‘n Toename in die laai kapasitiet is gesien met ‘n toename in die hydrofobiese bloklengte. Die invloed van die hoeveelheid geneesmiddel op die laai kapasitiet en die inkapsuleer doeltreffendheid is ook ondersoek. Die optimale formulasie is gevind en verder gebruik vir in vitro studies. Die stabiliteit van die geneesmiddeldraer in fisiologiese omstandighede (pH 7.4, 37 °C) is ook beskryf. Resultate toon aan dat die sisteem stabiel is onder hierdie omstandighede in die afwesigheid en aanwesigheid van serum. In vitro eksperimente is op MCF12A epiteel-borsselle en MDA-MB-231 epiteelborskankerselle getoets om die anti-tumoraktiwiteit te ondersoek. Resultate toon aan dat die PVP-b-PVAc geen sitotoxiese effek op die selle het nie, wat aandui dat die polimere bioverenigbaar is. Verder is dit bewys dat die PVP-b-PVAc geneesmiddel formualsie ’n hoër sitotoxisiteit besit as die vry-geneesmiddel. Fluoresent studies het aangetoon dat die geneesmiddeldraer na 3 uur opgeneen word deur MDA-MB231 selle en gelokaliseerd is in die sitoplasma en in die omgewing van die kern van die selle. In die algemeen is dit aangetoon dat PVP-b-PVAc blokkopolimere potensiële kandidate vir die lewering van hydrofobiese geneesmiddels is.

Thesis (PhD)--Stellenbosch University, 2012.
ENGLISH ABSTRACT: In materials chemistry, surface-initiated reversible deactivation radical polymerisation (SI-RDRP) has emerged as one of the most versatile routes to synthesising inorganic/organic hybrid materials consisting of well-defined polymers. The resultant materials often exhibit a remarkable improvement in bulk material properties even after the addition of very small amounts of inorganic modifiers like clay. A novel cationic reversible addition–fragmentation chain transfer (RAFT) agent with the dual purpose of modifying the surface of Laponite clay and controlling the polymerisation of monomer therefrom, was designed and synthesised. Its efficiency to control the polymerisation of styrene was evaluated and confirmed through investigating the molar mass evolution and chain-end functionality. The surface of Laponite clay was modified with the cationic chain transfer agent (CTA) via ion exchange and polymerisation performed in the presence of a free non-functionalised CTA. The addition of the non-functionalised CTA gave an evenly distributed CTA concentration and allowed the simultaneous growth of surface-attached and free polystyrene (PS). Further analysis of the free and grafted PS using analytical techniques developed and published during the course of this study, indicated that the free and grafted PS chains were undergoing different polymerisation mechanisms. For the second monomer system investigated n-butyl acrylate, it was apparent that the molar mass targeted and the monomer conversions attained had a significant influence on the simultaneous growth of the free and grafted polymer chains. Additional analysis of the grafted polymer chains indicated that secondary reactions dominated in the polymerisation of the surface-attached polymer chains. A new approach to separating the inorganic/organic hybrid materials into their various components using asymmetrical flow field-flow fractionation (AF4) was described. The results obtained not only gave an indication of the success of the in situ polymerisation reaction, but also provided information on the morphology of the material. Thermogravimetric analysis (TGA) was carried out on the polymer-clay nanocomposite samples. The results showed that by adding as little as 3 wt-% of clay to the polymer matrix, there was a remarkable improvement in the thermal stability.
AFRIKAANSE OPSOMMING: Oppervlakgeïnisieerde omkeerbare deaktiveringsradikaalpolimerisasie (SI-RDRP) is een van die veelsydigste roetes om anorganiese/organiese hibriedmateriale (wat bestaan uit goed-gedefinieerde polimere) te sintetiseer. Die produk toon dikwels ʼn merkwaardige verbetering in die makroskopiese eienskappe – selfs na die toevoeging van klein hoeveelhede anorganiese modifiseerders soos klei. ʼn Nuwe kationiese omkeerbare addisie-fragmentasie kettingoordrag (RAFT) middel met die tweeledige doel om die modifisering van die oppervlak van Laponite klei en die beheer van die polimerisasie van die monomeer daarvan, is ontwerp en gesintetiseer. Die klei se doeltreffendheid om die polimerisasie van stireen te beheer is geëvalueer en bevestig deur die molêre massa en die funksionele groepe aan die einde van die ketting te ondersoek. Die oppervlak van Laponite klei is gemodifiseer met die kationiese kettingoordragmiddel (CTA) deur middel van ioonuitruiling en polimerisasie wat uitgevoer word in die teenwoordigheid van ʼn vrye nie-gefunksionaliseerde CTA. Die toevoeging van die nie-gefunksionaliseerde CTA het ʼn eweredig-verspreide konsentrasie CTA teweeggebring en die gelyktydige groei van oppervlak-gebonde en vry polistireen (PS) toegelaat. Verdere ontleding van die vrye- en geënte PS met behulp van analitiese tegnieke wat ontwikkel en gepubliseer is gedurende die verloop van hierdie studie, het aangedui dat die vry- en geënte PS-kettings verskillende polimerisasiemeganismes ondergaan. n-Butielakrilaat is in die tweede monomeer-stelsel ondersoek en dit was duidelik dat die molêre massa wat geteiken is en die geënte polimeerkettings. ʼn Nuwe benadering tot die skeiding van die anorganiese/organiese hibriedmateriale in hulle onderskeie komponente met behulp van asimmetriese vloeiveld-vloei fraksionering (AF4) is beskryf. Die resultate wat verkry is, het nie net 'n aanduiding gegee van die sukses van die in-situ polimerisasiereaksie nie, maar het ook inligting verskaf oor die morfologie van die materiaal. Termogravimetriese analise (TGA) is uitgevoer op die polimeer-klei nanosaamgestelde monsters. Die resultate het getoon dat daar 'n merkwaardige verbetering in die termiese stabiliteit was na die toevoeging van so min as 3 wt% klei by die polimeermatriks.

Thesis (PhD)--Stellenbosch University, 2008.
ENGLISH ABSTRACT: This study concerns the synthesis, properties and quantitative analysis of polydiallyldimethylammonium chloride (polyDADMAC), a water-soluble polymer used world-wide for potable water purification. The special interest in this polymer is the result of its widespread use and the current lack of adequate analytical methods for it. This is especially important for water treatment organisations. A novel gel permeation chromatography (GPC) method was developed and evaluated for polymer analysis. The scope was extended to determine the presence of unreacted monomer (DADMAC) as well as the percentage active polymer. polyDADMAC was first prepared using a known synthesis method. The product was purified and characterized by GPC and 13C-NMR spectroscopy. New and conclusive evidence of the existence of a five-member pyrrolidine ring system was obtained. A proposed mechanism of polymerization was determined. The activity of the synthesized polyDADMAC was evaluated and it was found to perform effectively as a coagulant. The physical and chemical properties of polyDADMAC were then studied under simulated water treatment conditions. The polymer reaction with chlorine revealed the formation of trihalogenated methane compounds (THMs). Gas chromatography–mass spectrometry (GC–MS) was used to conclusively identify the formation of chloroform. The polymer stability under different conditions of heat exposure, UV radiation and pH variations was studied. GPC results indicated that polyDADMAC is a very stable polymer and undergoes structural change only when subjected to extremes of pH, temperature and UV conditions. Results of a short study on microbial degradation indicated growth of the cultures, and subsequent polymer degradation. Reactions of polyDADMAC were concluded with a study of the impact of ozone on polyDADMAC. GPC results indicated a significant change in the ozonated polymer peak profile. Analytical methods to determine polyDADMAC residues in water were reviewed and critically evaluated. Methods based on complex formation/spectroscopy suffered from severe limitations and produced no meaningful results, contrary to claims made by previous researchers. Colloid titration based on an established method was promising but required extensive modification for quantitative analysis. Finally four novel methods were developed, including: solid phase extraction, membrane filtration-GPC, the HACH complexation method, and a GPC method with indirect UV detection. The study is concluded with a chemical risk assessment that indicated minimal human health risks associated with the production and use of polyDADMAC.
AFRIKAANSE OPSOMMING:Hierdie studie behels die sintese, eienskappe en kwantitatiewe analise van polidiallielmetielammoniumchloried (polyDADMAC), 'n wateroplosbare polimeer wat wêreldwyd vir drinkwatersuiwering gebruik word. Die belangstelling in hierdie spesifieke polimeer is as gevolg van die wydverspreide gebruik daarvan en die feit dat daar tans onvoldoende eenvoudige analitiese metodes daarvoor bestaan. Dit is veral belangrik vir waterbehandelingsorganisasies. 'n Nuwe gelpermeasiechromatografie (GPC) metode is ontwikkel en geevalueer vir die analise van hierdie polimeer. Die omvang van die studie is later uitgebrei om die teenwoordigheid van ongereageerde monomeer (DADMAC) asook die persentasie aktiewe polimeer te bepaal. polyDADMAC is eers volgens 'n bekende sintesemetode berei. Die produk is gesuiwer en gekarakteriseer m.b.v. GPC en 13C-KMR. Nuwe bewyse vir die bestaan van 'n vyflid pirollidoonringsisteem is verkry. 'n Meganisme vir hierdie polimerisasie metode is vasgestel. Die aktiwiteit van die bereide polyDADMAC is geevalueer en daar is bevind dat dit effektief as koaguleermiddel optree. Daarna is die chemiese en fisiese eienskappe van polyDADMAC onder gesimuleerde waterbehandelingskondisies bepaal. polyDADMAC het met chloor gerageer om trihalogeneerde metaanverbindings (THMs) te vorm. Gaschromatografie–massa-spektrometrie (GC–MS) is gebruik om die ontstaan van chloroform te bevestig. Daarna is die stabiliteit van die polimeer onder verskei reaksiekondisies bepaal: hitte, UV-bestraling, en pH. GPC-resultate het aangeduiui dat polyDADMAC baie stabiel is en ondergaan strukturele veranderings slegs onder uiterste kondisies van pH, temperatuur en UV. 'n Kort studie van die effek van mikro-organismes op polyDADMAC het egtermikrobiese kultuurgroei met die gevolglike afbreek van die polimeer getoon. Resultate van 'n studie van die impak van osoon op polyDADMAC het getoon dat daar 'n groot verandering in die GPC-profiel van die ge-osoneerde vorm van die polimeer was. Verdere analitiese metodes wat al gebruik is om polyDADMAC residue in water te bepaal, is uitgevoer en krities geevalueer. Metodes gebasseer op kompleksvorming/ spektroskopie het erge beperkings gehad en het nie betekenisvolle resultate gelewer nie. Dit was in teenstelling met wat voorheen deur ander navorsers bevind is. 'n Kolloiedtitrasie gebasseer op 'n bestaande metode het goeie resultate gelewer maar het omvattende veranderings benodig om kwantitatiewe resultate te lewer. Ten slotte is vier nuwe metodes ontwikkel: soliede fase-ekstraksie, membraanfiltrasie-GPC, die HACH-komplekseringsmetode, en 'n GPC-metode met indirekte UV-waarneming.. Die studie is afgesluit met 'n bepaling van die chemiese risiko wat poly DADMAC vir die gesondheid van die mens inhou. Daar is tot die gevolgtrekking gekom dat die produksie en gebruik van poly DADMAC slegs‘n minimum gesondheidsrisiko inhou.

Thesis (PhD)--Stellenbosch University, 2013.
ENGLISH ABSTRACT: Solution electrospinning is a technique used to produce polymer micro- or nanofibres. Recently a great deal of research has been done on the application of polymer nanofibres produced by this method. The solution electrospinning of polyolefins have not been researched in-depth mainly due to the difficulty in dissolving these polymers in suitable electrospinning solvents. We managed to electrospin polypropylene copolymers at room temperature, obtaining both polymer micro- and nanofibres. A suitable solvent system was developed (cyclohexane/DMF/acetone) that allowed for the room temperature solution electrospinning of these crystalline polypropylene copolymers. It was also shown that using propylene-1-alkene copolymers with a low comonomer content was a facile way of producing crystalline polyolefins nano – and microfibers. Similar attempts to electrospin isotactic polypropylene were unsuccessful, even though lower molecular weight materials were used than in the case of the copolymers. This lead to an investigation of solution melting temperature by SCALLS. The copolymers showed great variance in their solution melting temperatures despite the fact that they all had more or less the same crystallinity and amount of comonomer, indicating that the type of comonomer played an important role in the solubility of the copolymer. The effect of different collectors was investigated, but in the end it was found that between spinning unto ice, foil on ice of just foil, foil still seemed to be the best collector. Comparing crystallinity of the polymer powders with that of the polymer fibres by DSC and WAXD, it was found that there is a difference in the crystallinity of the fibres and the powders. EVOH is a polymer with excellent properties and electropspinning of this polymer is relatively easy due to the fact that it dissolves quite easily in conductive solvents. DMF, Isopropanol/water and DMSO were all tested as suitable solvents and the morphology was compared through the use of SEM. The morphology of the fibres indicated that DMSO was the best solvent. The influence of the spinning parameters was determined for both systems of DMF and DMSO. These nanofibres were used as reinforcement in LDPE matrix and the mechanical properties of the LDPE matrix was improved with the addition of both aligned and unaligned fibres. The next step was the electrospinning of EVOH fibres containing MWCNT. TEM, FE-SEM and TGA were used to confirm the presence of the MWCNT as well as determine the distribution of the MWCNT inside the nanofibres. The nanotubes were distributed through the fibres; however agglomeration of the nanotubes did still take place. The nanofibres containing MWCNT were also used to make composites where the fibres were melted, leaving the MWCNT behind in the polymer matrix. This was done in both LDPE and EVOH matrices. The LDPE/MWCNT composites did not give positive results, on the other hand the EVOH/MWCNT composite showed an improvement in the mechanical properties compared to pure EVOH. The attachment of fluorescent dye molecules to the surface of the MWCNT was attempted and through fluorescent microscopy and the dispersion of the nanotubes inside the fibres as well as the composite could be seen. This study proved that polyolefin nanofibres could be obtained, giving rise to more applications for these versatile polymers. It also confirmed the importance of nanofibres as reinforcement and the use of nanofibres as a way to incorporate MWCNT in a polymer matrix.
AFRIKAANSE OPSOMMING: Elektrospin in ‘n oplosmiddel is ‘n tegniek wat gebruik word om polimeer mikro- en nanovesels te produseer. Die afgelope tyd word baie navorsing gedoen oor die aanwending van polimeer nanovesels wat geproduseer word op hierdie manier. Daar is nog min navorsing gepubliseer wat handel oor die elektrospin van poliolefiene uit ‘n oplosmiddel, deels oor hoe moeilik dit is om ‘n geskikte elektrospin oplosmiddel te vind vir hierdie polimere. In hierdie studie het ons mikro- en nanovesels verkry deur polipropileen kopolimere te elektrospin by kamertemperatuur. Die polimere is opgelos in ‘n oplosmiddel sisteem wat bestaan uit sikloheksaan/dimetielformamied/asetoon, by hoë temperatuur en het toegelaat dat die polimere in oplossing bly by kamertemperatuur. Hierdie diverse kopolimere het verskillende resultate gegee, sommige polimere het mikrovesels produseer, waar ander nanovesels geproduseer het. Die vessel morfologie is ondersoek deur die gebruik van Skandering Elektron Mikroskopie (SEM) en daar is gevind dat die vesels nie ‘n gladde voorkoms het nie, maar dat daar kraalvormige morfologie gesien kon word. Om dit te voorkom is sout by die oplosmiddel sisteem gevoeg. Die invloed van die verskillende parameters op die vesels se deursnit is ondersoek vir al die kopolimere. Die byvoeging van sout het gelei tot ‘n meer gladde vesel morfologie. Die effek van die gebruik van verskillende oppervlaktes om die vesels op te vang is ondersoek en die die kristalliniteit van die polimeer poeiers is vergelyk met die kristalliniteit van die polimeer vesels met die hulp van DSC en WAXD. ‘n Poging is aangewend om isotaktiese polipropileen te elektrospin uit oplossing, maar ons kon nie daarin slag om die polimeer op te los nie, al was die molekulêre gewig minder as die van die kopolimere. Dit het gelei tot die ondersoek van die smeltpunt temperatuur in oplossing deur die gebruik van oplossing kristallisasie-analise deur laser lig verstrooing (SCALLS). Al die kopolimere het min of meer dieselfde kristalliniteit en hoeveelheid komonomer bevat, tog het hulle smeltpunt temperatuur in oplossing baie verskil. Dit het gedui op die feit dat die tipe komonomeer ‘n groot rol speel in die oplosbaarheid van die kopolimeer. Die elektrospin van etileen-ko-vinielalkohol (EVOH) is ook ondersoek. DMF, Isopropanol/Water en Dimetielsulfoksied (DMSO) is getoets as geskikte oplosmiddels en die morfologie van die vesels is vergelyk deur die gebruk van SEM. Die tyd wat die polimeer in oplossing gebly het asook die morfologie van die vesels, het aangedui dat DMSO die mees geskikte oplosmiddel was. Die invloed van die elektrospin parameters was vasgestel vir beide DMF en DMSO sisteme. Hierdie nanovesels is gebruik as versterking in ‘n LDPE matriks en die meganiese eienskappe van die LDPE matriks is verbeter deur die toevoeging van beide nie-geweefde en gerigte veselsopppervlakte. Die volgende stap was die elektrospin van EVOH vesels wat multi-ommuurde koolstof nanobuisies (MWCNT) bevat. TEM, FE-SEM en TGA was gebruik om te bevestig dat die vesels wel MWCNT bevat asook om die verspreiding van MWCNT in die vesels aan te dui. Die nanobuisies was versprei deur die vesels, maar bundels nanobuisies het tog voorkom in sommige plekke. Die nanovesels wat MWCNT bevat is ook gebruik om nanosamestellings te maak, waar die vesels gesmelt is om net MWCNT agter te laat in die polimeer matriks. Hierdie was gedoen in beide LDPE en EVOH matrikse. Geen positiewe resultate is verkry vir die LDPE/MWCNT nanosamestelling nie, maar die EVOH/MWCNT nanosamestelling het aan die anderkant ‘n groot verbetering getoon in die meganiese eienskappe in vergelyking met EVOH sonder MWCNT. ‘n Poging was aangewend om fluoreseerende molekules aan die oppervlak van MWCNT te voeg en deur fluoresensie mikroskopie kon die verspreiding van die MWCNT in die vesels asook in die nanosamestellings gesien word. Hierdie studie het bewys dat poliolefien nanovesels gemaak kan word wat lei tot die aanwending van hierdie polimere in nog meer toepassings. Dit het ook die belangrikheid van die gebruik van nanovesels as versterking in nanosamestellings bevestig asook die gebruik van nanovesels as ‘n manier om MWCNT in ‘n matriks te plaas.

Thesis (MSc) -- Stellenbosch University, 1999.
ENGLISH ABSTRACT: A free-radical polymerisation process, which has characteristics of a living polymerisation system, as it is capable of producing polymers of pre-determined molecular masses with a narrow molecular mass distribution, is discussed. It is also possible to make blockcopolymers by adding adding different monomers. The basic objective was to describe, discuss and explain the results of the effects of alkyl iodides as chain transfer agents on the seeded emulsion homo- and co-polymerisation of styrene and butyl acrylate. lodoacetonitrile and 1-phenylethyliodide were used as alkyliodides, acting as degenerative chain transfer agents. First, the effects of these alkyl iodides as chain transfer agents on the molecular mass, molecular mass distribution, glass transition temperature, conversion and particle size for the seeded emulsion polymerisation of styrene were studied. Second, the effects of alkyl iodides as chain transfer agents on the kinetics of radical emulsion polymerisation, especially the average amount of radicals per latex particle, were investigated. Third, the possibility of producing block-copolymers by emulsion polymerisation, using alkyl iodides as chain transfer agents, was investigated. To the best of the author's knowledge, results of work carried out in this study offer the first proof that the "living"/controlled radical polymerisation of styrene, with alkyl iodides as chain transfer agents, can be successfully carried out in emulsion. Addition of different alkyl iodides as chain transfer agents, in different concentrations, led to marked changes in the molecular mass, molecular mass distribution, glass transition temperature, conversion and particle size for the seeded emulsion polymerisation of styrene. The molecular masses of the polystyrene that was produced ranged from 156 to 663 577 while the average molecular mass distribution was below 2. Addition of these alkyl iodides to a seeded styrene polymerisation under zero-one conditions led to an average number of free radicals per latex particle that was greater than 1. A styrene seed latex with functional iodine end-groups was created and was successfully co-polymerised with butyl acrylate to produce a perfect styrene-butyl acrylate block-copolymer. This work has industrial importance as it allows the molecular mass, molecular mass distribution and particle size of polymers to be controlled. These factors are directly related to their micro- and macrostructure of polymers.
AFRIKAANSE OPSOMMING: Die vrye-radikaal polimerisasie proses wat die eienskappe van In lewendige polimerisasie sisteem toon, omdat dit moontlik is om 'n polimeer met voorafbepaalde molekulêre massas en 'n baie klein molekulêre massa verspreiding te berei, is bespreek. Dit is ook moontlik om, deur die byvoeging van 'n tweede monomeer, 'n blok ko-polimere te maak. Die doel was om die effekte wat alkieljodiede as ketlingoordragagente op die "seed" homo- en ko-polimerisasie van stireen en butiel akrielaat gehad het te beskryf en te verklaar. Jodoasetonitriel en 1-fenieletieljodied is gebruik as degeneratiewe kettingoordragagente. Eerstens is die uitwerking van hierdie alkieljodiede as kettingoordragagente op die molekulere massa, molekulere massa verspreiding, glas oorgang temperatuur, opbrengs en partikelgrote van die "seed" emulsie polimerisasie van stireen bestudeer. Tweedens is na die uitwerking van alkiekjodiede op die kinetika van In emulsie radikaal polimerisasie gekyk met spesifieke 1