Thesis (PhD)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The use of co-sonication (ad-miniemulsion) polymerisation for the preparation of highly filled polymer/clay hybrid latexes is described. Laponite (Lap) content levels in the range of 10–50 wt% were effectively encapsulated in both polystyrene (PS) and polystyrene-co-butyl acrylate nanoparticles (PSBA). The latex and film morphological features of these highly filled hybrid materials were evaluated using both transmission electron microscopy (TEM) and small angle X-ray scattering (SAXS). PS/Lap latexes exhibited mixed particle morphologies from armoured particles at low clay content (10 wt%) to encapsulated particles at high clay content (50 wt%). However, PSBA/Lap hybrid latexes exhibited predominantly crumpled particle morphologies through the clay content studied. The resultant polymer/clay nanocomposites (PCNs) of PS/Lap and PSBA/Lap exhibited either partially or fully exfoliated structures. It was found that generally these PCNs exhibited superior properties than the neat polymers except for thermal stability properties. As much as 5000% storage modulus improvement was observed for both PS/Lap and PSBA/Lap relative to the neat polymers. The Tg of PSBA/Lap showed a 14 ºC shift towards higher temperature. Rheology tests showed that the resultant PCNs exhibited solid-like viscoelastic behaviour. The encapsulation of montmorilonite clay (MMT) using the ad-miniemulsion procedure was found to be ineffective. The MMT platelets remained adhered onto the polymer particles surfaces. Ineffective encapsulation of MMT platelets was attributed to their dimensions which were either large or equal to those of the polymer particles. Despite the ineffective encapsulation, the MMT platelets were completely exfoliated within the final PCNs as shown by both SAXS and TEM. Overall, the ad-miniemulsion was found to be an effective method for the preparation of highly filled water based polymer/clay hybrid latexes. However, the clay encapsulation in polymer particles and the extent of clay exfoliation were found to be dependent on clay dimensions relative to the polymer particles, monomer/clay compatibility and clay modifier reactivity. It was found that clay dimensions and use of clay modifier that improve monomer/clay compatibility enhances encapsulation. On the other hand, the modifier reactivity influenced the extent of clay exfoliation in the final PCN, irrespective of clay encapsulation in the polymer particles. These findings were based on comparative studies conducted on the use of Lap versus MMT and non-reactive modifier versus reactive modifier during ad-miniemulsion polymerisation. / AFRIKAANSE OPSOMMING: Die gebruik van mede-sonikasie (ad-miniemulsie) polimerisasie vir die voorbereiding van die hoogsgevulde polimeer/klei hibriedlatekse word beskryf. Laponiet (Lap) vlakke in hoeveelhede van 10-50 gew% is effektief ge-inkapsuleer in beide polistireen (PS) en polistireen-ko-butielakrilaat nanopartikels (PSBA). Die morfologiese eienskappe van die latekse en films van hierdie hoogsgevulde hibried materiale is geëvalueer deur beide transmissie-elektronmikroskopie (TEM) en klein-hoek X-straal-verstrooiing (SAXS). PS/Lap latekse het gemengde partikel morfologieë getoon, bv. vanaf gepantserde partikels by lae kleihoeveelhede (10 gew%) tot ge-inkapsuleerde partikels by hoë kleihoeveelhede (50 gew%). Daarteenoor het PSBA/Lap hibriedlatekse „n oorwegend verkreukelde partikelmorfologie getoon vir die reeks kleihoeveelhede wat bestudeer is. Die gevolglike polimeer/klei nanokomposiete (PKNs) van PS/Lap en PSBA/Lap het, óf gedeeltelike, óof ten volle geëksfolieerde strukture getoon. Oor die algemeen is bevind dat hierdie PKNs beter eienskappe as die suiwer polimere getoon het, behalwe vir die termiese stabiliteit eienskappe. Verbeteringe van soveel as 5000% in die stoormodulus is waargeneem vir beide PS/Lap en PSBA/Lap met betrekking tot die suiwer polimere. Die Tg van PSBA/Lap het „n 14°C verskuiwing na „n hoër temperatuur getoon. Reologiese toetse het getoon dat die gevolglike PKNs vastestofagtige visko-elastiese gedrag getoon het. Die inkapsulering van montmorilonietklei (MMT), deur middel van die ad-miniemulsieproses, was ondoeltreffend. Die MMT plaatjies het agtergebly op die oppervlaktes van die polimeerpartikel. Oneffektiewe inkapsulering van MMT plaatjies is toegeskryf aan hul grootte, wat óf groter, óf gelyk was aan dié van die polimeerpartikels. Ten spyte van die oneffektiewe inkapsulering was al die MMT plaatjies in die finale PKNs geëksfolieer soos deur beide SAXS en TEM aangedui. Oor die algemeen is bevind dat ad-miniemulsie „n effektiewe metode is vir die voorbereiding van hoogsgevulde waterbasis polimeer/klei hibriedlatekse. Daar is egter bevind dat klei inkapsulering in polimeerpartikels asook die omvang van klei eksfoliëring, afhanklik is van die klei afmetings in verhouding tot die polimeerpartikels, monomeer/klei verenigbaarheid en die reaktiwiteit van die kleiwysiger. Daar is bevind dat die klei afmetings en die gebruik van „n kleiwysiger wat die monomeer/klei verenigbaarheid verbeter, inkapsulering bevorder. Aan die ander kant het die reaktiwiteit van die kleiwysiger die omvang van klei eksfoliëring in die finale PKNs beïnvloed, ongeag van klei inkapsulering in die polimeerpartikels. Hierdie bevindings is gebaseer op vergelykende studies van die gebruik van Lap teenoor MMT en nie-reaktiewe wysiger teenoor reaktiewe wysiger gedurende ad-miniemulsiepolimerisasie.

Thesis (PhD)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: An instrument, named solution crystallization analysis by laser light scattering (SCALLS), that measures the solution melting and crystallization of polymers in solution was developed further in this study. The instrument was tested in a theoretical study to evaluate the Flory-Huggins relationship of melting point depression in solution of copolymers. It was found that the solvent interaction parameter for propylene/higher 1-alkene copolymers, with low comonomer content is dependent on the comonomer type. It was also showed that the melting point depression is dependent on both the type and amount of comonomer included in the copolymer. The instrument was further developed to include a total of three lasers with different wavelengths. Initial problems with laser interference was rectified by the introduction of dichroic mirrors to direct the laser light to the relevant detectors and broad pass filters in front of the the detectors to ensure that only the relevant laser light passes through. For homogenous polypropylene samples it was found that even though a slower cooling rate increases the relative peak temperatures as well as the relative temperature differences between the peaks, detail in the peak profiles is the same for the faster cooling rate. The subsequent heating analysis does show that there is a definite dependence on the cooling rate. The ZNPP-4 sample shows that the appearance of a shoulder in the heating analysis becomes more defined as a peak if the preceding cooling analysis is slower. Complex impact-polypropylene samples, differing only in the amount of ethylene were analysed and even small differences between samples were detected. The possible application of the SCALLS instrument was investigated. It was proven that the instrument can be used as a screening method for prep-TREF to determine the fractionation temperatures. / AFRIKAANSE OPSOMMING: 'n Instrument, genoem oplossing kristallisasie-analise deur laser lig verstrooiing (SCALLS), wat die smeltpunt asook die kristallisasie temperatuur in oplossing kan meet is verder ontwikkel in hierdie studie. Die Flory-Huggins verhouding oor die smeltpunt depressie in oplossing van ko-polimere is ondersoek in ‘n teoretiese studie. Daar is bevind dat die oplossing interaksie parameter vir propileen/hoër 1-alkeen kopolimere, met lae ko-monomeer inhoud is afhanklik op die ko-monomeer tipe. Dit is ook getoon dat die smeltpunt depressie afhanklik is van beide die tipe en hoeveelheid ko-monomeer in die ko-polimeer. Die instrument is verder ontwikkel om 'n totaal van drie lasers met verskillende golflengtes in te sluit. Aanvanklike probleme met laser inmenging is reggestel deur die bekendstelling van dichromatiese spieëls wat die laser lig na die regte ooreenstemmende detektor rig en filters voor die detektors verseker dat net die relevante laser lig die detektor bereik. Vir homogene polipropileen monsters is dit bevind dat selfs al is die analises gedoen teen ‘n stadiger afkoelings tempo wat lei tot ‘n verhoging in die piek kristallisasie temperatuur asook die relatiewe temperatuur verskille tussen die lasers, bly die detail in die piek profiele dieselfde as wat gesien word met ‘n vinniger afkoelings tempo. Die daaropvolgende verhitting analise toon dat die analise definitief afhanklik is op die voorafgaande afkoelings analise. Die ZNPP-4 monster toon dat die voorkoms van 'n skouer in die verwarming-analise word meer gedefinieerd en ‘n piek word gevorm soos die voorafgaande afkoelings tempo verlaag. Komplekse impak-polipropileen monsters, wat net verskil in die hoeveelheid etileen inhoud is geanaliseer en verskille is bepaal. Moontlike toepassings van die SCALLS instrument is ondersoek. Dit is bewys dat die instrument gebruik kan word om die fraksionering temperature vooraf te bepaal vir prep-TREF.

Thesis (PhD)--Stellenbosch University, 2012. / See full text for abstract. / Sien volteks vir opsomming

Thesis (PhD)--Stellenbosch University, 2013. / ENGLISH ABSTRACT: In this thesis, the recovery of RhIII from both synthetically prepared and authentic industrial PGM-containing solutions was systematically investigated via organic precipitation methods using several commercially available, N-containing organic receptors including (amongst others) diethylenetriamine (Deta), triethylenetetramine (Teta), tetraethylenepentamine (Tepa) and tris(2-aminoethyl)amine (Tren). These organic receptors act as precipitating agents in the presence of an appropriate protonating agent (HCl) by lowering the solubility of the PGM chlorido-anions through an ion-pairing mechanism. The recovery of RhIII from synthetically prepared PGM (RhIII and PtIV) containing solutions using these precipitants was excellent, while poor Rh recovery from authentic industrial process solutions was achieved. The poor Rh recovery from these process solutions was ascribed to the species distribution of the [RhCln(H2O)6-n]3-n complexes. In order to validate the proposition that RhIII speciation effects are responsible for the poor Rh recovery observed during the precipitation studies, attempt were made to describe the species distribution of the [RhCln(H2O)6-n]3-n (n=3-6) by means of high-resolution 103Rh NMR spectroscopy. A detailed high-resolution 103Rh NMR spectroscopic study of the series of [RhCln(H2O)6-n]3-n (n=3-6) complexes was conducted. During this study, all six RhIII aqua chlorido-complexes have unambiguously been characterized by means of high-resolution 103Rh NMR spectroscopy, proving the powerful analytical capability of this technique. Characterization of these complexes is based on the detailed analysis of the 35Cl/37Cl isotope effects which is observed in the 19.11 MHz 103Rh NMR resonances of the [RhCln(H2O)6-n]3-n (n=3-6) complexes in aqueous HCl solutions at 292 K. These resonances show that the “finestructure” of each of the 103Rh resonances may be understood in terms of its unique isotopologue, and in certain cases, the isotopomer distribution of each complex, which manifests as a result of its statistically expected 35Cl/37Cl isotopologue and isotopomer distributions. As a result, the 103Rh NMR resonance structure serves as a unique “NMRfingerprint”, which allows for the unambiguous assignment of [RhCln(H2O)6-n]3-n (n=3-6) complexes, without the reliance on accurate δ(103Rh) chemical shifts. Furthermore, this study reports the first direct species distribution diagram for the [RhCln(H2O)6-n]3-n (n=3-6) series of complexes (in aqueous HCl solutions at 292 K) as a function of the “free” (unbound) chloride concentration, constructed from 103Rh NMR measurements. The need for a revised speciation diagram of [RhCln(H2O)6-n]3-n (n=3-6) complexes is clearly reflected by the vast differences observed in the literature reported species distribution diagrams, which makes it difficult to decide which set of experimental conditions (if any) is required for the quantitative and “selective” recovery of RhIII from aqueous HCl solutions containing associated PGMs (Pt, Pd, Ir, Ru) as well as other transition metals. The documented species distribution diagrams for RhIII have been generally constructed via data from indirect (kinetic and spectrophotometric) measurements using dilute RhIII solutions at relatively high HCl concentrations, which implies that the RhIII:Clmole ratio is higher than what may be expected in authentic process solutions – an important aspect to consider when optimizing RhIII recovery methods. In addition, RhIII kinetic investigations reported in this study shows that ionic strength and temperature effects are important factors that dramatically influences the rate of RhIII ligand exchange (i.e. RhIII aquation reactions) which, in turn, have contributing effects on the species distribution of [RhCln(H2O)6-n]3-n complexes. Notable differences exist between the speciation diagram reported in this study and those documented in literature, especially at a “free” chloride concentration of 1.0 M. At this “free” chloride concentration, the [RhCl5(H2O)]2- complex anion was found to have an abundance of 34%, while literature reports an abundance of 80%. In order to ascertain its practical relevance, the proposed 103Rh NMR speciation method was extended, for the first time, to authentic industrial Rh feed solutions (Anglo Platinum PLC). Each of the 103Rh resonances was unambiguously assigned, and each species quantified. Moreover, the RhIII species distribution of the industrial Rh feed solution was accurately predicted by the “direct” speciation diagram constructed form 103Rh NMR measurements. After careful optimization of the Heraeus industrial feed solutions (optimal chloride concentration followed by thermal treatment for enhancing RhIII chloride anation reactions), the recovery of Rh via precipitation was repeated. In this instance, Rh recovery improved dramatically, with up to 95% of Rh removed from solution. This improvement is ascribed primarily to the increased “free” (unbound) chloride concentration. The presence of associated PGMs as well as other transition metals would lower the effective “free” chloride concentration, since these metals would act as “chloride binders”. By adjusting the total chloride concentration, RhIII chloride anation reactions is enhanced which leads to the [RhCln(H2O)6-n]3-n (n=5,6) complex anions being the dominant species in solution, therefore leading to improved Rh recovery. Moreover, it was shown that, under carefully controlled conditions, “selective” recovery of Rh is achieved using tris(2-aminoethyl)amine (Tren). Considering the fact that Rh is the last precious metal recovered in all PGM refineries, this can possibly provide a cost-effective route for the “upfront” (early stage) recovery of Rh from industrial PGM feed solutions. / AFRIKAANSE OPSOMMING: In hierdie tesis word die herwinning van RhIII uit laboratorium voorbereide sowel as ware industriële PGM-bevattende oplossings sistematies ondersoek deur middel van organiese neerslag metodes, deur gebruik te maak van verskeie kommersieël beskikbare, Nbevattende organiese reseptore insluitende dietileentriamien (Deta), tri-etileentetramien (Teta), tetra-etileenpentamien (Tepa) en tris(2-aminoetiel)amien (Tren). Hierdie organiese reseptore tree op as neerslag-agente in die teenwoordigheid van 'n geskikte protoneringsagent (in hierdie geval HCl) deur 'n verlaging van die oplosbaarheid van die PGM chloriedanione deur middel van 'n ioon parings meganisme. Die herwinning van RhIII vanuit laboratorium voorbereide PGM (RhIII en PtIV) oplossing met behulp van hierdie organiese neerslag-agente was uitstekend, terwyl Rh herwinning vanuit ware industriële oplossings swak was. Die onvolledige Rh herwinning uit hierdie industriële oplossings word toegeskryf aan die spesie-verspreiding van die [RhCln(H2O)6-n]3-n komplekse. Ten einde die effek van RhIII spesie-verspreiding op die herwinning van Rh te bestudeer, is gepoog om die spesieverspreiding van [RhCln(H2O)6-n]3-n (n=3-6) komplekse, deur middel van hoë resolusie 103Rh KMR spektroskopie, te beskryf. 'n Gedetailleerde hoë resolusie 103Rh KMR spektroskopiese studie van die reeks van [RhCln(H2O)6-n]3-n (n=3-6) komplekse was uitgevoer. Tydens hierdie studie was al ses RhIII aqua chlorido-komplekse ondubbelsinnig gekarakteriseer deur middel van hoë resolusie 103Rh KMR spektroskopie, wat bewys lewer van die kragtige analitiese vermoë van hierdie tegniek. Karakterisering van hierdie komplekse is gebaseer op die gedetailleerde analise van die 35Cl/37Cl isotoop effekte wat waargeneem word in die 19.11 MHz 103Rh KMR resonansies van die [RhCln(H2O)6-n]3-n (n=3-6) komplekse in HCl oplossings by 292 K. Hierdie resonansies toon dat die "fyn struktuur" van elk van die 103Rh resonansies verstaan kan word in terme van die unieke isotopoloog, en in sekere gevalle, die isotopomeer verspreiding van elke kompleks, wat manifesteer as 'n gevolg van die die statisties verwagte 35Cl/37Cl isotopoloog en isotopomeer verspreiding. Die 103Rh KMR resonansie-struktuur kan sodoende dien as 'n unieke "KMR-vingerafdruk", wat voorsiening maak vir die ondubbelsinnige karakterisering van [RhCln(H2O)6-n]3-n (n=3-6) komplekse, sonder om vertroue op akkurate δ(103Rh) chemiese verskuiwings te plaas. Hierdie studie rapporteer verder die eerste direkte spesie-verspreiding-diagram vir die [RhCln(H2O)6-n]3-n (n=3-6) reeks komplekse (in HCl oplossings by 292 K) as 'n funksie van die "vrye"(ongebonde) chloried-konsentrasie, verkry van 103Rh KMR metings. Die behoefte vir 'n aangepasde spesiasie-diagram vir die [RhCln(H2O)6-n]3-n (n=3-6) komplekse word duidelik weerspieël deur die groot verskille waargeneem in die literatuur gerapporteerde verspreidings diagramme, wat dit moeilik maak om te besluit watter stel eksperimentele toestande (indien enige) benodig word vir die kwantitatiewe en “selektiewe” herwinning van RhIII in HCl oplossings in die teenwoordigheid van gepaardgaande PGM (Pt, Pd, Ir, Ru) sowel as ander oorgangsmetale. Die gedokumenteerde spesie-verspreiding-diagramme vir RhIII is oor die algemeen verkry via data vanaf indirekte (kinetiese en spektrofotometriese metings) deur gebruik te maak van verdunde RhIII oplossings in relatiewe hoë HCl konsentrasies, wat impliseer dat die RhIII:Cl mol verhouding hoër is as wat verwag kan word in ware industriële proses oplossings - 'n belangrike aspek om te oorweeg gedurende die optimalisering van RhIII herwinning-metodes. Verder, die RhIII kinetiese ondersoeke gerapporteer in hierdie studie toon dat ioniese sterkte sowel as temperatuur effekte belangrike faktore is wat die tempo van RhIII ligand uitruiling (d.w.s. RhIII “aquation” reaksies), wat ‘n betekenisvolle invloed hê op die spesie-verspreiding van [RhCln(H2O)6-n]3-n komplekse. Aansienlike verskille bestaan tussen die spesiasie-diagram gerapporteer in hierdie studie en dit gedokumenteer in die literatuur, veral by 'n "vrye" chloried-konsentrasie van 1.0 M. By hierdie "vrye" chloried-konsentrasie was die [RhCl5(H2O)]2- komplekse anioon gevind om in 34% teenwoordig te wees (hierdie studie), terwyl die publiseerde verslae 80% rapporteer. Ten einde die praktiese toepaslikheid van die voorgestelde 103Rh KMR spesiasiemetode te bepaal, was (vir die eerste keer) ware industriële Rh oplossings (Anglo Platinum PLC) gebruik. Elk van die 103Rh resonansies was ondubbelsinnig gekarakteriseer, en elke Rh spesie teenwoordig gekwantifiseer. Daarbenewens is die RhIII spesie-verspreiding van die industriële Rh oplossing deur die "direkte" spesiasie-diagram saamgestel vanuit 103Rh KMR metings akkuraat voorspel. Die berekende RhIII spesie-verspreiding van die industriële Rh oplossings was akkuraat voorspel deur die voorgestelde “direkte” spesiasie-diagram soos saamgestel vanuit die 103Rh KMR metings. Na deeglike optimalisering van Heraeus industriële oplossings (optimale chloriedkonsentrasie gevolg deur termiese behandeling vir effektiewe RhIII chloried anasie reaksies), is die herwinning van Rh via neerslag metodes herhaal. In hierdie geval, het die Rh herwinning dramaties verbeter, met tot 95% van die Rh uit oplossing verwyder. Hierdie verbetering is hoofsaaklik toegeskryf aan die verhoogde "vry" (ongebonde) chloriedkonsentrasie. Die teenwoordigheid van geassosieerde PGM's sowel as ander oorgangsmetale sal die effektiewe "vrye" chloried-konsentrasie verlaag, aangesien hierdie metale sou optree as "chloried-binders". Deur die aanpassing van die totale chloried-konsentrasie, word RhIII chloried anasie reaksies verbeter, wat daartoe lei dat [RhCln(H2O)6-n]3-n (n = 5,6) komplekse anione die dominante spesies in oplossing word, en dus lei tot verbeterde Rh herwinning. Daarbenewens word verder aangetoon dat, onder noukeurig gekontroleerde voorwaardes, "selektiewe" herwinning van Rh bereik word deur gebruik te maak van tris(2-aminoetiel)amien (Tren). Met inagneming van die feit dat Rh die laaste edelmetaal is wat verhaal word in alle PGM-raffinaderye, kan dit 'n koste-effektiewe roete word vir die "vooraf" (vroeë-stadium) herwinning van Rh vanuit industriële PGM bevattende oplossings.

Thesis (MSc)--Stellenbosch University, 2012. / Please refer to full text for abstract.

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)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: The combination of natural and synthetic polymers allow for the synthesis of advanced hybrid copolymers. These hybrid copolymers have applications in biomedical areas, one such area being in drug delivery systems (DDS). In this study, a modular approach was used to prepare amphiphilic block copolymers with the ability to self-assemble into three dimensional structures. Reversible addition-fragmentation chain transfer (RAFT) was the synthetic tool used to mediate the polymerization of N-vinylpyrrolidone. RAFT is a versatile method to prepare polymers with control over molecular weight and dispersity. A xanthate chain transfer agent (CTA) was used to obtain the hydrophilic poly(N-vinylpyrrolidone) (PVP) block. An aldehyde functionality could be introduced due to the lability of the xanthate moiety, the procedure of which was effectively optimized to produce quantitative conversion. A dixanthate CTA was synthesized to produce a PVP chain which after the modification reaction, resulted in a α,ω-telechelic polymer. A polypeptide was synthesized via the ring-opening polymerization of Ncarboxyanhydrides (ROP NCA). The living and controllable ROP of NCAs is a method which results in polypeptides, but without a well-defined amino acid order. Poly(γ- benzyl-L-glutamate) (PBLG) was synthesized with a narrow dispersity (Đ = 1.10 – 1.15) using conditions that promote the retention of a terminal primary amine. A protected cysteine functionality was introduced via the terminal amine PBLG chain-end, using peptide synthesis techniques. This resulted in the conjugation of the aldehyde functional PVP and the cysteine terminal PBLG using a covalent, non-reducible thiazolidine linkage. The deprotection of the cysteine, more specifically the deprotection of the thiol was a non-trivial procedure. The thiol protecting acetamidomethyl (Acm) group could not be cleaved using traditional methods, but instead a modified procedure was developed to effectively remove the Acm group while inhibiting hydrolysis of the benzyl esters. It was determined that the conjugation reaction could effectively proceed in N,Ndimethylformamide (DMF) at a slightly elevated temperature and so continued to prepare the amphiphilic hybrid block copolymers, PVP-b-PBLG. A structurally different PBLG chain, namely PBLG-b-Cys was conjugated to the ω-aldehyde PVP and the conjugation efficiency was compared to our PBLG-Cys block. In the case of PBLG-b- Cys the in situ deprotection and conjugation as well as a two-step deprotection and conjugation reaction with PVP resulted in very low conjugation efficiency. The cysteine end-functional PBLG resulted in near quantitative conjugation with PVP. The critical micelle concentration (CMC) for PVP90-b-PBLG54 was determined to be 6 μg/mL, using fluorescence spectroscopy. Particle sizes were determined with TEM and DLS and found to range from 25 nm to 120 nm depending on the polymer block lengths as well as hydrophobic/hydrophilic block length ratios. Furthermore, when the micelles were subjected to an increased acidic environment, the labile benzyl ester bonds were hydrolyzed. This was observed with TEM where the particle sizes increased 10-fold to form vesicular structures. Hydrolysis was further confirmed with ATR-FTIR and 1H-NMR spectroscopy. Cytotoxicity tests confirmed that the copolymer micelles had good cell compatibility at high concentrations such as 0.9 mg/mL. Investigation into drug loading using a pyrene probe confirmed the viability of using PVP-b-PBLG as a responsive DDS. / AFRIKAANSE OPSOMMING: Die kombinasie van natuurlike en sintetiese polimere maak dit moontlik vir die sintese van gevorderde hibried kopolimere. Hierdie kopolimere het aanwending in biomediese gebiede, een so 'n gebied is in medisinale vervoer sisteme (MVS). 'n Modulêre benadering is in hierdie studie gebruik om amfifiliese blok kopolimere te berei. Omkeerbare addisie-fragmentasie kettingoordrag (OAFO) is gebruik as die sintetiese tegniek vir die polimerisasie van N-vinielpirolidoon (NVP). OAFO is 'n veelsydige metode om polimere te berei met beheer oor molekulêre gewig en dispersiteit (Đ). 'n Xantaat kettingoordrag agent (KOA) is gebruik om die hidrofiliese poli(N-vinielpirolidoon) (PVP) blok te sintetiseer. ‘n Aldehied endgroep was deur die terminale xantaat funksionaliteit berei, ‘n proses wat geoptimiseer is tot kwantitatiewe omsetting. 'n Di-xantaat KOA is gesintetiseer om, na modifikasie, 'n α, ω-telecheliese polimeer te produseer. Die polipeptied was gesintetiseer deur middel van ’n ringopening polimerisasie van Nkarboksianhidriede (ROP NKA). Die lewende en beheerbare ROP van NKAe is 'n metode wat lei tot polipeptiede sonder ’n gedefinieerde aminosuur volgorde. Poli(γ- benzyl-L-glutamaat) met 'n lae dispersiteit (Đ = 1.10 – 1.15), is gesintetiseer deur gebruik te maak van kondisies wat die behoud van 'n terminale primêre amien bevorder. 'n Beskermde sistien-funksionaliteit is ingebou via die terminale amien met behulp van peptiedsintese tegnieke. Die tiol beskerming van die asetamidometiel (Asm) groep kon nie gekleef word deur gebruik te maak van tradisionele metodes nie, maar ‘n nuwe proses is ontwikkel om die Asm groep te kleef sowel as om die hidrolise van die bensiel esters te inhibeer. Die koppelings reaksie het effektief verloop in DMF by 'n effens verhoogde temperatuur en sodoende is die amfifiliese hibried blok-kopolimere, PVP-b-PBLG berei. Twee verskillende PBLG kettings is gekoppel aan die ω-aldehied PVP en die koppeling doeltreffendheid is vergelyk. Daar is bevind dat net die sistien end-funksionele PBLG tot kwantitatiewe konjugasie kon lei. Die kritiese misel konsentrasie is bepaal vir PVP90-b-PBLG54 as 6 μg/mL met behulp van fluoressensie spektroskopie. Die deeltjie-groottes is bepaal met TEM en DLS en wissel van 25 nm tot 120 nm, afhangende van die polimeer bloklengtes sowel as hidrofobiese / hidrofiliese blok lengte verhoudings. Die miselle is blootgestel aan 'n verhoogde suur omgewing, wat tot die hidrolise van die bensiel ester groepe gelei het. TEM het getoon dat die deeltjie-groottes met 10-voud vergroot het tot vesikulêre strukture. Hidrolise is verder bevestig met ATR-FTIR en 1H-KMR spektroskopie. Sitotoksiese toetse het bevestig dat die miselle geen of min toksisiteit toon teenoor eukariotiese selle nie, selfs teen 'n hoë konsentrasies soos 0.9 mg/ml. Die medisinale behoud vermoë is met behulp van pireen bevestig en dus ook die potensiaal van PVP-b-PBLG as ‘n moontlike MVS.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2006. / This study concerns the phenomenon of environmental stress cracking resistance (ESCR) in three impact polypropylene copolymers (IPPCs). The main purpose was to correlate the ESCR with their properties such as microstructure, molecular weight (MW), molecular weight distribution (MWD), crystallinity and morphology. Initially the selection of a suitable test method and an active stress cracking agent (SCA) were the preliminary concerns. The Bell telephone test was used to evaluate SCAs, while a published procedure for determining ESCR of ethylene based plastics was adapted for the purpose of this study. Isopropanol was selected as SCA. Polymers were fully characterized by FTIR, 13C NMR, DSC and high temperature GPC. Optical microscopy was used to investigate craze formation and crack growth, and scanning electron microscopy (SEM) was used to study the morphology of the polymers. Since IPPCs are known to have multi-fraction copolymeric structures and each of these fractions has significantly different average properties, fractions were selectively removed from the materials, either by solvent extraction at room temperature, or by TREF fractionation. The effect of removing these fractions on the ESCR was determined. The effect of the molecular composition of the three IPPCs on the ESCR of these materials, as well as the effect of the removal of the selected molecular fractions on the ESCR, morphology and molecular characteristics are discussed and compared. Conclusions are drawn as to the factors controlling ESCR in these materials.

Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: This thesis reports an in-depth investigation of the intermolecular interaction motifs in secondary, primary and ammonium carboxylate salts. The investigation was conducted using the Cambridge Structural Database (CSD), together with a systematic steric-specific experimental study. The tendency in the literature has been to analyse organic salt crystal structures in terms of hydrogen bonding patterns, almost ignoring cation-anion interactions. This study focuses on the cation-anion interactions in secondary, primary and ammonium carboxylate salts, which have a direct effect on the formation of specific structural motifs. The ideas of ring-stacking and ring-laddering, which arise from the tendency of cations and anions to arrange themselves so as to maximise electrostatic interactions, have been applied to ammonium carboxylate salts. An extensive survey of organic ammonium carboxylate salt structures in the CSD has been carried out. The structural motifs in ammonium carboxylates were investigated, and a set of predictive rules for the pattern of intermolecular interactions in these salts was developed. Using these results, the formation of ring-stacking or ring-laddering in primary ammonium carboxylate salts can be predicted. The results from the CSD survey are discussed in Chapter 3. An experimental study has been carried out, which complements the results obtained from the CSD survey. The experimental study formed 19 novel ammonium carboxylate salts, of which 2 formed hydrates and 2 co-crystals of salts. The experimental results confirm what was found in the CSD survey, and this is discussed in Chapter 4. This study has found that the principle of ring-stacking and ring-laddering can be applied in a general form to the crystal structures of organic ammonium carboxylate salts. The size of the cation and the anion in these salts has a significant effect on the formation of structural motifs in the solid state. Interactions between cation and anion substituents also play an important role in the formation of particular structural motifs in ammonium carboxylate salts. / AFRIKAANSE OPSOMMING: In hierdie tesis word die intermolekulêre interaksie motiewe in die sekondêre, primêre en ammonium karbosilaat soute in-diepte ondersoek. Die studie is gedoen met behulp van die Cambridge Strukturele Databasis (CSD), saam met ‟n sistematiese steriesspesifieke eksperimentele studie. Die neiging in die literatuur is om organiese sout kristal strukture in terme van waterstofbindings patrone te analiseer sonder om katioon-anioon interaksies in ag te neem. Die studie fokus juis op hierdie katioon-anioon interaksies tussen sekondêre, primêre en ammonium karbosilaat soute wat ‟n direkte effek het op die vorming van spesifieke strukturele motiewe naamlik „ring-stacking‟ en „ring-laddering‟ wat hul oorsprong kry vanaf die neiging van katione en anione om hulself op so ‟n wyse te rangskik sodat die elektrostatiese interaksies ‟n maksimum kan bereik, op die ammonium karboksilaat soute. ‟n Volledige ondersoek van ammonium karboksilaat soute in die CSD is gedoen. Die strukturele motiewe in ammonium karboksilaat is ondersoek, en ‟n stel reels wat die patrone van intermolekulêre interaksies in hierdie soute voorspelis ontwikkel. Hierdie resultate kan gebruik word om die vorming van „ring-stacking‟ en „ring-laddering‟ in primêre ammonium karbosilaat soute te voorspel. Die resultate van die CSD ondersoek word bespreek in Hoofstuk 3. ‟n Eksperimentele studie is uitgevoer en die resultate hiervan komplimenteer die resultate van die CSD ondersoek. In die eksperimentele studie is 19 nuwe ammonium karboksilaat soute gekristaliseer, waarvan 2 hidraat-soute en 2 ko-kristal-van-soute is. Die eksperimentele resultate bevestig die bevindings van die CSD ondersoek, en dit word bespreek in Hoofstuk 4. Hierdie studie het gevind dat die beginsel van „ring-stacking‟ en „ring-laddering‟ kan in „n algemene vorm in die kristal strukture van organiese ammonium karboksilaat soute toegepas word. Die grootte van die katioon en anion in hierdie soute het ‟n beduidende effek op die vorming van strukturele motiewe in die vaste toestand. Interaksie tussen die katioon en anioon substituente speel „n belangrike rol in die vorming van spesifieke motiewe in ammonium karbosilaat soute.

Thesis (DSc)--Stellenbosch University, 2012. / ENGLISH ABSTRACT: Examples of the use of NMR spectroscopy in the study of radical polymerization processes have been described. The studies presented have made a significant contribution to the understanding of the fundamental mechanistic processes in these polymerization systems. It is pointed out that NMR in conventional radical polymerization is of limited use due to the concurrent occurrence of all elementary reactions (initiation, propagation and termination). Conversely, for living radical polymerization, NMR has great value. In that case, the elementary reactions are somewhat more restricted to specific times of the polymerization process. This allows for example the detailed study of the early stages of chain growth in Reversible Addition-­‐Fragmentation Chain Transfer (RAFT) mediated polymerization. Two different studies are described. The first is related to the early stages of RAFT-­‐mediated polymerization. A process for which we coined the name initialization was studied via in situ 1H NMR spectroscopy. It is shown that in many cases, there is a selective reaction that converts the original RAFT agent into its single monomer adduct. A few different examples and their mechanistic interpretation are discussed. It is also shown that NMR spectroscopy can be a valuable tool for the assessment of a RAFT agent in conjunction with a specific monomer and polymerization conditions. In the second study, 15N NMR, 31P NMR and 1H NMR are used for two different types of experiments. The first is a conventional radical copolymerization in which the growing chains are trapped by a 15N labeled nitroxide to yield a stable product. In the second experiment, a similar copolymerization is conducted under nitroxide-­‐mediated conditions. The nitroxide of choice contains phosphorous, which enables the quantification of the terminal monomer in the dormant chains. Each of the experiments individually provides interesting information on conventional radical copolymerization and nitroxide-­‐mediated copolymerization, respectively. Combination of the experimental data reveals an interesting discrepancy in the ratio of terminal monomer units in active chains and dormant chains. Although not unexpected, this result is interesting and useful from a mechanistic as well as a synthetic point of view. In terms of future perspectives, it is expected that the advanced analytical techniques as described here will remain crucial in polymer science. Present developments in radical polymerization, such as investigations into monomer sequence control, rely on accurate knowledge of kinetic and mechanistic details of elementary reactions. It is expected that such detailed studies will be a main challenge for the next decade of polymer research. / AFRIKAANSE OPSOMMING: Voorbeelde van die gebruik van KMR-­‐spektroskopie in die studie van radikaalpolimerisasies word beskryf. Hierdie studies het ʼn beduidende bydrae gelewer tot die verstaan van die fundamentele meganistiese prosesse in hierdie polimerisasiesisteme. Dit het daarop gewys dat KMR beperkte gebruike het in konvensionele radikaalpolimerisasies as gevolg van die gelyktydige voorkoms van alle basiese reaksies (afsetting, voortsetting en beëindiging). Aan die anderkant het KMR groot waarde vir lewende radikaalpolimerisasie. In hierdie geval is die elementêre reaksies ietwat meer beperk tot spesifieke tye van die polimerisasieproses. Gedetailleerde studies kan byvoorbeeld van die vroeë stadiums van die kettinggroei in Omkeerbare Addisie-­‐Fragmentasie-­‐ KettingOordrag (OAFO)-­‐bemiddelde polimerisasie gedoen word. Twee verskillende studies is beskryf. Die eerste het betrekking op die vroeë stadiums van die OAFO-­‐bemiddelde polimerisasie. 'n Proses wat “inisialisering” genoem is, is bestudeer deur middel van in situ 1H KMR-­‐spektroskopie. Dit is bewys dat daar in baie gevalle 'n selektiewe reaksie is wat die oorspronklike OAFO-­‐agent in sy enkelmonomeeradduk verander voor polimerisasie. 'n Paar ander voorbeelde en hul meganistiese interpretasie is bespreek. Dit is ook bewys dat KMR-­‐spektroskopie 'n waardevolle hulpmiddel kan wees vir die assessering van 'n OAFO-­‐agent in samewerking met 'n spesifieke monomeer en polimerisasie toestande. In die tweede studie is 15N KMR, 31P KMR en 1H KMR gebruik vir twee verskillende tipes van die eksperiment. Die eerste is 'n konvensionele radikaalkopolimerisasie waarin die groeiende kettings vasgevang word deur 'n 15N-­‐gemerkte nitroksied om 'n stabiele produk te lewer. In die tweede eksperiment is 'n soortgelyke kopolimerisasie gedoen onder nitroksied-­‐ bemiddelde toestande. Die gekose nitroksied bevat fosfor wat die kwantifisering van die terminale monomeer in die dormante kettings moontlik maak. Elkeen van die individuele eksperimente lewer interessante inligting oor konvensionele radikale kopolimerisasie en nitroksied-­‐bemiddelde kopolimerisasie, onderskeidelik. ʼn Kombinasie van die eksperimentele data toon 'n interessante verskil aan in die verhouding van die terminale monomeereenhede in die aktiewe en sluimerende kettings. Alhoewel dit nie onverwags is nie, is die resultate interessant en van waarde vanuit 'n meganistiese-­‐ sowel as 'n sintetiese oogpunt. In terme van toekomstige perspektiewe word daar verwag dat gevorderde analitiese tegnieke soos hier beskryf, belangrik sal bly in polimeerwetenskap. Huidige ontwikkelinge in radikaalpolimerisasie, soos ondersoeke na die beheer van monomeervolgorde, maak staat op akkurate kennis van kinetiese en meganistiese besonderhede van die basiese reaksies. Daar word verwag dat sulke gedetailleerde studies ʼn uitdaging sal bied vir die volgende dekade van polimeernavorsing.