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Thesis (MSc (Chemistry and Polymer Science))--University of Stellenbosch, 2007. / Hybrid A-B type block copolymers of polydimethylsiloxane (PDMS) and polystyrene (PS) were synthesised. Three different synthetic routes, which allowed control over polymer structure, were chosen to synthesise these block copolymers. The first technique, coupling of functional prepolymers, involved using anionic polymerisation to produce PDMS and PS functional prepolymers of controlled structure. These prepolymers were functionalised with either silane or allyl functionality and then coupled using a hydrosilylation reaction with Karstetds platinum catalyst. This technique was the least efficient in block synthesis due to the incompatibility of the disparate prepolymers. The second technique under study, sequential anionic polymerisation, gave excellent block copolymer formation with good control over the chain architecture. The final technique employed atom transfer radical polymerisation (ATRP) of styrene using a bromoisobutyrate functionalised PDMS macroinitiator. Silane functional PDMS molecules underwent a hydrosilylation reaction with allyl-2-bromo-2-methyl-propionate to produce the bromoisobutyrate functionalised polymer in excellent yields. Subsequent ATRP with styrene allowed the successful synthesis of block copolymers of controlled structure. Chromatographic systems that allowed liquid chromatography at the critical conditions (LC-CC) of PS and gradient elution chromatography (GEC) of the products were developed. GEC was used successfully in the monitoring of the presence and removal of PDMS homopolymer present in the block copolymer products. LCCC at the critical point of PS allowed successful chromatographic separation of PS homopolymer from the block material, as well as, the molecular weight distribution of the block material according to the segmental length of the PDMS component. LC-CC coupled to FT-IR using a LC-transform device allowed successful characterisation of the block copolymer chemical composition. Corona treatment was used to modify the surface structure of the block copolymer films. Optical microscopy and slow positron beam studies highlighted the formation of a thin silica like layer on the surface of the films after corona. The positron studies enabled determination of the silica like layer’s thickness. Contact angle studies provided the first evidence of hydrophobic loss and recovery for these PDMS containing hybrid polymer materials after corona treatment. A novel offline coupling technique was developed between LC-CC separation and transmission electron microscopy (TEM) analysis. This allowed easy sample preparation without the difficult bulk extraction procedures needed to remove homo-PS contaminants from the block copolymer. This technique also provided morphological information as a function of PDMS segmental length.

Thesis (PhD)--Stellenbosch University, 2015. / ENGLISH ABSTRACT: Maceration enzymes for the wine industry are preparations containing mainly pectinases, cellulases and hemicellulases, used during wine making to degrade the berry cell walls and release polyphenolic and aroma molecules to increase wine quality. These types of enzymes are also used for the harvesting of revenue-generating molecules from pomace (skins, pulp and seeds from grape processing waste), or as processing aids when used in the production of bioethanol. Grape berry cell walls are recalcitrant towards degradation, therefore knowledge about their structures and compositions, as well as how the application of enzymes modify these structures is essential in order to optimise these processes. The aim of this study was to extend current knowledge by using a mixture of existing and novel methodologies to study grape berry cell walls by focusing on the profiles of polymers present in the walls. Cell wall profiling techniques used in this study include the Comprehensive Microarray Polymer Profiling (CoMPP) method that employs monoclonal antibodies and Carbohydrate Binding Modules (CBM) which specifically recognise the polymers in the plant cell wall. With this method we measured the abundance of specific polymers and traced the fluctuation in their levels of abundance as influenced by external factors such as enzyme hydrolysis. The CoMPP method was coupled with monosaccharide profile analysis by GC-MS to determine the building blocks of the cell wall polymers, as well as with Infrared Spectroscopy to monitor the changes in the bulk chemistry profile. Data sets generated by the cell wall profiling methods were analysed with uni- and multivariate statistical methods to detect the major patterns in the data. This study highlighted the cell wall differences on the polymer level, in the berry skin cells of Pinotage grapes at different ripeness levels and how it changes during a standard wine fermentation, leading to the release of homogalacturonans and the exposing of arabinogalactan proteins. When maceration enzymes were added, further depectination was evident and the enzymes unravelled the cell wall of the ripe grapes. In overripe grapes no additional degradation could be observed due to maceration enzyme actions, presumably indicating that the endogenous grape enzymes already caused extensive degradation. When purified enzymes were incubated under buffered conditions with isolated skin cell walls from Pinotage grapes or with Chardonnay grape pomace, different levels of enzymatic hydrolysis were observed and defined. The sequence in which cell wall polymers were extracted, and the influence of specific enzymes in facilitating the extraction process, provided important information on the accessibility of specific cell wall polymers. Synergistic action between, for example an endo-polygalacturonase (EPG) and an endo-glucanase (EG) was demonstrated with CoMPP. This EPG and EG synergism was also demonstrated with a yeast strain (a Saccharomyces paradoxus x S. cerevisiae hybrid) fermented in a buffered pomace suspension. This yeast strain has a native EPG and was engineered to also express a recombinant EG from a genome integrated cassette. The cell walls isolated from the pomace after fermentation were unravelled and depectination took place, as evident from CoMPP data. The cell wall profiling techniques used in this study were proven to be fast and sensitive. It provided insights into the structure of grape cell walls and was used to evaluate the changes due to ripening, fermentation, enzymatic hydrolysis and a heat pre-processing treatment. In addition to the knowledge gained, we also demonstrated that these techniques can be used to evaluate different enzymes and enzyme combinations as well as the potential of microorganisms to degrade grape tissue. / AFRIKAANSE OPSOMMING: Maserasie ensieme vir die wynindustrie is ensiem mengsels wat hoofsaaklik pektinases, sellulases en hemisellulases bevat en word tydens wynbereiding gebruik om die druifkorrel se selwand af te breek, die polifenole en aroma molekules vry te stel en sodoende die wyn kwaliteit te verbeter. Hierdie soort ensieme word ook gebruik om inkomste-genererende molekules vanuit druiweprosesserings afval (doppe, pulp en pitte) te isoleer, en ook as prosesserings hulpmiddels in die produksie van bioetanol. Druifkorrel selwande is weerstandig teen ensiem afbraak en daarom is kennis oor die struktuur en samestelling van die selwand, asook hoe die selwand strukture deur die toediening van ensieme verander word noodsaaklik om sodoende hierdie prosesse te optimaliseer. Die doel van hierdie studie was om die huidige kennis uit te brei deur bestaande asook nuwe metodes te gebruik om die druifkorrel selwand te bestudeer met die fokus op die polimeerprofiel van die selwande. Selwand karakteriserings tegnieke wat in hierdie studie gebruik is sluit in die Comprehensive Microarray Polymer Profiling (CoMPP) metode wat monoklonale teenliggaampies en koolhidraat bindende modules (Carbohydrate binding modules, CBMs) wat spesifiek die selwandpolimere van die plant selwand herken, gebruik. Met hierdie metode het ons die vlakke van spesifieke polimere gemeet asook die skommeling in hulle vlakke soos dit beïnvloed is deur eksterne faktore soos ensiem hidroliese. Die CoMPP metode is tesame met monosakkaried profiel analise, met behulp van GC-MS, wat die boublokke van die selwand polimere bepaal, asook infrarooi spektroskopie om die veranderinge in die oorhoofse chemiese profiel te bepaal, gebruik. Datastelle wat met die selwand karakteriserings tegnieke gegenereer is, is ontleed met een- en multiveranderlike statistiese metodes om die hoof tendense in die data op te spoor. Hierdie studie het die selwand verskille, op die polimeervlak, van Pinotage druiwe uitgelig. Verskillende rypheidsgrade asook hoe dit verander tydens ‘n standaard wynfermentasie is gevolg. Laasgenoemde het die vrystelling van homogalakturonaan en die ontbloting van arabinogalaktoproteïene tot gevolg gehad. Met die byvoeging van maserasie ensieme was dit duidelik dat addisionele pektienverwydering plaasgevind het en dat die ensieme die selwand van die ryp druiwe ontrafel het. In oorryp druiwe was daar geen addisionele selwand afbreking sigbaar as gevolg van die aksie van maserasie ensieme nie, wat moontlik aandui dat die inherente druif ensieme reeds uitgebreide selwand afbraak versoorsaak het. Wanneer gesuiwerde ensieme met geïsoleerde selwande van Pinotage druiwedoppe en met Chardonnay druiweprosesserings afval geïnkubeer is onder gebufferde kondisies, is verskillende vlakke van ensiematiese hidroliese waargeneem en geklassifiseer. Die volgorde waarin die selwand polimere geëkstraheer is, asook die invloed van spesifieke ensieme in die bevordering van die ekstraksie proses, het belangrike inligting verskaf oor die toeganglikheid van spesifieke selwand polimere. Sinergistiese aksie tussen, byvoorbeeld ‘n endo-poligalakturonase (EPG) en ‘n endo-glukanase (EG) is geidentifiseer met behulp van die CoMPP data. Hierdie EPG en EG sinergisme is ook geïllustreer met ‘n gisras (‘n Saccharomyces paradoxus x S. cerevisiae hibried) wat in ‘n gebufferde druifprosesserings afval suspensie gefermenteer het. Hierdie gisras het ‘n endogene EPG en is ontwerp om ook ‘n rekombinante EG uit te druk vanaf ‘n genoom geïntegreerde kasset. Die selwande van die druiweprosesserings afval wat na die fermentasie geïsoleer is, was ontrafel en pektienverwydering het plaasgevind, soos bevestig met CoMPP data. In hierdie studie is bewys dat die selwand karakteriserings tegnieke vinnig en sensitief is. Dit het insigte verskaf oor die struktuur van die druifselwand en is gebruik om die veranderinge as gevolg van rypheidsverskille, wynfermentasie, ensiem hidroliese en hitte prosessering te evalueer. Buiten die bydraes tot kennis oor hierdie onderwerpe, is die bruikbaarheid van hierdie tegnieke ook aangetoon, veral in die evaluasie van verskillende ensieme en ensiemkombinasies, asook mikroörganismes vir die afbraak van druifweefsel.

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The research described in this thesis originated from an idea to develop new body protection for the sport of fencing. The ultimate goal is to develop body armour which would be flexible, wearable, washable, light and breathable, offer protection from injuries and cover the entire body of a sportsman. A new material which exhibits shear thickening behaviour has been specially developed for this purpose in the process of this investigation. The material was designed and synthesised as a soft polymeric system which is flexible, chemically stable and able to increase the value of its modulus of elasticity upon impact at a high strain rate, while remaining in its soft gel-like elastomeric state when low strain rate deformation is applied. The polymeric system that has been developed is based on interpenetrating polymeric networks (IPN) of immiscible polyurethane/urea-ester/ether and poly(boron)n(dimethylsiloxane)m (where on average m ≈ 16 n). In addition, as the polydimethylsilane (PDMS) based polymeric system strongly tends to phase separation, the siloxane polymeric network was chemically cross-linked to the polyurethane polymeric network through polyurethane chemical cross-link-bridges. In order to introduce polyurethane cross-links to a siloxane-based polymeric network, some of the attached methyl groups in the PDMS polymeric backbone were substituted by ε-pentanol groups. The resulting polymeric system combines properties of an alternating copolymer with IPN. The actual substitution of the methyl groups of PDMS into alternating ε-pentanol groups was performed by Grignard reaction of trifunctional chlorosilane monomers, magnesium and 1,5-dibromopentane. Chemical analytical techniques like FT-IR, 13C NMR and 1H NMR spectroscopy were used to reveal the chemical structure of the synthesised polymeric network. The mechanical and dynamical properties of the obtained polymeric system were analysed by dynamic mechanical analysis (DMA). This part of the investigation indicated that the novel polymeric system exhibited shear thickening behaviour, but only at a narrow diapason of deformations (i.e., deformations between 2 to 3 % of the length of the sample). At this limited diapason of deformation an effective increase of the modulus of elasticity from 6 MPa (at lower frequencies, i.e., up to ≤6 Hz of the applied oscillating stress) to 65 MPa (at frequencies between 12.5 to 25 Hz) was obtained. However, no increase in the modulus of elasticity was recorded at deformations below 1.5 % or above 3.5 % of length of the sample at the same frequencies (0 to 25Hz) of the applied oscillating stress.

Polyurethane (PU) bilden eine wichtige Klasse von Kunststoffen, die in vielen technischen Anwendungen zum Einsatz kommen. Damit verbunden sind hohe Ansprüche an die Stabilität und Lebensdauer derartiger Polymere. Das Verständnis wichtiger Abbauprozesse stellt somit die Voraussetzung zur Optimierung deren Einsatzes dar. In dieser Arbeit wurde die Degradation von Ether und Ester Polyurethan-Probenkörpern zuerst durch eine kombinierte Bewitterung aus photochemischer, hydrolytischer und thermischer Beanspruchung simuliert und mit verschiedenen spektroskopischen, massenspektrometrischen und chromatographischen Methoden untersucht. Durch die Wahl zum Teil neuartiger konnten individuelle Prüfkörperhergestellt werden. Analytischer Schwerpunkt der Untersuchungen stellte dabei die Gel-Permeations-Chromatographie (GPC) dar. Mit dieser Methode war es erstmals möglich, aus den zeitlichen Änderungen von Molmassen und Löslichkeiten während der Beanspruchung Rückschlüsse auf einzelne Degradationsmechanismen wie Kettenbruch, Vernetzung und Verzweigung zu ziehen. Kombiniert wurde diese Untersuchung mit spektroskopischen und massenspektrometrischen Verfahren. Die in dieser Arbeit präsentierten Ergebnisse zeigen, dass die Degradation von Polyurethanen nahezu ausschließlich durch Temperaturerhöhung und UV-Strahlung induziert wurde, während die Feuchtigkeit allein keinen signifikanten Einfluss hatte. Die beobachteten Effekte ließen sich überwiegend durch Kettenbrüche und Verzweigung bzw. Vernetzungen erklären, wobei sich beide Prozesse überlagerten. Die Ergebnisse lassen auch darauf schließen, das Ester PU bei identischen Degradationsbedingungen grundsätzlich stabiler sind und weniger stark abgebaut wurden, als Ether PU. Die Ergebnisse können dazu beitragen, die kombinierte Bewitterung, die einen natürlichen Abbau simulieren soll, besser zu verstehen und den Anteil der einzelnen Umweltfaktoren auf die Gesamtalterung der Materialen realistischer einzuordnen. / Polyurethanes (PU) are an important class of polymers that are used in many technical applications. Therefore, there are high demands regarding their stability and durability Thus, an understanding of important degradation processes is required for their optimized use. In this thesis, the degradation of ether and ester polyurethane samples was initially simulated by a combined weathering by photochemical, hydrolytic and thermal exposure and investigated with different spectroscopic and mass spectrometric methods. Using innovative manufacturing techniques (e.g. 3D printing, electrospinning) for the fabrication of specimens, individual samples from nano- to centimeter scale became available. Based on the results of the combined weathering, exposure scenarios were developed, which reduced the complexity of the degradation towards the investigation of individual parameters (temperature, UV radiation, humidity). The analytical investigations were focused on gel permeation chromatography (GPC). For the first time, time-depending degradation mechanisms such as chain scission, crosslinking and branching were derived from changes of molecular masses and solubilities during exposure. This chromatographic investigation was combined with spectroscopic and mass spectrometric methods. The results presented in this thesis show, that degradation of polyurethanes was induced almost exclusively by temperature and UV radiation, while moisture alone had no significant influence. The observed effects could mainly be explained by chain scission and branching/crosslinking affecting each other. The results also indicate that ester PU was more stable under identical degradation conditions and degraded less than ether PU. These results might contribute to a better understanding of the combined weathering, which is intended to simulate natural degradation, and might serve for a realistic evaluation of the contribution of single degradation parameters.