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A gel permeation chromatography (GPC) system, using two concentration detectors and a low angle laser light scattering (LALLS) detector, has been investigated for use in characterising copolymers. At each elution volume, the system allows the calculation of molecular weight, average composition, and compositional heterogeneity. Overall molecular weight, composition, and heterogeneity parameters can also be calculated. This characterisation method yields heterogeneity information previously unobtainable without the use of cross fractionation techniques which are far more time consuming but ultimately more thorough.

The area of chemical research and synthesis increasingly recognises the need for improved technologies and methods, which involves chemical processes with less energy consumption, time savings, reduction and/or minimisation of waste, simple processes and an overall clean production. Microwave heating has been exploited in a variety of disciplines for many useful applications and organic synthesis is an area, which has benefited significantly over the past decade. The present study investigates organic reactions accelerated under microwave irradiations. In particular, the study involves use of recyclable Polymer and Inorganic Solid Supported Reagents for application in transfer hydrogenation. Reductions of electron deficient alkenes have been studied using polymer and inorganic solid supported formates. Microwave irradiations have been used to study transfer hydrogenations in presence of Wilkinson's catalyst [RhCl(PPh3)3]. The application of the Polymer Supported Reagents (PSR) has been investigated for studying transfer hydrogenation in N-benzyl deprotections. Microwave assisted synthesis of formamides from primary and secondary amines have been studied using supported formates. Microwave irradiations have also been applied in studying heterocycle synthesis by cycloaddition of nitrones with Pt (II) and Pd(II) bound organonitriles. The study broadly demonstrates a means of simplifying reaction procedures and purification along with reduction in waste of reagents and release of toxic residues. More importantly, use of microwave irradiations has been used to substantially improve the reaction yields and reduce reaction times, lower energy consumption and solvent volumes. The use of this methodology significantly benefits in the development of "Green Chemistry" and automated systems for chemical synthesis in many industrial sectors.

Detailed information of the underlying mechanisms of macromolecular disintegration processes is not always fully available from lab-based experiments and GPC. A powerful computer simulation technique was thus indispensable in this respect whilst saving time, labour and expense. This project aims to develop an interactive computer program to capture the behaviour of a complex reactor and offer the following functionality: mathematical calculations, graph/chart generation, processing simulation-experiment pertaining to user-given scission and environmental characteristics, data saving and re-loading etc, Windows-style menu-driven interfaces provide templates for easy implementation of complex mathematical algorithms -a new simulation technique (Slider interfaces) presented in the thesis, based on cellulose-ageing study in electrical transformers (Heywood, 2000). A novel statistical concept was introduced to significantly improve real-tune performance of mathematical calculations to simulate polymer chain fragmentation phenomena, enabling transformation of the simple iterative to a semi-iterative and instant calculation algorithm. Three new mathematical functions were constructed - (a) Monte Carlo Dynamic (Slider), (b) Algebraic Exact, (c) Markov Statistical models, initially using an arbitrary time scale for degradation. Real-time simulation was developed using three time model variants that included the interpretation of deviations in the order reaction rate from linearity to an exponential type function. The above transformation enhanced reproducibility and accuracy of degraded MWD curve sampling whilst then- graphical display & clarity via 'Cubic B-Spline' smoothing-algorithm. Complex models were created from a ranking ensemble of single scission mechanisms, structured with levels of probability constructs to effectively simulate GPC-like curve-deformities and side-shifts. The simulation results provided new information in the following key areas: the temporal shift patterns of MWD/PCLD under different ageing conditions graphical comparisons between simulated and observed Idnetic and scission parameters. the dominant types of scission strategy at different reactor conditions, the dependence of reaction behaviour on the polymer structural order. An alternative way of predicting life expectancy of an ageing polymer via relating time- temperature to the magnitude of intermediate MWD curve shifts that is independent on DP. The latter is an average value and subjected to errors. An equation was derived for this. Introduction of a binary tree "death time" algorithm for calculation of the life expectancy of different categories of polymer chain species. Non-iterative techniques developed here opens up new avenues of further research. The developed algorithms and computer program may provide ample scope for investigating the ageing of other industrially important polymers and can be utilised in other areas of polymer research with little modification where probability distribution is sought.

Various technical lignins, e.g. industrial Softwood Kraft lignin (SKL), are now largely available while they are generally underutilized due to their heterogeneous and complicated structures and/or the poor properties. SKL has here been modified by physical, chemical and biochemical methods for preparation of lignin microspheres, phenol substitution in phenol-formaldehyde (PF) resin preparation and preparation of highly efficient fertilizers. Physically, a brand-new slow and exhaustive solution evaporation process was developed for the highly efficient and productive preparation of microsphere structures. Highly homogenous SKL hollow microspheres were obtained and for the first time, urea encapsulating SKL microspheres were similarly prepared which could be an excellent controlled release urea fertilizer. Chemically, Mannich reaction (one type of amination) was deeply investigated by including for the first time an LC-MS study of vanillin reaction, resulting in the establishment of a fast and reliable lignin reactivity (for phenol substation in PF resin) quantification method. In addition, SKL was functionalized using the Mannich reaction or esterification, leading to an improved hydrophobicity and compatibility for blending with polylactic acid (PLA). Using dip-coating technique for the first time, PLA-functionalised SKL-coated urea pellets were prepared, leading expectedly to a highly efficient urea fertilizer with simultaneous controlled- and slow- release and biological stabilization effects. Biochemically, SKL was demethylated via incubation with different laccase-mediator combinations, which in principle will increase its reactivity in PF resin preparation. However, polymerization occurred which would decrease the reactivity.  The overall effects need to be further investigated. Conclusively, broader or larger scale SKL applications can expectedly be realized after the development of SKL modifications tailored towards the optimum desired structures and properties. / <p>QC 170912</p>

Biotemplating is the art of using a biological structure as a scaffold which is decorated with a functional material. In this fashion the structures will gain new functionalities and biotemplating offers a simple route of mass-producing mesoscopic material with new interesting properties. Biological structures are abundant and come in a great variety of elaborate and due to their natural origin they could be more suitable for interaction with biological systems than wholly synthetic materials. Conducting polymers are a novel class of material which was developed just 40 years ago and are well suited for interaction with biological material due to their organic composition. Furthermore the electronic properties of the conducting polymers can be tuned giving rise to dynamic control of the behavior of the material. Self-assembly processes are interesting since they do not require complicated or energy demanding processing conditions. This is particularly important as most biological materials are unstable at elevated temperatures or harsh environments. The main aim of this thesis is to show the possibility of using self-assembly to decorate a conducting polymer onto various biotemplates. Due to the intrinsic variety in charge, size and structure between the available natural scaffolds it is difficult, if not impossible, to find a universal method. In this thesis we show how biotemplating can be used to create new hybrid materials by self-assembling a conducting polymer with biological structures based on DNA, protein, lipids and cellulose, and in this fashion create material with novel optical and electronic properties.

Metal-polymer nanocomposite materials were found to have highly tunable opti- cal properties. Density functional theory-based calculations were employed to study trends in Ag/polyvinylidene fluoride nanocomposite optical properties. The frequency- dependent imaginary part of the dielectric constant was calculated from dipolar inter- band transitions. The metallic inclusion introduced both occupied and unoccupied states into the large polymer band gap. Thus, higher inclusion volume fractions generally led to stronger composite optical response. Spectra from monodisperse sys- tems correlated well with nanoparticle quantum confinement models. A polydisperse system exhibited optical properties that correlated best with interparticle distances along the field direction. Nanodisk and nanorod-shaped inclusions had tunable re- sponse from field polarization, aspect ratio, crystallographic projections, and nanorod end-cap morphology. / Graduate / 0495

The interest for polymeric nanocomposites has rapidly grown during the last decades, fuelled by the great potential and superior properties of nanoparticles (NPs). The production volumes of commercial NPs have increased exponentially during the last ten years, and the quality has been significantly improved. The aim of this study was to design polymer grafted commercially available metal-oxide NPs, and graphene oxide (GO), to develop isotropic (homogeneous) and anisotropic (heterogeneous) polymer nanocomposites for dielectric applications. The motivation was to formulate functional insulation materials for compact components in future power-grid systems using high-voltage direct-current (HVDC) or high-voltage alternating-current (HVAC), and to fabricate responsive sensor materials for monitoring e.g. temperature and voltage fluctuations in so called “Smart Grids”. Aluminium oxide (Al2O3), zinc oxide (ZnO) and reduced GO (rGO) NPs were modified with sparse polymer grafts via a controlled “covalent route” and were mixed with silicone (PDMS) or polyethylene matrices (EBA and LDPE) commonly used in HV-cable systems. The graft length and the graft-to-matrix compatibility were tailored to obtain nanocomposites with various self-assembled NP-morphologies, including well-dispersed, connected and phase-separated structures. The graft length was used to adjust the inter-particle distance of nanocomposites with continuous morphologies or connected (percolated) NPs. It was found that nanocomposites with percolated NPs and short inter-particle distances exhibited 10-100 times higher conductivity than the unfilled (neat) polymer, or displayed a rapid non-linear increase in conductivity (~1 million times) with increasingelectric field, while well-dispersed NPs with long inter-particle distances exhibited 10-100 times lower conductivity (i.e. higher resistivity) as an effect of their trapping of charge carriers. These tunable and functional properties are desirable for HV-insulation, field-grading applications, and flexible electronics. In addition it was shown that GO modified with dense polymer grafts via a “physisorption route” formed suspensions with liquid crystals, or matrix-free GO-composites with well-dispersed GO in isotropic or nematic states. These materials were reinforced by the GO, and exhibited elevated glass transition temperatures and a rapid thermo-responsive shape-memory effect, and are thus proposed to have a great potential as sensor materials and responsive separation membranes. / Intresset för polymera nanokompositer har snabbt ökat under de senaste decennierna, drivet av den stora potentialen och de överlägsna egenskaperna hos nanopartiklar (NPs). Produktionsvolymerna för kommersiella NP har ökat exponentiellt under de senaste tio åren, och kvaliteten har förbättrats avsevärt. Syftet med denna studie var att polymer-ympa kommersiellt tillgängliga metalloxid-NPs, och grafenoxid (GO), för att designa isotropa (homogena) och anisotropa (heterogena) polymera nanokompositer för dielektriska tillämpningar. Motiveringen var att formulera funktionella isoleringsmaterial för kompakta komponenter i framtida kraftnätssystem som använder högspänd likström (HVDC) eller högspänd växelström (HVAC), samt att tillverka responsiva sensormaterial för övervakning av t.ex. temperatur- and spänningsvariationer i så kallade "Smart Grids". Aluminiumoxid (Al2O3), zinkoxid (ZnO) och reducerad GO (rGO) NPs modifierades med glesa polymerympar via en kontrollerad "kovalent väg" och blandades med silikon (PDMS) eller polyeten matriser (EBA och LDPE) som är vanliga i HV-kabelsystem. Ymplängden och ymp-till-matrix kompatibiliteten skräddarsyddes för att erhålla nanokompositer med olika självordnande NP-morfologier, inklusive väldispergerade, länkade och fasseparerade strukturer. Ymplängden användes för att justera partikelavståndet i nanokompositer med förbundna morfologier eller länkade NPs. Man fann att nanokompositer med länkade NPs och korta interpartikelavstånd uppvisade 10-100 gånger högre konduktivitet än den ofyllda (rena) polymeren, eller erhöll en snabb icke-linjär ökning i konduktivitet (~1 miljon gånger) med ökande elektriskt fält, medan väldispergerade NPs med långa interpartikelavstånd uppvisade 10-100 gånger lägre ledningsförmåga (dvs. högre resistivitet) som en effekt av deras infångande av laddningsbärare. Dessa inställbara och funktionella egenskaper är önskvärda för HV-isolering, fältstyrande applikationer och flexibel elektronik. Dessutom visades att GO, som modifierats med täta polymerympar via en "fysisorptionsväg", bildade suspensioner med flytande kristaller, eller matrisfria GO-kompositer med väldispergerad GO i isotropa eller nematiska tillstånd. Dessa material armerades av GO och uppvisade förhöjda glastransitionstemperaturer och en snabb värmeresponsiv form-minneseffekt, och föreslås därigenom ha en stor potential som sensor-material och responsiva separationsmembran. / <p>QC 20170323</p>

M.Ing. (Mechanical Engineering) / An investigation was made to determine the feasibility of using existing international developed compositions of furfuryl alcohol polymer concrete in South African applications. Problems were encountered with these formulations and modifications were required in order to enhance the application possibilities of the material. After these modifications were made, tests were conducted to determine the effects of temperature, humidity, specimen size and variations in constituent quantities on the polymerisation reaction and properties of the material. Engineering characteristics, such as, compressive strength and durability were investigated and large scale field tests were performed to demonstrate the feasibility and simplicity of using polymer concrete. The final mix design selected for use in South Africa, polymerised within 20 minutes obtaining a compressive strength of 20 MPa in that period. This material proved stable under adverse chemical conditions and was able to withstand elevated temperatures of up to 200°C. Tests on road pothole rehabilitation slabs showed that polymer concrete can resist high stresses successfully under repeated loads and can be installed in less than 30 minutes in order to minimize traffic hold-ups. Furfuryl alcohol polymer concrete can be made at a cost of approximately 50c/kg and proves to be cost-effective when compared with epoxies.