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This thesis presents a study on the effect of magnetic field on the distribution and orientation of magnetic particles in injection moulding. The experimental work, using various materials such as polyester resin, nickel particles, polypropylene (PP), polycarbonate (PC) and methods (single component injection and co-injection moulding), has led to a deeper understanding of the mechanism that governs magnetic particle orientation under an external magnet in the complex environment of polymer injection. A simulation model was developed to provide a theoretical basis for realistic magnetic mould tool design. As there was no previous data available, it was hoped to elucidate some gUidelines by simulation experiments. In addition, the relationship between the rheological property of the polymer mixtures and the relevant moulding parameters such as tool temperature, melt temperature and speed of injection moulding was investigated using a comprehensive design of experiments methodology. It was found that the ferromagnetic nickel flakes remained magnetic enough to overcome the strong drag forces imposed on them by the polymeric fluid matrix and were able to be orientated. The focus of the experimental work was carried out using both the single component injection and co-injection moulding processes. A link was established between the melt temperature gradient and magnet effect. In the co-injection moulding experiments, it became clear, that the core melt had a longer residence time due to the thermal barrier provided by the skin melt and this facilitated a much more visible magnetic effect compared with samples produced using the injection moulding process.

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This work explored the preparation (both reproduced and novel), characterisation and modification of polymers of intrinsic microporosity (PIMs) using the first member of the series, PIM-1, as a representative example. The preparation was carried out using tetrafluoroterephthalonitrile (TFTPN) and tetrachloroterephthalonitrile (TCTPN) along with 5,5',6,6'-tetrahydroxy-3,3,3',3'-tetramethyl-1,1'-spirobisindane (TTSBI), and compared the products from each synthetic route to assess which would be most appropriate for scale up. Routes incorporating TCTPN were studied as a means of developing a more economically viable route to PIM-1. Purification techniques were also reviewed and it was discovered that repeat washes of PIM-1 using 1,4-dioxane removed the majority of low molar mass polymer in the shortest period of time. Techniques including triple detector GPC, NMR (solution and solid state), ATR-IR and reversible gas sorption were used to characterise the polymer structure and understand the free-volume element within the material. The effect of molar mass on membrane fabrication was also studied, with results showing that 60, 000 g mol-1 is the minimum molar mass (MW) required to form a free-standing flexible membrane. The way PIM-1 interacts with foreign systems was examined from two different perspectives. First, solubility studies were able to qualify how PIM-1 behaves in a range of common solvents and how this solubility changes with molar mass. Second, attempts to quantify the swelling of the polymer in lower alcohols and water were made. N2 sorption proved the most quantitative method and showed that the size of the alcohol has an effect on how much excess free volume is available after the polymer has been exposed to alcohol. ATR-IR showed that alcohols have different effects on different functional groups with red shifts observed for the ether linkage, a result most likely due to hydrogen bonding, and blue shifts observed for the nitrile group. Wide angle X-ray scattering (WAXS) showed three amorphous halos present in the PIM-1 structure, the positions of which did not change after exposure to alcohols and water. There was a change in intensity of these halos after the polymer had been exposed to various solvents. The PIM-1 polymer backbone was also successfully modified by replacing the nitrile group to give Thioamide PIM-1, Thiazole PIM-1, Amide PIM-1 and Amine PIM-1, in both powder and membrane forms. All of the modified polymers were successfully characterised using IR, NMR (solution state where soluble and solid state), WAXS and thermogravimetric analysis (TGA). CO2 and N2 sorption was carried out on all modified polymers and Amine PIM-1 showed the highest CO2 uptake (2.3 mmol g-1 at 0.7 bar, 6.3 mmol g-1 at 10 bar). This increase is most likely due to favourable interactions between the amine functionalities and the CO2 probe molecule. Organic molecules of intrinsic microprosity (OMIMs) are a novel class of discrete materials prepared using the similar chemistry used to prepare PIM-1, and were compared to the polymer from the perspective of gas sorption. All OMIMs examined showed similar N2 uptake to that measured for an aged sample of PIM-1, ranging from 595 – 624 m2 g-1 (excluding OMIM-2), and sample history was found to have a large effect on the sorption characteristics of the molecules from the perspective of both N2 and a CO2 probe molecules.

The problems associated with x-ray-transparent denture base are defined and conventional approaches to their solution are assessed. Consideration of elemental absorption parameters leads to the postulation that atoms such as zinc, and bromine, may be effective radiopacifiers over at least part of the clinical x-ray spectrum. These elements had hitherto been considered too light to be effective. Investigation of copolymers of methylmethacrylate and p-bromostyrene revealed no deleterious effects arising from the aromatically brominated monomer (aliphatic bromination caused UV destabilisation). For effective x-ray absorption a higher level of bromination would be necessary, but the expense of suitable compounds made further study unjustifiable. Incorporation of zinc atoms into the polymer was accomplished by copolymerisation of zinc acrylate with methylmethacrylate in solution. At high zinc levels this produced a powder copolymer convenient for addition to dental polymers in the dough moulding process. The resulting mouldings showed increasing brittleness at high loadings of copolymer. Fracture was shown to be through the powder particles rather than around them, indicating the source of weakness to be in the internal structure of the copolymer. The copolymer was expected to be cross-linked through divalent zinc ions and its insolubility and infusibility supported this. Cleavage of the ionic cross links with formic acid produced a zinc-free linear copolymer of high molecular weight. Addition of low concentrations of acrylic acid to the dough moulding monomer appeared to 'labilise' the cross links producing a more homogeneous moulding with adequate wet strength. Toxicologically the zinc-containing materials are satisfactory and though zinc is extracted at a measurable rate in an aqueous system, this is very small and should be acceptable over the life of a denture. In other respects the composite is quite satisfactory and though a marketable product is not claimed the system is considered worthy of further study.