The dehydration behaviour of several crystalline materials has been investigated, by means of lab-based studies, using X-ray diffraction and Differential Scanning . Calorimetry, and molecular modelling techniques. A review of several groups of materials, namely sugars, amino acids, and pharmaceutically important materials was undertaken. This showed how difficult it is to make predictions about dehydration behaviour based solely on examination of the structure of hydrated forms. Few patterns could be seen, other than the size of the molecules is important in determining whether or not a material will form crystalline structures at all levels of hydration. Amino acids are largely affected by the nature of the side chains. The nature of the structure of some of the pharmaceuticals meant that the pattern of dehydration, and the means by which the water molecules left the structure was easy to predict. The dehydration characteristics of a-lactose monohydrate, citric acid monohydrate, and calcium sulphate dihydrate have been studied using experimental methods and molecular simulation methods. The kinetics of dehydration of a-lactose monohydrate and citrjc acid monohydrate have also been studied, using a cell 'designed for this study which enabled the progress of the phase change to be followed using X-ray diffraction. The morphologies of these materials were also investigated, and the surfaces of the hydrated forms studied in order'to establish whether or not there may be a preferential route by which water leaves the structure. For a-lactose monohydrate, a further study was undertaken to try to establish the cause of the tomahawk morphology seen when it is grown from solution. Whilst the results presented are not clear-cut, they do indicate that both polar effects and the presence of lactose in the crystailising solution both have an influence on the shape of the crystal.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:486701 |
| Date | January 2007 |
| Creators | Williams, Helen |
| Publisher | Heriot-Watt University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/10399/2084 |
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