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Polymorphic transformations in sulphathiazole

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dc.contributor.advisor Hodnett, Benjamin K. Munroe, Aine 2011-12-01T16:59:07Z 2011-12-01T16:59:07Z 2010
dc.description peer-reviewed en_US
dc.description.abstract This thesis investigated a number of solution mediated and solid state polymorphic transformations between the 5 known polymorphs Sulphathiazole. The polymorphs were isolated in their pure states and characterized. This work also proposes a new definitive naming system which eliminates any confusion that has been prevalent in the literature. A thorough study was undertaken to determine the stability order of the 5 polymorphs. To do this, a solubility study was completed in conjunction with a polymorphic stability study. The latter involved equilibration studies of binary mixtures of the pure polymorphs in different solvents at different temperatures. The main outcome from the stability study was that FII, FIII and FIV have very close solubility values and therefore thermodynamic stabilities. This was also evident in the binary mixture experiment as mixtures FII, FIII and FIV had a tendency not to transform below 30oC. The stability order was determined as FV≈FI<FIV≈FII≈FIII The mechanism whereby metastable polymorphs transform to more stable forms was investigated. The solution mediated polymorphic transformation of FV and FI Sulphathiazole was investigated in ethanol. The transformations were monitored with in-situ microscopy, X-Ray diffraction (XRD), Scanning Electron Microscopy (SEM) and Raman analysis. The FV transformation was observed to occur via surface nucleation of the stable form on the metastable FV. New crystals (FII&FIV) were observed to grow into the FV crystal. For the FI transformation a cooling crystallization typically used to prepare FII was monitored. FI needle like crystals were observed to nucleate initially and transformed via nucleation of the more stable polymorphs (FII & FIV) on the surface of the FI crystals. An interesting observation for the crystals harvested at the end of this transformation was a characteristic middle layer observed in the centre of the particle. Specific point analysis with Raman spectroscopy identified the middle layer as another polymorph, namely FIV. This FIV layer only becomes apparent in FII crystals when it begins to dissolve. The dissolving FIV layer has characteristic triangular and oblong shaped pits. Morphological analysis identified the FIV (10-1) and FII (100) planes as the planes in contact. The solid state transformation of the 5 polymorphs was also studied. When FII, FIII, FIV and FV Sulphathiazole are heated they all transform to FI. These transformations were fully characterized using in-situ high temperature XRD, Differential Scanning Calorimetry (DSC), Hyper DSC™ and optical microscopy. The stability order was observed to be FII<FIII<FIV<FV<FI at temperatures above 139oC. en_US
dc.description.sponsorship IRCSET
dc.description.sponsorship INTEL Ireland
dc.language.iso eng en_US
dc.publisher University of Limerick en_US
dc.subject polymorphic en_US
dc.subject sulphatheazole en_US
dc.title Polymorphic transformations in sulphathiazole en_US
dc.type Doctoral thesis en_US
dc.type.supercollection all_ul_research en_US
dc.type.supercollection ul_published_reviewed en_US
dc.type.supercollection ul_theses_dissertations en_US
dc.type.restriction none en

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