Polymorphic transformations in sulphathiazole

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