Introduction
There is enormous potential for utilisation of the solvent to control both the rate processes and product physical form characteristics in the isolation of active materials by crystallisation. This is because, while solvent crystallisation is widely used and solvent choice widely recognised to influence nucleation rates, crystal morphology and aggregation, little is known about the nature of molecular assembly processes in supersaturated solutions nor about the way in which solvents interact with and determine the structure of crystal faces.
This project aims to explore work on solvent effects in nucleation and growth processes, with the initial work exploring the nature between solution chemistry and crystallisation in a polymorphic system, tetrolic acid. This system has been chosen since, it is a simple monocarboxylic acid, CH3C=COOH, for which two crystal structures are known [1] and the difference between dimers and chains of carboxylic acids can be readily detected by a combination of Raman and infrared spectroscopy [2]. In the first year this detection strategy to differentiate between the two crystal packings of carboxylic acids was verified by a range of carboxylic acid and extended to saturated solutions, both yielding promising results. In second year, more emphasis was placed on tetrolic acid with attempts to crystallise and characterise both polymorphic forms, as well as solution spectroscopy utilising the optical probe, transmission cell and HC-32 cell accessories. In addition work has started on the use of atomic force microscopy to image the growing surfaces of molecular crystals with adipic acid chosen as the the first candidate for study.