Co-crystallisation is one of the methods by which the physicochemical properties of materials can be altered without the change in the molecular structure of the active pharmaceutical ingredient. The advantage of co-crystallisation is that there is no requirement of an ionisable centre which opens the door the creation of multiple co-crystal forms. Our current understanding of the co-crystallisation process is based on the solid-state characterisation of the final product.

The use of electron diffraction opens the door to elucidate the transition between reactant and product. This project will investigate the two different mechanisms for co-crystal formation using single particles to investigate whether transient phases exist at the particle level that conventional XRPD techniques fail to observe.