title: Formation of new polymorphs without any nucleation step. Desolvation of the rimonabant monohydrate: directional crystallisation concomitant to smooth dehydration.
abstract: Rimonabant monohydrate can be dehydrated at 100 °C or above with complete loss of structural information; in this case the amorphous material can lead to nucleation and crystal growth. The water molecules can also be removed by a smooth process below Tg (78 °C) of the anhydrous phase. In that latter process there is a structural filiation between the mother phase and the daughter phase. The solvent molecules escape from the mother structure by using a network of specific channels; the new non-solvated material undergoes a relaxation process similar to a directional crystallization. By this soft mode of desolvation inside a material which has a very limited mobility, the nucleation of a non-solvated material can be avoided. The structural information contained in the mother phase is not used as a template for crystal growth but it is more a progressive rearrangement of the new desolvated material towards the nearest well in energy. Thus, a metastable new polymorph of a non-solvated component can be obtained by: (i) the crystallization of the component as a solvate and (ii) a smooth desolvation at T < Tg. Other parameters liable to interfere with that transmission of structural information are discussed.
authors: Normandie Université, EA 3233 SMS, Crystal Genesis Unit, University of Rouen, F-76821 Mont Saint Aignan, France. gerard.coquerel@univ-rouen.fr.
authors: Baptiste
authors: B
authors: Fours
authors: Yohann
authors: Y
authors: Cartigny
authors: Samuel
authors: S
authors: Petit
authors: Gérard
authors: G
authors: Coquerel