Surface Mediated Structures: Stabilization of Metastable Polymorphs on the Example of Paracetamol

• Published in: Crystal growth & design 2014-08, Vol.14 (8), p.3680-3684
• Main Authors: Ehmann, Heike M. A., Werzer, Oliver
• Format: Article
• Language: English
• Subjects: Communication; Condensed matter: structure, mechanical and thermal properties; Crystal structure; Crystalline state (including molecular motions in solids); Crystallographic aspects of phase transformations; pressure effects; Exact sciences and technology; Heat treatment; Morphology; Physics; Silicon dioxide; Solid surfaces; Spin coating; Stabilization; Structure of solids and liquids; crystallography; Structure of specific crystalline solids
• ISSN: 1528-7483; 1528-7505
• DOI: 10.1021/cg500573e

The preparation of typically thermodynamically unstable polymorphic structures is a challenge. However, solid surfaces are well established aids for the formation and stabilization of polymorphic structures within, for instance, organic electronics. In this study, we report the stabilization of a pharmaceutically relevant substance via a solid surface at ambient conditions. Form III of paracetamol, which is typically unstable in the bulk at standard conditions, can be stabilized with a model silica surface by a standard spin coating procedure followed by rapid heat treatment. Such a preparation technique allows the use of atomic force microscopy and grazing incidence X-ray diffraction measurements revealing detailed information on the morphology and structure of the polymorph. Furthermore, the results exhibit that this polymorph is stable over a long period of time revealing surface mediated stabilization. These findings demonstrate a novel approach to provide thermodynamic stability when applied to similar molecules with specific applications.