title: Disappearing polymorphs revisited.
abstract: Nearly twenty years ago, Dunitz and Bernstein described a selection of intriguing cases of polymorphs that disappear. The inability to obtain a crystal form that has previously been prepared is indeed a frustrating and potentially serious problem for solid-state scientists. This Review discusses recent occurrences and examples of disappearing polymorphs (as well as the emergence of elusive crystal forms) to demonstrate the enduring relevance of this troublesome, but always captivating, phenomenon in solid-state research. A number of these instances have been central issues in patent litigations. This Review, therefore, also highlights the complex relationship between crystal chemistry and the law.
authors.affiliation: Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ (United Kingdom). d.bucar@ucl.ac.uk.
authors.forename: Dejan-Krešimir
authors.initials: DK
authors.lastname: Bučar
authors.affiliation: Department of Chemistry, University College London, 20 Gordon Street, London WC1H 0AJ (United Kingdom). r.lancaster@ucl.ac.uk.
authors.forename: Robert W
authors.initials: RW
authors.lastname: Lancaster
authors.affiliation: Faculty of Natural Sciences, New York University Abu Dhabi, P.O. Box 129188, Abu Dhabi (United Arab Emirates). joel.bernstein@nyu.edu, yoel@bgu.ac.il.|New York University Shanghai, Pudong New Area, Shanghai 200122 (China). joel.bernstein@nyu.edu, yoel@bgu.ac.il.|Department of Chemistry, Ben-Gurion University of the Negev, Beer Sheva, 84120 (Israel). joel.bernstein@nyu.edu, yoel@bgu.ac.il.
authors.forename: Joel
authors.initials: J
authors.lastname: Bernstein
keywords: crystallization; drug formulation; nucleation; polymorphism; solid-state chemistry