Crystal Adaptronics: Mechanically Reconfigurable Elastic and Superelastic Molecular Crystals

Abstract

Mechanically reconfigurable molecular crystals-ordered materials that can adapt to variable operating and environmental conditions by deformation, whereby they attain motility or perform work-are quickly shaping a new research direction in materials science, crystal adaptronics. Properties such as elasticity, superelasticity, and ferroelasticity, which are normally related to inorganic materials, and phenomena such as shape-memory and self-healing effects, which are well-established for soft materials, are increasingly being reported for molecular crystals, yet their mechanism, quantification, and relation to the crystal structure of organic crystals are not immediately apparent. This Minireview provides a condensed topical overview of elastic, superelastic, and ferroelastic molecular crystals, new classes of materials that bridge the gap between soft matter and inorganic materials. The occurrence and detection of these unconventional properties, and the underlying structural features of the related molecular materials are discussed and highlighted with selected prominent recent examples.

Is a Bent Crystal Still a Single Crystal?

“…[13] Bent crystals can also be obtained from metal coordination compounds;b ent single crystals of the Zn(II) complex of 3'-fluoro-4-styrylpyridine can grow from dimethylformamide/tetrahydrofuran or acetonitrile solutions. [15] Thep hotoinduced twisting, bending, and curling of single crystals have been extensively studied. [15] Thep hotoinduced twisting, bending, and curling of single crystals have been extensively studied.…”

“…Thed ifference between elastic and plastic crystals has already been addressed, [15] and only as ummary relevant to the retention of crystallinity will be presented here.There are no general rules or trends in packing motifs available for predicting elastic bending,and most examples are discovered empirically.The elastic nature of acocrystal of caffeine and 4chloro-3-nitrobenzoic acid was assigned to the weak interlocking interactions between 2D sheets of molecules and dispersive interactions in three mutually orthogonal directions. [23] In another case,t he elastic behavior of 4-bromo-3chlorophenol was rationalized by the hydrogen bonding and halogen bonding in its crystal packing.…”

Ist ein gebogener Kristall immer noch ein Einkristall?

“…[10] Lehmann, einer der Pioniere bei der Entwicklung des beheizbaren Mikroskops,hat gebogene Kristalle beobachtet, die aus festen Lçsungen von CrCl 2 und HgCl 2 ,c hiralem 1,2-Diphenylethan-1,2-diyldiacetat, (Z)-Zimtsäure und 2,5-Dihydroxy-3,6-dipropionylcyclohexa-2,5-dien-1,4-dion gewachsen sind. [15] Photoinduziertes Drehen, Biegen und Wçlben von Einkristallen wurde ausführlich untersucht. [12] Makrozyklisch konjugierte organische Dimere von 9,10-Bis(2-thienylethinyl)anthracen kçnnen auch in Form von gebogenen Einkristalle infolge von Phasenverunreinigungen auftreten.…”

“…Wenn Kristalle als elastisch [15] oder plastisch [21] klassifiziert werden, beschreiben diese Begriffe das primäre makroskopische Verhalten, das beobachtet werden kann. Wenn Kristalle als elastisch [15] oder plastisch [21] klassifiziert werden, beschreiben diese Begriffe das primäre makroskopische Verhalten, das beobachtet werden kann.…”

“…[15] Ausschließlich eine Zusammenfassung,d ie fürd ie Erhaltung von Kristallinität relevant ist, wird in der Folge betrachtet. [15] Ausschließlich eine Zusammenfassung,d ie fürd ie Erhaltung von Kristallinität relevant ist, wird in der Folge betrachtet.…”