cg050347j_si_001.pdf (488.81 kB)
Memory and Perfection in Ferroelastic Inclusion Compounds†
journal contribution
posted on 2005-11-02, 00:00 authored by Mark D. Hollingsworth, Matthew L. Peterson, Jeremy R. Rush, Michael E. Brown, Mark J. Abel, Alexis A. Black, Michael Dudley, Balaji Raghothamachar, Ulrike Werner-Zwanziger, Ezra J. Still, John A. VaneckoIn a series of ferroelastic urea inclusion compounds (UICs), in which domain reorientation occurs
upon application of an external anisotropic force, introduction of a relaxive impurity that disrupts a specific hydrogen-bonding network transforms a plastic (irreversible) domain-switching process into one that exhibits a striking memory
effect and “rubber-like behavior”, a form of pseudoelasticity. As expected for a highly cooperative process, the
ferroelastic response to the impurity concentration exhibits a critical threshold. Through synchrotron white-beam
X-ray topography (SWBXT) of crystals under stress, videomicroscopy of spontaneous repair during crystal growth,
acoustomechanical relaxation of daughter domains, kinetic measurements of spontaneous domain reversion, and
solid-state 2H NMR of labeled guests, this work shows how relaxive impurities lower the barrier to domain switching
and how differences in perfection between mother and daughter domains provide the driving force for the memory
effects. Although the interfacial effects implicated here are different from the volume effects that operate in certain
shape memory materials, the twinning and defect phenomena responsible for the rubber-like behavior and memory
effects should be generally applicable to domain switching in ferroelastic and ferroelectric crystals and to other
solid-state processes.