Surface Nanocrystallization of an Ionic Liquid

TitleSurface Nanocrystallization of an Ionic Liquid
Publication TypeJournal Article
Year of Publication2012
AuthorsJeon Y, Vaknin D, Bu W, Sung J, Ouchi Y, Sung W, Kim D
Journal TitlePhysical Review Letters
Date Published01
Type of ArticleArticle
ISBN Number0031-9007
Accession NumberWOS:000299830500008
Keywords1-butyl-3-methylimidazolium hexafluorophosphate, cation, CRYSTALLIZATION, dynamics, normal-alkanes, tension measurements

Surface crystallization at the vapor-liquid interface of the ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate) is observed in synchrotron x-ray diffraction studies. Sharp Bragg reflections emerge in grazing-angle x-ray diffraction patterns 37 degrees C above the bulk melting temperature, indicating the presence of a long-range ordered phase at the surface in coexistence with the bulk parent liquid. The unique structure of the vapor-liquid interface where butyl chains attached to the cations are expelled to the vapor side facilitates interionic electrostatic interactions that lead to the crystallization. Our results demonstrate the complexity of ionic-liquid structure with their tendency to spontaneously phase separate into nanodomains with finite correlation lengths in coexistence with the liquid phase. By virtue of interfacial boundary conditions, these nanodomains grow laterally to form quasi-two-dimensional crystals.

URL<Go to ISI>://WOS:000299830500008
Alternate JournalPhys. Rev. Lett.