title: Stable glasses of indomethacin and α,α,β-tris-naphthylbenzene transform into ordinary supercooled liquids.
abstract: Secondary ion mass spectrometry has been used to characterize translational motion in vapor-deposited glasses of indomethacin (IMC) and α,α,β-tris-naphthylbenzene (TNB). Vapor deposition onto substrates at ∼0.99 T(g) produced ordinary glasses that evolve according to fickian diffusion during annealing. The resulting self-diffusion coefficients for the supercooled liquids are in good agreement with previous reports. Deposition onto substrates at 0.85 T(g) produced highly stable glasses that transform with a propagating front mechanism. In contrast to previous reports, the liquid produced by this transformation has the same translational mobility as the ordinary supercooled liquid; we associate this result with lower impurity levels in the current samples. The front velocities for both TNB and IMC stable glasses are very similar functions of the translational self-diffusion coefficients of the supercooled liquids, consistent with view that the growth front velocity is controlled by mobility in the liquid adjacent to the stable glass.
authors.affiliation: Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA.
authors.forename: A
authors.initials: A
authors.lastname: Sepúlveda
authors.forename: Stephen F
authors.initials: SF
authors.lastname: Swallen
authors.forename: Laura A
authors.initials: LA
authors.lastname: Kopff
authors.forename: Robert J
authors.initials: RJ
authors.lastname: McMahon
authors.forename: M D
authors.initials: MD
authors.lastname: Ediger