Hiking down the energy landscape: progress toward the Kauzmann temperature via vapor deposition

J Phys Chem B. 2008 Apr 24;112(16):4934-42. doi: 10.1021/jp7113384. Epub 2008 Apr 3.

Abstract

Physical vapor deposition was employed to prepare amorphous samples of indomethacin and 1,3,5-(tris)naphthylbenzene. By depositing onto substrates held somewhat below the glass transition temperature and varying the deposition rate from 15 to 0.2 nm/s, glasses with low enthalpies and exceptional kinetic stability were prepared. Glasses with fictive temperatures that are as much as 40 K lower than those prepared by cooling the liquid can be made by vapor deposition. As compared to an ordinary glass, the most stable vapor-deposited samples moved about 40% toward the bottom of the potential energy landscape for amorphous materials. These results support the hypothesis that enhanced surface mobility allows stable glass formation by vapor deposition. A comparison of the enthalpy content of vapor-deposited glasses with aged glasses was used to evaluate the difference between bulk and surface dynamics for indomethacin; the dynamics in the top few nanometers of the glass are about 7 orders of magnitude faster than those in the bulk at Tg - 20 K.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Kinetics
  • Molecular Structure
  • Temperature*
  • Thermodynamics
  • Volatilization
  • Water / chemistry

Substances

  • Water