Joint U.S./German Investigation of Extraordinarily Stable Glasses by Nanocalorimetry

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Recent work has shown that organic glasses with remarkably high density and high stability can be prepared by physical vapor deposition. These glasses can be regarded as "super-aged" as they have properties that would require thousands of years or more to produce by conventional methods. These materials uniquely allow the exploration of the lower reaches of the potential energy landscape that governs the dynamics and thermodynamics of amorphous Systems. The most stable glasses and those most likely to be used in applications will be submicron films. The emerging technology of nanocalorimetry is the only method with sufficient sensitivity to measure the heat capacity and determine the position of such stable glasses on the energy landscape. We propose to develop a combined scanning/AC nanocalorimetry method for in situ characterization of vapor-deposited glasses and other Condensed phase Systems. We will vapor-deposit the best-characterized organic glassformers (o-terphenyl, glycerol, and triphenylphosphite). These activities will lead to an understanding of how fragility, hydrogen bonding, and molecular structure affect the ability to form stable glasses and more generally to an understanding of the relationship between deposition temperature and amorphous packing. This project can only achieve its objectives by combining the stable glass expertise of the Madison, WI, group with the nanocalorimetry expertise of the Rostock group. The exchange of students and the use of cyberinfrastructure will be critical to the success of this German/U.S. collaboration.