Using physical vapor deposition to prepare unusual liquids and unusual glasses Using physical vapor deposition to prepare unusual liquids and unusual glasses Overview: Experiments are proposed to investigate vapor-deposited glasses of simple organic molecules. The first objective of this work is to study unusual liquids produced by heating these glasses, where unusual is defined by persistent physical properties that differ from those of the liquid formed by melting the crystal. A second objective is to test whether intramolecular conformational changes in vapor-deposited glasses are suppressed relative to liquid-cooled glasses. In pursuing these two objectives, the molecules to be studied include decahydroisoquinoline, triphenyl phosphite, and a series of octanols. In situ experimental methods include nanocalorimetry, dielectric relaxation, ellipsometry, and x-ray scattering. Intellectual merit: There is strong recent interest in polyamorphism, i.e., the existence of at least two amorphous states with the same composition, with a first-order transition between the states. While polyamorphism is the analogue of polymorphism in crystals, polyamorphism cannot yet be predicted and is very rare, with only a few systems showing strong evidence for this designation. Polyamorphism may hold the key for understanding the unusual properties of water and it provides a unique opportunity to gain insight about structure/property relationships in liquids and glasses. Preliminary experiments suggest that vapor deposition is an especially effective route for producing unusual liquids. Even if the unusual liquids produced by vapor-deposition are not polyamorphic, their long lifetimes pose fundamental questions about the mechanism of their persistence. Regarding our second objective, recent work has established that vapor-deposited glasses can exhibit extraordinary kinetic stability and also have other properties expected only for glasses prepared by slow cooling from the liquid over the timescale of thousands of years. The nature of these stable glasses holds the key to understanding the ultimate properties of amorphous solids and the ultimate fate of liquids upon slow cooling. The proposed experiments will explore suppression of intramolecular conformational changes in vapor-deposited glasses as these processes are uniquely amenable to theoretical description among glassy relaxation processes. We expect relaxation times to slow by a factor of ~1000, which would be the largest impact on glassy relaxations reported to date as a result of efficient glass packing. Broader impacts: The proposed work will have a broad impact in two respects. The molecules to be studied here are model systems for technologically important amorphous materials like polymers and the low molecular weight glasses utilized in organic electronics. The proposed experiments will provide increased fundamental understanding and it is expected that this will enable the production of improved glasses that are useful in applications. For example, our experiments might lead to strategies for minimizing the strength of relaxation in the glassy state that could be adapted for use with devices used for quantum computing; superconducting qubits are embedded in glass and glass relaxation decreases the coherence time. In addition, the funding of this proposal will also advance the training of graduate, undergraduate, and high school students, through the integration of chemistry research and education activities. The PI and his students will help prepare high school students from under-represented groups for college by working with the University of Wisconsin-Madisons PEOPLE program. Those supported by this grant will refine a materials chemistry curriculum for summer educational outreach and each summer present a twenty-hour course for 15 high school juniors. The PEOPLE program has a proven track record of preparing students to succeed in college.
|Effective start/end date||9/1/19 → 8/31/22|
- National Science Foundation (NSF): $172,000.00
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