It has recently been discovered that it is possible to prepare supercooled liquids of trisnaphthylbenzene (TNB) and indomethacin (IMC) in which diffusion is unusually fast. That is, for a given temperature and pressure, these single component liquids exhibit diffusion coefficients which are 2-5 times larger than the known supercooled liquid values. The first objective of this project is to characterize translational and rotational mobility in these unusually mobile liquids. Secondary ion mass spectrometry (SIMS) will be used to measure translational diffusion. Optical photobleaching and dielectric relaxation experiments will be performed to measure molecular reorientation. All three methods will also be utilized in attempts to observe the transformation of the unusually mobile liquid into the ordinary supercooled liquid. The second objective of this project is to establish the origin of the unusually mobile liquids. Two possible origins are polyamorphism and a non-equilibrium distribution of regions of varying mobility. Establishing either of these would be an important advance in the understanding of supercooled liquids and glasses. Polyamorphism, the existence of more than one local packing arrangement in an amorphous system, provides a mechanism for resolving the Kauzmann entropy crisis. Alternately, if these liquids have a non-equilibrium distribution of mobilities, these experiments could measure the lifetimes of these regions. Both of these possible explanations have been matters of considerable recent interest and controversy. Insights from the proposed experiments on TNB and IMC are likely to be widely applicable to organic glassformers. The proposed work will have a broad impact in two respects. Although TNB and IMC are model glassformers, what is learned here will likely have an impact in organic electronics where the active materials are often glasses of a similar nature. Furthermore, experiments on organic liquids provide insight into the behavior of commercially important glass-forming materials such as polymers, pharmaceuticals, inorganic materials, and metallic glasses. Given that glassy dynamics are found in many systems that do not fit the traditional definition of a glass (proteins, foams, granular materials, ionic conductors), an enhanced fundamental understanding of supercooled liquids will likely benefit a variety of fields. In addition, the funding of this proposal will advance the training of graduate, undergraduate, and high school students, through the integration of chemistry research and education activities. The PI and his graduate and undergraduate students propose to work with the University of Wisconsin-Madisons PEOPLE program to prepare high school students from under-represented groups for college. Those supported by this grant will refine a physical science curriculum for summer educational outreach and each summer staff a thirty-hour course for 15 high school juniors. The PEOPLE program has a proven track record of preparing students to succeed in college. Currently, the University of Wisconsin-Madison has more than 200 undergraduates who participated in the PEOPLE program as high school students.
|Effective start/end date||9/1/10 → 8/31/12|
- National Science Foundation (NSF): $68,859.00