International Collaboration in Chemistry: Origins of the anomalous thermodynamics and dynamics of metastable liquid water

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In this project, supported by the Experimental Physical Chemistry Program, Professor Abraham Stroock of Cornell University and his research group will address two outstanding questions related to supercooled water and water at negative pressures: 1) What are the mechanisms of cavitation of water at negative pressures, and 2) What are the origins of observed thermodynamic and dynamic anomalies in supercooled water? Supercooled water exhibits a number of thermodynamic anomalies that have been extensively studied for the last decades: the temperature dependence of many parameters (e.g., compressibility, expansion coefficient, and transport coefficients) suggests a power-law divergence, at a temperature around -45°C at atmospheric pressure. A number of competing theories of this phenomenon have emerged, but the lack of experimental data has left the question unresolved. This project will entail the first measurements in the supercooled regime of viscosity away from ambient pressure (both positive and negative) and of diffusivity under tension. The tools utilized by the Stroock laboratory include Metastable Vapor Liquid Equilibrium (MVLE), Raman scattering, nuclear magnetic resonance (NMR), and microfluidic device technology. Professor Stroock's work will be complemented by Brillouin scattering, acoustically generated tension and optics-based density studies performed in the laboratory of Professor Frederic Caupin of the Laboratoire de Physique de l'Ecole Normale Superieure. The NSF proposal leading to this award was submitted in response to solicitation NSF 08-602: International Collaboration in Chemistry between US Investigators and their Counterparts Abroad (ICC).Water is among the most important and most studied substances on earth, yet, the origins of its anomalous thermodynamic, dynamic, and structural properties have eluded complete understanding. Scientific studies and technical developments related to the metastable states of liquid water could have broad impact on research and technology in a number of fields, from plant physiology to molecular modeling to manufacturing. The research conducted in this project may provide not only a fundamental foundation for new applications, but also the experimental tools that can facilitate the broader scientific and technical impacts of that knowledge. The richness of technical components (microfabrication, spectroscopy, environmental controls) and fundamental components (thermodynamics, dynamics, molecular structure) inherent in this project will provide an unusually broad training for students and post-docs involved in this research. Furthermore, the exchange of junior members of the US and French teams will allow these students to engage in the full breadth of the research and gain valuable exposure to a foreign scientific and national culture. Both PIs have a strong track record of involving undergraduates in research projects in their labs, and will actively recruit students to participate in this program. Stroock and his junior team member will also engage in K-12 educational activities such as giving lectures (e.g., How trees drink: the Nature of metastable liquids) at local science museums, home-school events, and teaching programs run by the Cornell NSF-MRSEC.