RUI: Dynamic Light Scattering Test of Bond Model Predictions for the Dynamics of Network-forming Liquids near the Glass Transition

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Technical AbstractThe amorphous solid phase is, in principle, endemic to all liquids despite a propensity for some liquids to crystallize when cooled. However, the manner in which a liquid thickens in advance of solidification is vastly different among different materials. Past research has demonstrated a clear link between the dynamics of a supercooled, glass-forming liquid and its chemical structure and thermodynamic properties referred to as "fragility". In this project, dynamic light scattering, Raman spectroscopy and differential scanning calorimetry are being applied to probe how liquid dynamics are directly affected by simple structural changes created in network-forming systems. The results will form a precise test of a proposed thermodynamic model (Bond Model) presently available. Work will be carried out both by graduate (MS) and undergraduate students providing hands-on research experience to augment their science education. Non-technical AbstractTechnology thrives on exploiting the novel properties of materials. Among these, glassy materials possess unique mechanical, optical and electrical properties of importance for many state-of-the-art devices. However, for their potential to be realized, glassy materials must be solidified from the liquid state without crystallization occurring. This then requires an understanding of the liquid-to-glass transition and in particular an understanding of how chemical structure of the liquid affects the thickening process itself. In this project, visible light scattered by a glass-forming liquid is used to monitor this thickening process on a microscopic level. A series of glass-forming liquids are to be investigated in which the chemical structure can be systematically altered by either increasing or decreasing the average number of chemical bonds present in the liquid. With each modification of the structure, the corresponding changes in dynamical properties of the liquid will be assessed to test predictions of a simple model based upon the average number of bonds present. Graduate (MS) and undergraduate students will conduct this research as means of training the next generation of professional scientists.