CAREER: Particle-by-Particle Studies of Heterogeneous Dynamics in Molecular and Colloidal Glasses

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In this award, funded by the Experimental Physical Chemistry Program of the Division of Chemistry, Professor Laura Kaufman of Columbia University, her postdoctoral fellows and graduate and undergraduate students are addressing fundamental aspects of heterogeneous behavior in systems in which the dynamics are strongly affected by either steric or electrostatic crowding. Small molecule glass formers, simulated model glassy liquids, and low volume fraction colloidal glasses and gels are being investigated. The heterogeneous dynamics, local properties, and cooperative rearrangements of these systems are being interrogated via three techniques that avoid ensemble averaging. These techniques are single molecule (SM) fluorescence measurements, molecular dynamics (MD) simulations, and coherent anti-Stokes Raman scattering (CARS) microscopy. The SM microscopy and MD simulations will clarify (1) if and how probe properties affect measured probe dynamics, (2) how these same properties potentially affect host dynamics and heterogeneities, and (3) how probe bearing experiments can report a length scale of heterogeneity in glassy systems. CARS imaging will be performed on low volume fraction colloidal glasses and gels. Here, the Kaufman group is investigating whether the dynamics of formation and relaxation of these systems exhibit the same sort of heterogeneous behavior and cooperative rearrangements that have been seen in high particle density glassy environments. Because all condensed phase systems display dynamics affected by crowding in some way, studying these effects in the systems most obviously impacted increases fundamental understanding of condensed phase chemistry. Understanding glassy dynamics, and the prevention of crystallization, is also important in diverse applications from petroleum transportation to cryopreservation of cells. Aside from the broader scientific impacts of this work, Professor Kaufman is presenting lectures on complex fluids to local elementary school students. Professor Kaufman continues to identify and mentor especially promising science students at Columbia University.