NIRT: Dynamic Heterogeneity and the Behavior of Glass-Forming Materials at the Nanoscale

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This NIRT award is being funded by the Polymers Program of the Division of Materials Research and the Interfacial, Transport and Thermodynamics Program of the Division of Chemical and Transport Systems. The work is aimed at understanding how spatially dynamic heterogeneity in polymeric and small molecule glass formers is influenced by confinement at the nanoscale, and how this in turn, influences the relaxation of molecular and thermodynamic properties. Dynamic heterogeneity will be systematically probed using fluorescent probe studies and solvation dynamics in nanoconfined materials as a function of confinement size. In addition, volume and enthalpy relaxation will be studied as a function of confinement with the specific aim of examining whether or not dynamic heterogeneity influences the relaxation of these properties and whether or not it is the cause of the divergence of times required to reach equilibrium. Nanoconfinement will include "soft" confinement of low molecular weight glass-formers in crosslinked rubber, "rigid" confinement of both low molecular weight glass-formers and polystyrene in nanoporous matrices, and confinement of polystyrene to ultrathin films. In addition, the macroscopic and molecular relaxation behavior of freeze-dried polystyrene glasses will be examined. The work will include many novel measurements that have not been performed previously and is anticipated to lead to an understanding of how dynamic heterogeneity is influenced by confinement, and more generally, the importance of dynamic heterogeneity on the relaxation of macroscopic properties near Tg.%%%The work will provide a better understanding of the behavior of materials near their glass temperatures at the meso- or nanometer scale and is important for the ultimate usefulness and function of materials in, for example, nanocomposites and nanoelectronics applications. The program will also provide excellent training for the graduate students and post-doctoral researchers and high school students. Efforts will be made to include undergraduate researchers and high school students. Efforts will be made to include women and underrepresented minorities through special recruiting efforts at women's and minority colleges in the Texas and southwest region. In addition, an effort will be made to include undergraduate students who participate in the TTU McNair Scholars Program for first generation college students (often minorities). The work will be broadly disseminated within the scientific community by presentation at national forums and publication in both proceedings conferences and archival journals. The results of the project will also be incorporated to the extent feasible in both undergraduate and graduate courses taught by the respective PIs.***