1. Universal Patterns in the Fragility of Network-forming Glasses David L. Sidebottom, Creighton University, DMR 0906640 One of the major quests for glass science has been to better understand how the complexity of the disordered glass structure influences the viscoelastic behavior of a glass-forming melt. This knowledge is not merely of academic interest, as the manufacture of numerous commercial products relies heavily on precise evaluation and control of the viscoelastic properties of the melt near the glass transformation range. Theoretical efforts to connect glassforming dynamics to underlying glass structure have largely focused on network-forming liquids: chalcogenides and oxides. The structure of these glasses consist of atoms that are covalently bonded into a continuous network of interconnected rigid struts. Depending on the chemical composition, these network structures can be tailored to produce a specific fragility (a primary measure of glassforming dynamics) by either adding or reducing the density of covalent bonds. In previous work, we demonstrated that the fragility of both chalcogenide networks and phosphate network-forming liquids share a common dependence on the average density of bridging bonds wherein fragility increased with decreasing density of bonds. However, a companion study of borate liquids seemed to defy this previous trend: the fragility increased with increasing bond density (see colored solid symbols in figure to right). Early this year, a resolution to the paradox may have been found in the unique intermediate range order (IRO) that appears in the borate network structure. By incorporating this IRO into how the bond density is defined produces precisely the needed shift of the borate fragility back onto the trend line reported previously (see colored open symbols in figure). Together with the chalcogenide and phosphate systems, a universal dependence of fragility on the average bond density is seen to emerge.

2. Universal Patterns in the Fragility of Network-forming Glasses David L. Sidebottom, Creighton University, DMR 0906640 Collaborations with SNL and ISU This year has also seen the initiation of collaboration efforts with two other institutions. Undergraduate student, Jamison Duckworth, is spending this summer at Sandia Labs in Albuquerque working with engineers there to produce aerogel samples for the encapsulation of ionic liquids. These confined liquids will be studied by ensemble-averaged light scattering here at Creighton later this year. Meanwhile, students working with Dr. Steve Martin at Iowa State University are assisting in the preparation of borophosphate glasses that will be investigated here at Creighton using dynamic light scattering. This work will form yet another critical test of our working hypothesis of the emerging relation between fragility and bond density. Mentoring the Next Generation The project has sponsored three students this past year (two graduate and one undergraduate) and seen the completion of one M.S. thesis project (Mr. Schnell completed light scattering studies of potassium borate glasses that resulted in a pending journal publication). Students receive valuable on-the-job training in laboratory and data analysis skills while completing their academic coursework. Applications to Protein Folding Although the role of bond density is here being considered for covalently-bonded liquids, there is evidence in the literature for the influence of bond density also in regards to the dynamics of protein folding [e.g., see A. J. Rader, etal., Proc. Natl. Acad. Sci. U.S.A. 99, 3540 (2002)]