Molecular Motions and the Beta Relaxation

Monday, November 8, 2010: 2:10 PM
Seminar Theater (Hilton)
David S. Simmons, Marcus T. Cicerone and Jack F. Douglas, Polymers Division, Materials Science & Engineering Laboratory, National Institute of Standards and Technology, Gaithersburg, MD

Whereas extensive research has examined the nature of the alpha relaxation of supercooled liquids, relatively less attention has been given the the nature of the beta relaxation. The Debye-Waller factor has been applied in simulation and experiment as a useful measure of dynamics on this timescale; however, the exact relationship between the Debye-Waller factor and the various beta relaxations is also not well understood. Such an understanding is of great importance both scientifically and in a variety of applications, having been implicated in the effects of antiplasticizers on glass dynamics (and hence on the nature of the glass transition) and, for example, in the preservation of proteins by sugar glasses. Accordingly, we present the results of molecular dynamics studies investigating the exact nature of molecular motions corresponding the the beta relaxation. Based on a coarse grained model of pure and antiplasticized polymers, we relate the nature of molecular motions and dynamic heterogeneity to the Debye-Waller factor and to the beta relaxation as determined from the intermediate scattering function.

Funding for this research has been provided by NIH Grant # R01 EB006398-01

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See more of this Session: Supercooled Liquids and Glasses
See more of this Group/Topical: Engineering Sciences and Fundamentals