GHz-THz Dynamics as the Key for Structural RelaxationAlexei P. Sokolov, University of Akron, DMR-0315388

Understanding the microscopic mechanism of the glass transition remains one of the main challenges in Materials Science. We discovered correlations between fast (picosecond) dynamics and behavior of structural relaxation on time scales seconds-hours.

We relate the steepness of the temperature dependence of viscosity (or structural relaxation time , m, to the ratio of instantaneous bulk and shear moduli, K/G. The stronger the system can resist shear deformation the weaker will be temperature variation of (or . This discovery leads to a better understanding of dynamics of complex systems, including liquids, polymers and proteins.

Nature 431, 961(2004); Macromolecules 37, 9273 (2004); Phys.Rev.E 71, 061501(2005).

Fragility index m characterizes the steepness of the temperature rise of log at Tg.

Correlation of m with K/G for various glass-forming systems.

0.4 0.6 0.8 1.0

-2

0

2

4

6

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12 m=d(log)/d(Tg/T)

Silica

glycerol

salol

log

[p

ois

e]

Tg/T

1 2 320

40

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m

K/G

GHz-THz Dynamics as the Key for Structural RelaxationAlexei P. Sokolov, University of Akron, DMR-0315388

Broader Impact:Applying the same ideas to analysis of protein dynamics in various solvents we have developed a formulation that can preserve proteins for more than 10 years. This discovery might be important for long term preservations of drugs and vaccines.J.Chem.Phys. 121, 1978 (2004) and Bioprocess

International 1, 2 (2003).

Education:Under this grant, two students, G. Caliskan (currently at Johns Hopkins U.) and Y. Ding (currently at NIST) have completed their PhD. Three more graduate students, B. Begen, J.H. Roh and A. Macy, and one REU undergraduate student, G. Burg, have been actively involved in the research. The picture on the right shows PI’s group.

Outreach:Each year, graduate students are involved in Science Fair and in Upward Bound Program for high school students sponsored by the University. Dr. Sokolov worked with Middle School students, in particular, helping them with preparation for Science Olympiad in 2004-2005.