Ultrafast Spectroscopy Provides Clear Understanding of How Glass Behaves

A research group led by University of Michigan (UM) (Ann Arbor, Michigan) chemist Kevin J. Kubarych has applied ultrafast spectroscopy to observe the fastest molecular motions of a liquid hovering just above its glass transition temperature.

“Progress in demystifying the glass transition can have a wide impact in many other fields, including predicting optical and mechanical properties of polymers and understanding crowded cellular environments of living organisms,” Kubarych said in a statement.

Working with UM chemistry graduate students John King and Matthew Ross, Kubarych found that even on the time scale of picoseconds there are signatures of “dynamic arrest” in which the molecules become locked into their positions and long-range motion grinds to a near halt, though structurally, the glass is indistinguishable from a liquid.

Typically, these effects are observed on much slower time scales of seconds, minutes, or even longer. A paper summarizing the research was published online on April 9 in Physical Review Letters. King is the first author of the paper. Ross is also a doctoral student in the UM Applied Physics Program.

The work was supported by the National Science Foundation (Arlington, Virginia) and the Camille and Henry Dreyfus Foundation (New York, New York).