Observation of Plastic Molecular Dynamics in Glass Sabyasachi Sen, University of CA Davis, DMR 06039

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Observation of Plastic Molecular Dynamics in
GlassSabyasachi Sen, University of CA Davis,
DMR 0603933

• Prof. Sabyasachi Sen and graduate student Erica
  Gjersing have recently discovered the existence
  of plastic dynamics in a molecular As-P-sulfide
  glass using variable temperature 31P Nuclear
  Magnetic Resonance spectroscopy.
• Typically rotational and translation motion of
  molecules are frozen in below glass transition
  temperature. Sen and Gjersing have observed
  isotropic tumbling motion (see movie on next
  slide) of the constituent molecules in their
  glass that is detectable even at 70 K below the
  glass transition temperature !
• Their results indicate that the translationally
  frozen molecules in the glass are performing
  rotational dynamics, much like whats observed in
  plastic crystals such as buckyball (C60) except
  in the latter the molecular positions show
  long-range ordering on a crystal lattice.

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Intermediate-range structure and dynamics in
complex Ge-As
Sabyasachi Sen, University of CA-Davis, DMR
0603933
Tumbling dynamics of PAs3S3 molecules S
(yellow) As (3 bottom purple) P (1 top purple)
The presence of this novel dynamical disorder
provides the much sought after evidence in favor
of a dynamical rather than thermodynamic origin
of glass transition. This research may have
strong impact in identifying novel plastic glassy
materials with liquid-like conductivity and
diffusivity while solid-like mechanical strength
and physical integrity for applications in the
areas of solid-state fuel cell or solar cell,
remote sensing etc.