The crystallization of synthetic polymers, in spite of its significant industrial importance,
continues to represent a primary challenge of polymer science and condensed matter physics.
Although kinetic theories on polymer crystallization enjoyed widespread acceptance, the
underlying dynamics of polymer crystallization is still unknown. Consequently, man's ability to
control polymer structure via crystallization is limited, particularly during its early stages and at
In this SGER proposal, the PIs propose to initiate research on the Terahertz (THz) dynamics
of polymer crystallization. THz dynamics originates from the collective modes of inter- and
intra-chain motions and is expected to be active during both stages of nucleation and growth. The
spectral fingerprints of the collective modes lie in the far-IR region, from a few wavenumbers to
some 300 cm-1. Energetically, they reside in the THz regime (1 THz = 1012 Hz).
It is the objective of this proposal to establish the role of THz dynamics in structural
formation during crystallization. Efforts will be focused on the stage of primary nucleation. The
specific aim is to establish concrete microscopy evidence that THz energy input is capable of
controlling nucleation behavior. Experimentally, brilliant monochromatic THz free-electron
laser (FEL), whose energy is characteristic of nucleation activation, will be used. In-situ
microscopy is employed to follow changes in nucleation behavior upon FEL illumination on
metastable polymer melts.
The goal is not only to establish the role of THz dynamics in polymer crystallization, but
also to introduce the concept of THz dynamics to study structural phase transformations in
polymer systems. The experimental strategy adopted in this proposal may also open the door for the
development of a groundbreaking nanotechnology for molecular engineering.
|Effective start/end date||5/1/05 → 10/31/07|
- National Science Foundation: $17,994.00