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07/14/2011
Recent research from the research group of Professor
Research by Assistant Professor Aaron Massari and his group is featured on the cover of the July 14 edition of The Journal of Physical Chemistry B. The article, "Static and Dynamic Structural Memory in Polyaniline Thin Films," highlights the recent work by graduate students Audrey Eigner and Brynna Jones, and undergraduate Bryce Koprucki.
Polyaniline is a popular organic material that can be chemically altered to conduct electricity through a process called doping. The conductivity of thin films of this polymer can be readily switched between conductive and non-conductive states by treatment with weak bases such as ammonia gas. This switching process is not perfectly reversible for reasons that are not fully understood, although it is often attributed to static morphological changes. In this work that was highlighted in the Journal of Physical Chemistry B, the Massari group used two-dimensional infrared (2D-IR) spectroscopy to characterize the fast molecular motions in polyaniline films over the course of a conductivity switching cycle. The researchers found that molecular dynamics primarily on the time scale of a few picoseconds (10-12 seconds) mirrored the reversible changes in film conductivity, while slower dynamics on the tens of picoseconds time scale were insensitive to the doping state of the polymer. It was also noted that very fast dynamics on a time scale of a few hundred femtoseconds were altered irreversibly, and were likely to be of the same origins (or perhaps the partial cause of) the irreversibility of the film conductance switching. This experimental work supports the notion that charge conduction in organic materials is not only dependent on the ways in which molecules are packed together, but also the manner in which they are able move.
It is hoped that this work will provide information to researchers about what molecular motions they need to control when creating new synthetic polymers.
To read the article and view the cover, go to the American Chemical Society's publication website.
