@inproceedings { , title = {A structural investigation of polypyrrole as a function of oxidation state}, journal = {Materials Research Society Spring Meeting}, volume = {871E}, year = {2005}, pages = {I6.1 pp. 1-6}, publisher = {Materials Research Society}, organization = {Materials Research Society}, address = {San Francisco}, abstract = {Polypyrrole exhibits actuation under electrochemical doping and undoping of the polymer matrix. Active strain and x-ray diffraction measurements are performed in order to correlate the microscopic and macroscopic structural changes occurring during actuation. Under galvanostatic reduction, the film shows first a linear contraction with oxidation state due to expulsion of small anions. At 50% of the as-grown doping level, the film reverses direction and begins to expand due to incorporation of the larger cations. X-ray diffraction, however, does not show a linear contraction in the crystalline portions of the polymer. The polymer crystallites go through a sudden contraction in one dimension of approximately 14%, and otherwise remain constant. The contraction in the polypyrrole crystals occurs at the 50% doping level, and appears to be correlated with the reversal of macroscopic actuation.}, URL = {http://www.mrs.org}, author = {Warren, M.R. and Madden, J. D.} }