Journal of Physical Chemistry B, Vol.115, No.16, 4583-4591, 2011
Ground-State Structural Dynamics in Doped and Undoped Polyaniline Films Probed by Two-Dimensional Infrared Vibrational Echo Spectroscopy
Two-dimensional infrared vibrational echo spectroscopy (2D-IR VES) provides information about the structural dynamics occurring on the ultrafast time scale, a temporal regime that is comparable to that of charge-hopping events in conducting polymer films. In this study, 2D-IR VES is used to study polyaniline (PANI) thin films in three states of varying conductivity emeraldine base (PANI-EB, semiconducting), emeraldine salt (PANI-ES) doped with dinoylnaphthalene sulfonic acid (conductive), and PANI-ES doped with camphor sulfonic acid (highly conductive). UV-visible and FTIR spectroscopies were used to chracterize the statci electronic and structural differences between these materials, and then these results were compared to the dynamical results from 2D-IR VES. The electronic ground state ultrafast dynamics for the PANI-EB reveal very fast motions that are not present in either of the PANI-ES samples. Despite differences in conductivity, no signifigant dynamical differences are observed fot the films prepared with the two dopants. We interpret these results in light of previous work on the structural ordering induced by soping with acids and the possible correlations between charge carrier mobilities and low frequency structural dynamics.