Static and dynamic structural memory in polyaniline thin films.

Steady-state UV-visible and FTIR spectroscopies were used to characterize the electronic and structural changes that occur in polyaniline (PANI) thin films over the course of a single deprotonation and reprotonation cycle. The dedoping from the emeraldine salt (PANI-ES) to the emeraldine base (PANI-EB) form was achieved by treatment with a weak base (ammonia gas), and the PANI-ES was recovered by exposure to humid air and then dry air. The spectroscopic changes were classified into two general categories: those in which the recovered sample features were intermediate to the initial PANI-ES and the deprotonated PANI-EB and those in which the recovered sample features changed monotonically from the starting PANI-ES toward a unique observable.

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 dinonylnaphthalene sulfonic acid (conductive), and PANI-ES doped with camphor sulfonic acid (highly conductive). UV-visible and FTIR spectroscopies were used to characterize the static electronic and structural differences between these materials, and then these results were compared to the dynamical results from 2D-IR VES.