Force field based molecular dynamics simulations in highly conducting compounds of poly(aniline). A comparison with quasi-elastic neutron scattering measurements

Dynamics of counter-ions in poly(aniline) doped with di-(2-butoxyethoxyethyl)ester of 4-sulfophthalic acid have been simulated using force field based molecular dynamics involving a semi-empirical charge equilibration procedure and charge rescaling based on DFT calculations. Due to particular relaxational and structural characteristics of such “plastdoped” poly(anilines), these simulations have proved to be a very effective tool for reproducing the main structural and dynamic features of the material. The experiment/simulation comparison for dynamics is very good in the 10−10-10−13 s time range. In particular, mean square displacements extracted from the molecular dynamics simulations for atoms in the counter-ions are in good agreement with the analytical model used to analyse the quasi-elastic neutron scattering data. The use of a larger simulation box and longer simulation time give good agreement in the extended time domain and reveal a dynamical heterogeneity between the counter-ions that was not foreseen in the analytical model.