Solvent effect on the nucleation and growth mechanisms of poly(thiophene)

Abstract

Applying the step potential method, the effect of parameters such as solvent, potential, electrolyte and monomer concentration on the nucleation and growth processes of poly(thiophene) on Pt electrode in tetrabuthylammonium hexafluorophosphate–acetonitrile or dichloromethane has been studied. The j/ t transients were generally fitted by means of a mathematical equation that considers different contributions. In acetonitrile the j/ t transient (0< t<30 s) present three contributions corresponding to the following mechanisms: two-dimensional instantaneous nucleation (IN2D), three-dimensional progressive nucleation (PN3D CT) under charge transfer control and three-dimensional progressive nucleation (PN3D dif) under diffusion control. Similar results were obtained in dichloromethane, but in this case the 3D CT nucleus presented an instantaneous nucleation mechanism (IN3D ct). A second wave has been observed in the j/ t transients obtained in CH 3CN at t>30 s, which was fitted by a mathematical equation that included two contributions corresponding to a PN3D CT and PN3D dif mechanisms. In general, the charge associated to each contribution depended on the solvent, the monomer and electrolyte concentration and the applied potential. However, the PN3D CT (CH 3CN) or IN3D CT (CH 2Cl 2) mechanisms were always the more important contributions. The scanning electron microscopy (SEM) analysis of the deposits morphology are in agreement with the nucleation and growth models that are proposed by this method.