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

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 CH3CN 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) (CH3CN) or IN3D(CT) (CH2Cl2) 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. (C) 2002 Elsevier Science Ltd. All rights reserved.