Electrochimica Acta 46 (2001) 4001 – 4006
Effects of the redox state on the morphology of the
regioregular sexi-3-alkylthiophene
M. Lapkowski
a,b,
*, J. Zak
a
, M. Kolodziej-Sadlok
a
, S. Guillerez
c
, G. Bidan
c
a
Department of Chemistry, Silesian Uniersity of Technology, ul. Strzody 9, 44 -100 Gliwice, Poland
b
Institute of Coal Chemistry, Polish Academy of Science, ul. Sowinskiego 5, 44 -121 Gliwice, Poland
c
De ´partement de Recherche Fondamentale sur la Matie `re Condense ´e, SI3M/EM, CEA Grenoble, 17 rue des Martyrs,
38054 Grenoble Cedex 09, France
Received 28 February 2001; received in revised form 25 April 2001
Abstract
The electrochemical properties of solid phase -monochloro substituted regioregular 3-alkylthiophene consisting of
six units of 3-octylthiophene (6OT) were studied in nonaqueous electrolyte solutions using cyclic voltammetry and
electrochemical atomic force microscopy (EC AFM). As confirmed by voltammetry, the 6OT molecules in an oxidized
form of monocation radical are not subject to consecutive reactions, due to the presence of the -substituent. In situ
AFM images of the thin films of 6OT cast on metal substrates revealed reversible, drastic changes of the film
morphology while applied potential was switched between values corresponding to the particular redox state.
Dimerization of the oligomers and -stacks formation is postulated to explain the observed morphology changes in
the 6OT films. © 2001 Elsevier Science Ltd. All rights reserved.
Keywords: Oligothiophenes; Molecular stacks; Self-organization; Atomic force microscopy
www.elsevier.com/locate/electacta
1. Introduction
A possibility of changing the existing intermolecular
bonding makes some systems interesting candidates for
materials chemistry. Manipulations with a redox state
are relatively easy under electrochemical conditions and
they may lead to supramolecular transitions in the
system. Recently, much of the research in this area has
been focused on conjugated thiophene oligomers [1,2].
These compounds, as being monodisperse in contrast to
polymers, are considered to have better defined effects
of their structure on physicochemical properties. Thus,
studies of basic properties of substituted oligoalkylthio-
phenes [3 – 6] are important since these molecules are
viewed as a short chain model of regiochemically well-
defined poly(alkylthiophenes). This model is especially
useful in recognition of basic electrochemical reactions,
including the doping process of these conductive poly-
mers. Electrochemical oxidation of thiophene oligomers
has been studied in homogenous solutions [7 – 10] rather
than in a solid phase [11]. Several applied science
aspects were indicated [12 – 15], emphasizing potential
applications of the compounds in molecular electronics
and optoelectronics [11].
In the paper, we present the electrochemical proper-
ties of solid phase -monochloro substituted regioregu-
lar sexi-3-octylthiophene (3,4,4,4,4,4-hexaoctyl-
5-chloro-2,2:5,2:5,2:5,2:5,2-sexithiophene,
6OT):
* Corresponding author. Tel.: +48-32-237-1743; fax: +48-
32-237-1509.
E-mail address: lapkowsk@zeus.polsl.gliwice.pl (M.
Lapkowski).
0013-4686/01/$ - see front matter © 2001 Elsevier Science Ltd. All rights reserved.
PII:S0013-4686(01)00711-3