Synthetic Metals, 45 (1991) 297-308 297 Influence of the crystalline surface structure of platinum on the electropolymerization of 3-methylthiophene P. Lang* Laboratoire des Matdriaux Moldculaires, 2 rue H. Dunant, 94320 Thiais (France) J. Clavilier Laboratoire d'Electrochimie Interfaciale, 1 place A. Briand, 92190 Meudon (France) Abstract The influence of the crystalline surface structure (c.s.s.) of the platinum electrode on the electropolymerization of 3-methylthiophene has been studied. A single crystal with a polyoriented surface possessing all the crystallographic orientations regularly distributed was used with a previous thermal treatment which gives a reproducible surface state. The growth nature studied with the usual nucleation and growth laws and the location of the polymer are greatly dependent on the c.s.s.; with a low electropolymerization potential, the (111) facets are first covered by the polymer film. The origin of the c.s.s. influence is discussed, especially in relation to the initial oxygen coverage and the vicinity of the platinum site. Introduction Many electrochemical syntheses of conducting polymers have been reported because of the great interest in the materials from a fundamental point of view and for their potential applications. Some studies concerning the first steps of the electropolymerization process have been devoted to the analysis of the nature of the first deposited species [1] and to the mechanism of nucleation and growth [2 ]. Nevertheless, very few works have been concerned with the influence of the electrode surface state and the mode of attachment of these polymers. Our interest in looking at the polymer/ metal interface comes from the necessity of obtaining reproducible polymer films of good quality. Moreover, the interface structure certainly determines adhesion, coverage level, charge transfer properties as well as bulk properties such as morphology, electrical and electrochemical properties. As an extension of our studies on the influence of the chemical pretreatments [lb, le], we thought that it would be of interest to study the influence of the physical state, i.e., the crystalline surface structure (c.s.s.) of the electrode. As a preliminary analysis, we used a single crystal electrode with a polyoriented surface which allows a rapid comparative study of the deposition on different crystallographic orientations. *Author to whom correspondence should be addressed. 0379-6779/91/$3.50 © 1991 -- Elsevier Sequoia, Lausanne