Polythiophene was formed by electropolymerization at the interface between two immiscible electrolyte solutions, using terthiophene as the starting monomer in 1,2-dichloroethane. The water phase contained a redox couple to allow removal of electrons through the interface. For the first time, a layer of polythiophene was produced which was strong enough to extract. The mechanism of electropolymerization was found to be similar to that in the electrodeposition of polythiophene on metals: progressive nucleation and 2D growth precedes 3D growth, ascribed to precipitation of oligomers from solution. The polymer extracted was found to be partially oxidized (irreversibly doped) to a conductive state, and stable in air. (c) 2006 Elsevier B.V. All rights reserved.