A conducting polymer has been obtained by anodic oxidation of 4-cyclopenta[2,1-b;3,4-b']dithiophen-4-ylidenemethyl-N,N-diethyl-benzene sulfonamide. In this novel polycyclopentadithiophene matrix, a cathodically sensitive aryl sulfonamide group is grafted through an ethylene junction to the polymer backbone. This polymer exhibits a remarkable electroactivity in organic and aqueous solvents allowing a smooth electrochemical cleavage of the S-N bond in both media. (C) 2004 Elsevier B.V. All rights reserved.