Covalently immobilized 1,4-phenylenediamine on 11-mercaptoundecanoic acid-coated gold: Effect of surface-confined monomers on the chemical in situ deposition of polyaniline and its derivatives

We present the study of polyaniline, poly(2-methoxyaniline), and poly(2,5-d imethoxyaniline) chemical deposition in situ on gold electrodes coated with thiol monolayers containing 4-aminophenyl groups in terminal positions. Th e thiol. monolayers were prepared by self-assembly of 11-mercaptoundecanoic acid on gold with subsequent covalent attachment of 1,4-phenylenediamine m olecules through the formation of a peptide bond with use of 1-ethyl-3-[3-( dimethylamino)propyl]carbodiimide as catalyst. Thus, the immobilized monome r molecules (H2N-C6H4-NHOC-C10H20SH) could act as nucleation sites for subs equent polymer formation by the chemical in situ method. The deposition pro cess of polymers was investigated with a quartz crystal microbalance. The e lectronic properties of such obtained polymers were studied by cyclic volta mmetry. Particularly interesting behavior was observed for polyaniline, whi ch exhibited unique voltammetric curves. We assigned this unusual behavior as the result of covalent attachment of some polymer chains to the surface.