Associating oriented polyaniline and eumelanin in a reactive layer-by-layer manner: Composites with high electrical conductivity

Eumelanin like coatings, often called “polydopamine” films are a new class of universal coatings allowing to coat almost all kinds of materials in a straightforward and one step reaction. To broaden the range of applications of such coatings particularly for biomedical applications and for the design of new biosensors, it is mandatory to provide an increased electrical conductivity to such coatings. Herein we produce composite films made of oriented polyaniline (PANI) and eumelanin (“polydopamine”) using a reactive layer-by-layer deposition approach. In this approach, the two constitutive components of the films are not deposited from solutions containing particles thereof but are produced through successive oxidation of aniline and dopamine in the appropriate reaction conditions. The composite films contain about 24% by weight of eumelanin and display a direct current (DC) electrical conductivity similar to that of oriented PANI, namely of the order of 1 S cm−1. An increase in the mass fraction of eumelanin in the composite films can be easily achieved by two successive deposition steps of eumelanin and leads to a significant reduction in the electrical conductivity of the whole material.