Influence of Different Solutions on Electrically Conductive Films Composed of Carbon Nanotubes and Polydimethyldiallylammonium

For engineering and biomedical applications, nanometer-thin films with high electrical conductivity in aqueous solutions are desirable. Multilayers of polydimethyldiallylammonium chloride (PDADMA) and oxidized carbon nanotubes (CNTs) were built using the layer-by-layer technique. CNTs with a low linear charge density were used. The surface coverage of the CNTs was monitored with optical absorption. The film thickness and the surface coverage of the CNTs increased linearly with the number of CNT/PDADMA bilayers deposited. On immersion into aqueous solutions, the film thickness decreased or remained constant. This finding is attributed to the hydrophobic character of the CNTs and the backbone of PDADMA. The films showed ohmic behavior, both in air and in solutions. The electrical conductivity was 0.95 × 104 S/m in air and increased to 1.36 × 104 S/m in solution, provided the thickness of the CNT/PDADMA bilayers was as low as 1.9 nm. We suggest that high electrical conductivity can be achieved by flat adsorption of the CNTs.