Neutron reflectivity investigations of self-assembled conjugated polyion multilayers

Neutron reflectivity has been used to study the organization of self-assembled multilayers of sulfonated polyaniline and polyallylamine. Films were prepared by the sequential adsorption of polycations and polyanions from dilute aqueous solutions. Scattering contrast was achieved by selective deuteration of the blocks of bilayers at varying intervals along the film. The multilayer structure was found to be preserved over 40 bilayer depositions, but with an internal organization which decays monotonically away from the substrate. These results suggest that the observed interfacial widths are primarily due to the accumulation of defects as the bilayers are deposited.