Super-lattice structure in PPV-based self-assembled films

Neutron and x-ray reflectivity studies of self assembled films prepared by layer-by-layer adsorption of polyelectrolytes are presented. The films are prepared from the water soluble deuterated precursor of poly-(p phenylene vinylene) (d-PPV), poly-(styrene sulfonate) (SPS) and poly (allylamine hydrochloride) (PAH) followed by thermal treatment. Super lattice structures are build with single layers of d-PPV separated by two different numbers of SPS/PAH double layers, In the neutron reflectivity data up to four well pronounced Bragg peaks show up which can also be seen in x-ray reflectivity as small quasi-Bragg peaks indicating variations in electron density of approx. 5%. From detailed analysis of the data an internal roughness between burried interfaces of approx. 15 A was derived.