The effect of anchoring PEI layer on the build-up of polyelectrolyte multilayer films at homogeneous and heterogeneous surfaces

Expanding area of applications of polyelectrolyte multilayers requires the extensive studies of the processes of their adsorption at real surfaces, which are often very rough and chemically heterogeneous. We investigated adsorption of polyelectrolytes at surfaces of polished and unpolished surgical stainless steel (used in medicine as a material for stents), at titanium plates (material for implants) and silicon plates (material for microelectronics). Films (PAH*/PSS)n, PEI(PSS/PAH*)n with a number of layers varied between 1 and 11 were formed on silicon wafers, stainless steel, titanium plates (PAH* - poly(fluorescein isothiocyanate allylamine hydrochloride), PSS - polysodium 4-styrenesulfonate, PEI - polyethyleneimine). The effect of the first polyethyleneimine layer and surface roughness on the formation of polyelectrolyte multilayer films on these surfaces was investigated. The amount of polymer adsorbed in the multilayer was determined by fluorescent microscopy. Film thickness formed on polished Si/SiO2 surface was measured by ellipsometry. Results obtained indicate that PEI anchoring layer has an influence on the PE film properties depending on the conditions of film formation and on the roughness of the supporting surface. At surfaces with higher roughness stronger effect of PEI is observed.