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Influence of charge density and ionic strength on the multilayer formation of strong polyelectrolytes

: Steitz, R.; Jaeger, W.; Klitzing, R. von


Langmuir. The ACS journal of surfaces and colloids 17 (2001), Nr.15, S.4471-4474
ISSN: 0743-7463
ISSN: 1520-5827
Fraunhofer IAP ()

The influence of ionic strength and polymer charge density on the multilayer formation of strong polyelectrolytes is investigated by X-ray reflectivity. To a first approximation the adsorption behavior as a function of the degree of charge, f, is binary: For f less than or equal to 50% the films are one order of magnitude thinner than those for f greater than or equal to 75%. This is due to a threshold of charge overcompensation after each adsorption step which seems to be at f between 50% and 75%. Above the charge reversal limit the thickness and the surface roughness increase with decreasing polymer charge. Below a charge density of 50% the film thickness cannot be changed by salt additive whereas the film thickness increases with C-NaCl(1/2) above a degree of charge of 75%. The density of all investigated films is quite similar.