Polyelectrolytes I: Polyanion/polycation multilayers at the air/monolayer/water interface as elements for quantitative polymer adsorption studies andpreparation of hetero-superlattices on solid surfaces

Polyanion/polycation multilayers floating at the air/water interface were p repared by consecutive adsorption of polyelectrolyte layers onto a Langmuir monolayer from aqueous polyelectrolyte subphase solutions. With the positi vely charged Langmuir monolayer headgroups of the lipid dimethyldioctadecyl ammonium bromide, the layer sequence starts with the negatively charged pol yelectrolyte polystyrene sulfonate. With the negatively charged monolayer d imyristoylphosphatidic acid, it starts with the positively charged polyally lamine. Equally charged monolayer headgroups and polyelectrolytes do not bi nd to each other. Consecutive subphase exchange cycles of polyelectrolyte s olutions with alternating charges and pure solvent in between lead to the f ormation of floating multilayers consisting of an alternating polyelectroly te sequence. Ellipsometric measurements show that the thickness (adsorbed a mount per unit area) of the multilayer film at the air/water interface grow s in proportion to the number of adsorbed polyelectrolyte layers. The thick ness of individual layers increases with increasing polyelectrolyte and/or ion subphase concentration, respectively. The floating multilayers can be d eposited as a sequence of layers of monomeric lipid and polyelectrolytes (h etero-superlattices) onto solid substrates via Langmuir-Blodgett transfer. UV-absorbance studies corroborate the quantitative interpretation of the el lipsometric data in terms of the polymer concentration in the layers, the i ndividual layer thicknesses, and the adsorbed amounts per unit area.