COMBINATION OF POLYCATION POLYANION SELF-ASSEMBLY AND LANGMUIR-BLODGETT TRANSFER FOR THE CONSTRUCTION OF SUPERLATTICE FILMS

The Langmuir-Blodgett transfer (LB) of amphiphile monolayers from the air/water interface onto solid supports is a powerful tool to create p eriodic lattices in many varieties, usually composed of bilayers. By s elf-assembly adsorption (SA) of polyelectrolytes, uniform molecular fi lms with very exact thickness adjustment are obtained. The combination of Langmuir-Blodgett transfer and polycation/polyanion self-assembly allows a precise extension of the LB lattice, and a superlattice is fo rmed by combination of LB and SA units. The superlattice was realized in a multicomponent film, in which additional polyelectrolyte sheets a re inserted between the amphiphile headgroups. At first, Langmuir-Blod gett films of the pure lipid/polyelectrolyte complex DODAB/PVS (dimeth yldioctadecylamonium bromide/poly(vinyl sulfate)) were prepared and a bilayer spacing of 4.43 nm was found. For the construction of film sup erlattices, sequences of polyelectrolyte layers were adsorbed between the PVS headgroups of the DODAB bilayer by the following method: After deposition of one bilayer, the wet substrate was removed from the Lan gmuir-Blodgett trough and PAH (poly(allylaminehydrochloride)) and PVS were adsorbed from their solutions. The resulting superlattice repeat unit consists therefore of one DODAB/ PVS bilayer and the inserted ass embly of polyelectrolyte layers. Samples of 1, 3, and 5 additional pol yelectrolyte layers per unit cell were prepared and investigated with small angle X-ray reflectivity. Variation of the repeat unit of superl attice results in a linear increase of the superlattice layer spacing of 0.4 nm per additionally inserted polycation/polyanion pair. Also co rrelation lengths and roughnesses were estimated, and a decrease of la yer correlation and an increase of roughness with increasing number of polyelectrolyte layers were found. Heating the samples to 70 degrees C and slowly cooling result in a remarkable improvement of the multila yer ordering.