Langmuir, Vol.12, No.3, 778-783, 1996
Direct Influence of the Interaction Between the First Layer and a Hydrophilic Substrate on the Transition from Y-Type to Z-Type Transfer During Deposition of Phospholipid Langmuir-Blodgett-Films
In view of obtaining homogeneous LB films, monolayers of dipalmitoylphosphatidic acid (DPPA) and of mixed DPPA and dipalmitoylphosphatidylcholine (DPPC) (molar ratio, 2:1) were transferred onto hydrophilic (fluorine, glass, and silicon) or hydrophobic (silanized glass) substrates with conditions derived from the optimized procedure previously proposed in our group for the transfer of a fatty acid monolayer. Whatever the substrate used, the phospholipid multilayers obtained are homogeneous through Nomarski microscopic observations. The silicon substrate appears to be the most efficient to build up Y-type multilayers. Anew type referred to as "YZ" was defined to describe the structure of the LB film stacking. We demonstrate that the transition observed between the different Y-, YZ-, and Z-types depends directly on the strength of the interaction between the first layer and the hydrophilic substrate surfaces.