STRUCTURES OF HEADGROUP AND TAIL-GROUP MONOLAYERS IN A LANGMUIR-BLODGETT-FILM

We have studied monolayer and multilayer Langmuir-Blodgett films of le ad stearate using x-ray diffraction and reflectivity. We show that it is possible to distinguish the scattering due to the head groups from that due to the alkane chains. The second and subsequent alkane monola yers are distorted hexagonal (the first monolayer is known to be hexag onal); successive monolayers are shifted laterally by one-fourth of an in-place lattice spacing, and the chains tilt by similar to 8 degrees towards a nearest neighbor. The lead ion monolayers are also distorte d hexagonal; successive monolayers are shifted laterally by a half lat tice spacing. From rod scan intensities, we have determined the relati ve positions of the lead and alkane chain lattices.