Microstructure of thin Langmuir-Blodgett films of dipalmitoylphosphatidylcholine: electron microscopic images replicated with plasma polymerized film by glow discharge

Abstract

Electron-microscopic images of 1- and 5-monolayer LB films of dipalmitoylphosphatidylcholine, transferred to a glass substrate at various surface pressures encompassing the plateau region of the surface pressure-area isotherm, were observed by using a plasma polymerization replica method. One-monolayer films are flat and there is no substantial evidence of structural defects up to the high surface pressures. Crystalline domain structures appear in the 5-monolayer films even at the low surface pressures below the plateau, which accords well with our previous spectroscopic results. The domains decrease their size with increases in surface pressure and finally disappear at the high surface pressures above the plateau. These are explained by the formation of a closely packed homogeneous structure around the plateau region. Further compression of the monolayer before the collapse pressure leads to the reappearance of the inhomogeneous crystalline domain structures, due to the local collapse of the monolayer just before the main collapse pressure.