THE TIME OF OBSERVATION OF PI-A ISOTHERMS .3. STUDIES ON THE MORPHOLOGY OF ARACHIDIC ACID MONOLAYERS, OBSERVED BY TRANSMISSION ELECTRON-MICROSCOPY OF REPLICA SAMPLES OF ONE-LAYER LANGMUIR-BLODGETT-FILMS USING PLASMA-POLYMERIZATION

An idea regarding the time of observation for measurement of pi-A isotherms of monolayers is proposed. Only pi-A isotherms measured for the same "times of observation" can be compared directly with each other. Transmission electron microscopic (TEM) observation of replica samples of one-layer LB films of archadic acid reveals that there are two kinds of three-dimensional structures in the collapsed films: platelet crystallites of the order of a few thousand nanometers and large numbers of granular structures of the lateral order of several tens of nanometers with a height of about 5 nm. By comparing the pi-A isotherms of a series of long-chain acids (C22, C20, C18, C-16, and C-15), measured for the same "time observation" and their TEM images, it is estimated that the granular structures are all generated simultaneously after some induction period following the collapse of the monolayers.