Dynamics on Molecular Films. Surface Structure and Surface Mechanical Properties of Organosilane Monolayers.

Surface structure and surface mechanical properties of organosilane monolayers prepared by the Langmuir-Blodgett (LB) and chemisorption methods were investigated. The organosilane monolayers with longer alkyl and fluoroalkyl chains were in crystalline state at 293 K. The lateral force of the organosilane monolayers increased with an increase in their chain length. The magnitude of lateral force of the fluoroalkylsilane monolayer was higher than that of the alkylsilane one. This can be attributed to the rigid characteristics of fluoroalkyl chain. The lateral force of the n-octadecyltrichlorosilane (OTS) monolayer prepared by the LB method was higher than that of the chemisorbed one because of the higher packing density of alkyl chain for the LB monolayer. Molecular aggregation state of the LB OTS monolayer changed from the rectangular phase to the amorphous one via the hexagonal phase with an increase of temperature. The distinct lateral force decrease for the OTS monolayer was observed at the corresponding temperature range.