Relationships between Aggregation Structure and Nanotribological Behaviors of Alkylsilane Monolayers

Atsushi Takahara¹, Ken Kojio², Tisato Kajiyama²

1) Institute for Fundamental Research of Organic Chemistry
2) Faculty of Engineering, Kyushu University, Higashi-ku, Fukuoka 812-8581, JAPAN

Nanotribological behaviors of organosilane monolayers prepared by the Langmuir-Blodgett (LB) and chemisorption methods were discussed in terms of their aggregation states. The organosilane monolayers with longer alkyl chains were in a crystalline state at 293 K. The lateral force of the organosilane monolayers at 293K increased with an increase in their chain length. The n-triacontyltrichlorosilane monolayer (C30:TATS) in a rectangular phase showed higher lateral force than that of the alkylsilane one with shorter alkyl chains in a hexagonal phase. The lateral force of the n-octadecyltrichlorosilane (C18: 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, though both monolayers are in a hexagonal phase at 293 K. Aggregation structure of the LB OTS monolayer changed from the rectangular phase to the amorphous one via the hexagonal phase with increasing temperature. The distinct lateral force decrease for the LB OTS monolayer was observed at the corresponding temperature range.