CHARACTERIZATION OF PARTIAL MONOLAYERS ON GLASS USING FRICTION FORCE MICROSCOPY

Partial octadecylsiloxane monolayers were formed on borosilicate glass substrates and characterized using friction force microscopy (FFM) an d contact angle techniques. Use of the friction force microscope allow ed the film composition to be investigated despite significant roughne ss of the underlying substrate. The height variations of the substrate were of the same order as the film thickness: a situation in which co nventional atomic force microscopy can produce ambiguous or inconclusi ve results. Substrates with a range of partial surface coverages were prepared, and contact angle measurements demonstrated the expected dec rease in wettability with increasing siloxane coverage. Friction force microscopy revealed a corresponding decrease in the friction coeffici ent of the surface with increasing coverage. Microscope resolution det ermined an upper limit of 15 nm for the lateral size of isolated silox ane domains for all coverages.