Contact Angle and Atomic Force Microscopy Study of Reactions of n-Alkyltrichlorosilanes with Muscovite Micas Exposed to Water Vapor Plasmas with Various Power Densities

Abstract

Monolayers of n-alkyltrichlorosilanes (CH3(CH2)n -1SiCl3: Cn) were formed on the surface of Muscovite micas after various numbers of reactive sites were formed on the mica surfaces by exposing the micas to water vapor plasmas whose power, P, varied from 0 to 100 W. Contact angle measurements of the monolayers showed that the coverages of Cn molecules at n≦8 on the mica surfaces increased with an increase in the plasma power on the micas. On the other hand, the coverages of Cn molecules at n>8 on the micas were not so sensitive to the plasma power as those at n≦8. The atomic force microscopy (AFM) observations of the growth process of the monolayers from C18 showed that island structures were formed on the mica surfaces at the low coverages of the monolayers and that each island grew and eventually came into contact with the other islands as the coverage increased. In contrast, island structures were not observed on the mica surfaces during the growth process of C4 monolayers. These results propose a reaction model of Cn molecules with micas, where Cn molecules at n>8 are hydrolyzed with adsorbed water on the micas in the Cn solutions, followed by condensing to form two-dimensional polymerized network domains; Cn molecules at n≦8 are hydrated with the adsorbed water on the micas in the Cn solutions, but the domain sizes of the two-dimensional polymerized network are not so large as those at n>8 because of a limitation of the condensation among the molecules.