Formation mechanism of n-octadecyltrichlorosilane monolayer prepared at the air/water interface

Abstract

The n-octadecyltrichlorosilane (OTS) monolayer was prepared by the Langmuir–Blodgett method. The formation mechanism of the OTS monolayer on the water subphase was investigated on the basis of electron diffraction (ED) study, Fourier transform infrared external reflection spectroscopic (FT-IR/ERS) measurement and high-resolution atomic force microscopic (AFM) observation. Morphological changes in the monolayer in a compression process were observed by AFM. FT-IR/ERS measurement was performed for the monolayer at the air/water interface, and that the ED and AFM observations were done for the monolayer transferred onto substrate. ED study and high-resolution AFM observation revealed that the OTS monolayer was in a crystalline state at 293 K. Also, FT-IR/ERS measurement and AFM observation showed that the OTS molecules crystallize and polymerize spontaneously right after spreading a toluene solution of OTS on the water subphase. Then, during a monolayer compression, the crystalline OTS monolayer domain did not form the larger ones by sintering at the crystalline domain interface at 293 K. Also, AFM and ED observations revealed that the defect-diminished OTS monolayer could be successfully prepared by using the multi-step creep method.