| Self-assembled monolayer (SAM) is ordered molecular assembly that is formed spontaneously by the adsorption of a surfactant with a specific affinity of itsheadgroup to a substrate. Self-assembled monolayer exhibits great potential in basic scientific research and morden engineering.This paper is composed of two parts. The formation of OTS SAM on stainless steel316L (SS316L) substrate was introduced in the first part. The study of octyltriethoxysilane (C8TES)/octadecyltrichlorosilane (OTS) homogeneously mixed SAM on silica was described in the second part.Alkyltrichlorosilane SAM was regarded as the most stable SAM on silicon/silica substrate, but it was rarely used on stainless steel316L (SS316L) substrate due to the surface corrosion caused by the hydrochloric acid which was released during the hydrolysis process of alkyltrichlorosilane molecules. In the first part, a novel technical route aiming at constructing stable OTS SAM on SS316L surface was put forward. By prolonging the storage time of OTS-toluene reaction solution and adding a moderate amount of alkali into the reaction solution, a well-ordered and integrated OTS SAM was successfully coated on SS316L surface. The obtained OTS SAM was characterized by contact angle, atomic force microscopy (AFM), scanning electron microscope (SEM) and attenuated total reflectance-Fourier transform infrared (ATR-FTIR). The long-term in vitro stability study of OTS SAM on SS316L showed that, even immersed in physiological saline or phosphate buffered saline (PBS) solution at37℃for60days, the sample surface still kept very good hydrophobic.In the second part, the wettability, surface topography, surface potential and order degree of molecules of C8TES/OTS homogeneously mixed SAM were characterized by means of contact angle, AFM, Electrostatic Force Microscopy (EFM) and Fourier Transform infrared spectroscopy (FTIR). The formation mechanism of C8TES/OTS homogeneously mixed SAM, which was constructed in step by step method by taking the advantage of the molecular steric hindrance of C8TES, was studied. The experimental results indicated that, integrated C8TES/OTS mixed SAM had a smooth surface with contact angle of105°and homogeneous surface potential distribution, the surface potential frequency distribution was very close to Normal distribution, the C8TES/OTS homogeneously mixed SAM had a double-layer film structure with different molecular densities in two layers, and the structure inside the mixed SAM was highly homogeneous at least from500nm×500nm to20μm×20μm scales. |
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