Synthesis of fluoroalkylsilane-coupling agents and their self-assembled monolayers

In this paper, 3-isocyanatepropyl triethoxysilane (IPTS) was synthesized using one-pot reaction using 3-aminopropyl triethoxysilane (APTES) and triphosgeneas as the raw materials. IPTS was then reacted with three kinds of perfluoroalkyl alcohol to obtain 3-(1H,1H,2H,2H-perfluoroalkoxyamidepropyl)-triethoxysilanes with different fluoroalkyl chain lengths. The silicon wafer was etched to obtain an active and coarse surface followed by coating with self-assembled monolayer (SAMs) using fluoroalkylsilane as materials. AFM were used to reflect the variation of the surface morphologies and roughness of self-assembled films before and after coating. ATR-IR test indicated that a combination of possible bonding forms the SAMs. EDS was used to characterize the distribution of the elements on the SAMs. The result of contact angle testing and surface energy counting showed that the SAMS have good water- and oil repellency, which improved with the increment of fluoroalkyl chain length. XPS were used to characterize the change of surface element content of SAMs before and after heat treatment, which resulted in the microphase separation on the film surfaces and made the fluoroalkyl migrate from the internal of the monolayer to the outermost surface. After heating, the fluoroalkyl accumulated on the surface, which lowered the surface energy further and obtained the better water- and oil repellency.