Formation of superhydrophobic polymerized n-octadecylsiloxane nanosheets

Superhydrophobic nanosheet assemblies of polymerized n-octadecylsiloxane (PODS) were obtained on glass using n-octadecyltricholorsilane (OTS) as a starting material and acetone as the extracting agent. The coating layers were characterized by infrared spectroscopy, X-ray diffractometry, X-ray photoelectron spectroscopy, and contact angle measurements. It was shown that the PODS nanosheets consist of stacks of bilayered polysilsequioxane of OTS in a head-to-head arrangement. The relative humidity of the environment was found to control the self-assembly and eventually the morphology of the final coating. A coating-formation mechanism was proposed to describe the formation of OTS nanosheets on the basis of quick OTS hydrolysis, fast self-assembly, and slow polycondensation (i.e., after OTS hydrolysis, nanosheets can be formed only when the self-assembly process proceeds at a faster rate than polycondensation, which implies critical controlling factors in the formation of well-ordered OTS self-assembled monolayers (SAMs)).