Preparation of Transparent Superhydrophobic Glass Slides: Demonstration of Surface Chemistry Characteristics

A demonstration for undergraduate teaching in upper-division physical Chemistry and materials science courses is described. A simple protocol was developed to prepare superhydrophobic and hydrophobic glass by treating standard microscope slides with methyltrichlorosilane and octadecyltrichlorosilane, respectively. The unique wetting, optical, and self-cleaning properties of the modified surfaces can be demonstrated to students in class. Octadecyltrichlorosilane forms a closely packed, methyl-terminated, self-assembled monolayer that changes the glass surface from hydrophilic to hydrophobic; treatment with methyltrichlorosilane yields 3-dimensional polymethylsiloxane networked nanostructures, which leads to a superhydrophobic surface, that is, water droplets sit atop in the Cassie Baxter state. In both cases, the glass slides maintain optical transparency despite remarkable changes in the surface wettability. A classroom demonstration of superhydrophobicity and self-cleaning using these surfaces, along with a brief explanation, motivates students to apply their basic knowledge of chemistry to study natural phenomena and practical applications.