Fluoroalkylated Silicon-Containing Surfaces−Estimation of Solid-Surface Energy

• Published in: ACS applied materials & interfaces 2010-12, Vol.2 (12), p.3544-3554
• Main Authors: Chhatre, Shreerang S, Guardado, Jesus O, Moore, Brian M, Haddad, Timothy S, Mabry, Joseph M, McKinley, Gareth H, Cohen, Robert E
• Format: Article
• Language: English
• Subjects: Computer Simulation; Hydrophobic and Hydrophilic Interactions; Materials Testing; Models, Chemical; Organosilicon Compounds - chemistry; Surface Properties
• ISSN: 1944-8244; 1944-8252
• DOI: 10.1021/am100729j

The design of robust omniphobic surfaces, which are not wetted by low-surface-tension liquids such as octane (γ lv = 21.6 mN/m) and methanol (γ lv = 22.7 mN/m), requires an appropriately chosen surface micro/nanotexture in addition to a low solid-surface energy (γsv). 1H,1H,2H,2H-Heptadecafluorodecyl polyhedral oligomeric silsesquioxane (fluorodecyl POSS) offers one of the lowest solid-surface energy values ever reported (γsv ≈ 10 mN/m) and has become the molecule of choice for coating textured surfaces. In this work, we synthesize and evaluate a series of related molecules that either retain the POSS cage and differ in fluoroalkyl chain length or that retain the fluorodecyl chains surrounding a linear or cyclic molecular structure. The solid-surface energy (γsv) of these molecules was estimated using contact angle measurements on flat spin-coated silicon wafer surfaces. Zisman analysis was performed using a homologous series of n-alkanes (15.5 ≤ γ lv ≤ 27.5 mN/m), whereas Girifalco−Good analysis was performed using a set of polar and nonpolar liquids with a wider range of liquid surface tension (15.5 ≤ γlv ≤ 72.1 mN/m). The hydrogen-bond-donating, hydrogen-bond-accepting, polar, and nonpolar (dispersion) contributions to the solid-surface energy of each compound were determined by probing the surfaces using a set of three liquid droplets of either acetone, chloroform, and dodecane or diiodomethane, dimethyl sulfoxide, and water.