Fluoroalkylated silicon-containing surfaces-estimation of solid-surface energy.
The design of robust omniphobic surfaces, which are not wetted by low-surface-tension liquids such as octane (γlv=21.6 mN/m) and methanol (γlv=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≤γlv≤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.
Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
Shreerang S
SS
Chhatre
Jesus O
JO
Guardado
Brian M
BM
Moore
Timothy S
TS
Haddad
Joseph M
JM
Mabry
Gareth H
GH
McKinley
Robert E
RE
Cohen
D003198:Computer Simulation; D057927:Hydrophobic and Hydrophilic Interactions; D008422:Materials Testing; D008956:Models, Chemical; D017646:Organosilicon Compounds / Q000737:chemistry*; D013499:Surface Properties
D017646:Organosilicon Compounds; C521417:polyhedraloligosilsesquioxane