The Lowest Surface Free Energy Based on −CF₃ Alignment

Abstract

Free energy was measured for the surface of regular aligned closest hexagonal packed −CF3 groups. n-Perfluoroeicosane was vapor deposited onto glass, which gave epitaxially grown single-like crystallites with their molecular axes perpendicular to the glass surface. The dynamic contact angle of water on its surface was 119°, which corresponds to a surface free energy of 6.7 mJ/m2. This value is considered to be the lowest surface free energy of any solid, based on the hexagonal closed alignment of −CF3 groups on the surface.

Control of morphology and surface wettability of anodic niobium oxide microcones formed in hot phosphate–glycerol electrolytes

“…To make the oxide surface hydrophobic, the anodized specimens were coated with FAP, which was selected for two main reasons. One is that CF 3 -terminal group is the most effective in reducing the surface energy [6] and another is that the fluoroalkyl phosphate is known to bring about higher CAs for water and oil rather than the often used fluoroalkylsilane coupling agents [35]. The FAP-coated anodic niobium oxide films were superhydrophobic, and the static CA for water could not be measured, because of the ready rolling of the water droplet from the surface.…”

“…In particular, to create a superhydrophobic surface that shows a static contact angle (CA) of greater than 150 o , with a small contact angle hysteresis (CAH) between advancing and receding contact angles, introduction of surface roughness is essential, since the maximum contact angle on a flat hydrophobic surface is ~120 o [6].…”

Effect of SiO2 nanoparticles on the hydrophobic properties of waterborne fluorine-containing epoxy coatings

“…Based on the lotus leaf effect and other natural phenomena [2][3][4][5][6] , highly hydrophobic surfaces have been prepared by roughening low surface energy materials. The chemical composition of a coating determines its surface free energy.…”

Wettability control of photocatalytic crystal layers by hydrophobic coating and subsequent UV light irradiation

“…Increasing a surface's water repellency can be achieved by both decreasing the free energy between it and water, and increasing its roughness [1,2]. Incorporating fluorine atoms, which have a small atomic radius and high electronegativity, can achieve a low surface free energy [3,4]. An ideally flat surface covered with regularly aligned and closely packed CF 3 groups shows a water contact angle of about 120° [4].…”

“…Incorporating fluorine atoms, which have a small atomic radius and high electronegativity, can achieve a low surface free energy [3,4]. An ideally flat surface covered with regularly aligned and closely packed CF 3 groups shows a water contact angle of about 120° [4]. To obtain a water-repellent surface showing a water contact angle greater than this value, a proper surface texture is crucial.…”