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Cloth, treated to be hydrophobic, shows a high contact angle. The theoretical description of contact angle arises from the consideration of a thermodynamic equilibrium between the three phases: the liquid phase (L), the solid phase (S), and the gas or vapor phase (G) (which could be a mixture of ambient atmosphere and an equilibrium concentration of the liquid vapor).
It is widely agreed that the water repellency of biological objects is due to the Cassie-Baxter equation. If water has a contact angle between 0 < θ < 90 ∘ {\displaystyle 0<\theta <90^{\circ }} , then the surface is classed as hydrophilic, whereas a surface producing a contact angle between 90 ∘ < θ < 180 ∘ {\displaystyle 90^{\circ ...
With GW calculation, the properties of graphene-based materials are accurately investigated, including bulk graphene, [30] nanoribbons, [31] edge and surface functionalized armchair oribbons, [32] hydrogen saturated armchair ribbons, [33] Josephson effect in graphene SNS junctions with single localized defect [34] and armchair ribbon scaling ...
Graphene oxide flakes in polymers display enhanced photo-conducting properties. [10] Graphene is normally hydrophobic and impermeable to all gases and liquids (vacuum-tight). However, when formed into graphene oxide-based capillary membrane, both liquid water and water vapor flow through as quickly as if the membrane was not present. [11]
The surface energy of a liquid may be measured by stretching a liquid membrane (which increases the surface area and hence the surface energy). In that case, in order to increase the surface area of a mass of liquid by an amount, δA, a quantity of work, γ δA, is needed (where γ is the surface energy density of the liquid).
The hydrophobic effect represents the tendency of water to exclude non-polar molecules. The effect originates from the disruption of highly dynamic hydrogen bonds between molecules of liquid water. Polar chemical groups, such as OH group in methanol do not cause the hydrophobic effect.
[1] [2] The word hydrophobic literally means "water-fearing", and it describes the segregation of water and nonpolar substances, which maximizes the entropy of water and minimizes the area of contact between water and nonpolar molecules. In terms of thermodynamics, the hydrophobic effect is the free energy change of water surrounding a solute. [3]
Water on hydrophobic surfaces will exhibit a high contact angle. Examples of hydrophobic molecules include the alkanes, oils, fats, and greasy substances in general. Hydrophobic materials are used for oil removal from water, the management of oil spills, and chemical separation processes to remove non-polar substances from polar compounds. [2]