Hydrophob

Hydrophob (often written hydrophobic in English) describes the property of repelling water or failing to mix with water. It applies to substances, surfaces, or molecular regions that are nonpolar and do not form favorable interactions with the polar water molecules. The term originates from Greek roots meaning water and fear, reflecting the tendency of hydrophobic materials to avoid contact with water.

Hydrophobicity is usually contrasted with hydrophilicity, the tendency to attract and interact with water. Many molecules are amphiphilic, possessing both hydrophobic and hydrophilic parts, which enables them to form organized structures such as micelles or lipid bilayers in aqueous environments.

Biological systems highlight the importance of hydrophobic interactions. The hydrophobic effect is a major driving force in protein folding and membrane assembly: nonpolar amino acid residues tend to be buried in the interior of proteins, and fatty acid tails assemble into a hydrophobic core inside lipid membranes, excluding water. These interactions influence the structure, stability, and function of biomolecules.

Measurement and surfaces: hydrophobicity can be assessed by contact angle measurements, where a contact angle greater than 90 degrees indicates a hydrophobic surface. Highly hydrophobic or superhydrophobic surfaces may show contact angles above 150 degrees and exhibit low adhesion and self-cleaning properties under certain conditions.

Applications and examples include hydrophobic materials such as hydrocarbons and fluoropolymers, and coatings or textiles designed to resist wetting. In chemistry, nonpolar solvents like hexane are immiscible with water. Hydrophobic principles are exploited in oil-water separation, waterproofing, anti-icing, and various surface engineering technologies.