hydrofobe

Hydrofobe, or hydrophobic substances, are chemical species that repel water and do not dissolve readily in it. The term is commonly used in chemistry to describe nonpolar or weakly polar molecules and surfaces. In English, the standard term is hydrophobic; in French and some other languages, hydrofobe is used.

Hydrophobicity results from the lack of favorable interactions with water, such as hydrogen bonding or strong dipole moments. Nonpolar molecules experience only weak London dispersion forces, which makes them minimize contact with water by aggregating or separating from the aqueous phase. On surfaces, hydrophobicity is often quantified by the water contact angle; angles greater than 90 degrees indicate hydrophobic surfaces. Solubility in water and partition coefficients (log P) are common indicators of hydrophobic character.

Typical hydrophobic substances include alkanes, oils, fats, waxes, and many plastics. In biology, hydrophobic interactions drive the folding of proteins and the formation of cell membranes, where nonpolar lipid tails face the interior. Hydrophobic residues in proteins tend to group away from water, helping stabilize three-dimensional structure.

Applications and implications of hydrophobic materials include water-repellent coatings, anti-wetting surfaces, and the design of drugs and materials with limited water solubility. In environmental science, hydrophobic pollutants can accumulate in sediments and within organisms, influencing transport, persistence, and remediation strategies.