Hydrophilic

Hydrophilic is a property of substances that readily interact with water through hydrogen bonding or electrostatic interactions. The term derives from Greek hydro- water and philos loving. Hydrophilic compounds are typically polar or ionic; they dissolve well in water and can form hydration shells around ions or polar molecules. It contrasts with hydrophobic substances, which repel water due to nonpolar character.

Mechanism and characteristics: Water molecules form hydrogen bonds with hydrophilic functional groups such as hydroxyl, carbonyl, amine, and carboxyl groups, leading to solvation and increased affinity for aqueous environments. Surface hydrophilicity reduces the contact angle of a water droplet, enhancing wettability. In polymers and materials, hydrophilicity can be modulated by chemical composition and surface treatments.

Examples: Sugars like glucose, salts such as sodium chloride, amino acids, and many alcohols are hydrophilic. Materials including cellulose, silica, poly(vinyl alcohol), and hydrogels exhibit hydrophilicity.

Applications: Hydrophilic properties are exploited in chromatography (hydrophilic interaction chromatography, HILIC), drug delivery, tissue engineering, contact lenses, and coatings to improve dispersion, lubrication, and biocompatibility.

In biology, many proteins expose hydrophilic residues on their surfaces, and cell membranes contain hydrophilic polar heads that interface with the aqueous exterior and interior. Hydrophilicity often influences solubility, transport, and interactions in chemical and biological systems.