Hydrofiilisyydestä

Hydrophilicity describes the affinity of a substance for water, meaning the substance tends to attract and dissolve in water molecules. The term comes from Greek roots hydro (water) and philia (love). Materials that are hydrophilic are often capable of forming hydrogen bonds with water, causing them to absorb or spread water across their surface. Hydrophobic substances, by contrast, repel water and typically cannot form such hydrogen bonds.

A useful quantitative measure of hydrophilicity is the contact angle, the angle formed at the contact point between a droplet of water and a solid surface. Surfaces with contact angles below 90 degrees are considered hydrophilic, while those above 90 degrees are hydrophobic. Contact angle can be measured with goniometry, allowing researchers to compare materials or treat surfaces with coatings to adjust their wettability.

Examples of hydrophilic materials include cellulose, gelatin, and most proteins, which contain polar groups such as hydroxyl, amine, or carboxyl groups. Many synthetic polymers, like polyethylene glycol or polyvinyl alcohol, are also designed to be hydrophilic for biomedical applications such as drug delivery, tissue engineering, and wound dressings. Hydrophilicity is crucial for processes like filtration, catalysis, and sensor performance, where easy access of water to active sites enhances efficiency.

In environmental contexts, hydrophilic surfaces help in water retention and soil moisture dynamics. In contrast, hydrophobic coatings are often employed to reduce corrosion or to create self-cleaning surfaces, demonstrating the practical importance of controlling hydrophilicity.