geliytymisen

Geliytyminen, or gelation in Finnish usage, refers to the process by which a liquid sol transitions into a gel—a semi-solid, three-dimensional network that immobilizes a substantial portion of the solvent. This transformation can be driven by physical interactions or chemical crosslinking, and it results in a material that exhibits solid-like mechanical properties while retaining some liquid content.

There are two broad mechanisms. Physical gelation arises from non-covalent interactions such as hydrogen bonding, ionic interactions, or entanglements, often producing thermo-reversible gels that form or dissolve with changes in temperature, pH, or salt concentration. Chemical gelation involves covalent crosslinking, typically through polymerization or crosslinking agents, yielding more persistent networks that are less sensitive to environmental changes.

Common systems include natural polymers like gelatin, agar, alginates crosslinked with calcium ions, and pectin gels; synthetic networks such as polyacrylamide or polyurethane gels. Gel points are studied using rheological measurements, where the storage modulus (G') and loss modulus (G'') indicate the emergence of a connected network. Other indicators include swelling behavior and network mesh size.

Applications are wide and include the food industry (textured gels and desserts), biomedicine (tissue engineering scaffolds, drug delivery hydrogels), cosmetics, and industrial materials (soft sensors and elastomeric foams). Safety and biocompatibility are important considerations, particularly for medical uses, with natural polymers often favored for their lower toxicity.

See also: gel, hydrogel, crosslinking, polymerization, rheology. Geliytymisen is a fundamental concept in polymer science and materials science.