Hydrogel

A hydrogel is a water-swollen network of polymer chains. Its cross-linked structure holds water while maintaining a distinct shape.

Polymer network: A connected structure of polymer chains joined at multiple points. Hydrogels hold water within this connected chain structure.
Hydrophilicity: The tendency of a substance to interact favorably with water. Hydrophilic polymer groups attract and retain water inside the network.
Contact lens: A thin lens placed on the eye's surface to correct vision or serve another optical purpose. Hydrogel materials can provide soft lenses that hold water against the eye.
Hydrocolloid: A substance that forms a colloidal mixture with water, often thickening or gelling it. Hydrocolloids may thicken water without forming the persistent cross-linked network characteristic of a hydrogel.
Cross-link: A bond or molecular connection joining separate polymer chains. Cross-links prevent dissolved chains from separating and help a swollen gel keep its shape.
Hydrogen bond: An attractive interaction involving a hydrogen atom bonded to an electronegative atom. Hydrogen bonding helps water interact with many hydrogel polymers.
Wound dressing: A covering applied to a wound to protect it and support healing. Hydrogel dressings maintain a moist wound environment and can absorb exudate.
Aerogel: A highly porous solid formed by replacing the liquid in a gel with gas while preserving its network. Aerogels retain a porous framework but contain gas rather than water in their pores.
Swelling: An increase in a material's volume as it takes up a fluid. Water uptake expands a hydrogel until polymer elasticity and osmotic forces balance.
Polymerization: A chemical process that joins small molecules into polymer chains or networks. Hydrogel polymers are made or assembled through polymerization and related network-forming reactions.

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