Chemically cross-linked polymers hydrogels

Hydrogels are physically or chemically cross-linked polymer networks swollen with large amounts of water. Due to their crosslinked nature, these gels do not dissolve in aqueous media but contain an enormous amount of solvated water molecules within the entangled polymer chain matrix. Hydrogel properties are reviewed elsewhere in this book. This chapter is dedicated to a unique hydrogel family that responds to... 

A nanogel is a nanosized hydrogel made of physically or chemically cross-linked polymers that are water-soluble. A nanogel that is composed of responsive polymers may change volume depending on the external environment [23]. 

The term nanogel or microgel usually defines aqueous dispersions of hydrogel particles or colloidal networks formed by physically or chemically cross-linked polymer chains of nano-or microscale size. 

Figure 2.1 Schematic diagram of the two main classes of hydrogels produced by chemically cross-linked polymers (a) and (macro) molecules forming noncovalent structures (b).

Gel—A chemically or physically cross-linked polymer that is highly swollen with solvent. Called a hydrogel if the solvent is water (e.g., gelatin). 

Fig. 1 Representative methods of hydrogel formation. (A) Chemically cross-linked hydrogels are prepared from monomers, oligomers, or polymers in the presence of cross-linking agents. The chemical cross-linking proceeds via radical polymerization or polycondensation reaction. (B) Physically cross-linked hydrogels can be formed by ionic interactions, hydrophobic interaction, or hydrogen bonding.

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