Poly(ethylene glycol) (PEG) is a biocompatible inert synthetic polymer with repeating units of ether oxygen (-CH₂-CH₂-O-). It can be synthesized via anionic polymerization of ethylene oxide. It is extensively used in biological and medical applications due to its non-immunogenicity and high water solubility.

PEG can be used to functionalize magnetite nanoparticles. The coating of the magnetic core with PEG provides good stabilization while maintaining the magnetic properties of the nanoparticles.

It can be used to modify the surface of photocatalytic TiO₂ nanopowder for its application in self-cleaning paints. PEG-coated TiO₂ nanopowder can be prepared under mild conditions and show excellent colloidal stability.

It can be used as a cross-linker to prepare poly(N-isopropylacrylamide) based thermosensitive injectable hydrogels. The addition of PEG improves the chemical and mechanical properties of hydrogel and prevents it from dissolving in the swelling medium. Owing to their biocompatibility and biodegradability, these hydrogels are widely used for biomedical applications.

Molecular weight: M_n 3,015-3,685