Poly(ethylene glycol) and Poly(ethylene oxide)

Poly(ethylene glycol) (PEG), otherwise known as poly(oxyethylene) or poly(ethylene oxide) (PEO), is a synthetic polyether that is readily available in a range of molecular weights. Materials with Mw <100,000 are usually called PEGs, while higher molecular weight polymers are classified as PEOs. These polymers are amphiphilic and soluble in water as well as in many organic solvents (e.g., methylene chloride, ethanol, toluene, acetone, and chloroform). Low molecular weight (Mw <1,000) PEGs are viscous and colorless liquids, while higher molecular weight PEGs are waxy, white solids with melting points proportional to their molecular weights to an upper limit of about 67 °C.1

PEG has been found to be nontoxic and is approved by the FDA for use as excipients or as a carrier in different pharmaceutical formulations, foods, and cosmetics.2 Most PEGs with Mw <1,000 are rapidly removed from the body unaltered with clearance rates inversely proportional to polymer molecular weight.3 This property, combined with the availability of PEGs with a wide range of end-functions, contributes to the wide use of PEGs in biomedical research: drug delivery, tissue engineering scaffolds, surface fucntionalization, and many other applications.4 This section lists PEG and PEO polymers classified by end-group functions. Note that methyl-terminated PEGs are classified as Monofunctional PEGs.

References
1. Bailey, F.E.; Koleske, J.V. Poly(Ehtylene Oxide), Academic Press, New York, (1976).
2. Fuertges, F.; Abuchowski, A. Journal of Controlled Release, 11, 139 (1990).
3. Working, P.K. et al., Safety of poly(ethylene glycol) and poly(ethylene glycol) derivatives. In Harris, J.M., and Zalipsky, S. (eds), Polyethylene Glycol Chemistry and Biological Applications, American Chemical Society, Washington DC, p. 45 (1997).
4. Mahato, R.I. Biomaterials for delivery and targeting of proteins and nucleic acids, CRC Press (2005) (Ald. Cat. No. Z705102).