polyethyleneglycol

Polyethylene glycol (PEG) is a polyether compound with the repeating unit −O−CH2−CH2− that forms HO−(CH2−CH2−O)n−H when end groups are hydrogen. It is produced by polymerizing ethylene oxide and water, yielding a broad distribution of chain lengths. PEGs are available across a wide range of molecular weights, from a few hundred to several million daltons, which determines their physical form, solubility, and viscosity. Lower molecular weight grades are typically liquids or waxy solids, while higher grades are pastes or solids.

Properties of PEG include high water solubility, chemical stability, low toxicity, non-ionic character, and biocompatibility. The polymers are usually described by their weight-average molecular weight (for example PEG 3350, PEG 400, PEG 1000). They are commonly sold as mixtures of chain lengths with hydroxyl end groups, HO-PEG-OH, and can be end-capped or modified to create derivatives.

Uses of PEG span pharmaceutical, cosmetic, and industrial sectors. In medicines, PEG serves as an excipient, solvent, plasticizer, or binder, and PEGylation—the covalent attachment of PEG chains to drugs or biomolecules—improves solubility, pharmacokinetics, and reduces immunogenicity. PEG 3350 is a well-known osmotic laxative. In cosmetics, PEGs act as thickeners, humectants, and emulsifiers. Industrially, they function as lubricants, surfactants, phase-transfer catalysts, and carriers for active ingredients.

Safety and regulation: PEGs are widely used and generally regarded as safe for many applications, though high-dose ingestion can cause electrolyte disturbances. They are poorly absorbed from the GI tract and exhibit low immunogenicity. Environmental behavior varies with molecular weight; PEGs are not readily biodegradable and production standards aim to limit residual solvents such as 1,4-dioxane.