polyoxyethylene

Polyoxyethylene, commonly referred to as polyethylene glycol (PEG) or poly(ethylene oxide) (PEO), is a synthetic polymer composed of repeating ethylene oxide units linked by ether bonds. Its general structure is HO-(O-CH2-CH2)n-H, with hydroxyl end groups that confer water solubility and low reactivity. The term polyoxyethylene also encompasses a family of related polymers with varying degrees of polymerization and molecular weight.

Production and properties: Polyoxyethylene is produced by the ring-opening polymerization of ethylene oxide using an initiator such as water, an alcohol, or another glycol. The resulting polymer covers a broad range of molecular weights, from a few hundred to several hundred thousand daltons, which influences viscosity, solubility, and physical behavior. It is typically a nonionic polyether with low toxicity and good water miscibility. The properties of PEG/PEO depend on chain length and end groups, allowing tailoring for specific applications.

Applications: In pharmaceuticals and biomedicine, PEG is widely used as an excipient, solvent, plasticizer, tablet binder, and osmotic laxative (e.g., PEG 3350). It is also employed to conjugate biomolecules in PEGylation to improve stability and circulation time. In cosmetics, PEGs act as thickening agents, emollients, and solvent carriers. Industrially, they serve as lubricants, anti-foaming agents, surfactants, and components in coolant formulations. PEG chains are common as polyether segments in nonionic surfactants such as polyoxyethylene alkyl ethers.

Safety and regulation: PEGs are generally regarded as safe for many uses but can cause hypersensitivity in rare cases and may be contaminated with impurities if not properly purified. They are minimally absorbed from the GI tract and are excreted largely unchanged in urine. Environmental and regulatory considerations vary with molecular weight and formulation.