What Is Polyethylene Glycol?

Polyethylene glycol (PEG) is a general term for ethylene glycol polymers containing α,ω-dihydroxyl groups at both ends. Also known as polyethylene oxide (PEO) or polyoxyethylene (POE), it is a non-irritating polymer. slightly bitter in taste, highly water-soluble, and highly compatible with many organic compounds. It possesses excellent lubricity, moisturizing properties, dispersibility, and adhesion, and can be used as an antistatic agent and softener, among other applications. It is widely used in industries such as cosmetics, pharmaceuticals, synthetic fibers, rubber, plastics, papermaking, paints, electroplating, pesticides, metal processing, and food processing; It is also a food additive, commonly used for coating candies and chocolate products, and can serve as a film-forming agent, dispersant, or binder in food; it is used to modify drug proteins, protect drug molecules, extend their half-life, or act as a linking chain.

Chemical Properties

Polyethylene glycol exhibits varying properties depending on its molecular weight, ranging from a colorless, odorless, viscous liquid to a waxy solid. It is soluble in water, ethanol, and many other organic solvents; has low vapor pressure; and is stable to heat, acids, and bases. It possesses good hygroscopicity, lubricity, and adhesive properties. It is non-toxic and non-irritating.
Under normal conditions, polyethylene glycol is very stable; however, at temperatures of 120°C or higher, it reacts with oxygen in the air. In an inert atmosphere (such as nitrogen or carbon dioxide), it remains unchanged even when heated to 200–240°C; thermal cracking occurs when the temperature rises to 300°C. The addition of antioxidants, such as 0.25%–0.5% by mass of phenothiazine, can improve its chemical stability. All of its decomposition products are volatile and do not form hard crusts or slimy precipitates.
Polyethylene glycol is a polymer derived from the hydrolysis of ethylene oxide; it is non-toxic and non-irritating and is widely used in various pharmaceutical formulations. Low-molecular-weight polyethylene glycols are relatively more toxic; overall, however, the toxicity of diols is quite low. Topical application of polyethylene glycol, particularly when administered to mucous membranes, can cause stinging pain.
As molecular weight increases, water solubility, vapor pressure, water absorption, and solubility in organic solvents decrease accordingly, while the freezing point, relative density, flash point, and viscosity increase. It is thermally stable, reacts with few chemicals, and does not undergo hydrolysis..

Properties

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Risk and Safety Statements

What Is Polyethylene Glycol Used For?

Polyethylene glycol and polyethylene glycol fatty acid esters are widely used in the cosmetics and pharmaceutical industries. This is because polyethylene glycol possesses many excellent properties, including water solubility, non-volatility, physiological inertness, mildness, lubricity, and the ability to moisturize and soften the skin, providing a pleasant after-feel. PEGs of different molecular weight grades can be selected to alter a product’s viscosity, hygroscopicity, and texture. Low-molecular-weight PEGs (Mr < 2000) are suitable as wetting agents and thickening agents in creams, lotions, toothpaste, and shaving cream, as well as in leave-in hair care products, where they impart a silky luster to the hair. High-molecular-weight polyethylene glycol (Mr > 2000) is suitable for lipsticks, deodorant sticks, soaps, shaving soaps, foundations, and cosmetic products. In cleansers, polyethylene glycol is also used as a suspending agent and thickener. In the pharmaceutical industry, it serves as a base for ointments, emulsions, creams, washes, and suppositories.
Polyethylene glycol is widely used in various drug formulations, such as injectables, topical preparations, ophthalmic preparations, and oral and rectal preparations. Solid-grade polyethylene glycol can be added to liquid polyethylene glycol to adjust viscosity for use in topical ointments; polyethylene glycol mixtures can be used as a base for suppositories; aqueous solutions of polyethylene glycol can serve as suspending agents or be used to adjust the viscosity of other suspension media; when combined with other emulsifiers, polyethylene glycol enhances the stability of emulsions. In addition, polyethylene glycol is used as a film coating agent, a tablet lubricant, and a controlled-release material, among other applications.