Physicochemical properties of polyethylene glycol(PEG)



Polyethylene glycol is a high molecular polymer, the chemical formula is HO(CH2CH2O)nH, non-irritating, slightly bitter taste, good water solubility, and good compatibility with many organic components. It has excellent lubricity, moisture retention, dispersibility and adhesion, and can be used as an antistatic agent and softener. It is widely used in processing and other industries.

Physicochemical Properties:

Melting point: 64-66℃
Boiling point: >250℃
Density: 1.27 g/mL at 25℃
Vapor Density: >1 (vs air)
Refractive index: n=1.469
Flash point: 270℃
Storage conditions: 2-8℃
Solubility: H2O: 50 mg/mL, clear, colorless
Form: viscous liquid→waxy solid
Sensitivity: Hygroscopic
Merck: 147568
Stability: Stable, will be oxidized by strong oxidants
NIST Chemical Substance Information: Polyethylene glycol(25322-68-3)
EPA Chemical Substance Information: Poly(oxy-1,2-ethanediyl), (25322-68-3)

Chemical Structure:

HO(CH2CH2O)nH is formed by the stepwise addition polymerization of ethylene oxide and water or ethylene glycol.

Chemical Properties:

The properties vary according to the molecular weight, from colorless and odorless viscous liquid to waxy solid. Those with a molecular weight of 200 to 600 are liquid at room temperature, and those with a molecular weight of more than 600 gradually become semi-solid. With the difference of the average molecular weight, the properties are also different. From colorless and odorless viscous liquid to waxy solid. As the molecular weight increases, its hygroscopic ability decreases accordingly. This product is soluble in water, ethanol and many other organic solvents. Low vapor pressure, stable to heat, acid and alkali. Does not work with many chemicals. It has good hygroscopicity, lubricity and adhesion. Non-toxic and non-irritating. The average molecular weight is 300, n=5~5.75, the melting point is -15~8℃, and the relative density is 1.124~1.130. The average molecular weight is 600, n=12~13, the melting point is 20~25℃, the flash point is 246℃, and the relative density is 1.13 (20℃). The average molecular weight is 4000, n=70~85, and the melting point is 53~56℃.
Under normal conditions, polyethylene glycol is very stable, but it can interact with oxygen in the air at temperatures of 120°C or higher. In an inert atmosphere (such as nitrogen and carbon dioxide), it will not change even if it is heated to 200 to 240 °C, and thermal cracking will occur when the temperature rises to 300 °C. Adding antioxidants, such as phenothiazine with a mass fraction of 0.25% to 0.5%, can improve its chemical stability. Any of its decomposition products are volatile and do not form crusty or slimy deposits.
Polyethylene glycol is a polymer of ethylene oxide hydrolysis product, which is non-toxic and non-irritating, and is widely used in various pharmaceutical preparations. Low-molecular-weight polyethylene glycols are relatively toxic, and on the whole, the toxicity of glycols is quite low. Topical application of polyethylene glycol, especially mucosal administration, can cause irritating pain. In topical lotions, this product increases skin flexibility and provides a moisturizing effect similar to glycerin. Diarrhea may occur with large oral doses. In injections, the maximum concentration of polyethylene glycol 300 is about 30% (V/V), and hemolysis can occur at concentrations greater than 40% (V/V).
Addition polymer of polyethylene oxide and water. Those whose molecular weight is below 700 are colorless, odorless, non-volatile, viscous liquid at 20°C with slight water absorption. Those with a molecular weight between 700 and 900 are semi-solids. Those with a molecular weight of 1000 and above are light white waxy solids or flake-like paraffins or flowable powders. Miscible in water, soluble in many organic solvents, such as alcohols, ketones, chloroform, glycerides and aromatic hydrocarbons; insoluble in most aliphatic hydrocarbons and ethers.
With the increase of molecular weight, its water solubility, vapor pressure, water absorption and solubility of organic solvents decrease correspondingly, while freezing point, relative density, flash point and viscosity increase correspondingly. Thermally stable, does not work with many chemicals, does not hydrolyze.


Polyethylene glycol is a non-ionic water-soluble polymer, which can be compatible with many substances with high polarity, but has poor compatibility with low-polar substances, and polyethylene glycol with low relative molecular mass has good compatibility. Polyethylene glycol is compatible or partially compatible with oxidized starch, nitrocellulose, polyvinyl acetate and zein. Immiscible with beeswax, castor oil, gelatin, gum arabic, mineral oil, olive oil and paraffin.


  1. Liquid and solid grades of polyethylene glycol are incompatible with certain pigments;
  2. Can reduce the activity of antibiotics, especially penicillin and bacitracin;
  3. The preservatives of hydroxyphenyl esters can weaken the preservative effect due to the complexation of polyethylene glycol;
  4. Phenol, tannic acid, salicylic acid can soften and liquefy it;
  5. Sulfonamides and dithranol can change color with their action;
  6. Compatibility with sorbitol can produce precipitation.