Polyethylene glycol

Polyethylene glycol (PEG) and polyethylene oxide (PEO) are viscosity) due to chain length effects, their chemical properties are nearly identical. Derivatives of PEG and PEO are in common use, the most common derivative being the methyl ether (methoxypoly (ethylene glycol)), abbreviated mPEG.

Their melting points vary depending on the Formula Weight of the polymer. PEG or PEO has the following structure:

HO-(CH₂-O-CH₂)_n-H

The numbers that are often included in the names of PEGs and PEOs indicate their average molecular weights, e.g. a PEG with n=80 would have an average molecular weight of approximately 3500 mass spectroscopy.

PEGylation is the act of covalently coupling a PEG structure to another larger molecule, for example, a therapeutic protein (which is then referred to as PEGylated). PEGylated interferon alfa-2a or -2b is a commonly used injectable treatment for Hepatitis C infection.

PEG is soluble in water, surfactants.

Production

Poly (ethylene glycol) is produced by the interaction of polydispersity (narrow molecular weight distribution). Polymer chain length depends on the ratio of reactants.

HOCH₂CH₂OH + n(CH₂CH₂O) → HO(CH₂CH₂O)_n+1H

Depending on the catalyst type, the mechanism of polymerization can be cationic or anionic. The anionic mechanism is preferable because it allows one to obtain PEG with a low Polymerization of ethylene oxide is an exothermic process. Overheating or contaminating ethylene oxide with catalysts such as alkalis or metal oxides can lead to runaway polymerization which can end with an explosion after few hours.

Polyethylene oxide or high-molecular polyethylene glycol is synthesized by suspension polymerization. It is necessary to hold the growing polymer chain in solution in the course of the polycondensation process. The reaction is catalyzed by magnesium-, aluminium- or calcium-organoelement compounds. To prevent dimethylglyoxime are used.

Alkali catalysts such as sodium carbonate Na₂CO₃ are used to prepare low-molecular polyethylene glycol.

Clinical uses

Polyethylene glycol has a low toxicity^[2] and is used in a variety of products. It is the basis of a number of laxatives (e.g. tegaserod.^[5]

Research for New Clinical Uses

• High-molecular weight PEG, e.g., PEG 8000, is a strikingly potent dietary preventive agent against colorectal cancer in animal models.^[6]

The Chemoprevention Database shows it is the most effective agent to suppress chemical carcinogenesis in rats. Cancer prevention in humans has not yet been tested in clinical trials.

• The injection of PEG 2000 into the bloodstream of guinea pigs after spinal cord injury leads to rapid recovery through molecular repair of nerve membranes.^[7] The effect of this treatment to prevent paraplegia in humans after an accident is not known yet.
• Research is being done in the use of PEG to mask antigens on red blood cells. Various research institutes have reported that using PEG can mask antigens without damaging the functions and shape of the cell.

PEG is being used in the repair of motor neurons damaged in crush or laceration incidence in vivo and in vitro. When coupled with melatonin, 75% of damaged sciatic nerves were rendered viable.^[8]

Other uses

PEG is used in a number of toothpastes as a dispersant; it binds water and helps keep silicone, another elastomer.

Since PEG is a flexible, water-soluble polymer, it can be used to create very high osmotic pressures (tens of atmospheres). It also is unlikely to have specific interactions with biological chemicals. These properties make PEG one of the most useful molecules for applying osmotic pressure in biochemistry experiments, particularly when using the osmotic stress technique.^{[citation needed]}

PEO (poly (ethylene oxide)) can serve as the separator and lithium ion battery technologies.

When working with phenol in a laboratory situation, PEG 300 can be used on phenol skin burns to deactivate any residual phenol.

Poly (ethylene glycol) is also commonly used as a polar stationary phase for gas chromatography, as well as a heat transfer fluid in electronic testers.

PEG is included in many or all formulations of the soft drink Dr Pepper, purportedly as an anti-foaming agent.

PEG has also been used to preserve objects which have been salvaged from underwater, as was the case with the warship Vasa in Stockholm.^[11] It replaces water in wooden objects, which makes the wood dimensionally stable and prevents warping or shrinking of the wood.

PEG is often seen (as a side effect) in mass spectrometry experiments with characteristic fragmentation patterns.

In the field of microbiology, PEG precipitation is used to concentrate viruses.

PEG is also used in lubricant eye drops. PEG derivatives such as surfactants.

Dimethyl ethers of PEG are the key ingredient of hydrogen sulfide from the gas waste stream.

References

See also

• PEGylation