Polyethylene glycol (PEG; ) is a
polyether
In organic chemistry, ethers are a class of compounds that contain an ether group—an oxygen atom connected to two alkyl or aryl groups. They have the general formula , where R and R′ represent the alkyl or aryl groups. Ethers can again be ...
compound derived from
petroleum
Petroleum, also known as crude oil, or simply oil, is a naturally occurring yellowish-black liquid mixture of mainly hydrocarbons, and is found in geological formations. The name ''petroleum'' covers both naturally occurring unprocessed crud ...
with many applications, from industrial manufacturing to
medicine
Medicine is the science and practice of caring for a patient, managing the diagnosis, prognosis, prevention, treatment, palliation of their injury or disease, and promoting their health. Medicine encompasses a variety of health care pr ...
. PEG is also known as polyethylene oxide (PEO) or polyoxyethylene (POE), depending on its
molecular weight
A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bioch ...
. The structure of PEG is commonly expressed as H−(O−CH
2−CH
2)
n−OH.
Uses
Medical uses
* Pharmaceutical-grade PEG is used as an
excipient
An excipient is a substance formulated alongside the active ingredient of a medication, included for the purpose of long-term stabilization, bulking up solid formulations that contain potent active ingredients in small amounts (thus often referred ...
in many pharmaceutical products, in oral, topical, and parenteral dosage forms.
* PEG is the basis of a number of
laxative
Laxatives, purgatives, or aperients are substances that loosen stools and increase bowel movements. They are used to treat and prevent constipation.
Laxatives vary as to how they work and the side effects they may have. Certain stimulant, lubri ...
s (as ''MiraLax'').
Whole bowel irrigation
Whole bowel irrigation (WBI) is a medical process involving the rapid administration of large volumes of an osmotically balanced macrogol solution (GoLYTELY, CoLyte), either orally or via a nasogastric tube, to flush out the entire gastrointesti ...
with polyethylene glycol and added
electrolytes is used for bowel preparation before
surgery or
colonoscopy.
* PEG is used in medicines for treating disimpaction and maintenance therapy for children with constipation.
* When attached to various protein
medication
A medication (also called medicament, medicine, pharmaceutical drug, medicinal drug or simply drug) is a drug used to diagnose, cure, treat, or prevent disease. Drug therapy ( pharmacotherapy) is an important part of the medical field and ...
s or drug carriers, polyethylene glycol of suitable length slows down their clearance from the blood.
* The possibility that PEG could be used to fuse
axon
An axon (from Greek ἄξων ''áxōn'', axis), or nerve fiber (or nerve fibre: see spelling differences), is a long, slender projection of a nerve cell, or neuron, in vertebrates, that typically conducts electrical impulses known as action p ...
s is being explored by researchers studying
peripheral nerve
A nerve is an enclosed, cable-like bundle of nerve fibers (called axons) in the peripheral nervous system.
A nerve transmits electrical impulses. It is the basic unit of the peripheral nervous system. A nerve provides a common pathway for the e ...
and
spinal cord injury
A spinal cord injury (SCI) is damage to the spinal cord that causes temporary or permanent changes in its function. Symptoms may include loss of muscle function, sensation, or autonomic function in the parts of the body served by the spinal cor ...
.
*An example of PEG
hydrogels (see
Biological uses
Biology is the scientific study of life. It is a natural science with a broad scope but has several unifying themes that tie it together as a single, coherent field. For instance, all organisms are made up of cells that process hereditary i ...
section) in a therapeutic has been theorized by Ma et al. They propose using the hydrogel to address
periodontitis
Periodontal disease, also known as gum disease, is a set of inflammatory conditions affecting the tissues surrounding the teeth. In its early stage, called gingivitis, the gums become swollen and red and may bleed. It is considered the main cau ...
(gum disease) by encapsulating
stem cells in the gel that promote healing in the gums. The gel and encapsulated stem cells was to be injected to the site of disease and crosslinked to create the microenvironment required for the stem cells to function.
*
PEGylation
PEGylation (or pegylation) is the process of both covalent and non-covalent attachment or amalgamation of polyethylene glycol (PEG, in pharmacy called macrogol) polymer chains to molecules and macrostructures, such as a drug, therapeutic protein ...
of
adenoviruses
Adenoviruses (members of the family ''Adenoviridae'') are medium-sized (90–100 nm), nonenveloped (without an outer lipid bilayer) viruses with an icosahedral nucleocapsid containing a double-stranded DNA genome. Their name derives from the ...
for
gene therapy
Gene therapy is a medical field which focuses on the genetic modification of cells to produce a therapeutic effect or the treatment of disease by repairing or reconstructing defective genetic material. The first attempt at modifying human DN ...
can help prevent adverse reactions due to pre-existing adenovirus immunity.
* A
PEGylated
PEGylation (or pegylation) is the process of both covalent and non-covalent attachment or amalgamation of polyethylene glycol (PEG, in pharmacy called macrogol) polymer chains to molecules and macrostructures, such as a drug, therapeutic protein ...
lipid is used as an excipient in both the
Moderna
Moderna, Inc. ( ) is an American pharmaceutical and biotechnology company based in Cambridge, Massachusetts that focuses on RNA therapeutics, primarily mRNA vaccines. These vaccines use a copy of a molecule called messenger RNA (mRNA) to pro ...
and
Pfizer–BioNTech vaccines for
SARS-CoV-2
Severe acute respiratory syndrome coronavirus 2 (SARS‑CoV‑2) is a strain of coronavirus that causes COVID-19 (coronavirus disease 2019), the respiratory illness responsible for the ongoing COVID-19 pandemic. The virus previously had a ...
. Both
RNA vaccines
An mRNA vaccine is a type of vaccine that uses a copy of a molecule called messenger RNA (mRNA) to produce an immune response. The vaccine delivers molecules of antigen-encoding mRNA into immune cells, which use the designed mRNA as a blueprin ...
consist of
messenger RNA, or mRNA, encased in a bubble of oily molecules called
lipids
Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include ...
. Proprietary lipid technology is used for each. In both vaccines, the bubbles are coated with a stabilizing molecule of polyethylene glycol. As of December 2020 there is some concern that PEG could trigger allergic reaction,
and in fact allergic reactions are the driver for both the United Kingdom and Canadian regulators to issue an advisory, noting that: two "individuals in the U.K. ... were treated and have recovered" from
anaphylactic
Anaphylaxis is a serious, potentially fatal allergic reaction and medical emergency that is rapid in onset and requires immediate medical attention regardless of use of emergency medication on site. It typically causes more than one of the follo ...
shock.
As of 18 December, the US CDC stated that in their jurisdiction six cases of "severe allergic reaction" had been recorded from more than 250,000 vaccinations, and of those six only one person had a "history of vaccination reactions".
Chemical uses
![MaryRose-conservation2](https://upload.wikimedia.org/wikipedia/commons/9/92/MaryRose-conservation2.jpg)
* Because PEG is a
hydrophilic
A hydrophile is a molecule or other molecular entity that is attracted to water molecules and tends to be dissolved by water.Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon'' Oxford: Clarendon Press.
In contrast, hydrophobes are ...
molecule, it has been used to passivate microscope glass slides for avoiding non-specific sticking of proteins in single-molecule fluorescence studies.
* Polyethylene glycol has a low toxicity and is used in a variety of products. The polymer is used as a lubricating coating for various surfaces in aqueous and non-aqueous environments.
* Since PEG is a flexible, water-soluble polymer, it can be used to create very high
osmotic pressures (on the order of 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
Biochemistry or biological chemistry is the study of chemical processes within and relating to living organisms. A sub-discipline of both chemistry and biology, biochemistry may be divided into three fields: structural biology, enzymology and ...
and
biomembrane
A biological membrane, biomembrane or cell membrane is a selectively permeable membrane that separates the interior of a cell from the external environment or creates intracellular compartments by serving as a boundary between one part of the c ...
s experiments, in particular when using the
osmotic stress technique.
* Polyethylene 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 frequently used to
preserve waterlogged wood and other organic artifacts that have been salvaged from underwater archaeological contexts, as was the case with the warship ''
Vasa'' in Stockholm, and similar cases. It replaces water in wooden objects, making the wood dimensionally stable and preventing warping or shrinking of the wood when it dries.
In addition, PEG is used when working with
green wood
Green wood is wood that has been recently cut and therefore has not had an opportunity to season (dry) by evaporation of the internal moisture. Green wood contains more moisture than seasoned wood, which has been dried through passage of time or ...
as a stabilizer, and to prevent shrinkage.
* PEG has been used to preserve the painted colors on
Terracotta Warriors
The Terracotta Army is a collection of terracotta sculptures depicting the armies of Qin Shi Huang, the first emperor of China. It is a form of funerary art buried with the emperor in 210–209 BCE with the purpose of protecting the emperor in ...
unearthed at a UNESCO World Heritage site in China. These painted artifacts were created during the
Qin Shi Huang
Qin Shi Huang (, ; 259–210 BC) was the founder of the Qin dynasty and the first emperor of a unified China. Rather than maintain the title of " king" ( ''wáng'') borne by the previous Shang and Zhou rulers, he ruled as the First Empero ...
(first emperor of China) era. Within 15 seconds of the terra-cotta pieces being unearthed during excavations, the lacquer beneath the paint begins to curl after being exposed to the dry
Xi'an
Xi'an ( , ; ; Chinese: ), frequently spelled as Xian and also known by other names, is the capital of Shaanxi Province. A sub-provincial city on the Guanzhong Plain, the city is the third most populous city in Western China, after Chongqi ...
air. The paint would subsequently flake off in about four minutes. The German Bavarian State Conservation Office developed a PEG preservative that when immediately applied to unearthed artifacts has aided in preserving the colors painted on the pieces of clay soldiers.
* PEG is often used (as an internal calibration compound) in
mass spectrometry experiments, with its characteristic fragmentation pattern allowing accurate and reproducible tuning.
* PEG derivatives, such as
narrow range ethoxylates, are used as
surfactants.
* PEG has been used as the hydrophilic block of
amphiphilic
An amphiphile (from the Greek αμφις amphis, both, and φιλíα philia, love, friendship), or amphipath, is a chemical compound possessing both hydrophilic (''water-loving'', polar) and lipophilic (''fat-loving'') properties. Such a compo ...
block
copolymers
In polymer chemistry, a copolymer is a polymer derived from more than one species of monomer. The polymerization of monomers into copolymers is called copolymerization. Copolymers obtained from the copolymerization of two monomer species are some ...
used to create some
polymersome In biotechnology, polymersomesDischer B M; Won Y Y; Ege D S; Lee J C; Bates F S; Discher D E; Hammer D A ''Science'' (1999), ''284''(5417), 1143-6. are a class of artificial vesicles, tiny hollow spheres that enclose a solution. Polymersomes are ma ...
s.
*PEG is a component of the propellent used in
UGM-133M Trident II Missiles, in service with the
United States Navy
The United States Navy (USN) is the maritime service branch of the United States Armed Forces and one of the eight uniformed services of the United States. It is the largest and most powerful navy in the world, with the estimated tonnage ...
.
Biological uses
* PEG can be modified and crosslinked into a
hydrogel and used to mimic the
extracellular matrix
In biology, the extracellular matrix (ECM), also called intercellular matrix, is a three-dimensional network consisting of extracellular macromolecules and minerals, such as collagen, enzymes, glycoproteins and hydroxyapatite that provide s ...
(ECM) environment for cell encapsulation and studies.
**An example study was done using PEG-diacrylate hydrogels to recreate vascular environments with the encapsulation of
endothelial
The endothelium is a single layer of squamous endothelial cells that line the interior surface of blood vessels and lymphatic vessels. The endothelium forms an interface between circulating blood or lymph in the lumen and the rest of the vessel ...
cells and
macrophages. This model furthered vascular disease modeling and isolated macrophage phenotype's effect on blood vessels.
*PEG is commonly used as a crowding agent in ''in vitro'' assays to mimic highly crowded cellular conditions.
* PEG is commonly used as a
precipitant
In an aqueous solution, precipitation is the process of transforming a dissolved substance into an insoluble solid from a super-saturated solution. The solid formed is called the precipitate. In case of an inorganic chemical reaction leading ...
for plasmid DNA isolation and
protein crystallization
Protein crystallization is the process of formation of a regular array of individual protein molecules stabilized by crystal contacts. If the crystal is sufficiently ordered, it will diffract. Some proteins naturally form crystalline arrays, li ...
.
X-ray diffraction of protein crystals can reveal the atomic structure of the proteins.
* PEG is used to fuse two different types of cells, most often B-cells and myelomas in order to create
hybridomas.
César Milstein and
Georges J. F. Köhler originated this technique, which they used for antibody production, winning a
Nobel Prize in Physiology or Medicine
The Nobel Prize in Physiology or Medicine is awarded yearly by the Nobel Assembly at the Karolinska Institute for outstanding discoveries in physiology or medicine. The Nobel Prize is not a single prize, but five separate prizes that, accord ...
in 1984.
* Polymer segments derived from PEG
polyols
In organic chemistry, a polyol is an organic compound containing multiple hydroxyl groups (). The term "polyol" can have slightly different meanings depending on whether it is used in food science or polymer chemistry. Polyols containing two, thr ...
impart flexibility to
polyurethane
Polyurethane (; often abbreviated PUR and PU) refers to a class of polymers composed of organic units joined by carbamate (urethane) links. In contrast to other common polymers such as polyethylene and polystyrene, polyurethane is produced from ...
s for applications such as elastomeric
fiber
Fiber or fibre (from la, fibra, links=no) is a natural or artificial substance that is significantly longer than it is wide. Fibers are often used in the manufacture of other materials. The strongest engineering materials often incorpora ...
s (
spandex
Spandex, Lycra, or elastane is a synthetic fiber known for its exceptional elasticity. It is a polyether-polyurea copolymer that was invented in 1958 by chemist Joseph Shivers at DuPont's Benger Laboratory in Waynesboro, Virginia, US.
The g ...
) and
foam
Foams are materials formed by trapping pockets of gas in a liquid or solid.
A bath sponge and the head on a glass of beer are examples of foams. In most foams, the volume of gas is large, with thin films of liquid or solid separating the ...
cushions.
* In
microbiology, PEG precipitation is used to concentrate viruses. PEG is also used to induce complete fusion (mixing of both inner and outer leaflets) in liposomes reconstituted ''in vitro''.
*
Gene therapy
Gene therapy is a medical field which focuses on the genetic modification of cells to produce a therapeutic effect or the treatment of disease by repairing or reconstructing defective genetic material. The first attempt at modifying human DN ...
vectors (such as viruses) can be PEG-coated to shield them from inactivation by the immune system and to de-target them from organs where they may build up and have a toxic effect. The size of the PEG polymer has been shown to be important, with larger polymers achieving the best immune protection.
* PEG is a component of
stable nucleic acid lipid particles (SNALPs) used to package
siRNA
Small interfering RNA (siRNA), sometimes known as short interfering RNA or silencing RNA, is a class of double-stranded RNA at first non-coding RNA molecules, typically 20-24 (normally 21) base pairs in length, similar to miRNA, and operating ...
for use ''in vivo''.
* In
blood banking
A blood bank is a center where blood gathered as a result of blood donation is stored and preserved for later use in blood transfusion. The term "blood bank" typically refers to a department of a hospital usually within a Clinical Pathology labora ...
, PEG is used as a
potentiator
In clinical terms, a potentiator is a reagent that enhances sensitization of an antigen. Potentiators are used in the clinical laboratory for performing blood banking procedures that require enhancement of agglutination to detect the presence of ...
to enhance detection of
antigen
In immunology, an antigen (Ag) is a molecule or molecular structure or any foreign particulate matter or a pollen grain that can bind to a specific antibody or T-cell receptor. The presence of antigens in the body may trigger an immune respons ...
s and
antibodies.
* When working with
phenol
Phenol (also called carbolic acid) is an aromatic organic compound with the molecular formula . It is a white crystalline solid that is volatile. The molecule consists of a phenyl group () bonded to a hydroxy group (). Mildly acidic, it ...
in a laboratory situation,
PEG 300
PEG or peg may refer to:
Devices
* Clothes peg, a fastener used to hang up clothes for drying
* Tent peg, a spike driven into the ground for holding a tent to the ground
* Tuning peg, used to hold a string in the pegbox of a stringed instrumen ...
can be used on phenol skin burns to deactivate any residual phenol.
* In
biophysics
Biophysics is an interdisciplinary science that applies approaches and methods traditionally used in physics to study biological phenomena. Biophysics covers all scales of biological organization, from molecular to organismic and populations. ...
, polyethylene glycols are the molecules of choice for the functioning ion channels diameter studies, because in aqueous solutions they have a spherical shape and can block ion channel conductance.
Commercial uses
* PEG is the basis of many
skin creams (as ''
cetomacrogol'') and
personal lubricant
Personal lubricants (colloquially termed lube) are specialized lubricants used during sexual acts, such as intercourse and masturbation, to reduce friction to or between the penis and vagina, anus or other body parts or applied to sex toys to red ...
s (frequently combined with
glycerin
Glycerol (), also called glycerine in British English and glycerin in American English, is a simple triol compound. It is a colorless, odorless, viscous liquid that is sweet-tasting and non-toxic. The glycerol backbone is found in lipids known ...
).
* PEG is used in a number of
toothpaste
Toothpaste is a paste or gel dentifrice used with a toothbrush to clean and maintain the aesthetics and health of teeth. Toothpaste is used to promote oral hygiene: it is an abrasive that aids in removing dental plaque and food from the teeth, ...
s
as a
dispersant
A dispersant or a dispersing agent is a substance, typically a surfactant, that is added to a suspension of solid or liquid particles in a liquid (such as a colloid or emulsion) to improve the separation of the particles and to prevent their se ...
. In this application, it binds water and helps keep
xanthan gum
Xanthan gum () is a polysaccharide with many industrial uses, including as a common food additive. It is an effective thickening agent, emulsifier, and stabilizer that prevents ingredients from separating. It can be produced from simple sugars ...
uniformly distributed throughout the toothpaste.
* PEG is also under investigation for use in
body armor, and in
tattoo
A tattoo is a form of body modification made by inserting tattoo ink, dyes, and/or pigments, either indelible or temporary, into the dermis layer of the skin to form a design. Tattoo artists create these designs using several tattooing ...
s to monitor
diabetes
Diabetes, also known as diabetes mellitus, is a group of metabolic disorders characterized by a high blood sugar level ( hyperglycemia) over a prolonged period of time. Symptoms often include frequent urination, increased thirst and increased ...
.
* In low-
molecular-weight
The molecular mass (''m'') is the mass of a given molecule: it is measured in daltons (Da or u). Different molecules of the same compound may have different molecular masses because they contain different isotopes of an element. The related quanti ...
formulations (e.g.
PEG 400
PEG 400 (polyethylene glycol 400) is a low-molecular-weight grade of polyethylene glycol. It is a clear, colorless, viscous liquid. Due in part to its low toxicity, PEG 400 is widely used in a variety of pharmaceutical formulations.
Chemical pr ...
), it is used in
Hewlett-Packard designjet
printers
Printer may refer to:
Technology
* Printer (publishing), a person or a company
* Printer (computing), a hardware device
* Optical printer for motion picture films
People
* Nariman Printer ( fl. c. 1940), Indian journalist and activist
* Jam ...
as an ink solvent and lubricant for the print heads.
* PEG is also used as an anti-foaming agent in food and drinks – its
INS number
The International Numbering System for Food Additives (INS) is a European-based naming system for food additives, aimed at providing a short designation of what may be a lengthy actual name."Class Names and the International Numbering System for Fo ...
is 1521 or E1521 in the EU.
Industrial uses
* A
nitrate ester
In chemistry, an ester is a compound derived from an oxoacid (organic or inorganic) in which at least one hydroxyl group () is replaced by an alkoxy group (), as in the substitution reaction of a carboxylic acid and an alcohol. Glycerides a ...
-plasticized polyethylene glycol (
NEPE-75) is used in
Trident II
A trident is a three- pronged spear. It is used for spear fishing and historically as a polearm.
The trident is the weapon of Poseidon, or Neptune, the God of the Sea in classical mythology. The trident may occasionally be held by other marine ...
submarine-launched ballistic missile solid rocket fuel.
* Dimethyl ethers of PEG are the key ingredient of
Selexol, a solvent used by
coal
Coal is a combustible black or brownish-black sedimentary rock, formed as rock strata called coal seams. Coal is mostly carbon with variable amounts of other elements, chiefly hydrogen, sulfur, oxygen, and nitrogen.
Coal is formed when ...
-burning,
integrated gasification combined cycle
integrated gasification combined cycle (IGCC) is a technology using a high pressure gasifier to turn coal and other carbon based fuels into pressurized gas—synthesis gas (syngas). It can then remove impurities from the syngas prior to the electr ...
(IGCC) power plants to remove
carbon dioxide
Carbon dioxide ( chemical formula ) is a chemical compound made up of molecules that each have one carbon atom covalently double bonded to two oxygen atoms. It is found in the gas state at room temperature. In the air, carbon dioxide is trans ...
and
hydrogen sulfide from the
syngas stream.
* PEG has been used as the gate insulator in an electric double-layer transistor to induce superconductivity in an insulator.
* PEG is also used as a polymer host for solid polymer electrolytes. Although not yet in commercial production, many groups around the globe are engaged in research on solid polymer electrolytes involving PEG, with the aim of improving their properties, and in permitting their use in batteries, electro-chromic display systems, and other products in the future.
* PEG is injected into industrial processes to reduce foaming in separation equipment.
* PEG is used as a
binder in the preparation of technical
ceramic
A ceramic is any of the various hard, brittle, heat-resistant and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcelain ...
s.
* PEG was used as an additive to silver halide photographic
emulsions.
Entertainment uses
* PEG is used to extend the size and durability of very large
soap bubbles
A soap bubble is an extremely thin film of soap or detergent and water enclosing air that forms a hollow sphere with an iridescent surface. Soap bubbles usually last for only a few seconds before bursting, either on their own or on contact ...
.
* PEG is the main ingredient in many
personal lubricant
Personal lubricants (colloquially termed lube) are specialized lubricants used during sexual acts, such as intercourse and masturbation, to reduce friction to or between the penis and vagina, anus or other body parts or applied to sex toys to red ...
s. (Not to be confused with
propylene glycol
Propylene glycol (IUPAC name: propane-1,2-diol) is a viscous, colorless liquid, which is nearly odorless but possesses a faintly sweet taste. Its chemical formula is CH3CH(OH)CH2OH.
Containing two alcohol groups, it is classed as a diol. It i ...
.)
* PEG is the main ingredient in the paint (known as "fill") in
paintball
Paintball is a competitive team shooting sport in which players eliminate opponents from play by hitting them with spherical dye-filled gelatin capsules called paintballs that break upon impact. Paintballs are usually shot using low-energy a ...
s.
Health effects
PEG is considered biologically inert and safe by the FDA.
However, a growing body of evidence shows the existence of a detectable level of anti-PEG
antibodies in approximately 72% of the population, never treated with
PEGylated
PEGylation (or pegylation) is the process of both covalent and non-covalent attachment or amalgamation of polyethylene glycol (PEG, in pharmacy called macrogol) polymer chains to molecules and macrostructures, such as a drug, therapeutic protein ...
drugs, based on plasma samples from 1990 to 1999. Due to its ubiquity in a multitude of products and the large percentage of the population with antibodies to PEG, hypersensitive reactions to PEG are an increasing concern.
Allergy to PEG is usually discovered after a person has been diagnosed with an allergy to an increasing number of seemingly unrelated products, including processed foods, cosmetics, drugs, and other substances that contain PEG or were manufactured with PEG.
Available forms and nomenclature
''PEG'', ''PEO'', and ''POE'' refer to an
oligomer or polymer of
ethylene oxide
Ethylene oxide is an organic compound with the formula . It is a cyclic ether and the simplest epoxide: a three-membered ring consisting of one oxygen atom and two carbon atoms. Ethylene oxide is a colorless and flammable gas with a faintly sw ...
. The three names are chemically synonymous, but historically ''PEG'' is preferred in the biomedical field, whereas ''PEO'' is more prevalent in the field of polymer chemistry. Because different applications require different polymer chain lengths, ''PEG'' has tended to refer to oligomers and polymers with a molecular mass below 20,000g/mol, ''PEO'' to polymers with a molecular mass above 20,000g/mol, and ''POE'' to a polymer of any molecular mass. PEGs are prepared by
polymerization
In polymer chemistry, polymerization (American English), or polymerisation (British English), is a process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks. There are many fo ...
of
ethylene oxide
Ethylene oxide is an organic compound with the formula . It is a cyclic ether and the simplest epoxide: a three-membered ring consisting of one oxygen atom and two carbon atoms. Ethylene oxide is a colorless and flammable gas with a faintly sw ...
and are commercially available over a wide range of molecular weights from 300g/mol to 10,000,000g/mol.
[
PEG and PEO are liquids or low-melting solids, depending on their ]molecular weight
A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bioch ...
s. While PEG and PEO with different molecular weights find use in different applications, and have different physical properties (e.g. viscosity
The viscosity of a fluid is a measure of its resistance to deformation at a given rate. For liquids, it corresponds to the informal concept of "thickness": for example, syrup has a higher viscosity than water.
Viscosity quantifies the inte ...
) due to chain length effects, their chemical properties are nearly identical. Different forms of PEG are also available, depending on the initiator
An initiator can refer to:
* A person who instigates something.
* Modulated neutron initiator, a neutron source used in some nuclear weapons
** Initiator, an Explosive booster
** Initiator, the first Nuclear chain reaction
* Pyrotechnic initiato ...
used for the polymerization process – the most common initiator is a monofunctional methyl ether PEG, or methoxypoly(ethylene glycol), abbreviated mPEG. Lower-molecular-weight PEGs are also available as purer oligomers, referred to as monodisperse, uniform, or discrete. Very high-purity PEG has recently been shown to be crystalline, allowing determination of a crystal structure by x-ray crystallography
X-ray crystallography is the experimental science determining the atomic and molecular structure of a crystal, in which the crystalline structure causes a beam of incident X-rays to diffract into many specific directions. By measuring the angles ...
. Since purification and separation of pure oligomers is difficult, the price for this type of quality is often 10–1000 fold that of polydisperse PEG.
PEGs are also available with different geometries.
* ''Branched'' PEGs have three to ten PEG chains emanating from a central core group.
* ''Star'' PEGs have 10 to 100 PEG chains emanating from a central core group.
* ''Comb'' PEGs have multiple PEG chains normally grafted onto a polymer backbone.
The numbers that are often included in the names of PEGs indicate their average molecular weights (e.g. a PEG with would have an average molecular weight of approximately 400 daltons, and would be labeled PEG 400
PEG 400 (polyethylene glycol 400) is a low-molecular-weight grade of polyethylene glycol. It is a clear, colorless, viscous liquid. Due in part to its low toxicity, PEG 400 is widely used in a variety of pharmaceutical formulations.
Chemical pr ...
). Most PEGs include molecules with a distribution of molecular weights (i.e. they are polydisperse). The size distribution can be characterized statistically by its weight average molecular weight The molar mass distribution (or molecular weight distribution) describes the relationship between the number of moles of each polymer species (Ni) and the molar mass (Mi) of that species. In linear polymers, the individual polymer chains rarely have ...
(''M''w) and its number average molecular weight The molar mass distribution (or molecular weight distribution) describes the relationship between the number of moles of each polymer species (Ni) and the molar mass (Mi) of that species. In linear polymers, the individual polymer chains rarely have ...
(''M''n), the ratio of which is called the polydispersity index
In chemistry, the dispersity is a measure of the heterogeneity of sizes of molecules or particles in a mixture. A collection of objects is called uniform if the objects have the same size, shape, or mass. A sample of objects that have an inconsi ...
(''Đ''M). ''M''w and ''M''n can be measured by mass spectrometry.
PEGylation
PEGylation (or pegylation) is the process of both covalent and non-covalent attachment or amalgamation of polyethylene glycol (PEG, in pharmacy called macrogol) polymer chains to molecules and macrostructures, such as a drug, therapeutic protein ...
is the act of covalently coupling a PEG structure to another larger molecule, for example, a therapeutic protein, which is then referred to as a ''PEGylated'' protein. PEGylated interferon alfa-2a or alfa-2b are commonly used injectable treatments for hepatitis C infection.
PEG is soluble in water
Water (chemical formula ) is an Inorganic compound, inorganic, transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance, which is the main constituent of Earth's hydrosphere and the fluids of all known living ...
, methanol, ethanol
Ethanol (abbr. EtOH; also called ethyl alcohol, grain alcohol, drinking alcohol, or simply alcohol) is an organic compound. It is an alcohol with the chemical formula . Its formula can be also written as or (an ethyl group linked to a ...
, acetonitrile, benzene
Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms ...
, and dichloromethane, and is insoluble in diethyl ether
Diethyl ether, or simply ether, is an organic compound in the ether class with the formula , sometimes abbreviated as (see Pseudoelement symbols). It is a colourless, highly volatile, sweet-smelling ("ethereal odour"), extremely flammable li ...
and hexane
Hexane () is an organic compound, a straight-chain alkane with six carbon atoms and has the molecular formula C6H14.
It is a colorless liquid, odorless when pure, and with boiling points approximately . It is widely used as a cheap, relatively ...
. It is coupled to hydrophobic molecules to produce non-ionic surfactants.
PEGs potentially contain toxic impurities, such as ethylene oxide and 1,4-dioxane
1,4-Dioxane () is a heterocyclic organic compound, classified as an ether. It is a colorless liquid with a faint sweet odor similar to that of diethyl ether. The compound is often called simply dioxane because the other dioxane isomers ( 1 ...
. Ethylene glycol and its ethers are nephrotoxic Nephrotoxicity is toxicity in the kidneys. It is a poisonous effect of some substances, both toxic chemicals and medications, on kidney function. There are various forms, and some drugs may affect kidney function in more than one way. Nephrotoxins ...
if applied to damaged skin.
PEG and related polymers (PEG phospholipid constructs) are often sonicated when used in biomedical applications. However, as reported by Murali et al., PEG is very sensitive to sonolytic degradation and PEG degradation products can be toxic to mammalian cells. It is, thus, imperative to assess potential PEG degradation to ensure that the final material does not contain undocumented contaminants that can introduce artifacts into experimental results.
PEGs and methoxypolyethylene glycols are manufactured by Dow Chemical under the trade name ''Carbowax'' for industrial use, and ''Carbowax Sentry'' for food and pharmaceutical use. They vary in consistency from liquid to solid, depending on the molecular weight, as indicated by a number following the name. They are used commercially in numerous applications, including foods, in cosmetics
Cosmetics are constituted mixtures of chemical compounds derived from either natural sources, or synthetically created ones. Cosmetics have various purposes. Those designed for personal care and skin care can be used to cleanse or protect ...
, in pharmaceutics, in biomedicine
Biomedicine (also referred to as Western medicine, mainstream medicine or conventional medicine) , as dispersing agents, as solvents, in ointments, in suppository
A suppository is a dosage form used to deliver medications by insertion into a body orifice where it dissolves or melts to exert local or systemic effects. There are three types of suppositories, each to insert into a different sections: rectal ...
bases, as tablet excipient
An excipient is a substance formulated alongside the active ingredient of a medication, included for the purpose of long-term stabilization, bulking up solid formulations that contain potent active ingredients in small amounts (thus often referred ...
s, and as laxative
Laxatives, purgatives, or aperients are substances that loosen stools and increase bowel movements. They are used to treat and prevent constipation.
Laxatives vary as to how they work and the side effects they may have. Certain stimulant, lubri ...
s. Some specific groups are lauromacrogols, nonoxynol Nonoxynols also known as nonaethylene glycol or polyethylene glycol nonyl phenyl ether are mixtures of nonionic surfactants used as detergents, emulsifiers, wetting agents or defoaming agents. The most commonly discussed compound nonoxynol-9 is a s ...
s, octoxynol
Triton X-100 (''n'') is a nonionic surfactant that has a hydrophilic polyethylene oxide chain (on average it has 9.5 ethylene oxide units) and an aromatic hydrocarbon lipophilic or hydrophobic group. The hydrocarbon group is a 4-( 1,1,3,3-tetrame ...
s, and poloxamer
Poloxamers are nonionic triblock copolymers composed of a central hydrophobic chain of polyoxypropylene (poly(propylene oxide)) flanked by two hydrophilic chains of polyoxyethylene (poly(ethylene oxide)). The word was coined by BASF inventor, I ...
s.
Macrogol
Macrogol, also known as polyethylene glycol (PEG), is used as a medication to treat constipation in children and adults. It is also used to empty the bowels before a colonoscopy. It is taken by mouth. Benefits usually occur within three days. ...
, MiraLax
Macrogol, also known as polyethylene glycol (PEG), is used as a medication to treat constipation in children and adults. It is also used to empty the bowels before a colonoscopy. It is taken by mouth. Benefits usually occur within three days. ...
, GoLytely, Colace
Docusate is the common chemical and pharmaceutical name of the anion bis(2-ethylhexyl) sulfosuccinate, also commonly called dioctyl sulfosuccinate (DOSS).
It is on the World Health Organization's List of Essential Medicines.
Salts of this anion ...
used as a laxative, is a form of polyethylene glycol. The name may be followed by a number which represents the average molecular weight (e.g. macrogol 3350, macrogol 4000 or macrogol 6000).
Production
The production of polyethylene glycol was first reported in 1859. Both A. V. Lourenço and Charles Adolphe Wurtz
Charles Adolphe Wurtz (; 26 November 181710 May 1884) was an Alsatian French chemist. He is best remembered for his decades-long advocacy for the atomic theory and for ideas about the structures of chemical compounds, against the skeptical opinio ...
independently isolated products that were polyethylene glycols. Polyethylene glycol is produced by the interaction of ethylene oxide
Ethylene oxide is an organic compound with the formula . It is a cyclic ether and the simplest epoxide: a three-membered ring consisting of one oxygen atom and two carbon atoms. Ethylene oxide is a colorless and flammable gas with a faintly sw ...
with water, ethylene glycol
Ethylene glycol (IUPAC name: ethane-1,2-diol) is an organic compound (a vicinal diol) with the formula . It is mainly used for two purposes, as a raw material in the manufacture of polyester fibers and for antifreeze formulations. It is an odo ...
, or ethylene glycol oligomers.Polyethylene glycol
Chemindustry.ru The reaction is catalyzed by acidic or basic catalysts. Ethylene glycol and its oligomers are preferable as a starting material instead of water, because they allow the creation of polymers with a low
polydispersity (narrow molecular weight distribution). Polymer chain length depends on the ratio of reactants.
:HOCH
2CH
2OH + n(CH
2CH
2O) → HO(CH
2CH
2O)
n+1H
Depending on the catalyst type, the mechanism of
polymerization
In polymer chemistry, polymerization (American English), or polymerisation (British English), is a process of reacting monomer molecules together in a chemical reaction to form polymer chains or three-dimensional networks. There are many fo ...
can be cationic or anionic. The anionic mechanism is preferable because it allows one to obtain PEG with a low
polydispersity. 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 in an explosion after a few hours.
Polyethylene oxide, or high-molecular-weight polyethylene glycol, is synthesized by
suspension polymerization. It is necessary to hold the growing polymer chain in
solution
Solution may refer to:
* Solution (chemistry), a mixture where one substance is dissolved in another
* Solution (equation), in mathematics
** Numerical solution, in numerical analysis, approximate solutions within specified error bounds
* Soluti ...
in the course of the
polycondensation
In polymer chemistry, condensation polymers are any kind of polymers whose process of polymerization involves a condensation reaction (i.e. a small molecule, such as water or methanol, is produced as a byproduct). Condensation polymers are for ...
process. The reaction is catalyzed by magnesium-, aluminium-, or calcium-organoelement compounds. To prevent
coagulation
Coagulation, also known as clotting, is the process by which blood changes from a liquid to a gel, forming a blood clot. It potentially results in hemostasis, the cessation of blood loss from a damaged vessel, followed by repair. The mechanis ...
of polymer chains from solution, chelating additives such as
dimethylglyoxime
Dimethylglyoxime is a chemical compound described by the formula CH3C(NOH)C(NOH)CH3. Its abbreviation is dmgH2 for neutral form, and dmgH− for anionic form, where H stands for hydrogen. This colourless solid is the dioxime derivative of the dike ...
are used.
Alkaline catalysts such as
sodium hydroxide (NaOH),
potassium hydroxide
Potassium hydroxide is an inorganic compound with the formula K OH, and is commonly called caustic potash.
Along with sodium hydroxide (NaOH), KOH is a prototypical strong base. It has many industrial and niche applications, most of which exp ...
(KOH), or
sodium carbonate (Na
2CO
3) are used to prepare low-molecular-weight polyethylene glycol.
See also
*
Ethylene
*
Propylene glycol
Propylene glycol (IUPAC name: propane-1,2-diol) is a viscous, colorless liquid, which is nearly odorless but possesses a faintly sweet taste. Its chemical formula is CH3CH(OH)CH2OH.
Containing two alcohol groups, it is classed as a diol. It i ...
*
Monoethylene glycol
*
Diethylene glycol
Diethylene glycol (DEG) is an organic compound with the formula (HOCH2CH2)2O. It is a colorless, practically odorless, and hygroscopic liquid with a sweetish taste. It is a four carbon dimer of ethylene glycol. It is miscible in water, alcohol, ...
*
PEGylation
PEGylation (or pegylation) is the process of both covalent and non-covalent attachment or amalgamation of polyethylene glycol (PEG, in pharmacy called macrogol) polymer chains to molecules and macrostructures, such as a drug, therapeutic protein ...
*
PEG-PVA
*
Lauryl methyl gluceth-10 hydroxypropyl dimonium chloride
*
Polyethylene glycol propylene glycol cocoates
*
Lysozyme PEGylation
Lysozyme PEGylation is the covalent attachment of Polyethylene glycol (PEG) to Lysozyme, which is one of the most widely investigated PEGylated proteins.
The PEGylation of proteins has become a common practice of modern therapeutic drugs, as ...
References
External links
Oregon State University informational paper on using PEG as a wood stabilizer
{{DEFAULTSORT:Polyethylene Glycol
Biomaterials
Coolants
Excipients
Laxatives
Polyethers
Polymers
Ether solvents
E-number additives
Allergology