โพลีเอทิลีนไกลคอล, Polyethylene Glycol

โพลีอีเทอร์ไกลคอล,

โพลีเอทิลีนไกลคอล, Polyether Glycol, Polyethylene

Glycol, PEG

คาร์โบแวกซ์, CARBOWAX, PEG 100, PEG 200, PEG 300, PEG 400,

PEG 600, PEG 1000

Polyethylene glycol (PEG) is a

polyether compound with many applications from industrial manufacturing to

medicine. It has also been known as polyethylene oxide (PEO) or polyoxyethylene

(POE), depending on its molecular weight, and under the tradename Carbowax.

PEG, PEO, or POE refers to an oligomer or polymer of ethylene oxide. The three

names are chemically synonymous, but historically PEG has tended to refer to

oligomers and polymers with a molecular mass below 20,000 g/mol, PEO to

polymers with a molecular mass above 20,000 g/mol, and POE to a polymer of any

molecular mass.[2] PEG and PEO are liquids or low-melting solids, depending on

their molecular weights. PEGs are prepared by polymerization of ethylene oxide

and are commercially available over a wide range of molecular weights from 300

g/mol to 10,000,000 g/mol. While PEG and PEO with different molecular weights

find use in different applications and have different physical properties

(e.g., viscosity) due to chain length effects, their chemical properties are

nearly identical. Different forms of PEG are also available dependent on the

initiator used for the polymerization process, the most common of which is a

monofunctional methyl ether PEG (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 an xray

crystal structure.[3] 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?100 PEG chains emanating from a central core group. Comb PEGs have

multiple PEG chains normally grafted to a polymer backbone. Their melting

points vary depending on the Formula Weight of the polymer. PEG or PEO has the

following structure. The numbers that are often included in the names of PEGs

indicate their average molecular weights, e.g., a PEG with n=9 would have an

average molecular weight of approximately 400 daltons and would be labeled PEG

400. 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 (Mw) and its number

average molecular weight (Mn), the ratio of which is called the polydispersity

index (Mw/Mn). Mw and Mn can be measured by mass spectrometry.

Polyethylene glycol (PEG) is a

polyether compound with many applications from industrial manufacturing to

medicine. The structure of PEG is (note the repeated element in parentheses):  H-(O-CH2-CH2)n-OH

PEG is also known as polyethylene

oxide (PEO) or polyoxyethylene (POE), depending on its molecular weight.

Production

Polyethylene glycol is produced by

the interaction of ethylene oxide with water, ethylene glycol, or ethylene

glycol oligomers.[5] 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.

 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

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

in the course of the polycondensation process. The reaction is catalyzed by

magnesium-, aluminium-, or calcium-organoelement compounds. To prevent

coagulation of polymer chains from solution, chelating additives such as

dimethylglyoxime are used.

Alkali catalysts such as sodium

hydroxide (NaOH), potassium hydroxide (KOH), or sodium carbonate (Na2CO3) are

used to prepare low-molecular-weight polyethylene glycol.

Medical uses

PEG is the basis of a number of

laxatives (e.g., macrogol-containing products, such as Movicol and polyethylene

glycol 3350, or SoftLax, MiraLAX,ClearLAX, or GlycoLax). Whole bowel irrigation

with polyethylene glycol and added electrolytes is used for bowel preparation

before surgery or colonoscopy. The preparation is sold under the brand names

GoLYTELY, GaviLyte C, NuLytely, GlycoLax, Fortrans, TriLyte, Colyte,

Halflytely, Softlax, Lax-a-Day, ClearLax and MoviPrep. In the United States,

MiraLAX and Dulcolax Balance are sold without prescription for short-term

relief of chronic constipation. Miralax is currently FDA approved for adults

for a period of seven days, and is not approved for children.  A 2007 comparison showed that patients

suffering from constipation had a better response to PEG medications than to

tegaserod. These medications soften the fecal mass by osmotically drawing water

into the GI tract. It is generally well tolerated, however, side effects are

possible bloating, nausea, gas, and diarrhea (with excessive use).

When attached to various protein

medications, polyethylene glycol allows a slowed clearance of the carried

protein from the blood. This makes for a longer-acting medicinal effect and

reduces toxicity, and allows longer dosing intervals. Examples include

PEG-interferon alpha, which is used to treat hepatitis C, and PEGfilgrastim

(Neulasta), which is used to treat neutropenia. It has been shown that

polyethylene glycol can improve healing of spinal injuries in dogs. One of the

earlier findings, that polyethylene glycol can aid in nerve repair, came from

the University of Texas (Krause and Bittner). Polyethylene glycol is also

commonly used to fuse B-cells with myeloma cells in monoclonal antibody

production. PEG is used as an excipient in many pharmaceutical products.

Lower-molecular-weight variants are used as solvents in oral liquids and soft

capsules, whereas solid variants are used as ointment bases, tablet binders, film

coatings, and lubricants.

PEG is also used in lubricating

eye drops.

Research for new clinical uses

 PEG, when labeled with a near-infrared

fluorophore, has been used in preclinical work as a vascular agent, lymphatic

agent, and general tumor-imaging agent by exploiting the Enhanced permeability

and retention effect (EPR) of tumors. High-molecular-weight PEG (e.g. PEG 8000)

has been shown to be a dietary preventive agent against colorectal cancer in

animal models. The Chemoprevention Database shows PEG is the most effective

known agent for the suppression of chemical carcinogenesis in rats. Cancer

prevention applications in humans, however, have 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. The effectiveness of this treatment to prevent paraplegia in

humans after an accident is not known yet.  PEG is being used in the repair of motor

neurons damaged in crush or laceration incidents in vivo and in vitro. When

coupled with melatonin, 75% of damaged sciatic nerves were rendered viable.

Chemical uses

 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 and

biomembranes 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.

PEO (polyethylene oxide) can serve

as the separator and electrolyte solvent in lithium polymer cells. Its low

diffusivity often requires high temperatures of operation, but its high

viscosity ? even near its melting point ? allows very thin electrolyte layers

to be created. While crystallization of the polymer can degrade performance,

many of the salts used to carry charge can also serve as a kinetic barrier to

the formation of crystals. Such batteries carry greater energy for their weight

than other lithium ion battery technologies.

 PEG has also been used to preserve objects

that have been salvaged from underwater, as was the case with the warship Vasa

in Stockholm,[18] the Mary Rose in England and the Ma'agan Michael Ship in

Israel. 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 as a stabilizer, and to

prevent shrinkage. 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 block copolymers used to create some

polymersomes.

Biological uses

 PEG is commonly used as a precipitant for

plasmid DNA isolation and protein crystallization. X-ray diffraction of protein

crystals can reveal the atomic structure of the proteins. Polymer segments

derived from PEG polyols impart flexibility to polyurethanes for applications

such as elastomeric fibers (spandex) and foam 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 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 for use in vivo. In blood

banking, PEG is used as a potentiator to enhance detection of antigens and

antibodies.  When working with phenol in

a laboratory situation, PEG 300 can be used on phenol skin burns to deactivate

any residual phenol.

Commercial uses

 PEG is the basis of many skin creams (as

cetomacrogol) and personal lubricants (frequently combined with glycerin). PEG

is used in a number of toothpastes as a dispersant. In this application, it

binds water and helps keep xanthan gum uniformly distributed throughout the

toothpaste. PEG is also under investigation for use in body armor, and in tattoos

to monitor diabetes. In low-molecular-weight formulations (i.e. PEG 400), it is

used in Hewlett-Packard designjet printers as an ink solvent and lubricant for

the print heads. PEG is also one of the main ingredients in paintball fills, due

to its thickness and flexibility. However, as early as 2006, some Paintball

manufacturers began substituting cheaper oil-based alternatives for

PEG.[citation needed]

 PEG is a major ingredient in e-liquid, used in

electronic cigarettes. It is generally used as a 30%?50% proportion of the

liquid that is vaporized. Its use is designed to give a smoother effect to the

vaporizing action. PEG is also used as an anti-foaming agent in food ? its INS

number is 1521 or E1521 in the EU.

Industrial uses

 Nitrate ester-plasticized polyethylene glycol

is used in Trident II ballistic missile solid rocket fuel. Dimethyl ethers of

PEG are the key ingredient of Selexol, a solvent used by coal-burning,

integrated gasification combined cycle (IGCC) power plants to remove carbon

dioxide and hydrogen sulfide from the gas waste 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 used as a binder in the preparation of technical ceramics.

Choose from CARBOWAX? PEGs in a

variety of molecular weights, viscosities and in several physical forms. Each

product grade is designated numerically by its average molecular weight. For

example, CARBOWAX? PEG 600 consists of a distribution of polymers of varying

molecular weights with an average of 600. Molecular weight has an effect on the

physical properties of each product grade. Increased molecular weight results

in decreased solubility in water and solvents, decreased hygroscopicity and

vapor pressure, and increased melting/freezing range and viscosity.

CARBOWAX? SENTRY? PEGs are

available in average molecular weights ranging from 300 to 8000 in a variety of

viscosities and physical forms. CARBOWAX? SENTRY? PEGs meet all applicable

requirements in the National Formulary (NF) for use in drug applications, Food

Chemicals Codex (FCC) requirements for use in certain food applications and

personal care products.

 

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