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PEG 4000

CAS No. : 25322-68-3
EC No. : 500-038-2

Synonyms:
POLYETHYLENE GLYCOL 4000; Polyethylene glycol 4000; Polyethylene Glycol 4000; poli etilen glikol 4000; peg4000; Peg 4000, polietilenglikol 4000, poli etilen glikol 4000, cas no : Cas No: 25322-68-3, macrogol, carbowax; poly(ethylene glycol); polietilen glikol; poli etilen glikol; poli etilenglikol; PEG-4000; poli etilen glikol; ETHYLENE GLYCOL; 1,2-ethanediol; Ethane-1,2-diol; 107-21-1; glycol; monoethylene glycol; 1,2-Dihydroxyethane; 2-hydroxyethanol; Glycol alcohol; Ethylene alcohol; polyethylene glycol; Macrogol; Fridex; Tescol; Ethylene dihydrate; Norkool; Macrogol 400 BPC; Dowtherm SR 1; ethanediol; Zerex; Ucar 17; Lutrol-9; Polyethylene glycol 200; ethyleneglycol; PEG 4000 (Powder); Aethylenglykol; Glycol, ethylene-; 1,2-Ethandiol; Glycols, polyethylene; Caswell No. 441; Ethylenglycol; Aethylenglykol [German]; ethylen glycol; ethylene-glycol; Lutrol; PEG 400; Polyethylene glycol 600; 146AR; Polyethylene glycol 1000; UNII-FC72KVT52F; Lutrol 9; Carbowax 20; NSC 93876; Carbowax 4000; Carbowax 400; CCRIS 3744; Carbowax 1000; Dowtherm 4000; 1,2-ethylene glycol; 1,2-dihydroxy ethane; Ethylene glycol polymer; HSDB 5012; NCI-C00920; HOCH2CH2OH; Union Carbide XL 54 Type I De-icing Fluid; PEG 4000; EINECS 203-473-3; M.e.g.; Ethylene glycol homopolymer; Polyethylene Glycol 4000; EPA Pesticide Chemical Code 042203; 1,2-Ethanediol homopolymer; FC72KVT52F; AI3-03050; PEG; DTXSID8020597; CHEBI:30742; PEG 4000; 1, 2-Ethanediol; DuPont Zonyl FSO Fluorinated Surfactants; alpha-Hydro-omega-hydroxypoly(oxyethylene); DSSTox_CID_597; H(OCH2CH2)nOH; Ethylene glycol, technical; Polyethylene oxide; DSSTox_RID_75680; Polyethylene Glycol 400; DSSTox_GSID_20597; alpha-Hydro-omega-hydroxypoly(oxy-1,2-ethanediyl); Glycol, polyethylene; Carbowax; Miralax; Ethylene glycol, 99.5%, for analysis; CAS-107-21-1; Polyethylene Glycols; Ethylene glycol, 99.8%, anhydrous, AcroSeal(R); Polyethylene glycol 4000; Polyethylene Glycol 4000; ethyleneglycole; Athylenglykol; Aquaffin; Badimol; Modopeg; Nosilen; Nycoline; ehtylene glycol; etylene glycol; Carbowax Sentry; 2-ethanediol; Pluracol E; Polyaethylenglykol; Aquacide III; Ilexan E; Bradsyn PEG; ethylene alcohol; Merpol OJ; Polyaethylenglykole; MEG 100; Alkox SR; Oxide Wax AN; Oxyethylene polymer; Poly-G; Solbanon (TN); 1,2-ethane diol; 1,2-ethane-diol; ethane-1.2-diol; peg4000; GXT; PEG 1000; 1,2-ethyleneglycol; ethan-1,2-diol; mono-ethylene glycol; Carbowax 100; Carbowax 200; Carbowax 600; Macrogol 400; Polyox wsr-N 60; Mono Ethylene Glycol; Carbowax 1350; Carbowax 1500; Carbowax 1540; Carbowax 4000; Carbowax 4500; Carbowax 4600; 1,2-ethylene-glycol; Breox 20M; Lutrol E (TN); Ethylene oxide polymer; Gafanol E 200; Pluriol E 200; Carbowax 14000; Carbowax 20000; Carbowax 25000; Emkapol 4200; Alcox E 30; Alkox E 45; Alkox E 60; Alkox E 75; Alkox R 15; Antarox E 4000; Atpeg 4000; Breox 550; Breox PEG 4000; Alkox E 100; Alkox E 130; Alkox E 160; Alkox E 240; Alkox R 150; Alkox R 400; Breox 2000; Breox 4000; Poly-G600; polyethylene glycol-400; Macrogol 400 (TN); Polyethylene oxide (NF); Alkox R 1000; Polyethylene glycol (NF); Sentry polyox WSR (TN); Macrogol 1500 (TN); Macrogol 4000 (TN); Macrogol 4000 (TN); EC 203-473-3; PEG 4000 (Powder); Ethoxylated 1,2-ethanediol; Macrogol ointment (JP17); WLN: Q2Q; Glycol, polyethylene(4000); HO(CH2)2OH; M.E.G; NCIOpen2_001979; NCIOpen2_002019; NCIOpen2_002100; Macrogol 400 (JP17); Polyethylene Glycol 4000 NF; CCRIS 979; Ethylene glycol 5 M solution; Polyethylene glycol, diglycidyl bisphenol A polymer; BIDD:ER0283; FisherFresh™ Concentrate; Macrogol 1500 (JP17); Macrogol 4000 (JP17); Macrogol 4000 (JP17); CAFO 154; CHEMBL457299; LS-8; PEG 4000DS; Ethylene glycol, AR, >=99%; Ethylene glycol, LR, >=99%; Macrogol 20000 (JP17); BDH 301; PEG1000; Poly(oxy-1,2-ethanediyl), .alpha.-hydro-.omega.-hydroxy-; Poly(ethylene glycol) methyl ether; Polyethylene glycol 4000 (USP); WT931; Ethylene glycol, p.a., 99.5%; 1,2-ETHANEDIOL (GLYCOL); PEG 3600; PEG-1000; poly (ethylene glycol) methyl ether; ZINC5224354; Ethylene glycol, analytical standard; Tox21_202038; Tox21_4000637; ANW-15497; Ethane-1,2-diol (Ethylene Glycol); Ethylene glycol, anhydrous, 99.8%; HM 500; Polyethylene Glycol 4000, NF FCC; M.W range 3,000-3,700; AKOS000119039; alpha,omega-hydroxypoly(ethylene oxide); 61266-70-4 2-Hydroxymethyloxethane; DuPont Zonyl FSE Fluorinated Surfactants; NCGC00259587-01; AK116144; BP-13454; BP-24366; BP-31056; M430; Oxirane, 2,2'-((1-methylethylidene)bis(4,1-phenyleneoxymethylene))bis-, polymer with alpha-hydro-omega-hydroxypoly(oxy-1,2-ethanediyl); polyethylene glycol (m w 200-9,500); SC-47188; SMR001262244; Dihydrocarveol, (-)-, mixture of isomers; ETHYLENE GLYCOL HIGH PURITY GRD 1L; Ethylene glycol, ReagentPlus(R), >=99%; DuPont Zonyl FSE Fluorinated Surfactants; Polyethylene glycol tridecyl ether phosphate; 2610033; Trideceth-3 phosphate; Trideceth-6 phosphate; Trideceth-10 phosphate; PEG 4000 (Powder); PEG-3 Tridecyl ether phosphate; PEG-6 Tridecyl ether phosphate; DTXSID70873400; PEG-10 Tridecyl ether phosphate; Poly(oxy-1,2-ethanediyl), ?-tridecyl-?-hydroxy-, phosphate; Poly(oxy-1,2-ethanediyl), .alpha.-tridecyl-.omega.-hydroxy-, phosphate; Tridecyl alcohol, ethoxylated, phosphated; 2-(Tridecyloxy)ethyl dihydrogen phosphate; Polyoxyethylene (3) tridecyl ether phosphate; Polyoxyethylene (6) tridecyl ether phosphate; Polyoxyethylene (10) tridecyl ether phosphate; Polyethylene glycol (3) tridecyl ether phosphate; Polyethylene glycol 4000 tridecyl ether phosphate; Polyethylene glycol 500 tridecyl ether phosphate; Phosphoric acid, (ethoxylated tridecyl alcohol) esters; Poly(oxy-1,2-ethanediyl), alpha-tridecyl-omega-hydroxy-, phosphate

PEG 4000

Polyethylene glycol (PEG 4000; /ˌpɒliˈɛθəlˌiːn ˈɡlaɪˌkɒl, -ˌkɔːl/) is a polyether compound with many applications, from industrial manufacturing to medicine. PEG 4000 is also known as polyethylene oxide (PEO) or polyoxyethylene (POE), depending on its molecular weight. The structure of PEG 4000 is commonly expressed as H−(O−CH2−CH2)n−OH.
Uses of Polyethylene glycol (PEG 4000
Medical uses of Polyethylene glycol (PEG 4000)
Main article: Macrogol
PEG 4000 is the basis of a number of laxatives.[4] Whole bowel irrigation with polyethylene glycol and added electrolytes is used for bowel preparation before surgery or colonoscopy.
PEG 4000 is also used as an excipient in many pharmaceutical products.
When attached to various protein medications, polyethylene glycol allows a slowed clearance of the carried protein from the blood.[5]
The possibility that PEG 4000 could be used to fuse axons is being explored by researchers studying peripheral nerve and spinal cord injury.[4]
Chemical uses of Polyethylene glycol (PEG 4000)
The remains of the 16th century carrack Mary Rose undergoing conservation treatment with PEG 4000 in the 1980s

Terra cotta warrior, showing traces of original color
Because PEG 4000 is a hydrophilic molecule, it has been used to passivate microscope glass slides for avoiding non-specific sticking of proteins in single-molecule fluorescence studies.[6]
Polyethylene glycol has a low toxicity and is used in a variety of products.[7] The polymer is used as a lubricating coating for various surfaces in aqueous and non-aqueous environments.[8]
Since PEG 4000 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 4000 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.
PEG 4000 has also been used to preserve objects that have been salvaged from underwater, as was the case with the warship Vasa in Stockholm,[9] 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.[4] In addition, PEG 4000 is used when working with green wood as a stabilizer, and to prevent shrinkage.[10]
PEG 4000 has been used to preserve the painted colors on Terracotta Warriors unearthed at a UNESCO World Heritage site in China.[11] These painted artifacts were created during the Qin Shi Huang (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 air. The paint would subsequently flake off in about four minutes. The German Bavarian State Conservation Office developed a PEG 4000 preservative that when immediately applied to unearthed artifacts has aided in preserving the colors painted on the pieces of clay soldiers.[12]
PEG 4000 is often used (as an internal calibration compound) in mass spectrometry experiments, with its characteristic fragmentation pattern allowing accurate and reproducible tuning.
PEG 4000 derivatives, such as narrow range ethoxylates, are used as surfactants.
PEG 4000 has been used as the hydrophilic block of amphiphilic block copolymers used to create some polymersomes.[13]
PEG 4000 has also been used as a propellent on the UGM-133M Trident II Missile, in service with the United States Air Force.[14]

Biological uses
PEG 4000 is commonly used as a crowding agent in in vitro assays to mimic highly crowded cellular conditions.[6]
PEG 4000 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.
PEG 4000 is used to fuse two different types of cells, most often B-cells and myelomas in order to create hybridomas.
Polymer segments derived from PEG 4000 polyols impart flexibility to polyurethanes for applications such as elastomeric fibers (spandex) and foam cushions.
In microbiology, PEG 4000 precipitation is used to concentrate viruses. PEG 4000 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 4000-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.[15] The size of the PEG 4000 polymer has been shown to be important, with larger polymers achieving the best immune protection.
PEG 4000 is a component of stable nucleic acid lipid particles (SNALPs) used to package siRNA for use in vivo.
In blood banking, PEG 4000 is used as a potentiator to enhance detection of antigens and antibodies.
When working with phenol in a laboratory situation, PEG 4000 300 can be used on phenol skin burns to deactivate any residual phenol (some references are required).
In biophysics, 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 4000 is the basis of many skin creams (as cetomacrogol) and personal lubricants (frequently combined with glycerin).
PEG 4000 is used in a number of toothpastes[4] as a dispersant. In this application, it binds water and helps keep xanthan gum uniformly distributed throughout the toothpaste.
PEG 4000 is also under investigation for use in body armor, and in tattoos to monitor diabetes.
In low-molecular-weight formulations (e.g. PEG 4000 400), it is used in Hewlett-Packard designjet printers as an ink solvent and lubricant for the print heads.
PEG 4000 is also used as an anti-foaming agent in food and drinks[23] – its INS number is 1521 or E1521 in the EU.

Industrial uses
A nitrate ester-plasticized polyethylene glycol (NEPE-75) is used in Trident II submarine-launched ballistic missile solid rocket fuel.[26]
Dimethyl ethers of PEG 4000 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 4000 has been used as the gate insulator in an electric double-layer transistor to induce superconductivity in an insulator.[27]
PEG 4000 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 4000, 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 4000 is injected into industrial processes to reduce foaming in separation equipment.
PEG 4000 is used as a binder in the preparation of technical ceramics.[28]

Recreational uses
PEG 4000 is used to extend the size and durability of very large soap bubbles.
PEG 4000 is the main ingredient in many personal lubricants.
Health effects
PEG 4000 is considered biologically inert and safe by the FDA. However, a growing body of evidence shows the existence of anti PEG 4000 antibodies in approximately 72% of the population based on plasma samples from 1990–1999.[medical citation needed] The FDA has been asked to investigate the possible effects of PEG 4000 in laxatives for children.[29]
Due to its ubiquity in a multitude of products and the large percentage of the population with antibodies to PEG 4000, hypersensitive reactions to PEG 4000 are an increasing concern.[medical citation needed] Allergy to PEG 4000 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 4000 or were manufactured with PEG 4000.[30]
When PEG 4000 is chemically attached to therapeutic molecules (such as protein drugs or nanoparticles), it can sometimes be antigenic, stimulating an anti-PEG 4000 antibody response in some patients. This effect has only been shown for a few of the many available PEG 4000 therapeutics, but it has significant effects on clinical outcomes of affected patients.[31] Other than these few instances where patients have anti-PEG 4000 immune responses, it is generally considered to be a safe component of drug formulations.

Available forms and nomenclature
PEG 4000, PEO, and POE refer to an oligomer or polymer of ethylene oxide. The three names are chemically synonymous, but historically PEG 4000 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 4000 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.[32] PEG 4000s 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.[33]
PEG 4000 and PEO are liquids or low-melting solids, depending on their molecular weights. While PEG 4000 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 4000 are also available, depending on the initiator used for the polymerization process – the most common initiator is a monofunctional methyl ether PEG 4000, or methoxypoly(ethylene glycol), abbreviated mPEG 4000. Lower-molecular-weight PEG 4000s are also available as purer oligomers, referred to as monodisperse, uniform, or discrete. Very high purity PEG 4000 has recently been shown to be crystalline, allowing determination of a crystal structure by x-ray diffraction.[33] 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 4000.

PEG 4000s are also available with different geometries.
Branched PEG 4000s have three to ten PEG 4000 chains emanating from a central core group.
Star PEG 4000s have 10 to 100 PEG 4000 chains emanating from a central core group.
Comb PEG 4000s have multiple PEG 4000 chains normally grafted onto a polymer backbone.
The numbers that are often included in the names of PEG 4000s indicate their average molecular weights (e.g. a PEG 4000 with n = 9 would have an average molecular weight of approximately 400 daltons, and would be labeled PEG 4000 400.) Most PEG 4000s 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.
PEG 4000ylation is the act of covalently coupling a PEG 4000 structure to another larger molecule, for example, a therapeutic protein, which is then referred to as a PEG 4000 protein. PEG 4000 interferon alfa-2a or −2b are commonly used injectable treatments for hepatitis C infection.

PEG 4000 is soluble in water, methanol, ethanol, acetonitrile, benzene, and dichloromethane, and is insoluble in diethyl ether and hexane. It is coupled to hydrophobic molecules to produce non-ionic surfactants.[34]
PEG 4000s potentially contain toxic impurities, such as ethylene oxide and 1,4-dioxane.[35] Ethylene Glycol and its ethers are nephrotoxic if applied to damaged skin.[36]
Polyethylene oxide (PEO, Mw 4 kDa) nanometric crystallites (4 nm)
Polyethylene glycol (PEG 4000) and related polymers (PEG 4000 phospholipid constructs) are often sonicated when used in biomedical applications. However, as reported by Murali et al., PEG 4000 is very sensitive to sonolytic degradation and PEG 4000 degradation products can be toxic to mammalian cells. It is, thus, imperative to assess potential PEG 4000 degradation to ensure that the final material does not contain undocumented contaminants that can introduce artifacts into experimental results.[37]

PEG 4000s and methoxypolyethylene glycols are manufactured by Dow Chemical under the tradename 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 as surfactants, in foods, in cosmetics, in pharmaceutics, in biomedicine, as dispersing agents, as solvents, in ointments, in suppository bases, as tablet excipients, and as laxatives. Some specific groups are lauromacrogols, nonoxynols, octoxynols, and poloxamers.
Macrogol, used as a laxative, is a form of polyethylene glycol. The name may be followed by a number which represents the average molecular weight.

Production of Polyethylene glycol (PEG 4000)
Polyethylene glycol 400, pharmaceutical quality
Polyethylene glycol 4000, pharmaceutical quality
The production of polyethylene glycol was first reported in 1859. Both A. V. Lourenço and Charles Adolphe Wurtz independently isolated products that were polyethylene glycols.[38] Polyethylene glycol is produced by the interaction of ethylene oxide with water, ethylene glycol, or ethylene glycol oligomers.[39] 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 4000 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.
Alkaline catalysts such as sodium hydroxide (NaOH), potassium hydroxide (KOH), or sodium carbonate (Na2CO3) are used to prepare low-molecular-weight polyethylene glycol.

Polyethylene glycol (PEG 4000) is a versatile polyether being utilized in various applications, in particular in medicine. Polyethylene oxide (PEO) is another name for PEG 4000. Typically, ethylene oxide macromolecules (Fig. 18.9) with molecular weights less than 20,000 g/mol are called PEG 4000, while those having values above 20,000 g/mol are named PEO. It is reported that PEG 4000 is soluble in water, ethanol, acetonitrile, benzene, and dichloromethane, while it is insoluble in diethyl ether and hexane. PEG 4000 is available in different structures such as branched, star, and comb-like macromolecules. PEG 4000ylation is an attractive process in which PEG 4000 is bonded to another molecule, which is promising in therapeutic methods. PEG 4000 can hinder the protein adsorption which is essential in drug delivery to minimize the protein corona formation [29].
Polyethylene glycol (PEG 4000) is a hydrophilic polymer of ethylene oxide. The non-immunogenic, biocompatible and flexible nature of PEG 4000 makes it a suitable synthetic dressing material for wound healing. The low toxic PEG 4000 macromers are well bonded with growth factor like EGF and can be delivered at the wound site [98]. The mechanical stability of PEG 4000 can be enhanced by blending PEG 4000 with chitosan and PLGA. Blending also increases thermal stability and crystallinity of the particular polymer [99]. Such PEG 4000-based dressings have been widely used to treat a diabetic wound by promoting and inducing growth of skin cells and collagen deposition. It also reduces scar formation [100]. The injectable hybrid hydrogel dressing system is developed from PEG 4000-based hyperbranched multiacrylated co-polymer and HA in combination with adipose-derived stem cells to support the viability of cells in vitro and in vivo. It prevents wound contraction and enhances angiogenesis by acting as temporary hydrogel for wound healing purpose [101].

Hydrophilic Materials Based on Polyethylene Glycol
Polyethylene glycol (PEG 4000) is the most relevant antifouling polymer in biomedical devices. PEG 4000 antifouling properties are thought to be related to surface hydration and steric hindrance effects (Chen et al., 2010). PEG 4000 chains linked to a material surface assume a brush-like configuration at the water/surface interface, limiting the approach to the surface by bacteria. Compression of the highly hydrated layer of PEG 4000 chains is unfavorable because it would involve a reduction in PEG 4000 chain mobility and removal of water molecules. Surface packing density and polymer chain length can be used to control PEG 4000 antifouling properties (Roosjen et al., 2004). PEG 4000-functionalized PUs were developed by PEG 4000 introduction either in the polymer backbone (Corneillie et al., 1998) or polymer side chain (Francolini et al., 2019). Auto-oxidization in the presence of oxygen, metal ions, and enzymes able to oxidize PEG 4000 hydroxyl groups, however, may limit long-term effectiveness.
Polyethylene glycol (PEG 4000) is another important type of PCM for textile applications. The repeating unit in PEG 4000 is oxyethylene (–O–CH2–CH2–) containing hydroxyl group on either side of the chain. The melting point of PEG 4000 depends on its molecular weight and is proportional as the molecular weight increases. The phase-change temperature of PEG 4000 can be determined using DSC (Pielichowski and Flejtuch, 2002). PEG 4000 with degree of polymerization 1000 has phase-change temperature of 35°C, while PEG 4000 with degree of polymerization 20,000 has melting temperature of 63°C (Craig and Newton, 1991; Hopp et al., 2000).
Jiang et al. (2016) synthesized a dual-functional magnetic microcapsules containing a PCM core and an organo-silica shell for the electromagnetic shielding and thermal regulating applications. Fig. 20.6 shows the resulting DSC curves where the areas under the peaks indicate the amount of latent heat contained using different organosilanes/PEG 4000 weight ratios.

PEG 4000 is the basis of a number of laxatives.[3] Whole bowel irrigation with polyethylene glycol and added electrolytes is used for bowel preparation before surgery or colonoscopy. PEG 4000 is also used as an excipient in many pharmaceutical products. When attached to various protein medications, polyethylene glycol allows a slowed clearance of the carried protein from the blood.[4] The possibility that PEG 4000 could be used to fuse nerve cells is being explored by researchers studying spinal cord injury.[3] Chemical uses The remains of the 16th century carrack Mary Rose undergoing conservation treatment with PEG 4000 in the 1980s Terra cotta warrior, showing traces of original color Because PEG 4000 is a hydrophilic molecule, it has been used to passivate microscope glass slides for avoiding non-specific sticking of proteins in single-molecule fluorescence studies.[5] Polyethylene glycol has a low toxicity and is used in a variety of products.[6] The polymer is used as a lubricating coating for various surfaces in aqueous and non-aqueous environments.[7] 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 4000 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.

PEG 4000 has also been used to preserve objects that have been salvaged from underwater, as was the case with the warship Vasa in Stockholm,[8] 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.[3] In addition, PEG 4000 is used when working with green wood as a stabilizer, and to prevent shrinkage.[9] PEG has been used to preserve the painted colors on Terracotta Warriors unearthed at a UNESCO World Heritage site in China.[10] These painted artifacts were created during the Qin Shi Huang Di dynasty (first emperor of China). 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 Xian air. The paint would subsequently flake off in about four minutes. The German Bavarian State Conservation Office developed a PEG 4000 preservative that when immediately applied to unearthed artifacts has aided in preserving the colors painted on the pieces of clay soldiers.[11] PEG 4000 is often used (as an internal calibration compound) in mass spectrometry experiments, with its characteristic fragmentation pattern allowing accurate and reproducible tuning. PEG 4000 derivatives, such as narrow range ethoxylates, are used as surfactants. PEG 4000 is a polyol and can be reacted with an isocyanate to make polyurethane. PEG 4000 has been used as the hydrophilic block of amphiphilic block copolymers used to create some polymersomes.[12] Biological uses PEG 4000 is commonly used as a crowding agent in in vitro assays to mimic highly crowded cellular conditions.

PEG 4000 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. 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 in 1984.[3] Polymer segments derived from PEG polyols impart flexibility to polyurethanes for applications such as elastomeric fibers (spandex) and foam cushions. In microbiology, PEG 4000 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.[13] 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.[3][16] When working with phenol in a laboratory situation, PEG 300 can be used on phenol skin burns to deactivate any residual phenol. In biophysics, 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.

What is Polyethyleneglycol?
Polyethyleneglycol, or PEG 4000 for short, is a polyether consisting of a (-O-CH2-CH2-) backbone that is commonly used in many fields of academic research, industrial processing and commercial applications. PEG 4000s can also commonly be referred to as polyoxyethylene (POE) and polyethyleneoxide (PEO), but regardless of the name that is used, the simple structure of PEG 4000s (which consists of solely carbon, hydrogen and oxygen, see image below) affords safe compounds that are used throughout everyday life.

Additionally, it is this simple structure that separates PEG 4000s from similar compounds like propylene glycol and polypropyleneglycol. The two aforementioned compounds (polyethyleneglycol vs. propylene glycol) are derivatives of propylene oxide, which, when polymerized, bestows a completely different set of physical characteristics to the compound as compared to PEG 4000.
The method in which PEG 4000s are created allows for a wide variability in their physical attributes, allowing them to be utilized by many commercial markets. By controlling a PEG 4000’s size (i.e. molecular weight) and its size distribution, a wide variety of physical properties can be achieved, which sets Oxiteno’s line of PEG 4000 products, the 6000 powder series, apart from other name brands of polyethyleneglycols.

Due to the vast number of product types offered 6000 powder products (click here for a full listing), many physical forms (liquids, pastes, solids, flakes, powder, etc.) and viscosities of PEG 4000s are available. It is the numerous attributes of PEG 4000s that allow for their inclusion in a vast array of applications, ranging from the pharmaceutical industry to cosmetic markets. While the structure of PEG 4000 is simple, it is this compound’s solubility in water is what makes it such a versatile additive to enhance many industrial applications.

Because line of PEG 4000 products are non-toxic and hydrophilic (water-loving), these polymers are used in the home (i.e. to treat surfaces in cleaning agents made by cleaning chemicals manufacturers) as well as in the food production industry (to reduce the amount of foam during the processing of food products). PEG 4000s are generally considered to be biologically inert, making them safe to use throughout the medical and food-processing industries.

What is Polyethyleneglycol Used For?
Due to the variety of physical properties that can be achieved through PEG 4000 series, formulators in nearly all industries can benefit from this line of PEG 4000 products. A PEG 4000’s unique ability to enhance a dye’s solubility in aqueous formulations causes it to be used throughout the textile industry as dye carriers. PEG 4000s are also exceptional at retaining moisture in complex formulations, as well as to an applied surface, making them excellent humectants and anti-caking agents for cosmetic chemical suppliers and coatings chemical suppliers.

This unique relationship with water is further exploited by many other markets as PEG 4000s can help to stabilize emulsions and act as water-miscible co-solvents for aqueous formulations. The food industry uses these compounds as additives to reduce the amount of foam during food processing. Additionally, PEG 4000s find themselves very useful in the pharmaceutical industry due to their ability to act as rheological modifiers, thus being used as excipients.
New research techniques are increasingly incorporating PEG 4000 compounds via the use of ‘PEG 4000ylation’ onto protein and peptide therapeutics, thus improving their pharmacokinetics and leading to safer and more effective drugs1-2. Many of PEG 4000 series meet the requirements set forth by the National Formulary (NF) guidelines for safe preparation, manufacture and use of a variety of PEG 4000 compounds that can be used as excipients, botanicals and other similar products.

Is Polyethyleneglycol Safe?
PEG 4000s are generally considered to be a biologically inert substance, meaning that this class of oligomers and polymers are recognized to be safe for use in food, cosmetic and pharmaceutical applications. So, is polyethyleneglycol toxic? Due to the PEG 4000’s structure and its water solubility, these compounds are generally considered to be non-toxic, as studies of demonstrated their safety for use within the field of drug delivery1-2, for application to the skin in cosmetics3 and as additives in the food and vitamin processing industry4.
Where applicable, line of PEG 4000s, 6000 powder, adhere to the guidelines for the manufacturing set forth by the National Formulary (NF). Having initially been established by the U.S. Federal Food, Drug, and Cosmetics Act of 1938, these guidelines are currently recognized by the U.S. Food and Drug Administration (FDA). These manufacturing and production guidelines are annually reviewed, requiring to not only adhere to these strict standards, but maintain constant surveillance over the preparation of these non-toxic additives. Additionally, many of PEG 4000 products that are used in agricultural applications are safe for the environment and are on the Environmental Protection Agencies’ (EPA) inert ingredient list, meeting the requirements set forth in 40 CFR 180.910 and 40 CFR 180.930. This makes PEG 4000s attractive for agrochemical companies.

Polyethylene Glycol
· Adhesives
· Agriculture
· Ceramics
· Chemical Intermediates
· Cosmetics
· Toiletries
· Electroplating / Electropolishing
· Food Processing
· Household Products
· Lubricants
· Metal / Metal Fabrication
· Paints & Coatings
· Paper Industry
· Pharmaceuticals
· Printing
· Rubber & Elastomers
· Textiles
· Wood Processing

AVAILABLE FORMS AND NOMENCLATURE
PEG 4000, PEO, and POE refer to an oligomer or polymer of ethylene oxide. The three names are chemically synonymous, but historically PEG 4000 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 4000 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 PEG 4000s 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.[
PEG 4000 and PEO are liquids or low-melting solids, depending on their molecular weights. While PEG 4000 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 4000 are also available, depending on the initiator used for the polymerization process - the most common initiator is a monofunctional methyl ether PEG 4000, or methoxypoly(ethylene glycol), abbreviated mPEG 4000. Lower-molecular-weight PEG 4000s are also available as purer oligomers, referred to as monodisperse, uniform, or discrete. Very high purity PEG 4000 has recently been shown to be crystalline, allowing determination of a crystal structure by x-ray diffraction 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 4000.
PEG 4000s are also available with different geometries.
The numbers that are often included in the names of PEG 4000s indicate their average molecular weights (e.g. a PEG 4000 with n = 9 would have an average molecular weight of approximately 400 daltons, and would be labeled PEG 4000 400.) Most PEG 4000s 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.

PEG 4000 is the act of covalently coupling a PEG 4000 structure to another larger molecule, for example, a therapeutic protein, which is then referred to as a PEG 4000 protein. PEG 4000 interferon alfa-2a or -2b are commonly used injectable treatments for hepatitis C infection.
PEG 4000 is soluble in water, methanol, ethanol, acetonitrile, benzene, and dichloromethane, and is insoluble in diethyl ether and hexane. It is coupled to hydrophobic molecules to produce non-ionic surfactants.
PEG 4000s potentially contain toxic impurities, such as ethylene oxide and 1,4-dioxane. Ethylene Glycol and its ethers are nephrotoxic if applied to damaged skin.
Polyethylene oxide (PEO, Mw4 kDa) nanometric crystallites (4 nm)
Polyethylene glycol (PEG 4000) and related polymers (PEG 4000 phospholipid constructs) are often sonicated when used in biomedical applications. However, as reported by Murali et al., PEG 4000 is very sensitive to sonolytic degradation and PEG 4000 degradation products can be toxic to mammalian cells. It is, thus, imperative to assess potential PEG 4000 degradation to ensure that the final material does not contain undocumented contaminants that can introduce artifacts into experimental results.
PEG 4000s and methoxypolyethylene glycols are manufactured by Dow Chemical under the tradename 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 as surfactants, in foods, in cosmetics, in pharmaceutics, in biomedicine, as dispersing agents, as solvents, in ointments, in suppository bases, as tablet excipients, and as laxatives. Some specific groups are lauromacrogols, nonoxynols, octoxynols, and poloxamers.
Macrogol, 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 4000, macrogol 4000 or macrogol 6000).

PRODUCTION
Polyethylene glycol 400, pharmaceutical quality
Polyethylene glycol 4000, pharmaceutical quality
The production of polyethylene glycol was first reported in 1859. Both A. V. Laurence and Charles Adolphe Wurtz independently isolated products that were polyethylene glycols.[ Polyethylene glycol is produced by the interaction of ethylene oxide with water, ethylene glycol, or ethylene glycol oligomers.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 4000 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 dimethylglyoximeare used.
Alkaline 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 4000 is the basis of a number of laxatives.[ Whole bowel irrigation with polyethylene glycol and added electrolytes is used for bowel preparation before surgery or colonoscopy.
PEG 4000 is also used as an excipient in many pharmaceutical products.
When attached to various protein medications, polyethylene glycol allows a slowed clearance of the carried protein from the blood.
The possibility that PEG 4000 could be used to fuse nerve cells is being explored by researchers studying spinal cord injury.

CHEMICAL USES
The remains of the 16th century carrack Mary Rose undergoing conservation treatment with PEG 4000 in the 1980s
Terra cotta warrior, showing traces of original color
Because PEG 4000 is hydrophilic 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 4000 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 4000 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.
PEG 4000 has also been used to preserve objects that have been salvaged from underwater, 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 4000 is used when working with green wood as a stabilizer, and to prevent shrinkage.
PEG 4000 has been used to preserve the painted colors on Terra-Cotta Warriors unearthed at a UNESCO World Heritage site in China.]These painted artifacts were created during the Qin Shi Huang Di dynasty (first emperor of China). 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 Xian air. The paint would subsequently flake off in about four minutes. The German Bavarian State Conservation Office developed a PEG 4000 preservative that when immediately applied to unearthed artifacts has aided in preserving the colors painted on the pieces of clay soldiers
PEG 4000 is often used (as an internal calibration compound) in mass spectrometry experiments, with its characteristic fragmentation pattern allowing accurate and reproducible tuning.
PEG 4000 derivatives, such as narrow range ethoxylates, are used as surfactants.
PEG 4000 is a polyol and can be reacted with an isocyanate to make polyurethane.
PEG 4000 has been used as the hydrophilic block of amphiphilic block copolymers used to create some polymersomes.

BIOLOGICAL USES
PEG 4000 is commonly used as a crowding agent in in vitro assays to mimic highly crowded cellular conditions
PEG 4000 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.
PEG 4000 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 Medicinein 1984.
Polymer segments derived from PEG 4000 polyols impart flexibility to polyurethanes for applications such as elastomeric fibers (spandex) and foam cushions.
In microbiology, PEG 4000 precipitation is used to concentrate viruses. PEG 4000 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 4000-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.[21] The size of the PEG 4000 polymer has been shown to be important, with larger polymers achieving the best immune protection.
PEG 4000 is a component of stable nucleic acid lipid particles (SNALPs) used to package siRNA for use in vivo.
In blood banking, PEG 4000 is used as a potentiator to enhance detection of antigens and antibodies.
When working with phenol in a laboratory situation, PEG 4000 300 can be used on phenol skin burns to deactivate any residual phenol.
In biophysics, 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.

Polyethylene glycol (PEG 4000; /ˌpɒliˈɛθəlˌiːn ˈɡlaɪˌkɒl, -ˌkɔːl/) is a polyether compound with many applications, from industrial manufacturing to medicine. PEG 4000 is also known as polyethylene oxide (PEO) or polyoxyethylene (POE), depending on its molecular weight. The structure of PEG 4000 is commonly expressed as H−(O−CH2−CH2)n−OH.[
Uses of Polyethylene glycol (PEG 4000
Medical uses of Polyethylene glycol (PEG 4000
Main article: Macrogol
PEG 4000 is the basis of a number of laxatives.[4] Whole bowel irrigation with polyethylene glycol and added electrolytes is used for bowel preparation before surgery or colonoscopy.
PEG 4000 is also used as an excipient in many pharmaceutical products.
When attached to various protein medications, polyethylene glycol allows a slowed clearance of the carried protein from the blood.[5]
The possibility that PEG 4000 could be used to fuse axons is being explored by researchers studying peripheral nerve and spinal cord injury.[4]
Chemical uses of Polyethylene glycol (PEG 4000
The remains of the 16th century carrack Mary Rose undergoing conservation treatment with PEG 4000 in the 1980s

PEG 4000 is often used (as an internal calibration compound) in mass spectrometry experiments, with its characteristic fragmentation pattern allowing accurate and reproducible tuning.
PEG 4000 derivatives, such as narrow range ethoxylates, are used as surfactants.
PEG 4000 has been used as the hydrophilic block of amphiphilic block copolymers used to create some polymersomes.[13]
PEG 4000 has also been used as a propellent on the UGM-133M Trident II Missile, in service with the United States Air Force.[14]
Biological uses
PEG 4000 is commonly used as a crowding agent in in vitro assays to mimic highly crowded cellular conditions.[6]
PEG 4000 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.
PEG 4000 is used to fuse two different types of cells, most often B-cells and myelomas in order to create hybridomas.
Polymer segments derived from PEG 4000 polyols impart flexibility to polyurethanes for applications such as elastomeric fibers (spandex) and foam cushions.

In microbiology, PEG 4000 precipitation is used to concentrate viruses. PEG 4000 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 4000-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.[15] The size of the PEG 4000 polymer has been shown to be important, with larger polymers achieving the best immune protection.
PEG 4000 is a component of stable nucleic acid lipid particles (SNALPs) used to package siRNA for use in vivo.[16][17]
In blood banking, PEG 4000 is used as a potentiator to enhance detection of antigens and antibodies.[4][18]
When working with phenol in a laboratory situation, PEG 4000 300 can be used on phenol skin burns to deactivate any residual phenol (some references are required).
In biophysics, 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.

Industrial uses
A nitrate ester-plasticized polyethylene glycol (NEPE-75) is used in Trident II submarine-launched ballistic missile solid rocket fuel.
Dimethyl ethers of PEG 4000 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 4000 has been used as the gate insulator in an electric double-layer transistor to induce superconductivity in an insulator.[27]
PEG 4000 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 4000, 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 4000 is injected into industrial processes to reduce foaming in separation equipment.
PEG 4000 is used as a binder in the preparation of technical ceramics.

Due to its ubiquity in a multitude of products and the large percentage of the population with antibodies to PEG 4000, hypersensitive reactions to PEG 4000 are an increasing concern.[medical citation needed] Allergy to PEG 4000 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 4000 or were manufactured with PEG 4000.[30]

When PEG 4000 is chemically attached to therapeutic molecules (such as protein drugs or nanoparticles), it can sometimes be antigenic, stimulating an anti-PEG 4000 antibody response in some patients. This effect has only been shown for a few of the many available PEG 4000 therapeutics, but it has significant effects on clinical outcomes of affected patients.[31] Other than these few instances where patients have anti-PEG 4000 immune responses, it is generally considered to be a safe component of drug formulations.

PEG 4000 and PEO are liquids or low-melting solids, depending on their molecular weights. While PEG 4000 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 4000 are also available, depending on the initiator used for the polymerization process – the most common initiator is a monofunctional methyl ether PEG 4000, or methoxypoly(ethylene glycol), abbreviated mPEG 4000. Lower-molecular-weight PEG 4000s are also available as purer oligomers, referred to as monodisperse, uniform, or discrete. Very high purity PEG 4000 has recently been shown to be crystalline, allowing determination of a crystal structure by x-ray diffraction.[33] 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 4000.

PEG 4000s are also available with different geometries.
Branched PEG 4000s have three to ten PEG 4000 chains emanating from a central core group.
Star PEG 4000s have 10 to 100 PEG 4000 chains emanating from a central core group.
Comb PEG 4000s have multiple PEG 4000 chains normally grafted onto a polymer backbone.
The numbers that are often included in the names of PEG 4000s indicate their average molecular weights (e.g. a PEG 4000 with n = 9 would have an average molecular weight of approximately 400 daltons, and would be labeled PEG 4000 400.) Most PEG 4000s 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.
PEG 4000 is the act of covalently coupling a PEG 4000 structure to another larger molecule, for example, a therapeutic protein, which is then referred to as a PEG 4000 protein. PEG 4000 interferon alfa-2a or −2b are commonly used injectable treatments for hepatitis C infection.

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.
Alkaline catalysts such as sodium hydroxide (NaOH), potassium hydroxide (KOH), or sodium carbonate (Na2CO3) are used to prepare low-molecular-weight polyethylene glycol.