PEG 9000

PEG 9000 is used as a stabilizing agent for fragrance in the fabric care market and as a binder for solid particle delivery. 
PEG 9000 acts as a binder and filler offering internal and external lubrication. 
PEG 9000 has been in pharmaceutical granulation technology for decades.

CAS Number: 25322-68-3
Synonyms
PEG 9000, Poly(ethylene glycol) 9,000

PEG 9000 is a polyether compound derived from petroleum with many applications, from industrial manufacturing to medicine. 
PEG 9000 is also known as polyethylene oxide (PEO) or polyoxyethylene (POE), depending on its molecular weight. 
The structure of PEG 9000 is commonly expressed as H−(O−CH2−CH2)n−OH.
PEG 9000 is commonly incorporated into hydrogels which present a functional form for further use.

Uses
Medical uses
Main articles: Macrogol and PEGylation
Pharmaceutical-grade PEG 9000 is used as an excipient in many pharmaceutical products, in oral, topical, and parenteral dosage forms.
PEG is the basis of a number of laxatives (as MiraLax, RestoraLAX, MoviPrep, etc.).
Whole bowel irrigation with PEG 9000 and added electrolytes is used for bowel preparation before surgery or colonoscopy or for children with constipation.
Macrogol (with brand names such as Laxido, Movicol and Miralax) is the generic name for PEG 9000 used as a laxative. 
The name may be followed by a number that represents the average molecular weight (e.g. macrogol 3350, macrogol 4000, or macrogol 6000).
The possibility that PEG 9000 could be used to fuse axons is being explored by researchers studying peripheral nerve and spinal cord injury.
An example of PEG 9000 hydrogels (see Biological uses section) in a therapeutic has been theorized by Ma et al. 

They propose using the hydrogel to address periodontitis (gum disease) by encapsulating stem cells in the gel that promote healing in the gums.
The gel with encapsulated stem cells was to be injected into the site of disease and crosslinked to create the microenvironment required for the stem cells to function.
PEGylation of adenoviruses for gene therapy can help prevent adverse reactions due to pre-existing adenovirus immunity.
A PEGylated lipid is used as an excipient in both the Moderna and Pfizer–BioNTech vaccines for SARS-CoV-2. 
Both RNA vaccines consist of messenger RNA, or mRNA, encased in a bubble of oily molecules called lipids. 
Proprietary lipid technology is used for each. 
In both vaccines, the bubbles are coated with a stabilizing molecule of PEG 9000.
PEG 9000 could trigger allergic reaction, and 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 shock.
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
PEG 9000 can serve as a green reaction medium in a variety of organic reactions.
PEG 9000 is also commonly used as a polar stationary phase for gas chromatography, as well as a heat transfer fluid in electronic testers.
PEG 9000 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. 
PEG 9000 replaces water in wooden objects, making the wood dimensionally stable and preventing the warping or shrinking of the wood when it dries.
In addition, PEG 9000 is used when working with green wood as a stabilizer, and to prevent shrinkage.
PEG 9000 has been used to preserve the painted colors on Terracotta Warriors unearthed at a UNESCO World Heritage site in China.
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 preservative that when immediately applied to unearthed artifacts has aided in preserving the colors painted on the pieces of clay soldiers.
PEG 9000 is often used (as an internal calibration compound) in mass spectrometry experiments, with its characteristic fragmentation pattern allowing accurate and reproducible tuning.
PEG 9000 derivatives, such as narrow range ethoxylates, are used as surfactants.
PEG 9000 has been used as the hydrophilic block of amphiphilic block copolymers used to create some polymersomes.
PEG 9000 is a component of the propellent used in UGM-133M Trident II Missiles, in service with the United States Navy.
PEG 9000 has been used as a solvent for aryl thioether synthesis.

Biological uses
An example study was done using PEG 9000-diacrylate hydrogels to recreate vascular environments with the encapsulation of endothelial cells and macrophages. 
This model furthered vascular disease modeling and isolated macrophage phenotype's effect on blood vessels.
PEG 9000 is commonly used as a crowding agent in in vitro assays to mimic highly crowded cellular conditions.
Although PEG 9000 is considered biologically inert, it can form non-covalent complexes with monovalent cations such as Na+, K+, Rb+, and Cs+, affecting equilibrium constants of biochemical reactions.
PEG 9000 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 9000 is used to fuse two different types of cells, most often B-cells and myelomas 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.
In microbiology, PEG 9000 precipitation is used to concentrate viruses. 
PEG 9000 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 9000-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 9000 is important, with larger polymers achieving the best immune protection.
PEG 9000 is a component of stable nucleic acid lipid particles (SNALPs) used to package siRNA for use in vivo.
In blood banking, PEG 9000 is used as a potentiator to enhance detection of antigens and antibodies.
When working with phenol in a laboratory situation, PEG 9000 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 channel diameter studies, because in aqueous solutions they have a spherical shape and can block ion channel conductance.

Production
The production of PEG 9000 was first reported in 1859. Both A. V. Lourenço and Charles Adolphe Wurtz independently isolated products that were polyethylene glycols.
PEG 9000 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 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. 
PEG 9000 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.