Polyglycols, also called polyether glycols or polyols, are chemical compounds with the general formula
HO[-(CH2)mO-]n-(CH2)m-OH.
They are viscose liquids or waxy solids depending on molecular weight and hydroxyl content due to the
weak intermolecular attractive forces (low polarity). The only exception is polyoxymethylene
(see Polyacetal) which is a highly crystalline polymer.
The three most important polyglycols are poly(ethylene glycol), poly(propylene glycol) and poly(tetrahydrofuran). Poly(ethylene glycol) and poly(propylene glycol) with a molecular weight of less than 20,000 g/mol are obtained from the ring-opening polymerization of oxirane and methyloxirane. Poly(tetrahydrofuran) is commonly prepared by acid-catalyzed polymerization of tetrahydrofuran.
Polyglycols have superior lubricity and solvency properties and therefore, are part of many functional fluids. They are also known to greatly improve the flexibilty and toughness of polyesters and urethanes when copolymerized with them.
| Polyether | Repeat Unit | Trade Name |
| Polyacetal, Paraformaldehyde (POM) | −CH2O− | Delrin®, Duracon® Celcon®, Ultraform® |
| Polyethylene glycol PEG), Polyethylene oxide (PEO), Polyoxyethylene (POE) | −CH2CH2O− | Carbowax™, Pluriol A-E® |
| Polypropylene glycol (PPG), Polypropylene oxide (PPOX), Polyoxypropylene (POP) | −CH2CH(CH3)O− | DOW P Series® |
| Polytetrsamethylene glycol (PTMG), polytetramethylene ether glycol (PTMEG), Polytetrahydrofuran (PTHF) | −CH2CH2CH2CH2O− | Terathane®, PolyTHF® |
Polyglycols are sold under various trade names, including Carbowax™, Pluriol® , Jeffox®Polyglycol, Polymeg®, Terathane®, and PolyTHF®. Some well-known large volume producers are Dow, BASF, Bayer and Invista.
Most commercial materials have a molecular weight in the range of 500 and 10,000 g/mol. Ethylene oxide polymers with molecular weights of 105 - 106, referred to as poly(ethylene oxide), are also produced.
Polyglycols are used in a variety of products, including elastomers, adhesives, sealants and epoxy flexibilizers. With the exception of polyoxymethylene (see polyacetal polymers), unmodified aliphatic polyethers (polyglycols) cannot be used as engineering plastics due to their waxy nature. When used in engineering plastics, they are usually copolymerized with other monomers to produce polyurethane and polyester block copolymers, including thermoplastic polyurethane and polyester elastomers. They greatly improve the flexibility and impact toughness of these materials. They are also used as hydraulic fluids and lubricants, as additives in cosmetics, and as binders in ceramic and metalic powders.
Among all polyglycols, polyethylene glycol (PEG) is probably the most versatile glycol. It is soluble in water, methanol, ethanol, acetonitrile, benzene, and dichloromethane, but insoluble in diethyl ether and hexane. It is frequently used in combination with glycerin in skin creams, personal lubricants, and in toothpastes as a dispersant and to bind water. PEG is also used as an anti-foaming agent in food.
Some grades have been functionalized with various end groups for various other chemical applications. For example, PEGs are coupled to hydrophobic molecules to produce non-ionic surfactants.
Poly(ethylene glycol) has lately received increased interest for use as a biomedical polymer due to its bio- and blood compatibility in linear, grafted, and gel form. It is believed that it has no specific interactions with biological materials. These properties make PEG one of the most useful macromolecules in biochemistry.