PEG and PEO are synonymous – they are different names for the same polymer. The word "glycol" refers to any organic compound containing two hydroxyl (OH) groups bound to different carbon atoms. Historically, PEG has tended to be used to refer to polymers with a molecular mass below 20,000 g/mol, whereas PEO has been used for larger polymers, though many people use the names interchangeably or prefer one over the other.
Polyethylene oxides and polyethylene glycols have a similar chemical structure. Differences lie in that polyethylene oxides are obtained by polymerization of ethylene oxide, and polyethylene glycols polycondensation of ethylene glycol molecules. Given the fact that the ethylene oxide in water easily reveals epoxide ring, turning into ethylene glycol, can be concluded about the identity of these polymer systems.
Polyethylene Oxide is a different material than Polyethylene Glycol even though the two materials have the same CAS number. The differences are molecular weight and the manufacturing process. Polyethylene Oxide should not be called Polyethylene Glycol.
The molecular weight of Polyethylene Oxide begins at 100,000 and goes up to 7,000,000 whereas Polyethylene Glycol only goes up to a molecular weight of 40,000.
The Polyethylene Oxides have not been consistently named in the IID. The same family of material has been described as Polyethylene Oxide Oral and Polyethylene Oxide 200K Oral and 7000K Oral with various maximum potency limits. All of these materials are the same product with the only difference being molecular weight. The molecular weight difference does not impact toxicity.