The most effective catalyst for the polymerization of ethylene oxide to produce high molecular weight polyethylene oxide also known as polyethylene glycol or PEG is typically a metal-based catalyst, such as an organometallic compound. One of the most widely used catalysts for this purpose is potassium alkoxide, specifically potassium tert-butoxide t-BuOK . This catalyst has been shown to provide high molecular weight PEG with good control over the polymerization process. Other metal alkoxides, such as sodium or magnesium alkoxides, can also be used as catalysts for this reaction. However, potassium tert-butoxide is generally considered to be the most effective due to its high reactivity and selectivity.