Definition and Applications :
The production of polyethylene glycol was first reported in 1859. Both AV Laurence and Charles Adolphe Wurtz independently isolated the products with polyethylene glycols. Polyethylene glycol is produced by the interaction of ethylene oxide, water, ethylene glycol or ethylene glycol oligomers. The reaction is catalyzed by acidic or basic catalysts. Ethylene glycol and its oligomers are preferred as a starting material over water, as they allow the production of polymers with low polydispersity (narrow molecular weight distribution). The polymer chain length depends on the ratio of reactants.
HOCH 2 , CH 2 , OH + n (CH 2 CH 2 O) → HO (CH 2 CH 2 O) n + 1 'H
Depending on the nature of the catalyst, the polymerization mechanism can be cationic or anionic. The anionic mechanism is preferred because PEG with low polydispersity can be obtained. Ethylene oxide polymerization is an exothermic process. Overheating or contamination of ethylene oxide with catalysts such as alkalis or metal oxides can cause excessive polymerization, which can lead to explosion after a few hours.
Polyethylene oxide or high molecular weight polyethylene glycol is synthesized by suspension polymerization. It is necessary to keep the growing polymer chain in solution during the multiple condensation process. The reaction is catalyzed by magnesium, aluminum, or calcium organoelement compounds. Clipping additives such as dimethylglyoxime are used to prevent dissolution of the polymer chains.
Alkaline catalysts such as sodium hydroxide (NaOH), potassium hydroxide (KOH), or sodium carbonate (Na2CO3) are used to prepare a low molecular weight polyethylene glycol.