Oxyalkylation

Oxyalkylation is a chemical process that attaches alkylene oxide units to substrates bearing active hydrogens, typically alcohols, phenols, or amines, to form alkoxy-terminated polyethers. The resulting oxyalkylated derivatives are widely used as nonionic surfactants, plasticizers, and polyether polyols.

The most common forms are ethoxylation, using ethylene oxide (EO), and propoxylation, using propylene oxide (PO). In ethoxylation, a deprotonated substrate attacks the epoxide and sequentially adds ethoxy units to give poly(ethylene oxide) chains; propoxylation yields poly(propylene oxide) chains. Mixed EO/PO sequences are also prepared to tune properties.

Catalysts and conditions control rate, molecular weight, and polydispersity. Common catalysts include alkali metal hydroxides such as KOH or NaOH, sometimes with phase-transfer aids or Lewis acids. Reactions are conducted at elevated temperature, with controlled addition of oxide to manage heat and chain growth; batch and continuous processes are used.

Applications include nonionic surfactants such as alkyl ethoxylates and alkylphenol ethoxylates, detergents, cosmetics, coatings, and emulsions. Polyether polyols from oxyalkylation serve as precursors for polyurethanes. The process also enhances solubility and compatibility of substrates, with product properties determined by the EO/PO content and degree of polymerization.