Polyethyleneimine (Polyaziridine)

Properties and Applications

Polyethylenimines (PEI) are low to high molecular weight compounds with the general formula -[CH₂-CH₂-NH₂]-, made by ring opening polymerization of aziridine. These polymers are available as linear, partly branched or repetitively branched polymers (dendrimers). The linear form contains only primary amines in the backbone whereas branched PEI also contains secondary and tertiary amines. Thus, these polymers have different properties and reactivities. Linear high MW PEI is usually solid at room temperature while branched PEIs are typically liquids at all molecular weights. All three forms are soluble in water, methanol, ethanol, and chloroform but insoluble in solvents of low polarity such as benzene, ethyl ether, and acetone.

Polyethyleneimines and polyaziridines are used for various applications in numerous products including detergents, cosmetics, adhesives, printing inks, paper, wood laminates, cement, and bricks. They are used as cross-linkers (aziridine), flocculating agents, textile coating additives, adhesion promoters, enzyme carriers, wet-strength agents and as chelating agents which form complexes with metal ions. The largest use of PEIs is in the paper industry. It increases paper strength and fine solid flocculation in the waste stream for recycling.

Manufacturers & Distributors

¹PEI quickly dissolves in hot water at low pH but only slowly in cold water at pH 7.