Polyethyleneimines

Polyethyleneimines (PEIs) are a group of synthetic polymers composed of repeating ethyleneimine units. They are characterized by a branched or linear structure, with primary, secondary, and tertiary amine groups along the polymer chain. This high density of amine groups makes PEIs particularly reactive and versatile in their applications. The charge density of PEIs is highly pH-dependent due to the protonation of these amine groups, a property crucial for many of their uses.

PEIs are synthesized through the ring-opening polymerization of aziridine, also known as ethyleneimine. Depending on the reaction conditions and catalysts used, either linear or branched PEIs can be produced. Branched PEIs are more common and are synthesized using an acid-catalyzed polymerization, while linear PEIs are typically produced via a more controlled cationic ring-opening polymerization.

The applications of PEIs are diverse. Their cationic nature at physiological pH makes them excellent candidates for gene delivery, where they can complex with negatively charged DNA or RNA to facilitate cellular uptake. They are also employed as flocculants in water treatment, adhesives, coatings, and as additives in various industrial processes. Furthermore, PEIs serve as building blocks for more complex macromolecular architectures and are used in the development of novel materials with tailored properties. The ability to modify PEIs through functionalization further expands their utility in areas such as drug delivery and diagnostics.