Synthesis of Linear Polyethyleneimine by Living Anionic Polymerizations

The Problem:
Polyethyleneimine (PEI) is a unique polymer that has a wide range of commercial and research applications. It is most commonly formed by the cationic ring-opening polymerization (CROP) method, which creates a highly branched polymeric structure. The high degree of branching is the result of secondary amines along an existing PEI chain inducing the ring-opening of unreacted aziridine monomers. However, the CROP of aziridine to form branched PEI is difficult to control and reproduction between batches is problematic.

The Solution:
Researchers have produced a method for the production of the linear format polyethyleneimine (PEI). The method first polymerizes N-sulfonyl aziridines to form N-sulfonyl ethyleneimines, which are then converted into linear PEI. This allows for the creation of soluble living polymers and for the production of block co-polymers with PEI (which is currently not possible with non-linear PEI). The method additionally allows for the varying of molecular weight of the polymer.


  • Does not require 2-substituted sulfonylaziridines.
  • Polymerization occurs at room temperature.
  • Only requires a common solvent.
  • Resulting polymers have improved solubility with more accessible amine groups.
  • Allows for greater control and ability to be reproduced.

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