Living anionic polymerization of aziridines tolerates water and gives fast access to amphiphilic multi-block copolymers

The synthesis of well-defined polyamines remains a challenge in polymer science. Poly(ethylene imine) (PEI) and derivatives are normally produced via cationic polymerization of poly(2-oxazoline)s. Gene delivery applications for instance require accurate control over polymer architecture and weights. Living anionic polymerization (LAP), the superior method for well-defined polymers, is an ideal platform to prepare PEI architectures from activated aziridines with high structural control.
A major paradigm of LAP is the demanding synthesis, as high purity of reagents and solvents are essential to produce well-defined high molar mass polymers. Traces of water will terminate carbanionic or initiate oxyanionic polymerizations. This poster presents the living anionic polymerization of aziridines, which remain living with high control over molar mass and dispersity although in the presence of protic “impurities” such as water and alcohols.
A second paradigm in LAP is that statistical copolymerization produces gradient copolymers or no copolymers (if the monomer reactivities are too different). Again, LAP of activated aziridines breaks this paradigm as the statistical copolymerization with ethylene oxide leads to perfect diblock copolymers with basically no tapering. Various polymer structures such as multiblock polymers with linear or branched architecture are accessible, which can act as non-ionic surfactants.
Furthermore, mild desulfonylation of polysulfonamides can be performed to access well-defined linear PEIs which are usually exclusively synthesized by cationic ring-opening polymerization of oxazolines.
We believe that the LAP of aziridines in combination with other anionically polymerizable monomers and its efficient desulfonation process will provide straightforward access to novel polyamides and –amines with interesting properties for a great number of applications.