Solvent and catalyst-free modification of hyperbranched polyethyleneimines by ring-opening-addition or ring-opening-polymerization of N-sulfonyl aziridines

An easy, efficient, and solvent/catalyst-free synthetic methodology was developed for the modification of hyperbranched polyethyleneimines (PEI) by ring-opening-addition or ring-opening-polymerization of N-sulfonyl aziridines. Under melting and open-flask conditions, the nucleophilic primary and secondary amino groups of PEI attack the N-sulfonyl aziridines to afford, depending on the ratio of aziridine/PEI, sulfonamide-functionalized PEIs or PEI grafted by poly(sulfonamide)s, either by ring-opening-addition or ring-opening-polymerization. Surprisingly, without any conjugated fluorophore in the system, the grafted PEIs show strong fluorescence in the solution. Besides, the amphiphilic poly(ethyleneimine sulfonamide)s present good removal efficiency of metal ions (Fe3+, Co2+, Cu2+, and Zn2+) from aqueous solutions and can be recycled without losing their adsorption efficiency after desorption. This work provides an atom-economical and facile synthetic method toward polyethyleneimine modified materials, which have unique fluorescence properties and the ability to remove hazardous metals.