Tributylphosphine-catalyzed aziridine-based cycloaddition polymerization toward thiacyclic polymers

An organocatalytic cycloaddition polymerization approach for the facile synthesis of thiacyclic polymers is established in this work. Bis(N-sulfonyl aziridine)s and diisocyanates are employed as the monomers, and they undergo cycloaddition polymerizations smoothly in the presence of tributylphosphine. Different kinds of bis(N-sulfonyl aziridine)s, including 2,3-disubstituted and 2-substituted ones, are applicable for this polymerization. Two kinds of diisocyanates, 1,4-phenylene diisothiocyanate and 1,4-butane diisothiocyanate, are used, and the produced poly(thiazolidin-2-imine)s exhibited different photophysical properties. The synthesized poly(thiazolidin-2-imine)s with alkyl linkages are luminous in the solid state and in solution, but the aryl-linked ones are nonluminous. In addition, the luminescent polymer can serve as a selective and sensitive fluorescence sensor for Fe³⁺.