Tetrabutylammonium fluoride initiated anionic ring-opening polymerizations of N-sulfonyl aziridines

Ionic pair tetrabutylammonium halide (TBAX) was efficient initiator in anionic ring-opening polymerizations (AROPs) of N-sulfonyl aziridines, in which the tetrabutylammonium fluoride (TBAF) was the optimal initiator effect controlled/living AROPs. TBAX initiated AROPs of 2-methyl-N-tosylaziridine (TsMAz) by relative activities on halide X in sequence of F > Cl > Br > I, which was corroborated to the nucleophilicities of the halides. Homopolymers and diblock copolymers of TsMAz and EsMAz were prepared. The AROPs possessed living nature by first order kinetics with fast polymerizations (0.5 to several hours), high conversions (90-99%), narrow dispersities (D < 1.16), and predicted molecular weights. Mechanism of initiation by direct attack on the aziridine ring with fluoride and propagation by sulfonyl amidate anion was proposed. This protocol provided new entry in design of catalyst/initiator of ionic pair for polymerizations, and developed synthetic toolbox for mild and efficient anionic ring-opening polymerizations.