Aziridine Termination of Living Anionic Polymerization

Abstract

A switch from carbanions to aza-anions is performed by the addition of N-tosylaziridine (TAz) to living poly(styryl) (PS) chains. This is the first example of carbanionic aziridine ring-opening which was previously activated by amidation with a tosyl group to enable nucleophilic ring-opening by the living chain end. Poly(styrene)-tosylaziridines (PS-TAz) with narrow molecular weight distributions and variable molecular weights are synthesized. The removal of the tosyl group and subsequent functionalization is shown, evidencing quantitative transfer to azaanionic species. All polymers are characterized in detail by (1) H NMR spectroscopy, DOSY (1) H NMR spectroscopy, and size exclusion chromatography (SEC). This strategy allows the introduction of amine groups via anionic polymerization in analogy to the well-established epoxide termination.

N-Ferrocenylsulfonyl-2-methylaziridine: the first ferrocene monomer for the anionic (co)polymerization of aziridines

“…Also butyl lithium can be used as an initiator, as it was previously shown that aza-anions propagate with lithium counter ions. 25 The polymerization of 1 was conducted under different conditions: polar solvents (DMF, THF, and DMSO) have been used, and the temperature, time (18-72 h) and initiators have been varied (Table 1, Scheme 2a). In all cases, the polymer precipitated during the reaction from solution.…”

The living anionic polymerization of activated aziridines: a systematic study of reaction conditions and kinetics

“…The azaanionic polymerization of activated aziridines was recently established. [4][5][6][7][8][9] To enable anionic polymerization of aziridines, the acidic proton at the nitrogen needs to be substituted by an activating group, e.g. a sulfonamide group (Scheme 1).…”

“…4,9 We have developed new monomers and initiator-systems during the last few years, expanding this still rather unexplored approach to polysulfonamides and amines. [5][6][7][8]15,16 With a similar ring-strain of 111 kJ mol −1 for ethylene imine as for ethylene oxide (114 kJ mol −1 ), the anionic ringopening polymerization should be feasible. 17,18 In contrast to unsubstituted ethylene imine, which can only be polymerized via a cationic mechanism, leading to branched PEI ( poly(ethylene imine)), 19 N-protected aziridines can also be polymerized anionically, due to their activating group.…”

Sequence-Controlled Polymers via Simultaneous Living Anionic Copolymerization of Competing Monomers

“…N ‐sulfonyl aziridines represent a rather new monomer class for the AROP, with a direct access to poly(ethylene imine)‐derivatives. With a comparable ring strain of ≈111 kJ mol −1 for ethylene imine and 114 kJ mol −1 for ethylene oxide, aziridines can undergo ring‐opening reactions and are typically polymerized by an uncontrolled cationic mechanism .…”