One-step synthesis of cyclic polypyrazole and the self-assembly vesicles driven by hydrogen bond

Abstract

The synthesis of cyclic polymer is an important topic in polymer chemistry. Herein, we report a one-step method to prepare cyclic polypyrazoles. Monomers with two functional groups, diazo and alkyne, were synthesized and polymerized via 1,3-diploar cycloaddition in bulk under heating without any catalyst. Polypyrazoles with molecular weights in the range of 3800-4400 g/mol and yields in the range of 78.8-98.7% were successfully synthesized. No chain end group was detected by LC-QTOF-MS and FTIR, which proves the cyclic structure of polypyrazoles. What is noteworthy is that the cyclic polypyrazoles can self-assemble into vesicles during the reprecipitation process, which was proved by the results of SEM and TEM. The reason for that is the formation of intermolecular hydrogen bond between NH and ester groups.