Metal-free click polymerizations of activated azide and alkynes

Abstract

The Cu(I)-catalyzed azide–alkyne click polymerization has become a powerful tool for the preparation of functional polytriazoles. However, copper residues in the products could harm the performance of optoelectronic devices and be cytotoxic in biological applications. The complete removal of these residues after reaction from the polymers is therefore necessary but difficult. The metal-free azide–alkyne click polymerization (MFCP) provides a solution to this problem. Currently, the MFCP is facilitated by activated alkynes, and no activated comonomer, i.e. azide, has been reported. In this paper, an activated azide, 4,4′-diazidoperfluorobenzophenone, was designed and synthesized. Compared to the ordinary azide, such a monomer can remarkably accelerate the MFCP with alkynes. Thus, a new MFCP of activated azide and alkyne was established, and polytriazoles with high regioregularity (fraction of 1,4-isomer higher than 82%) and satisfactory molecular weights (M_w up to 34 000) were produced in high yields (up to 95.1%).