Periodic polymers based on a self-accelerating click reaction

Abstract

A self-accelerating double-strain-promoted azide–alkyne cycloaddition reaction (DSPAAC) was employed for the formation of periodic polymers with ultrahigh molecular weights or a cyclic topology. DSPAAC-based stoichiometric imbalance-promoted step-growth polymerization was introduced to copolymerize sym-dibenzo-1,5-cyclooctadiene-3,7-diyne (DIBOD) and encoded bis-azide monomers (N₃–R–N₃) from a multicomponent reaction. With excess molar amounts of DIBOD to N₃–R–N₃, this novel step-growth polymerization produced the periodic polymers with absolute molecular weights above 6 × 10⁵ g mol⁻¹. This value is much higher than that (usually less than 5 × 10⁴ g mol⁻¹) of the periodic polymers obtained by traditional step-growth polymerization reported in the literature. With excess molar amounts of encoded N₃–R–N₃ to DIBOD, periodic telechelic polymers with azide terminals and relatively low molecular weights were prepared. They were then efficiently ring-closed in a highly dilute solution in the presence of excess molar amounts of DIBOD to produce the corresponding periodic cyclic polymers with high purity.