Self-Accelerating Click Reaction in Step Polymerization

A self-accelerating double-strain-promoted azide-alkyne cyclo-addition reaction (DSPAAC) was used in the step polymerization for the first time. This produced a novel stoichiometric imbalance-promoted homogeneous step polymerization method using sym-dibenzo-1,5-cyclooctadiene-3,7-diyne (DIBOD) and various bis-azide compounds (N-3-R-N-3) as respective monomers. Because of the self-accelerating property of DSPAAC reaction, the novel step polymerization method could prepare high molecular weight polymers under stoichiometry imbalance condition with excess molar amounts of DIBOD to N-3-R-N-3. Based on the click property of DSPAAC reaction, the novel step polymerization could be efficiently performed in very mild reaction conditions such as in air at room temperature without requiring any metal catalyst or chemical stimulus. Under the present polymerization condition, the preparation of high molecular weight polymers from this novel method was accompanied by the formation of cyclic oligomers with a weight content above 30%. The resultant polymers possessed a unique fluorescence property, which emitted strong fluorescence peaking at 412 nm under UV irradiation at 280 nm.