Step-Growth Polymerization Method for Ultrahigh Molecular Weight Polymers

The preparation of polymers with an ultrahigh molecular weight (>10⁶ g/mol; UHMW) is always a challenge for homogeneous step-growth polymerization. Herein, a unique homogeneous step-growth polymerization method was developed to prepare various UHMW polymers. In this approach, a double-strain-promoted azide-alkyne click reaction (DSPAAC) with a reactive intermediate was used as the polymerization reaction, and sym-dibenzo-1,5-cyclooctadiene-3,7-diyne (DIBOD) and bis-azide compounds with 2,6-diisopropylphenyl azide terminals were used as the monomer pairs. The DSPAAC reaction, with a reactive intermediate, facilitated this polymerization method to efficiently prepare UHMW polymers under convenient, stoichiometrically imbalanced conditions using a slight excess of DIBOD to bis-azide monomer. In addition, the click nature of the DSPAAC reaction facilitated this polymerization method to synthesize UHMW polymers under ambient conditions, requiring no catalysts. The resultant UHMW polymers presented strong fluorescence peaking at 423 nm, good thermal property with the glass transition temperature up to 270 °C, and good mechanical property with Young's modulus above 1 GPa.