Polyaddition of Azide-Containing Norbornene-Based Monomer through Strain-Promoted 1,3-Dipolar Cycloaddition Reaction

The azide-alkyne "click" reaction has been well known in the past decade, however, another kind of 1,3-dipolar cycloaddition, the azide-alkene reaction is not fully explored in polymer science to date. This contribution reports, for the first time, the discovery of a polyaddition of norbornene based monomer (NC11N3 ) containing both strained double bond and azide moieties. The reaction product is characterized by Fourier transform infrared spectroscopy (FTIR), NMR, gel permeation chromatography (GPC), and mass spectrometry (MS), which confirmed the mechanism that is through cycloaddition of azide to strained double bond on norbornene ring to form triazoline linkage. The reaction can proceed at room temperature as indicated by the increase of molecular weight and viscosity during storage. Monomer, dimer, trimer, tetramer, etc., and species with loss of N2 due to lability of triazoline moiety are identified in the mixture of reaction product. As a unique feature, elimination of N2 in the five-membered ring of triazoline affords a chance to form highly reactive materials, such as with aziridine, which can be a very powerful tool in chemical functionalizations, and find promising applications in reactive polymer resin industries.