Metal-Free A2/B2-Type Azide-Alkyne Polyaddition: Effect of Azides Structure on Their Reactivity and Properties of Polymerization Products.

Abstract

Non-isothermal calorimetry is performed to study the kinetics of metal-free A₂/B₂-type azide-alkyne polyaddition between the dipropargyl ether of bisphenol A with different organic diazides. The diazide structure is varied to probe the effect of the nature of a hydrocarbon spacer between the azide groups on their reactivity. Isoconversional analysis demonstrates that the polymerization processes are characterized by the same activation energy of 84 kJ mol^-1 for all studied diazides. It is found that diazides with aromatic spacers demonstrate ~1.6 times higher reactivity than that of diazides with the alkyl spacer. The difference in the reactivity is explained by the difference in the electronic effects of the hydrocarbon spacers on the azide groups as well as by the difference in their steric availability. The veracity of the obtained kinetic parameters is validated by a polymerization test at the time-temperature conditions predicted from the obtained kinetic data followed by independent assessment of the monomer conversion using FTIR.