Tuning the Viscosity Profiles of High-Tg Poly(1,2,3-triazolium) Covalent Adaptable Networks by the Chemical Structure of the N-Substituents

Abstract

A designed library of covalent adaptable networks (CANs) having 1,2,3-triazolium dynamic cross-links are obtained through the combination of solvent- and catalyst-free thermally induced azide–alkyne cycloaddition and N-alkylation reactions. The use of rigid heterocyclic or aromatic segments affords CANs with a greatly extended range of thermomechanical profiles, with Tgs up to 146 °C, dramatic changes in relaxation times (from 1.5 h to less than 2 min at 150 °C) depending on the chemical structure of the N-substituents of 1,2,3-triazolium cross-links, and tunable rubbery plateaus, with nearly constant elastic moduli up to ca. 160 °C. A detailed correlation between the rheological properties and the chemical compositions of these CANs shows that the relaxation dynamics of the networks are mainly determined by the chemical structure of the N-substituents of the 1,2,3-triazolium cross-links and are independent of both the composition of the surrounding polymer networks and the corresponding Tg, at temperatures ranging from Tg + 20 °C up to Tg + 180 °C.