Rheological Properties of Covalent Adaptable Networks with 1,2,3-Triazolium Cross-Links: The Missing Link between Vitrimers and Dissociative Networks

Abstract

Vitrimers, in stringent contrast to dissociative networks, involve associative covalent exchanges and remain fully cross-linked at all temperatures. However, we have previously reported on poly(1,2,3-triazolium) dynamic networks that exhibit linear rheological characterization indistinguishable from vitrimers although being based on a dissociative covalent exchange process, i.e., de-N-alkylation and re-N-alkylation reactions. Herein, we highlight the main features of dissociative and associative covalent adaptable networks (CANs) and discuss their respective linear rheological behaviors. After giving a detailed overview of the extent and potential of dynamic polymer networks having 1,2,3-triazolium cross-links in particular and CANs involving trans-N-alkylation exchanges in general, we perform a detailed rheological comparative characterization of previously described aliphatic 1,2,3-triazolium-based dynamic networks and a new bicomponent thermosetting system issued from the mixing of linear polystyrene chains having complementary benzyl iodide and 1,2,3-triazole pendent groups. We propose a simple but comprehensive rheological characterization methodology that enables proper comparison between all types of CANs, i.e., vitrimers and dissociative networks. Owing to the combination of a high glass transition temperature dynamic network and fast trans-N-alkylation exchanges in this new dissociative network, it is possible to characterize both glass transition and network relaxation with single rheological experiments. We provide clear experimental evidence that although located within a narrow temperature range, the temperature dependences of these two transitions are distinct and follow WLF and Arrhenius models, respectively.