Rheology of vitrimers

We describe the full rheology profile of vitrimers, from small deformation (linear) to large deformation (non-linear) viscoelastic behaviour, providing concise analytical expressions to assist the experimental data analysis, and also clarify the emerging insights and rheological concepts in the subject. We identify the elastic-plastic transition at a time scale comparable to the life-time of the exchangeable bonds in the vitrimer network, and propose a new method to deduce material parameters using the Master Curves. At large plastic creep, we describe the strain thinning when the material is subjected to a constant stress or force, and suggest another method to characterize the material parameters from the creep curves. We also investigate partial vitrimers including a permanent sub-network and an exchangeable sub-network where the bond exchange occurs. In creep, such materials can exhibit either strain thinning or strain thickening, depending on applied load, and present the phase diagram of this response.

Rheology studies on vitrimers have mostly focused on their linear viscoelasticity under small deformations. Here, the authors develop a full rheological understanding of vitrimer response that spans between small deformation and large-deformation regime, and across 22 decades of effective frequency, providing clear and concise analytical expressions to assist the experimental data analysis and propose a method to deduce material parameters using Master Curves.