Viscoelasticity of Polymers with Dynamic Covalent Bonds: Concepts and Misconceptions

Polymers with dynamic covalent bonds are an exciting class of materials with properties and potential applications that rapidly gain significant attention from diverse scientific communities. While the number of publications on this emerging topic increases exponentially, navigating through this literature reveals a series of physical inconsistencies in previously established concepts and some misconceptions in data analysis and interpretation. The current paper presents an analysis of practices often applied to the characterization of systems with dynamic bonds and emphasizes particular misconceptions that may lead to critical divergences and misinterpretations of the results. We particularly focus on practices that should be avoided in the interpretation of stress-relaxation and viscoelastic data and in estimates of the bond dissociation energy. Instead, we suggest using traditional approaches that have been applied to the analysis of polymer viscoelastic properties for decades. Lastly, we emphasize the current challenges in a full understanding of the microscopic behavior of vitrimers.