Rheology of vitrimers

TLDR

The study presents a comprehensive rheology profile of vitrimers, offering analytical expressions for both linear and nonlinear viscoelastic behavior and exploring partial vitrimers with permanent and exchangeable sub‑networks. The authors develop analytical expressions for linear and nonlinear viscoelasticity, identify elastic‑plastic transitions tied to bond‑exchange lifetimes, and propose parameter‑detection methods via Master Curves and creep curves, also mapping phase behavior of partial vitrimers. The study finds that the elastic‑plastic transition occurs at the bond‑exchange lifetime, introduces Master Curve and creep‑based methods to extract material parameters, and shows that partial vitrimers can display strain thinning or thickening with a load‑dependent phase diagram.

Abstract

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.