Molecular Understanding of Viscoelasticity in Transient Polymer Networks Based on Multiple Methods

Transient polymer networks are formed by dynamic crosslinks with a finite lifetime and therefore exhibit significant viscoelasticity, including non-Newtonian behaviors. Using the combination of multiple experimental techniques, such as viscoelastic measurements and spectroscopic analyses, these properties can be understood at the molecular level. This review classified transient polymer networks as side-chain and end-chain crosslinks, and viscoelastic studies of each type were presented. A combination of linear viscoelastic and spectroscopic methods revealed deviations between the viscoelastic properties of transient polymer networks and the molecular model. These deviations are sometimes attributed to dynamic heterogeneities potentially contained in the transient polymer network. These unexpected heterogeneous structures are challenging to control and impact viscoelasticity. Controlling and discussing these heterogeneities based on multiple experimental approaches is essential for a better molecular understanding of transient networks in the future.