Decoupling Multiple Relaxation Modes: Composition and Distribution of Terminal Relaxation Time in Associative Polymers

The distinctive rheological behavior of associative polymers (APs) is commonly attributed to the supramolecular interactions between stickers, where transient bonds are continually forming and breaking. This ongoing disruption and reconstruction significantly extend the terminal relaxation time, endowing APs with properties similar to those of entangled polymers. Based on the fundamental sticky Rouse model (SRM), the terminal relaxation of APs can be understood as a result of a combination of strand motion and associative interactions. However, this explanation may be overly simplistic. The presence of multiple relaxation modes arising from a broader range of molecular processes introduces complexity, and their individual contributions to the terminal relaxation time remain uncertain. In this work, we focus on decoupling these multiple relaxation modes. Our findings reveal that, beyond strand motion and associative interactions, the terminal relaxation time is also influenced by factors such as the loss of cross-links, reassociation dynamics, and small molecule reactants. Furthermore, the difference between the activation energy required for strand motion and the magnitude of reaction kinetic activation energy between stickers plays a crucial role in determining the distribution of the terminal relaxation time. We believe that this work offers significant insights into the linear viscoelasticity (LVE) of APs.