Macromolecular Rheology

Abstract

One of the most important features of polymeric systems is their response to weak external stimuli. Of utmost importance is their reaction to an imposed mechanical load, which reflects their viscoelasticity. The viscoelastic properties of polymers are central to their handling and are responsible for their wide‐ranging applications. In this article, we provide the basic elements of molecular rheology, the science of deformation and flow of matter, which is necessary for understanding polymer viscoelasticity and linking it to molecular characteristics of the studied macromolecules. The presentation is basic and does not require prior knowledge on the topic. It refers to amorphous flexible polymers with emphasis on melts. First, the fundamental aspects of rheological measurements are discussed, followed by a discussion on linear viscoelasticity. Then, the models for the linear viscoelastic response of both unentangled and entangled polymers are presented in detail for different architectures, linear, star, and well‐characterized branched polymers. Subsequently, we focus on the nonlinear viscoelastic regime with particular emphasis on the current state‐of‐the‐art and remaining challenges. Where appropriate, some applications of interest to the industrial practice are briefly discussed. Nonlinear phenomena such as flow instabilities, flow‐induced crystallization, and wall slip are not covered.