ABSTRACT

The last decade has witnessed some major strides in polymer rheology. The technological aspects of this highly interdisciplinary field are increasingly important. The role of polymer synthesis in determining the polymer structure and its effect, in turn, on flow behaviour has been recognized for a long time. In turn, the flow properties have a dominant effect on downstream processing. Modern materials, whether intended for industrial or personal use, are increasingly tailored to meet specific needs. The interaction between the structure of the material, the processing involved and the desired properties of the end product, is an area of significant commercial and intellectual interest. Furthermore, the material properties, in many cases, can either assist or hinder the processing steps. Conversely the processing steps can significantly change the material properties.

Extensional or stretching flows are often encountered in several industrial operations and these are qualitatively and quantitatively different from shear flows. The extent of deformation induced on the macromolecules in solution is also significantly different and consequently large stresses are generated. The research in this area is also motivated by the desire to understand the coupling between chain architecture and rheology and is driven by advances in our ability to synthesize polymers with controlled architecture. The advent of several new techniques and powerful theoretical insights has yielded a profound understanding of the nexus between deformation, chain conformation and stress.

The last decade has seen a vast improvement in our ability to quantitatively measure the extensional viscosity of polymer solutions. This has led to a new understanding of the physics involved in the deformation of macromolecules. This lecture traces these developments and shows how this is leading to a better understanding of processes where extensional flow dominates.