Pinching Dynamics and Extensional Rheology of Polyvinylpyrrolidone Solutions

Polyvinylpyrrolidone (PVP) is a water-soluble, non-ionic, synthetic polymer which has been extensively studied for its high hygroscopicity, complexation capabilities, biocompatibility, film-formation characteristics, and other highly sought-after properties. It is widely used in the food and beverage industry, pharmaceuticals and drug delivery, printing and coatings, and much more. For many of these applications, PVP in solution undergoes extensional flows during the manufacture and use of the products in which it is incorporated. While these solutions have been studied extensively under shear flows, a better understanding of PVP solutions under extension is still needed. This contribution characterizes the extensional behavior of dilute, semi-dilute, and entangled aqueous PVP solutions using Dripping-onto-Substrate rheometry protocols. Through the visualization and analysis of an unstable liquid bridge of aqueous PVP solution, formed between a dispensing nozzle and a partially wettable substrate, extensional relaxation times, and extensional viscosity are extracted.