Bridging the Gap between Polymer Melts and Solutions in Extensional Rheology

Since its inception, the tube model of polymer dynamics has undergone several modifications to account for observed experimental trends. One trend that has yet to be captured by a modified version of the tube model is the observed experimental difference between concentrated polymer solutions and polymer melts. We compare the nonlinear extensional rheology of a series of polystyrene solutions with wide concentration range between 10% and 100% (melt) in order to determine the key missing physics that can account for dilution effects. All the solutions studied have the same number of entanglements per chain and are diluted in the same solvent (oligomeric styrene). We show that the difference in nonlinear rheological behavior between polystyrene melts reported by Bach et al. and polystyrene solutions reported by Bhattacharjee et al. and Sridhar et al. can be bridged by changing the polystyrene concentration. The results presented represent a unique benchmark for all future modifications to the tube model.