Following the footsteps of Graessley to open the Pondera’s box in nonlinear polymer rheology

Modern research on nonlinear rheological responses of entangled polymers was initiated by the pioneering studies of Bill Graessley and others. One of Graessley's results [1] sent the earliest warning about lack of complete understanding after the creation of the tube model [2]: Polybutadiene melts showed ultra “strain softening” when examined with large stepwise shear. Along with Osaki, Graessley emphasized the importance to understand the anomaly associated with the stress relaxation. This presentation reviews the history of nonlinear polymer melt rheology, a subject we have devoted a decade of intense efforts [3] and indicates how the stress relaxation behavior has intrigued us all and revealed considerable insight into the essence of nonlinear responses.
[1] Vrentas CM, Graessley WW. Study of shear-stress relaxation in well characterized polymer liquids. J Rheol. 1982;26(4):359–71.
[2] Doi M, Edwards S. Dynamics of concentrated polymer systems. Part 4.—Rheological properties. J Chem Soc Faraday Trans 2 Mol Chem Phys. 1979;75:38–54.
[3] Nonlinear Polymer Rheology – macroscopic phenomenology and molecular foundation, Shi-Qing Wang, Wiley (2017).