Different temperature dependence of nonlinear rheological responses in melt stretching*

Decades of research in nonlinear polymer rheology [1] have not fully cleared all the confusion in the literature including one concerning the alleged difference in the rheological responses of entangled solutions and melts to fast extensional deformation. The idea of nematic interaction modification of chain friction has caused Huang et al. [2] to find support from the examination of three polystyrene solutions where the solvent is polystyrene of respective molecular weight equal 1 kg/mol (that has T_g = 20 ^oC), 2 kg/mol and 4 kg/mol with T_g ~ 75 ^oC. We refute this idea by investigating similar PS solutions to indicate a different interpretation by showing how a breakdown of the time-temperature superposition occurs in nonlinear responses of these solutions, causing the 1K solution to respond more strongly than a 5K solution where the 1K solution is examined at a lower temperature.

[1] Nonlinear Polymer Rheology: Macroscopic phenomenology and molecular foundation, S. Q. Wang, (Wiley, 2018).
[2] Huang, Alvarez, et al., ACS Maco Letters 2013, 2, 741.