Exploring Shear Thickening of Telechelic Associating Polymers through Stochastic Simulations

Hydrophobically modified exthoxylated urethane (HEUR) is one of the most popular examples of telechelic associating polymer. In a certain range of HEUR concentration in aqueous solution, (i) linear viscoelasticity follows a single-Maxwellian behavior with a characteristic time controlled by the network relaxation due to association/dissociation kinetics. In simple shear flows, HEUR systems often (ii) exhibit strain hardening in the transient startup when the shear rate exceeds the reciprocal relaxation time, and (iii) at steady state deviate from the Cox-Merz rule, deviations including (iv) a shear-thickening phenomenon. Recently, Park and Ianniruberto [1] suggested a new stochastic simulation to describe the complex rheological behavior listed in (i-iv). The results indicate that finite extensibility effects are mostly responsible for the strain hardening, while deviations from the Cox-Merz rule are due to the persistence of bridge chains. However, the detailed mechanism behind the shear thickening is still unclear. In this study, we show additional observables by using the same simulation method for a better understanding of the shear-thickening phenomenon. Furthermore, we extend the range of the parameter space explored in [1] by examining larger (and more reasonable) values of the ratio between the loop dissociation time and the Brownian diffusion time of flower-like micelles. [1] G. W. Park and G. Ianniruberto, J. Rheol. 61, 1293 (2017)