Microstructural Dynamics of Polymer Melts during Stretching: Radial Size Distribution

The transient elongational viscosity eta(e)(t) of the polymer melt is known to exhibit strain hardening, which depends on the strain rate (epsilon)over dot. This phenomenon was elucidated by the difference of chain stretching in the entanglement network between extension and shear. However, to date, the microscopic evolution of polymer melt has not been fully statistically analyzed. In this work, the radial size distributions P(R-g, t) of linear polymers are explored by dissipative particle dynamics during the stretching processes. In uniaxial extensional flow, it is observed that the mean radius of gyration (R) over bar (g)(t) and standard deviation sigma(t) remain unchanged until the onset of strain hardening, corresponding to linear viscoelasticity. Both (R) over bar (g) and s rise rapidly in the non-linear regime, and bimodal size distribution can emerge. Moreover, the onset of strain hardening is found to be insensitive to the Hencky strain ((epsilon)over dot(H)t) and chain length (N).

Automated summary

This work investigates the evolution of radial size distributions of linear polymers during stretching processes through dissipative particle dynamics simulations. In uniaxial extensional flow, it is observed that the mean radius of gyration and standard deviation remain unchanged until the onset of strain hardening, corresponding to linear viscoelasticity. Both parameters rise rapidly in the non-linear regime, and bimodal size distribution can emerge. Moreover, the onset of strain hardening is found to be insensitive to the Hencky strain and chain length.