Microstructural Dynamics of Polymer Melts during Stretching: Radial Size Distribution

Area of Science:

• Polymer Physics
• Rheology
• Materials Science

Background:

• Transient elongational viscosity in polymer melts exhibits strain hardening, influenced by strain rate.
• Differences in chain stretching between extension and shear explain this phenomenon.
• Microscopic evolution of polymer melts under extensional flow lacks comprehensive statistical analysis.

Purpose of the Study:

• To statistically analyze the microscopic evolution of linear polymers during stretching processes.
• To investigate the radial size distributions and their relationship with strain hardening.
• To determine the influence of Hencky strain and chain length on the onset of strain hardening.

Main Methods:

• Utilized dissipative particle dynamics simulations.
• Explored radial size distributions P(Rg,t) of linear polymers.
• Analyzed polymer behavior under uniaxial extensional flow.

Main Results:

• Mean radius of gyration R¯g(t) and standard deviation σ(t) remained constant during linear viscoelasticity.
• R¯g and σ increased rapidly in the non-linear regime, with potential for bimodal size distributions.
• The onset of strain hardening was independent of Hencky strain and chain length.

Conclusions:

• Polymer size distribution changes significantly during the non-linear extensional flow regime.
• The onset of strain hardening is a critical transition point in polymer melt dynamics.
• Dissipative particle dynamics provides insights into the microscopic origins of macroscopic rheological properties.