Strain softening and hardening of amorphous polymers: Atomistic simulation of bulk mechanics and local dynamics

¹ Group Polymer Physics, Eindhoven Polymer Laboratories and Dutch Polymer Institute - Technische Universiteit Eindhoven P.O. Box 513, 5600 MB Eindhoven, The Netherlands
² Institute of Chemical Physics - Moscow 119991, Russia
³ Institute of Mathematical Problems of Biology - Pushchino 142290, Russia

Corresponding author: A.V.Lyulin@tue.nl

Received: 4 April 2005
Accepted: 24 June 2005

Abstract

Molecular-dynamics (MD) simulations have been performed for two amorphous polymers with extremely different mechanical properties, atactic polystyrene (PS) and bisphenol A polycarbonate (PC), in the isotropic state and under load. The glass transition temperatures, Young moduli, yield stresses and strain-hardening moduli are calculated and compared to the experimental data. Both chemistry-specific and mode-coupling aspects of the segmental mobility in the isotropic case and under the uniaxial deformation have been identified. The mobility of the PS segments in the deformation direction is increased drastically beyond the yield point. A weaker increase is observed for PC.