Entropic Network Model for Star Block Copolymer Thermoplastic Elastomers

Uniaxial tensile deformation of star block polymer elastomers with up to 10 arms is studied with molecular dynamics simulations of a bead-spring representation at two different deformation rates. The mechanical response is rationalized in terms of an entropic network model, which we generalize from linear to star polymers. The model universally accounts for the stress in the entire deformation range well into the nonlinear regime. As the strain rate is increased, we find additional hardening as the number of arms increases, which can be attributed to the breakup of physical cross-links.