Molecular Dynamics Study on the Stress Concentration in Polymer Networks with Dangling Chains.

Owing to structural defects, stress concentration frequently occurs in polymer network materials (PEMs), significantly altering their overall mechanical properties. Here, we investigate the impact of dangling chain defects on the stress concentration in PEMs using coarse-grained molecular dynamics simulation. Stress distributions on the network structure are calculated by using graph theory, with considering the effects of defect ratio (ϕ) and the distance from defects. It is found that the existence of dangling chains can alleviate stress by dissipating more internal energy. When considering the effects of all defects statistically, the stress concentration consistently occurs near the joint segments between dangling chains and the bare network (i.e., removing all of the dangling chains from the network). The stress concentration effect is significant when defects are in the region near the network edges. Stress tends to concentrate more on the dangling chains at low ϕ, while it tends to concentrate more on the bare network at high ϕ because of the enhanced chain motions in bare network. This implies that the stress concentration effect near the joint segment is predominant at low ϕ, and it is slightly weak as ϕ increased.