Molecular Details of the "Catalytic Effect" of Long Chains on Short Chains in Stretch-Induced Polymer Crystallization

Using molecular dynamics simulation, strain-induced crystallization of polyethylene blends containing long and short chains was investigated. It was found that both long and short chains can participate in crystal nucleation. Meanwhile, the increase of the content of long chains leads to the decrease of the onset strain for crystallization, demonstrating that the presence of long chains can promote the conucleation of long and short chains. Further investigation revealed that the long-chain segments with a higher orientation along the stretching direction have a promoting effect on the deformation and orientation of short-chain segments located near them. Two effects contribute to this "catalytic effect": on one hand, there is a low interaction potential energy between the highly oriented long-chain bonds and highly oriented short-chain bonds; on the other hand, long chains can drive the deformation of short chains through the entanglement network between them.