Hierarchical orientational relaxation inducing shish-kebab formations in polymer melt crystallization.

We studied athermal relaxation of bulk extended chains by means of dynamic Monte Carlo simulations, and we got intermediately relaxed melts with a memory of chain orientations but no more crystalline order. The orientational memory in the melts dominated the crystal orientation and nucleation types. The difference in crystallization behaviors induced by orientational relaxation suggested the mechanism of hierarchical crystallization. Thus, we studied the isothermal crystallization of a binary blend of different relaxed chains. We observed the prior crystallization of less relaxed chains could act as a shish to induce epitaxial crystallization of more relaxed chains to form kebabs. This mechanism had demonstrated the structure of precursors and gave insight into the formation of shish-kebab crystals in polymer melts. The results suggested that in flow-induced polymer crystallization the hierarchical orientational relaxation of chains decided the formation of shish-kebabs.