Reexamination of shish kebab formation in poly(ethylene oxide) melts

Although recent experiments concerning shear effects on crystallization in polymer melts are inclined to support the oriented network model, two important questions still remain open: the effect of polydispersity on shish formation and the growth mechanism of shish. In this work, a narrowdisperse poly(ethylene oxide) (PEO) is chosen as a model system to clarify the role of polydispersity for shish kebab formation after a pulse of flow. The intact structure of shish kebab observed via scanning electron microscopy (SEM), with a 150 nm wide shish core and perpendicular epitaxially grown kebabs with a long period of about 35 nm, reveals that polydispersity is not a necessary condition for shish kebab formation. On the other hand, two-step shear experiment is utilized to elucidate the growth mechanism of shish. It has been proved in a latest study that shish growth is related to the size of the growing nuclei (interval time) and second step shear rate. In this manuscript, a third factor, shear time in the second step shear, is found to be an effective factor to promote the growth of shish, which might provide a convenient processing method.