| Abstract: | Morphological consequences of a localized diffusion of segregated species at crystal growth fronts have been studied in two specific contexts: (1) variation of texture in spherulites grown in unfractionated polyethylene over a range of crystallization temperatures mostly in regime II, and (2) development of elongated lamellar habits in spherulites of a polymer (isotactic polystyrene) whose native crystal habit is regularly polygonal. In relation to (1) it is shown that, as crystallization temperature is varied, there is a correlation between mean thickness of stacks of lamellae and an averaged diffusion range of segregated molecules of lower molecular weight. It is noted that lamellar organization appears to be significantly different in polyethylene fractions. In relation to (2) it is shown that principal contributors to the evolution of spherulitic texture from hedritic precursors are fragmentation of lamellae by screw dislocations and radially biased growth under the influence of concentration gradients of segregated species. |
