Crystallization of a poly(ethylene-co-octene): I. A precursor structure and two competing mechanisms

Observations of a sample of poly(ethylene-co-octene)in a polarizing optical microscope reveal peculiarities in its crystallization behavior. When cooled from the melt to a fixed crystallization temperature, at first a structure of diffuse appearance with variations on the length scale of micrometers forms rapidly. The transformation into the final semi-crystalline state then proceeds in two ways, by a continuous change of the inner structure of microm-sized objects and by the growth of spherulites. Time dependent small angle and wide angle X-ray scattering experiments corroborate the occurrence of the two crystallization mechanisms. Atomic force microscopy indicates that the change of the inner structure of the preformed objects is due to an in-filling of crystallites.