A search for the mosaic block structure in polyethylene single crystals

A diffraction contrast study with the aid of an image intensifier was undertaken to obtain direct evidence for the existence of a mosaic block structure in polyethylene single crystals grown by self seeding under isothermal conditions. Dark‐field microscopy indicates that the crystals do not contain a mosaic block structure. High‐resolution electron diffraction confirms that the crystal is coherent (i.e., mosaic block‐free) over regions of several thousands of Angstroms. It is concluded that a mosaic structure on the scale of ∼300 Å does not exist in polyethylene single crystals grown under carefully controlled conditions from dilute solutions. Possible reasons for previous results that indicate the presence of a ∼300 Å mosaic block structure are discussed.