Defect structures in lyotropic smectic phases revealed by freeze-fracture electron microscopy

Abstract

Freeze-fracture electron microscopy has been used to examine defect structures such as confocal domains, screw dislocations, disclinations, and walls in lamellar phospholipid phases containing known amounts of water (from about 5 to 65% by weight). In a concurrent study (Costello and Gulik-Krzywicki 1976) all samples were examined by X-ray diffraction before and after freeze-quenching to ensure that the freezing process had not induced a phase transition. Most of the prominent defect structures, especially confocal domains, have been observed in all samples. Electron micrographs showing the lamellar arrangements of the defects near their cores are presented. The most important observation about the frequency of occurrence of defects is the proliference of screw dislocations and the absence of edge dislocations. This lends support to the commonly proposed hypothesis that the deformation of smectic layers tends to occur at constant layer thickness.