Cryogenic Electron Microscopy of Micelles and Lyotropic Liquid Crystals in Some Polar Solvents

Abstract

Micelles and lyotropic liquid crystals in the polar solvents glycerol and formamide have been imaged at high resolution by cryo-transmission electron microscopy (cryo-TEM) of thin frozen samples. Sample films were prepared in a chamber in which temperature and component chemical activities in the surrounding vapor were controlled. The controlled evaporation of the solvent on the grid, the so-called on-grid processing technique, was used to prepare the viscous liquid crystal phase. In dilute solutions of cetyltrimethylammonium bromide (CTAB) in glycerol and sodium dodecyl sulfate (SDS) in formamide there were spherical micelles, while in the concentrated solution of CTAB in glycerol hexagonal liquid crystals formed. These structures resemble closely in appearance the corresponding structures in aqueous solution. Electron beam radiation damage is much more severe in nonaqueous solutions, and the contrast is much lower.