Molecular Packing and Textures of 1-Stearylamine-rac-glycerol Monolayers

Abstract

The phase behavior and the structural features of 1-stearylamine-rac-glycerol monolayers at the air−water interface are experimentally studied by surface pressure−area (π−A) isotherms, Brewster angle microscopy, and synchrotron X-ray diffraction at grazing incidence. The two-phase coexistence region defined for π > 0 mN/m exists at temperatures of ≥30 °C. In comparison to the monoglycerol ethers, esters, and amides of the same alkyl chain length, the monoglycerol amines have the highest phase transition pressure. At equilibrium, circular, faceted, or cardioid domains subdivided in six or seven segments are formed in the two-phase coexistence region. Fractal-like nonequilibrium domain patterns grow at usual monolayer compression. After compression stop, they are slowly transformed in the compact domains at equilibrium. The racemic 1-stearylamine-rac-glycerol monolayers have a rectangular-centered lattice structure. The tilt direction of the alkyl chains changes from NN to NNN already at low surface pressur...