6533b858fe1ef96bd12b5962

RESEARCH PRODUCT

Brewster angle microscopy and X-ray GID studies of morphology and crystal structure in monolayers of N-tetradecyl-γ,δ-dihydroxypentanoic acid amide

subject

description

First-order phase transitions from the low-density fluidlike phase to the condensed phase of monolayers of N-tetradecyl-γ,δ-dihydroxypentanoic acid amides at the air−water interface have been studied by π−A isotherms, Brewster angle microscopy (BAM), and synchrotron X-ray grazing incidence diffraction (GID). The thermodynamic differences between enantiomeric and racemic monolayers are too small to be measured. However, chiral discrimination is observable in the macroscopic domain morphology by BAM. The domains of the condensed phase grow dendritically. The characteristic shapes of domains of the pure S and R enantiomers are mirror images of each other. The domains of the racemic mixture are quite similar; however, they have no mirror symmetry. Synchrotron X-ray grazing incidence diffraction (GID) measurements reveal an oblique lattice with tilt direction of molecules close to one of the nearest neighbors for condensed-phase monolayers of both enantiomer and racemate. The molecules of the racemic monolayer...