Separation of enantiomers in a diol monolayer studied by fluorescence microscopy and grazing incidence X-ray diffraction

Summary Monolayers of a racemic mixture and of the pure S- and R-enantiomers of 3-hexadecyloxy-propane-1,2-diol have been investigated by fluorescence microscopy and grazing incidence X-ray diffraction. Above the transition pressureΠ _c domains with a polygonal shape appear. On compressing the monolayers shape instabilities occur. While the spirals of the S-enantiomer turn clockwise and the spirals of the R-enantiomer turn counterclockwise, the spirals from one domain of the racemate exhibit opposite handedness. This behaviour is explained by a separation of enantiomers on the molecular level. At all pressures investigated the enantiomers exhibit an oblique lattice. The tilt angle of the molecules decreases with increasing pressure. Paper presented at the I International Conference on Scaling Concepts and Complex Fluids, Copanello, Italy, July 4–8, 1994.