Formation of Chiral Interdigitated Multilayers at the Air-Liquid Interface Through Acid-Base Interactions

Abstract
Thin interdigitated films composed of a long-chain, water-insoluble chiral acid (p -pentadecylmandelic acid of absolute configuration R ) and a water-soluble chiral base (phenylethylamine, R′ ) were constructed at the air-solution interface. The ( R, R′ ) structure was characterized to near-atomic resolution by grazing-incidence x-ray diffraction (GIXD). The two diastereomeric systems, ( R, R′ ) and ( R, S′ ), demonstrate similar surface pressure-molecular area isotherms, but their structures are completely different on the molecular level, as monitored by GIXD. Complementary data on these two architectures were provided by atomic force microscopy.