A CONFORMATIONAL PHASE-TRANSITION IN A LANGMUIR FILM OF AN AMPHIPHILIC AZACROWN

We have used grazing-incidence X-ray diffraction, X-ray reflectivity, and Brewster-angle microscopy to study an amphiphilic azacrown derivat ive at the air-water interface. The compound studied has a ring-shaped , flexible core with six alkyl chains attached. As the density is incr eased, the molecules undergo a phase transition from a face-on structu re, with the alkyl tails extending away from the interface, to a thick er edge-on structure, with the tails extending radially away from the core. Concomitant with this rearrangement, the film develops long-rang e in-plane structural order.