Structure of a phenylacetylene macrocycle at the air-water interface

We have used grazing incidence X-ray diffraction and X-ray specular reflect ivity to study Langmuir films of a phenylacetylene macrocycle (PAM), a ring -shaped molecule known to form a tubular liquid crystal. PAM adopts an "edg e-on" molecular arrangement at the air-water interface. The local structure is quite similar to that of the corresponding bulk columnar liquid crystal , but with enhanced order in the intracolumnar direction. The columnar orde r is disrupted by CsCl in the subphase and strongly enhanced by KCl in the subphase.