We report the first unambiguous identification in a thermotropic liquid crystal of a heretic smectic-l, a phase with molecular tilt direction intermediate between those of the smectic-l and smectic-F, using electron diffraction in free-standing films of 5-(4"-hexyl, 3'-fluoro-p-terphenyl-4-oxy)-pentanoic acid ethyl ester. Our structural data directly support the proposed explanation of the unusual stripe phase observed optically. The films show a rich phase diagram as a function of thickness and temperature. A novel phase transition within the surface smectic-l phase is also observed.
MOLECULAR CRYSTALS AND LIQUID CRYSTALS SCIENCE AND TECHNOLOGY SECTION A-MOLECULAR CRYSTALS AND LIQUID CRYSTALS