# X-Ray and Optical Studies of the Thickness Dependence of the Phase Diagram of Liquid-Crystal Films

 Title: X-Ray and Optical Studies of the Thickness Dependence of the Phase Diagram of Liquid-Crystal Films Author: Sirota, E. B.; Pershan, Peter S.; Sorensen, L. B.; Collett, J. Note: Order does not necessarily reflect citation order of authors. Citation: Sirota, E. B., Peter S. Pershan, L. B. Sorensen, and J. Collett. 1987. X-ray and optical studies of the thickness dependence of the phase diagram of liquid-crystal films. Physical Review A 36(6): 2890-2901. Full Text & Related Files: Sirota_X-ray_1987.pdf (2.232Mb; PDF) Abstract: A comprehensive study of the thickness dependence of the phase diagram of freely suspended films of the liquid crystal 4-n-heptyloxybenzylidene-4-n-heptylaniline (7O.7) between $$50 and 69^{\circ}C$$ is reported. In thick films (thicker than about 300 layers and characteristic of bulk samples) there is a low-temperature crystalline-G phase followed by five crystalline-B phases with different stacking arrangements at higher temperatures. In thinner films there are two additional crystalline-B phases and two tilted hexatic phases, smectic-F and smectic-I, which do not appear in bulk samples. The in-plane and interlayer correlations in the tilted hexatic phases are anisotropic with a clear dependence on the molecular tilt direction; the in-plane correlations are more developed (longer range) perpendicular to the molecular tilt direction and the interlayer correlations are more developed parallel to the tilt direction. Published Version: doi:10.1103/PhysRevA.36.2890 Terms of Use: This article is made available under the terms and conditions applicable to Other Posted Material, as set forth at http://nrs.harvard.edu/urn-3:HUL.InstRepos:dash.current.terms-of-use#LAA Citable link to this page: http://nrs.harvard.edu/urn-3:HUL.InstRepos:10357473 Downloads of this work: