Reprinted with permission from J. Am. Chem. Soc., 2017, 139, pp 3841-3850. Copyright 2017 American Chemical Society.
Numerous applications of liquid crystals rely on control of molecular orientation at an interface. However, little is known about the precise molecular structure of such interfaces. In this work, synchrotron X-ray reflectivity measurements, accompanied by large-scale atomistic molecular dynamics simulations, are used for the first time to reconstruct the air-liquid crystal interface of a nematic material, namely, 4-pentyl-4′-cyanobiphenyl (5CB). The results are compared to those for 4-octyl-4′-cyanobiphenyl (8CB) which, in addition to adopting isotropic and nematic states, can also form a smectic phase. Our findings indicate that the air interface imprints a highly ordered structure onto the material; such a local structure then propagates well into the bulk of the liquid crystal, particularly for nematic and smectic phases. This research is a collaboration between the Institute of Molecular Engineering at the University of Chicago (including members of ChemMatCARS), the University of Illinois at Chicago, and the University of Wisconsin at Madison.
Monirosadat Sadati1,6, Hadi Ramezani-Dakhel1,2, Wei Bu3, Emre Sevgen1, Zhu Liang4, Cem Erol4, Mohammad Rahimi1, Nader Taheri Qazvini1,6, Binhua Lin3, Nicholas L. Abbott5, Benoı̂t Roux2, Mark L. Schlossman4, and Juan J. de Pablo1
1Institute for Molecular Engineering, University of Chicago, Chicago, Illinois 60637, United States
2Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, Illinois 60637, United States
3Center for Advanced Radiation Sources, University of Chicago, Chicago, Illinois 60637, United States
4Department of Physics, University of Illinois at Chicago, Chicago, Illinois 60607, United States
5Department of Chemical and Biological Engineering, University of Wisconsin−Madison, Madison, Wisconsin 53706, United States
6Argonne National Laboratory, Argonne, Illinois 60439, United States
J. Am. Chem. Soc., 2017, 139, pp 3841-3850