Macroscopic Biaxial Order in Multilayer Films of Bent-Core Liquid Crystals Deposited by Combined Langmuir–Blodgett/Langmuir–Schaefer Technique
Francesco Vita,
Fabrizio Corrado Adamo,
Mario Campana,
Blake Bordokas,
Federica Ciuchi,
Maria Penelope De Santo,
Daniel Hermida-Merino,
Angela Lisovsky,
Michela Pisani,
Diego Pontoni,
Eric Scharrer,
Oriano Francescangeli
Affiliations
Francesco Vita
Department of Science and Engineering of Matter, Environment and Urban Planning (SIMAU), Polytechnic University of Marche, Via Brecce Bianche, 60131 Ancona, Italy
Fabrizio Corrado Adamo
Department of Science and Engineering of Matter, Environment and Urban Planning (SIMAU), Polytechnic University of Marche, Via Brecce Bianche, 60131 Ancona, Italy
Mario Campana
ISIS Neutron and Muon Source, Rutherford Appleton Laboratory, Harwell Campus, Didcot OX11 0QX, UK
Blake Bordokas
Department of Chemistry, University of Puget Sound, Tacoma, WA 98416, USA
Federica Ciuchi
CNR-Nanotec c/o Physics Department, University of Calabria, Ponte Bucci, Cubo 31C, 87036 Arcavacata di Rende, Italy
Maria Penelope De Santo
CNR-Nanotec c/o Physics Department, University of Calabria, Ponte Bucci, Cubo 31C, 87036 Arcavacata di Rende, Italy
Daniel Hermida-Merino
DUBBLE@ESRF BP CS40220, 38043 Grenoble, France
Angela Lisovsky
Department of Chemistry, University of Puget Sound, Tacoma, WA 98416, USA
Michela Pisani
Department of Science and Engineering of Matter, Environment and Urban Planning (SIMAU), Polytechnic University of Marche, Via Brecce Bianche, 60131 Ancona, Italy
Diego Pontoni
ESRF—The European Synchrotron, 71 Avenue des Martyrs, 38043 Grenoble, France
Eric Scharrer
Department of Chemistry, University of Puget Sound, Tacoma, WA 98416, USA
Oriano Francescangeli
Department of Science and Engineering of Matter, Environment and Urban Planning (SIMAU), Polytechnic University of Marche, Via Brecce Bianche, 60131 Ancona, Italy
Bent-core liquid crystals, a class of mesogenic compounds with non-linear molecular structures, are well known for their unconventional mesophases, characterized by complex molecular (and supramolecular) ordering and often featuring biaxial and polar properties. In the nematic phase, their unique behavior is manifested in the formation of nano-sized biaxial clusters of layered molecules (cybotactic groups). While this prompted their consideration in the quest for nematic biaxiality, experimental evidence indicates that the cybotactic order is only short-ranged and that the nematic phase is macroscopically uniaxial. By combining atomic force microscopy, neutron reflectivity and wide-angle grazing-incidence X-ray scattering, here, we demonstrate that multilayer films of a bent-core nematic, deposited on silicon by a combined Langmuir–Blodgett and Langmuir–Schaefer approach, exhibit macroscopic in-plane ordering, with the long molecular axis tilted with respect to the sample surface and the short molecular axis (i.e., the apex bisector) aligned along the film compression direction. We thus propose the use of Langmuir films as an effective way to study and control the complex anchoring properties of bent-core liquid crystals.
