Paranematic-to-nematic ordering of a binary mixture of rodlike liquid crystals confined in cylindrical nanochannels

Sylwia Całus, Beata Jabłońska, Mark Busch, Daniel Rau, Patrick Huber, and Andriy V. Kityk
Phys. Rev. E 89, 062501 – Published 9 June 2014

Abstract

We explore the optical birefringence of the nematic binary mixtures 6CB1x7CBx (0x1) embedded into parallel-aligned nanochannels of mesoporous alumina and silica membranes for channel radii of 3.4R21.0 nm. The results are compared with the bulk behavior and analyzed with a Landau–de Gennes model. Depending on the channel radius the nematic ordering in the cylindrical nanochannels evolves either discontinuously (subcritical regime, nematic ordering field σ<1/2) or continuously (overcritical regime, σ>1/2), but in both cases with a characteristic paranematic precursor behavior. The strength of the ordering field, imposed by the channel walls, and the magnitude of quenched disorder varies linearly with the mole fraction x and scales inversely proportionally with R for channel radii larger than 4 nm. The critical pore radius, Rc, separating a continuous from a discontinuous paranematic-to-nematic evolution varies linearly with x and differs negligibly between the silica and alumina membranes. We find no hints of preferred adsorption of one species at the channels walls. By contrast, a linear variation of the nematic-to-paranematic transition point TPN and of the nematic ordering field σ versus x suggests that the binary mixtures of cyanobiphenyls 6CB and 7CB keep their homogeneous bulk stoichiometry also in nanoconfinement, at least for channel diameters larger than 7 nm.

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  • Received 4 January 2014

DOI:https://doi.org/10.1103/PhysRevE.89.062501

©2014 American Physical Society

Authors & Affiliations

Sylwia Całus1, Beata Jabłońska2, Mark Busch3, Daniel Rau4, Patrick Huber3,4,*, and Andriy V. Kityk1,†

  • 1Faculty of Electrical Engineering, Czestochowa University of Technology, 42-200 Czestochowa, Poland
  • 2Faculty of Environmental Engineering and Biotechnology, Czestochowa University of Technology, 42-200 Czestochowa, Poland
  • 3Materials Physics and Technology, Hamburg University of Technology (TUHH), D-21073 Hamburg-Harburg, Germany
  • 4FR 7.2 Experimental Physics, Saarland University, D-66123 Saarbrücken, Germany

  • *patrick.huber@tuhh.de
  • andriy.kityk@univie.ac.at

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Vol. 89, Iss. 6 — June 2014

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