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Issue 8, 2003
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Polycatenar mesogens with a perfluorinated moiety showing liquid crystalline polymorphism and, microscopically, a continuous smectic A to structured, fluid, optically isotropic phase transition

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Abstract

A polycatenar mesogen consisting of a stiff, four ring aromatic core with three long alkoxy chains and a bulky, perfluorinated substituent has been synthesized and the phase behavior investigated. Due to strong incompatibility among the constitutional moieties, the material can be expected to self-organize into nano-segregated structures. It has been found that the material shows the unique liquid crystalline polymorphism of a cubic phase, a columnar phase and a smectic A phase as a function of temperature. By analyzing small-angle reflection patterns, the cubic phase is assigned as Im3m symmetry with a unit cell parameter of a ≈ 28 nm, the columnar phase as tetragonal symmetry with a ≈ 11 nm and the smectic A phase as an interdigitated one with a layer separation of 8.2 nm. Interestingly a small-angle reflection is clearly observed far above the smectic A to isotropic phase transition temperature, which reveals that the isotropic phase is not a normal liquid phase, but rather a structured, fluid, optically isotropic (Iso) phase. Moreover the d-spacing and the half-width of the small-angle reflection are observed to continuously change at the smectic A to Iso phase transition, which indicates that the phase transition takes place continuously at the microscopic level.

Graphical abstract: Polycatenar mesogens with a perfluorinated moiety showing liquid crystalline polymorphism and, microscopically, a continuous smectic A to structured, fluid, optically isotropic phase transition

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Article information


Submitted
07 Apr 2003
Accepted
29 May 2003
First published
11 Jun 2003

J. Mater. Chem., 2003,13, 1887-1893
Article type
Paper

Polycatenar mesogens with a perfluorinated moiety showing liquid crystalline polymorphism and, microscopically, a continuous smectic A to structured, fluid, optically isotropic phase transition

E. Nishikawa, J. Yamamoto and H. Yokoyama, J. Mater. Chem., 2003, 13, 1887
DOI: 10.1039/B303776B

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