Fluorine-containing triphenylenes. Liquid crystalline properties and surface ordering

Abstract

The synthesis and liquid crystalline properties of two novel series of triphenylenes with 4 or 5 pentafuoropentyloxy tails and 1 or 2 alkoxy tails of varying length are reported. All compounds form wide-range hexagonal columnar phases. The isotropisation temperatures and the corresponding enthalpy changes for the compounds with 4 or 5 fluorinated tails are higher than for the compounds with 6 alkoxy tails, and also higher than for compounds with 6 fluorinated tails. These results indicate that the best ordering is obtained for compounds with a mix of fluorinated and non-fluorinated tails. With increasing length of the alkyl tails in HAT compounds with 4 or 5 fluoroalkoxy tails, the isotropisation temperatures decrease and the d-spacings as observed by XRD increase. All fluoro-containing compounds have a strong tendency for spontaneous homeotropic alignment on surfaces, both hydrophilic and hydrophobic.

Keywords:

• discotic
• fluorine
• surface ordering
• stacking

Acknowledgements

F. Claassen and P. Geutjes are thanked for instrumental assistance and Dr. L. Scheres of Surfix BV (Wageningen, the Netherlands) for providing the fluoroalkyl-coated glass slides.