Influence of fluorination and chain length on the static dielectric properties of nematogenic bi-cyclohexyl phenyl derivatives

ABSTRACT

Effects of fluorination and chain length of six bi-cyclohexyl phenyl compounds (3ccp-f, 3ccp-ff, 3ccp-fff, 5ccp-f, 5ccp-ff, 5ccp-fff) on their physical properties have been investigated. All the compounds exhibit nematic phase over a wide range of temperatures. Molecular mechanics calculation reveals that dipole moments of the molecules increases (1.93D to 3.37D) with fluorination in both propyl- and pentyl-based systems; increment in f to ff derivatives is more than in ff to fff derivatives. However, no change in dipole moment is observed with increased chain length. In the nematic phase, average value of dielectric constant (ϵ_avg) is less than the extrapolated values of ϵ_iso in isotropic phase. Increased fluorination also decreases splay elastic constant, and thus faster response is expected in triply fluorinated compounds.

KEYWORDS:

• Bi-cyclohexyl phenyl compounds
• dipole moments
• dielectric constant
• splay elastic constant

Acknowledgments

The authors would like to thank Prof. W. Haase, Institute of Physical Chemistry, Darmstadt University of Technology, Germany and R. Dabrowski, Institute of Chemistry, Military University of Technology, Warsaw, Poland for supplying the compounds.

Disclosure statement

No potential conflict of interest was reported by the authors.