Effective permittivity of liquid crystal nanodispersions and composites with different pore structure

ABSTRACT

The volume filling fraction dependence of the effective permittivity of the nematic liquid crystal 4-n-pentyl-4’-cyanobiphenyl embedded in different porous membranes and dispersed with aerosil nanoparticles was determined using broadband dielectric spectroscopy in the frequency range from 10⁶ to 10⁹ Hz. The experimental data were analyzed and compared with some existing theories based on the effective medium approximation and their modifications. The obtained effective permittivities as a function of the volume filling fraction lie between the lower limits of the Wiener and Hashin–Shtrikman bounds. The observed shift of the experimental points reflects the changes in the structure of the investigated composites.

KEYWORDS:

• Dielectric spectroscopy
• nematic liquid crystal
• Maxwell Garnett theory
• Wiener bounds
• Hashin–Shtrikman bounds

Acknowledgements

The author wishes to thank V. Yu. Reshetnyak for critical comments and helpful remarks. The author also acknowledges the receipt of a senior postdoctoral fellowship from the Research Council of K.U. Leuven.

Disclosure statement

No potential conflict of interest was reported by the author.