Regular Article

Phase transitions and dielectric properties in a symmetric liquid crystalline compound with central triaromatic group

¹ Institute of Physics, Lodz University of Technology, ul. Wólczańska 219, 90-924 Łódź, Poland
² Department of Industrial and Materials Chemistry, Rzeszow University of Technology, al. Powstańców Warszawy 6, 35-959 Rzeszów, Poland

^a e-mail: magdaw@p.lodz.pl

Received: 23 November 2016
Revised: 20 March 2017
Accepted: 5 May 2017
Published online: 9 June 2017

Abstract

Phase transitions and dielectric properties of a symmetric liquid crystalline compound with central triaromatic group are studied and compared with a similar epoxy compound (which has additional strong dipole moments in the tails). The base molecule consists of a central triaromatic group and two symmetric eight-segment aliphatic chains terminated with vinyl groups. The phase transition temperatures are determined through differential scanning calorimetry (DSC), optical data, wide-angle X-ray scattering (WAXS) technique and dielectric measurements. Complex dielectric permittivity is shown for the investigated compound with a sequence of phase transitions in a wide range of frequencies and temperature. In all the cases, phase transitions are clearly visible as the dielectric constant significantly changes near the transition. Physical properties of the material are compared to a closely related compound having polar groups as chain terminators. The impact of this modification of the molecular structure on phase transitions is demonstrated.