Impact of BaTiO$_3$ nanoparticles on phase transitions and dynamics in nematic liquid crystal - temperature and pressure studies

TL;DR

This study investigates how BaTiO₃ nanoparticles affect phase transitions and molecular dynamics in nematic liquid crystals under varying temperature and pressure conditions, revealing significant disorder effects and altered dynamical behavior.

Contribution

It provides new insights into the influence of BaTiO₃ nanoparticles on phase behavior and dynamics of liquid crystals under different thermodynamic paths.

Findings

Nanoparticles induce disorder affecting pretransitional behavior.

Different temperature and pressure paths lead to distinct features in nanocolloids.

Dynamical properties show fractional Debye-Stokes-Einstein behavior with different coefficients.

Abstract

Broadband dielectric spectroscopy (BDS) of pure 5OCB and nanocolloids consisting of 5OCB and paraelectric or ferroelectric BaTiO${_3}$ nanoparticles (NPs) was performed on varying pressure or temperature. We found strong impact of NPs on static and dynamic phase behavior. In particular, strongest effects on pretransitional behavior were observed for a relatively low concentration of NPs which we attribute to the NPs-induced disorder. Paramagnetic or ferromagnetic character of NPs did not significantly influence measurements. However, several features measured using temperature or pressure path in nanocolloids where significantly different, contrary to the observed behaviour in pure LC compounds. Dynamical properties were tested using the FDSE (fractional Debye-Stokes-Einstein) relation, yielding the fractional coefficient S = 0.71 and S = 0.3 for the temperature and pressure path, respectively.