The fluctuation-driven dielectric properties of liquid crystalline 8OCB and its nanocolloids

Abstract

Results of broadband dielectric spectroscopy studies in liquid crystalline octyloxycyanobiphenyl (8OCB) and its colloids with BaTiO3 nanoparticles (paraelectric, diameter d=50 nm) are presented. Studies were carried out in isotropic liquid,...

The Dominance of Pretransitional Effects in Liquid Crystal-Based Nanocolloids: Nematogenic 4-methoxybenzylidene-4′–butylaniline with Transverse Permanent Dipole Moment and BaTiO3 Nanoparticles

“…When discussing the behavior of the dielectric constant in the isotropic and nematic phases in MBBA and its nanocolloids with paraelectric BaTiO 3 nanoparticles, notable is the increase in the average value of the dielectric constant, reaching for nanocolloid. A similar behavior was observed in 5CB, 8OCB, 11CB, and 12CB nanocolloids with paraelectric BaTiO 3 nanoparticles [ 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 ]. All these suggest that paraelectric BaTiO 3 nanoparticles can introduce an endogenic arrangement of dipole moment associated with molecules, leading to significant changes in dielectric constant, both in the nematic mesophase and isotropic liquid phase.…”

“…Consequently, the dielectric constant within fluctuations is qualitatively lower than for the ‘non-ordered’ surroundings: . On approaching the I–N transition, the contribution from the volume related to fluctuations finally dominates, and the following crossover occurs [ 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 , 35 ]: in agreement with Equation (2).…”

“…Recent studies of nCB and nOCB liquid crystalline compounds showed that adding BaTiO 3 nanoparticles ( ) can create a unique endogenic permanent orientation of rod-like LC molecules in bulk [ 30 , 31 , 32 , 33 ]. It is reached without any strong external field (electric, magnetic).…”

“…Worth stressing is the significant shift in when changing the amount of NPs. For nanocolloids tested earlier based on 5CB, 11CB, 12CB, and 8OCB LC compounds with the addition of the same nanoparticles, the shift in was negligible [ 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 ]. These compounds are associated with the permanent dipole moment parallel to the long molecular axis.…”

“…Subsequent research reports showed the analogous pretransitional anomalies in nanocolloids based on rod-like LC with solid–nematic–isotropic mesomorphism (in pentylcyanobiphenyl (5CB) + NPs) or solid (S)–smectic A (SmA)–nematic (N)–isotropic (I), in undecylcyanobiphenyl (11CB + NPs), and octyloxycyanobiphenyl (8OCB + NPs) [ 27 , 28 , 29 , 30 , 31 , 32 , 33 ].…”