Pretransitional Behavior and Dynamics in Liquid Crystal–Based Nanocolloids

Abstract

The impact of nanoparticles on phase transitions in liquid crystal (LC)—nanoparticle nanocollids is still little known. This contribution results for dodecylcyanobiphenyl (12CB), pentylcyanobiphenyl (5CB), and hexyl isothiocyanatobiphenyl (6BT) as the LC host with the addition of BaTiO3 barium titanate barium titanate nanoparticles. The latter has a strong impact on the value of dielectric constant, relaxation time, and the discontinuity of the isotropic–mesophase transitions. The first-ever high-pressure studies in such systems are also presented.

Impact of ferroelectric and superparaelectric nanoparticles on phase transitions and dynamics in nematic liquid crystals

“…The parallel of such behavior was reported for the pressure path of approaching the mesophase (nematic, smectic) 4,12 :…”

“…The DSE relations (S = 1, translational -orientational coupling) converts into the fractional Debye -Stokes -Einstein (FDSE) relation for S ≠ 1 4,17,19 .…”

“…In the last decade liquid crystals (LCs) -nanoparticles (NPs) hybrid composites have become the hot topic in the soft matter and liquid crystals physics [1][2][3][4] . This is associated with their extraordinary metamaterial features, resulted from the mutually beneficial combination of unique semi-ordered fluids and solid nanoparticles.…”

“…However, the fundamental evidence regarding phase transitions is still surprisingly limited, despite the fact that adding of nanoparticles can notably change the LC host system, leading to the emergence of new meta-LC systems. Nanoparticles can act as the moderator of local molecular properties of the liquid crystalline host [4][5][6][7] . On the other hand, the local field or geometrical hindrances associated with NPs could influence the local LC symmetry leading to the shift of phase transition temperatures or the decrease of the switching voltage of structural transformations 5 .…”

“…However, evidences related to these issues for LCs+NPs composites are still very limited. In fact, the first experimental results focusing on critical exponents, the range of critical effects and the value of the discontinuity for weakly discontinuous phase transitions has reported only recently 1,4 . This was the case of dielectric constant behavior in BaTiO3 nanoparticles (non-ferroelectric) -dodecylcyanobiphenyl (12CB, isotropic -smectic A -solid mesomorphism) nanocolloid 1 .…”