Dynamics and Pretransitional Effects in C60 Fullerene Nanoparticles and Liquid Crystalline Dodecylcyanobiphenyl (12CB) Hybrid System

Abstract

The report shows the strong impact of fullerene C60 nanoparticles on phase transitions and complex dynamics of rod-like liquid crystal dodecylcyanobiphenyl (12CB), within the limit of small concentrations. Studies were carried out using broadband dielectric spectroscopy (BDS) via the analysis of temperature dependences of the dielectric constant, the maximum of the primary loss curve, and relaxation times. They revealed a strong impact of nanoparticles, leading to a ~20% change of dielectric constant even at x = 0.05% of C60 fullerene. The application of the derivative-based and distortion-sensitive analysis showed that pretransitional effects dominate in the isotropic liquid phase up to 65 K above the clearing temperature and in the whole Smectic A mesophase. The impact of nanoparticles on the pretransitional anomaly appearance is notable for the smectic–solid phase transition. The fragility-based analysis of relaxation times revealed the universal pattern of its temperature changes, associated with scaling via the “mixed” (“activated” and “critical”) relation. Phase behavior and dynamics of tested systems are discussed within the extended Landau–de Gennes–Ginzburg mesoscopic approach.

The impact of ionic contribution to dielectric permittivity in 11CB liquid crystal and its colloids with BaTiO3 nanoparticles

“…Such behavior is manifested via pretransitional effects explained within the Physics of Critical Phenomena [4]. For dielectric constant the following general relation describing such behavior can be concluded [18][19][20][21][22][23][24]:…”

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

“…Insight into the impact of pretransitional fluctuations on LC systems and their nanocolloids still constitutes a cognitive gap. 21–25…”

“…Insight into the impact of pretransitional fluctuations on LC systems and their nanocolloids still constitutes a cognitive gap. [21][22][23][24][25] This paper presents the results of broadband dielectric spectroscopy studies in n-octyloxycyanobiphenyl (8OCB) and its colloids with BaTiO 3 nanoparticles. Studies cover isotropic liquid, nematic, smectic A and solid phases.…”

Influence of Liquid Crystallinity and Mechanical Deformation on the Molecular Relaxations of an Auxetic Liquid Crystal Elastomer

“…It has been shown that the temperature-dependent behavior of the structural relaxation of LC materials is strongly influenced by pre-transitional phenomena in the isotropic phase [ 15 ]. It has also been shown that the addition of nanoparticles disrupts the pre-transitional phenomena present in the isotropic phase [ 76 , 100 ]. With low concentrations of nanoparticles, a cross-over from non-Arrhenius to Arrhenius behavior has been observed in the isotropic phase; further increase in the nanoparticle concentration causes a cross-over from Arrhenius to non-Arrhenius behavior [ 100 ].…”

“…It has also been shown that the addition of nanoparticles disrupts the pre-transitional phenomena present in the isotropic phase [ 76 , 100 ]. With low concentrations of nanoparticles, a cross-over from non-Arrhenius to Arrhenius behavior has been observed in the isotropic phase; further increase in the nanoparticle concentration causes a cross-over from Arrhenius to non-Arrhenius behavior [ 100 ]. Hence the difference in in the isotropic and nematic LCE could be understood by the presence of pre-transitional nematic regions and nematic correlations, respectively, and the relative size of these with respect to the length-scale of correlated motions of the relaxation.…”