Institute of High Pressure Physics

Research carried out at our Institute in the NL10 laboratory has shown interesting properties of nanocollides based on a liquid crystal (MBBA) with the addition of BaTiO₃ nanoparticles. Previous work by this group has already shown that adding a minimal amount of nanoparticles fundamentally changes the properties of the system. This time, the properties were examined in the direction perpendicular to the long axis of the molecules.

The studied nanocolloids showed that in the isotropic phase a pre-transition effect of the dielectric constant is observed, which can be related to the so-called negative specific heat. In the nematic phase, which undergoes supercooling, a very strong signature of passing the melting point appears despite the lack of crystallization. The very strong pre-melting effect in the solid phase is explained on the basis of a concept combining the Lipovsky model for nanolayers of liquids between two surfaces, and the hypothesis of the appearance of negative pressures in these layers - leading to the Mossotti Catastrophe behavior. This work also shows for the first time a simple parameterization of changes in electrical permittivity in the low-frequency region (which was a previously unsolved problem) and a previously unknown critical anomaly of the dissipation coefficient, i.e. D = tgδ related to energy dissipation.

Th work is published in Open Access paper: A. Drozd-Rzoska, J. Łoś, S.J. Rzoska, The dominance of pretransitional effects in the liquid crystal based nanocolloids: nematogenic MBBA with the transverse permanent dipole moment and BaTiO₃ nanoparticles, Nanomaterials 2024, 14, 655 (Impact Factor: 5.3).

Fig. Temperature evolutions for tgδ loss (energy dissipation) factor for frequency f=12Hz in MBBA and related nanocolloids with BaTiO₃ nanoparticles. The solid green and blue curves are for the critical-like empirical parametrization D(T)=tgδ=δ^*+d(T-T_δ)+D(T-T_δ)^Ѱ with exponent Ѱ≈4. Note the link of this magnitude to the power loss: P=ωCV²tgδ.