Modelling Ferroelectric Nanoparticles in Nematic Liquid Crystals (FERNANO).

摘要

The report provides the results of Monte Carlo computer simulation studies on systems of rod-like mesogens doped with nanoparticles. In particular, we have focused on the effects of nanoparticle shape (spherical, rod and disk like), strength of the specific interactions between nanoparticles and between nanoparticles and mesogens (solvent affinity), polarity of the nanoparticles on phase behavior, long-range positional and orientational order and overall organization of these mixture systems. The results clearly show that even a simple model based on a multi-site Gay Berne potential and dipolar interaction can help to figure out the features which favors the enhancement of the LC order as well as the formation of nanoparticle aggregates. In particular we found that doping a mesogenic system with nanoparticles of any shape has the overall effect of reducing both the orientational and positional order, with the most disordering effects observed for the embedded spherical nanoparticles. The specific nanoparticle-solvent interaction has a significant influence in determining the aggregation/dispersion state of the dopant NP, anyway all the mixtures evidence a shift of the TNI temperature towards lower values, if compared with the pure system. The only exception is given by the mesogenic system doped with polar rod-shaped NP with very low solubility features, which essentially shows invariance of the ordering properties and of the relevant transition temperatures. This behavior is related to the formation of nanoparticles aggregates, each aggregate containing a large number (> 20) of nanoparticles, overall oriented along the mesophase director.