  Several experiments have reported that ferroelectric nanoparticles have
drastic effects on nematic liquid crystals--increasing the isotropic-nematic
transition temperature by about 5 K, and greatly increasing the sensitivity to
applied electric fields. In a recent paper [L. M. Lopatina and J. V. Selinger,
Phys. Rev. Lett. 102, 197802 (2009)], we modeled these effects through a Landau
theory, based on coupled orientational order parameters for the liquid crystal
and the nanoparticles. This model has one important limitation: Like all Landau
theories, it involves an expansion of the free energy in powers of the order
parameters, and hence it overestimates the order parameters that occur in the
low-temperature phase. For that reason, we now develop a new Maier-Saupe-type
model, which explicitly shows the low-temperature saturation of the order
parameters. This model reduces to the Landau theory in the limit of high
temperature or weak coupling, but shows different behavior in the opposite
limit. We compare these calculations with experimental results on ferroelectric
nanoparticles in liquid crystals.
