Theoretical Study of the Electro-optic Response of Nanoparticle doped Ferroelectric Liquid Crystals

Abstract

Ferroelectric Liquid Crystals (FLC) show superior electro-optic response compared to conventional nematic phases due to their spontaneous polarizability. Despite this inherent polarization, high rotational viscosity and lack of self-healing capability strongly hinder the utility of FLCs as electro-optic devices. Nanoparticles (NP) can be used to mitigate these deficiencies effectively. To this end, it is crucial to understand the nature of the interaction between NPs and FLC molecules. Here a Landau-de Gennes type theory is developed to understand this interaction and its associated consequences on the electro-optic response of an NP-FLC composite medium. It is found that NP doping significantly alters the SmecticA* to SmecticC* transition temperature. The polarization of the nanocomposite also increases significantly, which changes the soft mode dielectric susceptibility of the medium. With an applied field, the ferroelectric equation of state for the nanocomposite is also investigated in detail with substantial changes found in the coercive field and remanent polarization. Furthermore, it is revealed that the electroclinic nature of the SmecticA* phase is significantly impacted by the NP doping and the closely associated dc quenching effect in the phase is also modified.