Executive Summary : | The field liquid crystals (LCs) has remained as one of the main topics of investigation, mainly due to their potential applications largely in display technology, including in energy harvesting and photovoltaic devices. LC Display (LCD) applications based on nematic (N) liquid crystals mainly rely on the Freedericksz transition, a collective reorientation of the nematic director along the direction of an applied electric field. Due to the anisotropic nature of the LC molecule, the NLC phase exhibits dielectric anisotropy, where dielectric constant components parallel and perpendicular to the molecular long axis are ε|| and ε|, respectively. The difference between ε|| and ε| is defined as dielectric anisotropy (Δε). Dielectric anisotropy is a measure of the nematic order parameter which governs the value of threshold voltage as well as electro-optic switching time. There are many reports which indicate the electro-optic response time can be improved by forming composites of LC with either quantum dots, carbon nanotubes (CNTs) or dyes. We have observed that the electro-optic switching parameters as well as response time of LC- CNT nanocomposites were improved when CNTs were dispersed either into LC host or in the alignment layer. Further, PI has recently observed a reduction in the total response time in twisted nematic (TN) mode in functionalized silver nanoparticles (f-AgNP) nanocomposites of NLC Though there is an improvement in the switching time, a satisfactory decay time still remains to be achieved. In conventional NLCs, rise-time of the display is dependent on the material property, rather than that of the anchoring at the interfaces, whereas the decay-time is mainly driven by the restoring elastic energy offered by the interfacial anchoring at substrates. In NLCs, ε|| and ε| as well as Δε at a given temperature vary with frequency. In a dual frequency NLC (DFNLC), at a given temperature Δε is positive at low frequency, and at certain frequency Δε = 0 , after which Δε becomes negative. The frequency at which ε|| = ε| i.e Δε = 0 is called the crossover frequency fc. This feature of DFNLC makes it possible to control the switching time of NLC by changing the frequency of applied electric field. The crossover frequency of DFNLC will be determined through dielectric spectroscopy using impedance analyzer (available in the PI’s institute) as a function of temperature using the proposed hot-stage. In dual frequency nematic liquid crystals, both rise-time as well as the decay-time of the display will be entirely dependent on the material property, rather than that of the anchoring at the interfaces. Here, our main focus is to optimize the crossover frequency of DFNLC in the frequency region of less than 10 kHz by incorporation of nanomaterials into NLCs without compromising on the transmission intensity of the electro-optic switching. For the display applications, this type of study would be beneficial. |