We measured the splay $\left(K_{11}\right)$ and bend $\left(K_{33}\right)$ elastic constants in the nematic phase of a bent-core liquid crystal. In the vicinity of the nematic-isotropic transition temperature $K_{33}$ is proportional to the square of the order parameter. In the nematic range $K_{11}$ increases monotonically with decreasing temperature, whereas $K_{33}$ is practically independent of temperature and is smaller than $K_{11}$. $K_{33}$ exhibits a pretransitional slow divergence toward the transition temperature to the smectic phase and becomes slightly larger than $K_{11}$. The small $K_{33}$ is explained on the basis of strong coupling of the bent shape of the molecules with the bend distortion.

We report temperature dependent measurements of birefringence (Δn), splay (K₁₁), bend (K₃₃) elastic constants and rotational viscosity (γ₁) of mixtures of rod-like and bent-core molecules. K₁₁ and Δn remain almost constant for all the mixtures whereas K₃₃ is always lower than K₁₁ and further decreases with increasing concentration of bent-core molecules in the mixtures. Apart from the large jump in Δn at the nematic-isotropic transition (NI) a significant jump in Δn at the nematic-smectic transition (NS) is also observed that increases with increasing mol% of the bent-core compound in the mixtures. Rotational viscosity increases by a factor of four when the concentration of the bent-core compound increased from 0 to 10 mol%. The results are discussed on the basis of their structural similarity and mutual alignment in the nematic phase.

We report the measurement of birefringence, dielectric constant, splay, bend elastic constants and rotational viscosity in the nematic phase (N) of a hockey stick-shaped compound exhibiting smectic-A (SmA) and anticlinic smectic-C (SmC_a) phase transitions at lower temperature. It is found that the physical properties are significantly different than calamitics and partially similar to the bent-core liquid crystals. It exhibits the positive dielectric and the negative elastic anisotropy. The optical and the thermal measurements show that all the transitions are first order. The rotational viscosity is comparatively higher than calamitic liquid crystals and exhibits weak pre-transitional divergence. The temperature dependent static dielectric measurements indicate antiparallel correlation of both the longitudinal and the transverse components of dipole moments in both the smectic phases. The parallel component of the dielectric constant exhibits a single Debye type relaxation in all the phases. The activation energy in the N, SmA and SmC_a phases are comparatively larger than that of the respective phases of calamitic liquid crystals and can partially be attributed to the higher rotational viscosity of the hockey stick-shaped compound.

We report a strong discontinuous orientational transition (anchoring transition) of liquid-crystal molecules with a large transverse dipole moment. A perfluoropolymer was used as an alignment layer and the transition was observed from planar to homeotropic with decreasing temperature in the nematic phase. Conversely a gradual variation in tilt angle from homeotropic to conical was observed in a liquid crystal with a comparatively smaller transverse dipole moment on the same alignment layer. The experimental results clearly demonstrate the competition between a short-range dipolar force and long-range van der Waals force at the interfacial region. Using discontinuous anchoring transition in the sample, we demonstrate a possible bistable device for memory and light-driven display.

We report magnetic field tuning of the structure and Whispering Gallery Mode lasing from ferromagnetic nematic liquid crystal micro-droplets. Microlasers were prepared by dispersing a nematic liquid crystal, containing magnetic nanoparticles and fluorescent dye, in a glycerol-lecithin matrix. The droplets exhibit radial director structure, which shows elastic distortion at a very low external magnetic field. The fluorescent dye doped ferromagnetic nematic droplets show Whispering Gallery Mode lasing, which is tunable by the external magnetic field. The tuning of the WGM lasing modes is linear in magnetic field with a wavelength-shift of the order of 1 nm/100 mT. Depending on the lasing geometry, the WGMs are red- or blue-shifted.

We create controllable active particles in the form of metal-dielectric Janus colloids which acquire motility through a nematic liquid crystal film by transducing the energy of an imposed perpendicular AC electric field. We achieve complete command over trajectories by varying the field amplitude and frequency, piloting the colloids at will in the plane spanned by the axes of the particle and the nematic. The underlying mechanism exploits the sensitivity of electro-osmotic flow to the asymmetries of the particle surface and the liquid crystal defect structure. We present a calculation of the dipolar force density produced by the interplay of the electric field with director anchoring and the contrasting electrostatic boundary conditions on the two hemispheres, which accounts for the dielectric-forward (metal-forward) motion of the colloids due to induced puller (pusher) force dipoles. These findings open unexplored directions for the use of colloids and liquid crystals in controlled transport, assembly, and collective dynamics.