Splay bend elasticity of a bent-core nematic liquid crystal.

We measured the splay $({K}_{11})$ and bend $({K}_{33})$ 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.