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.