High temperature-gradient refractive index liquid crystals.

We have analyzed the physical origins of the temperature gradient of the ordinary refractive index ( dn(o) /dT) of liquid crystals. To achieve a large dn(o) /dT , high birefringence and low clearing temperature play crucial roles. Based on these simple guidelines, we formulated two exemplary liquid crystal mixtures, designated as UCF-1 and UCF-2, and compared their physical properties with a commonly used commercial liquid crystal compound 5CB. The dn(o) /dT of UCF-1 is ~4X higher than that of 5CB at room temperature.