Low dielectric loss in quaterphenyl liquid crystal compounds via substituent group modifications

High-birefringence liquid crystals (LCs) are promising for microwave phase shifters, offering tunable phase control, low energy consumption, and cost-effectiveness. However, their application is hindered by high dielectric loss, primarily due to uneven electron distribution. By modifying terminal groups and lateral substituents in fluorine-containing quaterphenyl LCs, dielectric loss was reduced from 8.58 × 10⁻³ to 5.12 × 10⁻³ at 18.3 GHz. DFT calculations revealed that these modifications decrease molecular dipole, polarizability, and dihedral angles, promoting electron uniformity and lowering dielectric loss. This work provides critical insights for designing advanced LC-based microwave materials.