Optical and electro‐optic properties of some highly conjugated nematic liquid crystals (LCs): 4‐cyano‐4’‐n‐alkyltolanes (n‐CDP) and 4‐cyano‐4’‐n‐alkylstilbene (n‐CS) were studied at elevated temperature. Results are compared with 4‐cyano‐4’‐n‐pentylbiphenyl (5CB). These LCs exhibit large birefringence, small viscoelastic coefficient, and low threshold voltage. Their potential application for modulating visible and infrared radiation is addressed.