structural:scholar_edition, stylistic:style_transfer
Chemicals used

Several different families of liquid crystals are used in liquid crystal displays. The molecules used have to be anisotropic, and to exhibit mutual attraction. Polarizable rod-shaped molecules (biphenyls, terphenyls, etc.) are common. A common form is a pair of aromatic benzene rings, with a nonpolar moiety (pentyl, heptyl, octyl, or alkyl oxy group) on one end and polar (nitrile, halogen) on the other. Sometimes the benzene rings are separated with an acetylene group, ethylene, CH=N, CH=NO, N=N, N=NO, or ester group. In practice, eutectic mixtures of several chemicals are used, to achieve wider temperature operating range (−10..+60 °C for low-end and −20..+100 °C for high-performance displays). For example, the E7 mixture is composed of three biphenyls and one terphenyl: 39 wt.% of 4'-pentyl-4-carbonitrile (nematic range 24..35 °C), 36 wt.% of 4'-heptyl-4-carbonitrile (nematic range 30..43 °C), 16 wt.% of 4'-octoxy-4-carbonitrile (nematic range 54..80 °C), and 9 wt.% of 4 -pentyl-4-carbonitrile (nematic range 131..240 °C).