liquidcrystalline

Liquidcrystalline materials, often called liquid crystals, are substances that exhibit properties intermediate between conventional liquids and solid crystals. They contain anisotropic molecules that can retain some orientational or positional order over microscopic length scales, producing distinctive optical, electrical, and mechanical responses not found in simple liquids.

The molecular organization of liquidcrystalline phases gives rise to characteristic states. Nematic phases feature long-range orientational order but lack layered structure; smectic phases add one or more well-defined molecular layers; cholesteric (chiral nematic) phases display a helical twist due to molecular chirality. Liquid crystals can be thermotropic, changing phase with temperature, or lyotropic, forming liquid-crystalline phases in solution at certain concentrations. Blue phases are narrow-temperature-range states with three-dimensional order between nematic and isotropic phases.

Key properties include high optical birefringence, dielectric and magnetic anisotropy, and sensitivity to temperature, electric, and magnetic fields. These features enable rapid, controllable changes in alignment and optical transmission, which can be read out as images or modulated as lenses. The order parameter, describing the degree of molecular alignment, governs phase behavior and response times.

Historically, liquid crystals were first observed in the late 19th century by Friedrich Reinitzer and Otto Lehmann, who demonstrated their intermediary character between liquids and solids. The term liquid crystal and subsequent research laid the foundation for modern electro-optic devices and advanced materials.

Applications are broad, most notably liquid crystal displays (LCDs) used in watches, monitors, televisions, and portable devices. Additional uses include tunable optics, sensors, polymers and elastomers incorporating liquid-crystalline order, and specialized photonic materials.