A new memory effect: smectic liquid crystalline memory having both conductive and optical memory

Abstract

We report a memory effect of a smectic liquid crystal that is conductive. The smectic liquid crystalline materials investigated have two long alkyl chains and a long conjugated core. On forming the smectic phase, molecules order to form a continuum of conjugated cores. Since the latter is conductive as a result of charge hopping, smectic molecular ordering of these compounds produces charge transport ability. Because of the strong dispersion force between the alkyl chains, after cooling the smectic molecular order is memorised at room temperature. In addition, the charge transport ability is also memorised 1. The conductivity of a device with smectic liquid crystalline order is about 5×10⁷ times larger than that of a device that does not have any smectic order. Therefore, by using laser beam spot heating or by electrical heating, conductive spots can be written. These spots also can be read both by optical and electrical methods. Therefore, this is the first new type of memory that can be written and read both electrically and optically.