Optically Active Binary Liquid Crystal Thermometry

Research on the biological effects and medical applications of non-ionizing electromagnetic fields often requires the use of nonmetallic non-perturbing temperature sensors. The highly temperature dependent optical activity observed in certain types of liquid crystals makes possible the construction of very sensitive non-perturbing fiberoptic thermometers. A knowledge of the effect of various parameters on the optical rotatory power of the chosen liquid crystal is essential for the construction of such a device. The dependence of the optical rotatory power on temperature, composition, and sample thickness in a binary mixture of a nematic (MBBA) and a cholesteric (Cholesteryl Oleate) liquid crystal was studied. The dependence of effective pitch on composition was determined. Application of the data on rotatory power and effective pitch to the construction of devices is discussed. Illinois under Grant USPHSCA 09067.