Crossover temperature (TCO) and temperature gradient of refractive indices and length to breadth ratio of 4O.m mesomorphic compounds – an optical study

Abstract

Refractive indices as a function of temperature are measured in a number of liquid crystals which belong to the N-(p-n-butoxy benzylidene)-p-n alkyl anilines, 4O.m compounds of the famous Schiff’s base nO.m liquid crystal compounds with m = 4 to 10 and 12. The temperature gradient of refractive indices, dne/dT and dno/dT, of these compounds are estimated. It is well known that in the case of dno/dT, there exists a crossover temperature, TCO, which exhibits an odd–even effect with the alkyl chain length as expected. Further, using the birefringence data, the length to breadth ratio, k, for these compounds is estimated, which shows not exactly even–odd effect but irregular change with the chain number. The results are discussed with the body of the data.