Induced Reentrant Smectic A Phase in the Binary Mixtures of Nematic and Cholesteric Compounds

Abstract

The optical studies reveal that binary mixtures of nematic and cholesteric compounds viz., 4(2-2-ethoxy-ethoxy carbonyloxy-cinnamate of 4-hydroxy) 4′-methoxy azobenzol (ACZHM) and Cholesteryl ethyl carbonate (CEC) exhibit cholesteric, smectic end cholesteric phases in the concentration range of the mixture 1 to 9% of CEC, 10 to 40% of CEC and 41 t o 99% of CEC respectively. The mixtures with low percentage of CEC exhibit reentrant smectic A - smectic C - smectic A phases. With the help of the phase diagram of binary mixture, the phase behaviour is discussed. Ttie order parameter of the nematic compound ACZHM is estimated. Optical anisotropy of the mixtures is also estimated using density arid refractive index data. Numerous optical textures like striped pattern, focal conic, fan shaped and drops are illustrated. Pitch variation with concentration is discussed.