Abstract
We report the measurement of optical birefringence (Δn) of a binary liquid crystal system consisting of decyloxycyanobiphenyl (10OCB) and heptylcyanobiphenyl (7CB) by means of a high resolution temperature scanning technique. The birefringence data are found to be rather successful in studying the nature of the transition and the critical behavior at the nematic–smectic A (N–SmA) phase transition in these mixtures. In the vicinity of N–SmA phase transition the optical birefringence (Δn) data exhibit strong pretransitional behavior which gets enhanced as the nematic region diminishes. The critical exponent (α), when plotted against the McMillan ratio (TNA/TNI), a uniform crossover from second order to first order behavior have been observed with a tricritical point (TCP) at x10OCB=0.587. The 3D-XY limit for the N–SmA phase transition would hypothetically reach at the McMillan ratio equal to 0.937 for this binary system.
Published Version
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