Critical behavior of the layer-compressional elastic modulus at a smectic-smectic isolated critical point

Abstract

We report on the compressional-elastic-modulus critical behavior in the vicinity of the smectic-A2-smectic-Ad liquid-crystal critical point in mixtures of undecyloxyphenyl cyanobenzyloxy benzoate and nonyloxybiphenyl cyanobenzoate. Our results show a critical vanishing of the elastic modulus with an exponent about 0.4+0. 1, which appears to disagree with both mean-Geld (0.67) and Ising (0.79) predictions. This favors the idea that the smectic-A2smectic-Ad critical point belongs to a new universality class, as recently predicted. 422521