Thermal blooming measurement of specific heat and thermal conductivity in isotropic p-methoxy benzylidene p-butylanyline (MBBA) near clearing

Abstract

Using the thermal-lens effect, the specific heat Cp and the thermal conductivity Λ have been measured simultaneously in the isotropic phase of the liquid crystal MBBA (p-methoxy benzylidene p-butylanyline) near its isotropic-to-nematic transition. Accurate analysis of the lens dynamical behavior yields both transport coefficients provided the change of the refractive index with temperature, dndT, is known. A precise measurement of n(T) was carried out separately. The best fits yield the critical exponents 0.52 and 0.65 for Cp and Λ, respectively, with a critical temperature Tc equal to Tp-0.21±0.01°C, where Tp is the clearing temperature. The present measurements give the first conclusive results on the critical behavior of Cp in the isotropic phase of a liquid crystal. © 1976 The American Physical Society.