Thermal Diffusivity Measurements in Nematic and Smectic Phases by Forced Rayleigh Light Scattering

Abstract The forced Rayleigh light scattering technique has been applied to measurements of thermal diffusivity in liquid crystalline phases. In the nematic phase of p-methoxy benzylidene p-n-butyl aniline (MBBA), our results are in good agreement with the data obtained by classical methods. The thermal diffusivity anisotropy in smectic A and B phases has been measured here for the first time in p-butoxy benzylidene p-n-butyl aniline (BBOA). As in the nematic phase, the thermal diffusivity parallel to the long molecular axis is greater than perpendicular to it, i.e. D | > D ⊥. It is particularly striking that the thermal properties do not change significantly at the nematic to smectic phase transition. This suggests that the thermal diffusivity does not depend on the long range order properties of the various mesophases in a crucial manner, contrary to other transport properties such as the electrical conductivity. A tentative description of the thermal transport in terms of high frequency phonons seems a...

[1]  W. Urbach,et al.  A sensitive optical grating method for flash photolysis: application to the CIS-trans photochemical isomerization of azo dyes , 1978 .

[2]  G. Koren.  Thermal blooming measurement of specific heat and thermal conductivity in isotropic p -methoxy benzylidene p -butylanyline (MBBA) near clearing , 1976 .

[3]  S. Kuroda,et al.  Dynamical Study of Heat Conduction in Liquid Crystals by High-Speed Optical Holography , 1976 .

[4]  W. H. Jeu,et al.  MEASUREMENTS OF TRANSPORT PROPERTIES IN THE NEMATIC AND SMECTIC PHASES OF VARIOUS COMPOUNDS , 1975 .

[5]  T. Shinoda,et al.  Thermodynamic properties of N-(p-methoxybenzylidene)-p-n-butylaniline (mbba) from 2 K to its isotropic-liquid phase☆ , 1974 .

[6]  E. Guyon,et al.  Convective instabilities in nematic liquid crystals , 1974 .

[7]  P. Pieranski,et al.  Mesure de la conductivité thermique et détermination de l'orientation des molécules a l'interface nématique isotrope de MBBA , 1974 .

[8]  H. Eichler,et al.  Thermal diffusion measurements using spatially periodic temperature distributions induced by laser light , 1973 .

[9]  A. Arrott,et al.  Expansion Coefficient of Methoxybenzylidene Butylaniline through the Liquid-Crystal Phase Transition , 1973 .

[10]  J. Picot,et al.  Thermal Transport Phenomena in Nematic Liquid Crystals: A Review , 1973 .

[11]  F. Rondelez.  Conductance measurements above a smectic-C ⇹ nematic transition , 1972 .

[12]  J. Janik,et al.  Evidence of the existence of two solid phases of MBBA in specific heat measurements , 1972 .

[13]  John L. Janning.  Thin film surface orientation for liquid crystals , 1972 .

[14]  J. Picot,et al.  Thermal Conduction near an Interface in a Nematic Liquid Crystal Subjected to a Magnetic Field , 1971 .

[15]  A. Fredrickson,et al.  Transport Processes in Anisotropic Fluids II. Coupling of Momentum and Energy Transport in a Nematic Mesophase , 1969 .

[16]  P. A. Egelstaff,et al.  An introduction to the liquid state , 1967 .

[17]  W. J. Haas,et al.  The thermal conductivity of diamond and potassiumchloride , 1938 .