Heat Generation in Nematic Mesophases Subjected to Magnetic Fields

  • Chang-Koo Yun
  • A. G. Fredrickson


Moll and Ornstein and later Miesowicz and Jezewski observed that temperature changes were induced in nematic mesophases in the vicinity of solid interfaces by application or removal of magnetic fields. Such phenomena have been considered to be entropy effects associated with the ordering produced by the interface and the magnetic field. In the present work, these experiments have been conducted with two materials, p-azoxyanisole and p-n-decyloxy benzoic acid, but measurements of sample temperature were extended to much larger times and in larger volume that is relatively free of interfaces than those used by the earlier workers. It was found that the temperature rise upon application of a magnetic field was permanent rather than transient; the sample returned to the surroundings temperature only after the field was removed. Thus, a magnetic field causes a continuous generation of heat in a nematic mesophase, and this cannot be attributed simply to ordering effects.

Further experiments on this effect show that it is associated with nematic mesophases; thus, no temperature changes were observed in the isotropic phases of p-azoxyanisole or p-n-decyloxy benzoic acid or in the smectic phase of the latter. In addition, the magnitude of the heat generation rate is dependent on the past thermal history of the sample. Finally, the generation rate shows a saturation effect with respect to magnetic field strength. The implications of these findings are discussed and some possible sources for them are mentioned.


Magnetic Field Field Strength Temperature Rise Heat Generation Magnetic Field Strength 
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Copyright information

© Plenum Press, New York 1970

Authors and Affiliations

  • Chang-Koo Yun
    • 1
  • A. G. Fredrickson
    • 1
  1. 1.Chemical Engineering DepartmentUniversity of MinnesotaMinneapolisUSA

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