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Changes in Thermodynamic and Optical Properties Associated with Mesomorphic Transitions

  • J. R. Flick
  • A. S. Marshall
  • S. E. B. Petrie

Abstract

In parallel thermal and optical studies of the phase transitions in some liquid-crystal-forming compounds, it has been observed that the magnitude of the enthalpy change associated with small alterations in structural order is not an indication of the extent of the change in optical behavior to be anticipated. Of the multiple phase transformations observed in N,N’-bis(4-n-octyloxybenzylidene)-l,4-phenylenedlamine, the S2-S3 transition, which is accompanied by the smallest heat of transition, involves a marked difference in the characteristic textures of the smectic phases. The structural changes associated with some of the other S-S transitions in this compound, however, result in subtle textural changes that are difficult to detect, although the corresponding enthalpy changes are substantial. In 4-n-octyloxyphenyl 4-(4-n-octyloxybenzoyl-oxy)benzoate, the enthalpy change associated with the SA-SB transition at 145°C is so small that it would not be detected normally in dsc studies. This transition can be detected optically, however, by observing the change in the characteristic texture. Although the thermal effect in N,N’-terephthalylidenebis(4-n-butylaniline) is slightly greater, essentially similar results are obtained. It is advisable, therefore, to use several methods in studying the phase transitions in liquid-crystal-forming compounds in order to ensure that characterization of the compound is as complete as possible.

Keywords

Phase Transition Characteristic Texture Enthalpy Change Nematic Phase Optical Behavior 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© Plenum Press, New York 1974

Authors and Affiliations

  • J. R. Flick
    • 1
  • A. S. Marshall
    • 1
  • S. E. B. Petrie
    • 1
  1. 1.Research LaboratoriesEastman Kodak CompanyRochesterUSA

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