Dependence of Mesomorphism on Terminal End Group of a Molecule

Abstract

A novel azoester homologous series of liquid crystals consisting of 12 members is majorly nematogenic without the exhibition of smectic mesomorphism, except for the hexadecyloxy derivative. The methoxy and ethoxy members are monotropically nematic and the rest of the homologs are enantiotropically nematogenic. Transition temperatures and mesophase morphology were determined on an optical polarizing microscope equipped with a heating stage. The textures of the nematic mesophase are threaded or Schlieren in type. Infra red, ¹H NMR, mass spectral data, and elemental analysis data confirm the molecular structures of the novel homologs. The mesophase length varies from 00 to 72°C and the average thermal stability for the nematic phase is 133.5°C. Liquid crystal properties vary from homolog to homolog in present novel series. The liquid crystal behavior of the presently investigated novel series is compared with structurally similar known series. The transition curves (Cr-N/Cr-I and N-I/I-N) behave in a normal manner. The N-I/I-N transition curve exhibit an odd-even effect. The series is majorly nematogenic without exhibition of smectogenic character. Only the C₁₆ homolog is nonmesogenic.

Keywords:

• Azoester
• liquid crystal
• monotropy
• mesogen
• nematic

Acknowledgments

The authors are thankful to Head and Teaching staff of Applied Chemistry of Faculty of Technology and Engineering, The M.S. University of Baroda, Vadodara for their valuable cooperation in the work. Authors are also thankful to CSMCRI, Bhavnagar, for the analysis of samples.