Systematic study of structure and physical properties of smectogenic 2,7-diacylfluorenes

CHED 1041

Colleen E. Small,, Aurora A. Pribram-Jones,, Rachel N. Harris, Kimberly A. Dallas, Lucas Baker, and Gerald R. Van Hecke. Department of Chemistry, Harvey Mudd College, 301 Platt Blvd, Claremont, CA 91711
The library of synthesized homologous smectic liquid crystals based on the 2,7-diacylfluorenes with the two side chains containing a total of 18 carbons, provides compounds whose molar mass and overall length are the same. These compounds offer very subtle tests of structural changes against which to explain the observed trends in their transition temperatures, and enthalpies. To date compounds have been synthesized with chains 9+9, 10+8 through 14+4. Smectic phases are exhibited by each of these compounds but the temperature range of the phase existence was noticed to become smaller as the carbon difference between the side chains increased suggesting that the 15+3 homolog might not be liquid crystalline. The 15+3 compound was synthesized using a two step, one pot Friedel-Crafts acylation procedure in very low yield. Polarizing microscopy and DSC suggest that the 15+3 homolog does not exhibit liquid crystalline behavior.