Synthesis and mesomorphic behavior of terminal oligo(ethylene glycol) monomethyl ether-substituted low molecular weight thermotropic liquid crystals

A number of alkenyl monomers containing biphenyl benzoate-based on a mesogenic core with various lengths of oligo(ethylene glycol) monomethyl ether as the terminal group were synthesized. The purity, the thermotropic transition temperature, and the mesomorphic texture were investigated with 1H-nuclear magnetic resonance spectroscopy, differential scanning calorimetry, and optical polarized microscopy with a hot stage. The monomers studied in this project showed predominately nematic phases, whereas those with esterlinked derivatives studied in our previous work were able to present both nematic and smectic phases. They also exhibited higher isotropic transition temperatures than those of the ester-linked derivatives. The factors governing mesophase texture and transition temperature are discussed thoroughly. © 1994 John Wiley & Sons, Inc.